combined trailing arm mount/body outrigger

[uninformed]

Hey all,

I have had this idea for ages but for a few hurdles I havent done anything about it...I would like to increase the length of my rear trailing arms. The rear cab outrigger on my Def 110 CC is approx 250mm forward of the trailing arm mount. So I want to remove both the TA mount and the Body out rigger and fab a new one for both.

I have done a quick carboard mock up of the concept. The main body im thinking 3mm plate. Top and sides and end all one peice folded. There will be atleast one internal web and a bottom with, either dimple holes or holes with right angle banding.

Any thoughts, ideas and comments are welcome

http://www.aulro.com/afvb/attachments/modified-zone/51532d1348570848-combined-trailing-arm-mount-body-outrigger-chassis-mount-003-rs.jpg

http://www.aulro.com/afvb/attachments/modified-zone/51533d1348570887-combined-trailing-arm-mount-body-outrigger-chassis-mount-007-rs.jpg

http://www.aulro.com/afvb/attachments/modified-zone/51534d1348570938-combined-trailing-arm-mount-body-outrigger-chassis-mount-006-rs.jpg

[uninformed]

more pics:

http://www.aulro.com/afvb/attachments/modified-zone/51535d1348571143-combined-trailing-arm-mount-body-outrigger-chassis-mount-001-rs.jpg

http://www.aulro.com/afvb/attachments/modified-zone/51536d1348571169-combined-trailing-arm-mount-body-outrigger-chassis-mount-002-rs.jpg

http://www.aulro.com/afvb/attachments/modified-zone/51537d1348571199-combined-trailing-arm-mount-body-outrigger-chassis-mount-005-rs.jpg

[Slunnie]

For yours I wouldn't have made it cover the top of bottom plates of the chassis rails for cracking and complience reasons. I would also have changed the chassis mount to a Nissan Patrol rear link bush pattern - I think its a better arrangement

I would have just adapted a Series LWB rear spring mount by removing the spring mount on it and refabricating a Patrol type on the face of it. Then weld it on to the side of the chassis making sure it contacts the top and bottom plates.

https://www.aulro.com/afvb/images/imported/2012/09/245.jpg

[uninformed]

All im doing is duplicating what LR have done top and bottom on both the TA mount and the outrigger. Personally I think it very sound design. I feel that the way the bottom of the TA mount locates to the inside corner of the chassis rail much better than just the outside...

[Slunnie]

Sorry, I missed the outrigger being a body mount also.

Complience.... meaning engineer approvable.

[cal415]

I have been looking at doing exactly the same thing.... have you seen the gigglepin rear arms? i know they remove the standard mount and put a new one on further forward, i havnt seen any pics of how they do it exactly but its something i have wanted to do for some time and have been thinking of doing something almost identical to your drawing or doing similar but using square tube with a mount for a large bush similar to patrol or land cruiser...

I just bought a 93 defender with the intention of turning it into a comp truck so i will probably have a crack at making some for that first before giving it a go on my county

[uninformed]

Complience.... meaning engineer approvable.

Don't you swear at me!!!! :(


This being one of the hurdles....and I guess your concern is welding across the top and bottom flanges of the chassis rail. LR seem to have done it with success. If you look at the top that overlaps, the ends will be cut at an angle so the are not directly perpendicular to the flange. I'm even open to the idea of bending the lower piece that crosses the bottom flange, again so its not a direct 90 degree weld across the chassis.

[Slunnie]

:lol2:

Welding the top and bottom of the chassis is a little like wheel spacers. The manufacturer is allowed to fit them, but nobody else is subsequently.

[modman]

Make the mount on a folded c section to spread the load to wherever engineers need it
Gives options for plug and stitch joins
I'll have 2 please!
Dc
On a side note bill used to make complete bolt on kits to turn leafers
Into coilers
That's clamps around the rails for all mounts!

[uninformed]

Here you go Cal:

Gigglepin car 4x4 - YouTube

Not sure what all the froth on the patrol chassis end bush is about. Ill have to look at my neighbours when he gets home.....

There is definitely more than one way to skin a cat.......I guess what I am trying to achieve is a factory look ;)

Im very aware of the legalities and lets remember it changes from state to state, and who you are dealing with. Lets just leave it at that and when the time comes IF it happens I will pass on all/any info to help others do this sort of thing by the books.

Im more interested in the engineering, ie design and strength....

What I like about the factory TA mount is that, to me, I visualise the arm pushing (due to axle housing rotation) now the mount is in compression, this why it has folds and is double layered for most part (3mm+4mm to create 7mm thick in sections) So the angle section that comes off the mount up to the corner and top of the chassis rail is stoping the bracket folding off AND transmitting force along the chassis...BUT, if this was all there was the chassis would also be being loaded inward....the small section that goes under the bottom and is welded along the bottom inside corner is also transmitting thr force, and Im thinking somewhat balancing out the inward force of the mount....basicly its a more forward push on the chassis than just a mount mounted to the outside

BTW, Im not building a comp truck, I dont need to tuck this all up above the chassis rail.

[uninformed]

here are some more pics to ponder.....

Can someone tell me why the LR engineers chose to not weld the corners of the TA mount

http://www.aulro.com/afvb/attachments/modified-zone/51546d1348631694-combined-trailing-arm-mount-body-outrigger-trailing-arm-mount-001-rs.jpg

And then did weld the corners of the body outrigger

http://www.aulro.com/afvb/attachments/modified-zone/51547d1348631733-combined-trailing-arm-mount-body-outrigger-trailing-arm-mount-002-rs.jpg


My guess is that the outrigger mostly sees compressive forces, ie straight down, hence why the top is overlapped to the flange center line....but Im thinking maybe the TA mount sees more twisting???


I was thinking that a compromise may be to fold the bottom of the mount at the yellow line, forward say at 45 degrees, so that the welding was not directly "across" the bottom flange??

http://www.aulro.com/afvb/attachments/modified-zone/51548d1348631762-combined-trailing-arm-mount-body-outrigger-trailing-arm-mount-003-rs.jpg

[Dougal]

I think you are on the right track. I would also shape it to avoid any welding across a chassis rail. You may need to plate the chassis face and weld the outrigger to the plates.
It's not a bad thing that modifications need done to a higher standard than factory.

What's the story with compliance and engineers certs?

[wagoo]

Serg, I think you are on the right track with your combination outrigger design. The only possible reservation I have is the chassis rail itself. I recall looking at pieces of a written off early 110 chassis that had been cut up into manageable size chunks. The box section in the rear suspension area appeared to be virtually double skinned. I don't know if this double skinning extended as far forward as the trailing arm mounting area but it may be worth checking out.If it is double skinned there, I doubt it would extend as far forward as your new proposed location.
I believe LandRovers bean counters have made 'cost savings' on Defender chassis, particularly 130's,so it wouldn't surprise me if the double skinning disappeared years ago, along with Salisbury diffs etc.
I think you already have rock sliders fitted from memory. Tying all outriggers together with these should also help rigidify things a bit.
Bill.

[uninformed]

welding across the flanges:

Note that the top overlap of flange only goes to center, so any welding is not fully across the flange. As I said earlier I would cut the ends of this overlap so they are on an angle, say atleast 45 degrees...

Regarding the bottom section of the face that the TA mounts to, where it goes under the chassis and finishes at the bottom inside corner, Im thinking of folding this, forward, again at 45 degrees....Will this still help transmit the forces in the same manner?

I say all this based on the idea that welding at 45 degrees across is better than 90 degrees across :confused:

Seems like everyone is in favour of fish plating the outside face of the chassis rail before fitting of the mount. I have seen this done many times in various applictaions. If it is just a flat plate, then we are welding to the top and bottom corners of the box section...where I believe the "stresses" are stored??? Again I could fold up a "C" section so that the top and bottom folds return to the center line of chassis and weld along this (note that this is where the Box is its thickest as the 2 "C" sections that make up the box are overlapped and welded here.) The reason Im not sure about welding to "corners" of the box section/chassis rails are that, #1 I think it was Bush65 who said thats where the "stresses" are stored, and #2 taking a close look at the OEM TA mount, it appears that LR have avoided welding here...The top over laps to the center line, and where the bottom folds up and meets the bottom inside corner, it actuall has a small angle, say 25x25x2,sitting over this area, welded anlong its length (front to rear of vehicle) See pics:

Looking inside the bottom of the TA mount where it meets the bottom inside corner of box section chassis rails....note arrows showing no visable weld penetration:

http://www.aulro.com/afvb/attachments/modified-zone/51597d1348736353-combined-trailing-arm-mount-body-outrigger-trailing-arm-mount-002-rs.jpg

Looking up inside the TA mount where it meets the top outside corner of box section chassis rails...note arrows showing no visable weld:

http://www.aulro.com/afvb/attachments/modified-zone/51598d1348736390-combined-trailing-arm-mount-body-outrigger-trailing-arm-mount-012-rs.jpg

Looking at the inside bottom of box section chassis rail, note the angle and the arrrows showing the location of welds, away from the corner:

http://www.aulro.com/afvb/attachments/modified-zone/51599d1348736427-combined-trailing-arm-mount-body-outrigger-trailing-arm-mount-017-rs.jpg

[rick130]

You can have a close look at the plating/boxing/welding on the 130 on Tuesday/Wed week.

All Land Rover do is run a bandsaw through a 110 chassis and box/extend it.

[uninformed]

You can have a close look at the plating/boxing/welding on the 130 on Tuesday/Wed week.

All Land Rover do is run a bandsaw through a 110 chassis and box/extend it.

Thanks mate, It will be interesting to see, I have looked at the latest Defenders in LR dealer a few months ago...looks like they may have some more plating????from what I remember of the 130's

I had a quick look at mine after reading Bill's post. There are 2 holes in the web of the chassis between the TA mount and the crossmemeber that the A frame arms bolt to. These holes clearly show 2mm wall only....there is a possibliity that if there was a double skin internally, that there are larger holes in the inturnal section around these holes...:confused:

[uninformed]

PSimpson, If your watching Id like to get you to do the cad for the sheet laser cutting and folding.

cheers
Serg

[uninformed]

............What's the story with compliance and engineers certs?

so much hear say around this stuff....I went into my local DOT a few months ago and asked for a list of guys that could help....the guys they gave were simple "blue platers"...seat belt and seat mods, basic stuff that is outlined by DOT...NOT engineers :mad:

There is some very grey area, there is a light vehicle code to adhere to, but due to the nature of our LR's part thereof can fall under the heavy vehicle code, which allows different things to be done...btw light vehicle code is more so monocoque. Some guys will swear black and blue its not allowed, some get it done by blue platers sort of ok but maybe not.

I contacted a engineer that does some chassis stuff for trucks and cars. From the quick description/chat I had with him, he basicly said that if it was a kit and and designed for road use, came with full fitting instructions, then it was definitly doable. I said that I could do all that and he basicly said yes :confused:

I would like to finalise a design and procedure. Make one up and then front some serious people. I think a big part of it is attitude and showing them the concept and idea is safe...

then again they could do the usual, take the easy way out and just say NO

:mad::mad::mad:

[Slunnie]

Here is the NSW hearsay. Pg5. Goodluck if you think it doesn't apply to you, not my problem.

[uninformed]

If its not your problem then why post....but hey let's turn the tech into a ****ing match of legalities. I have heard pretty much yes and no to everything. But when you start to dig to ACTUALLY get it done the road becomes long and grey.

Like I said when I have a decent mock up I can approach the engineers and Dot and discuss further. I expect them to say maybe at best but to make changes. Talking about it with just an idea leads no where fast...

[Slunnie]

Serg, good luck. ;)

[uninformed]

Yep, thanks.....but I did ask for that side of it to be left out. FWIW, I know of a vehicle built on a full custom chassis with portals that is fully engineered here in QLD. Not some mate of a mate back yard deal/job either....AND it then had to be registered at DOT. They went over it thoroughly and gave it plates rego and thumbs up. It even had RTA pull up to it once,look over under it and get on their computer....end result was all good and they drove off. Many would bet their lives the above vehicle not possible or legal, but IT IS.

It comes down to many variables. Ie what you are doing, who you are dealing with, who you are and who you know.

Oh and the luck on the day.....

Btt. What are my options to get it to transfer to the bottom inside corner like i have without welding across the flange...

[Bush65]

One of the main issues with mounts on LR chassis concerns the thin chassis wall thickness of about 2.4mm.

There are large horizontal loads in the fore and aft direction of the vehicle due to the mass that has to be accelerated/decelerated (vehicle + payload), plus various resistances (wind, slope, obstructions, trailer, etc.). The traction loads are mostly transferred through compressive force in the rear TA's (trailing arms), with a lesser amount from tension in the front RA's (radius arms). Braking loads are mostly transferred through compressive force in the RA's with a much lesser amount through tension in the TA's.

The compressive force in the TA's acts along the long direction of the arm. This force is transferred into the mounts that must distribute/transfer it into a long length of thin chassis material. This length needs to be long enough so that the stress in the welds joining the mount to the thin chassis wall doesn't exceed the value allowed for fatigue of the weld or chassis wall.

It is important to not loose sight of the fact that for equilibrium to be satisfied (as it MUST be), the direction of the force in the TA's is the same as those forces transferred through the material of the mount and into the welds and the chassis.

For fatigue of the welded connections (mounts welded to the chassis), the allowable stress is highly dependent on the details/geometry. The Australian Standard for determining the fatigue strength of welded parts is merely a small sub-set of the British Standard, which is the best resource that I know of. Unfortunately I don't have my copies of either with me.
The worse case is when welds are made in the transverse direction of the force/stress the reduction in the allowable stress (compared to no weld in the parent material) is very great. From memory (I stand to be corrected) the allowable fatigue stress is in the order of 60 MPa in steel that has a yield strength of about 300 MPa and ultimate tensile strength of over 400 MPa. This is a gross simplification – the British standard runs to something like 100 pages.

The designers are allowed to weld across the chassis. Unlike many others making modifications, they can determine that the stresses are within the allowable limits for all possible load cases. Stress is load divided by area, so if the load cannot be reduced the stress can be reduced by increasing the area – this idea is like using a plate under a jack used on sand to reduce the pressure that the sand can withstand.

Regardless of fatigue or not (static load), because all fillet welds involve complex 3 dimensional stress, they have a greater load capacity when the direction of the weld is aligned (not transverse) with the load.

Getting back on topic now. The problem I see with the proposed mount, is that it is based upon the LR design for the body mount outrigger, modified to accept the TA. IMHO this outrigger design doesn't lend itself to adequately transferring the loads from the TA to the chassis. I believe it would be better to base it upon the design for the TA mount, suitably modified for the additional duty as a body mount outrigger.

I have cut-up rangie chassis and seen the various methods used to reinforce the chassis to accommodate concentrated local loads where they place mounts, also where the chassis kicks up/down. Sometimes it is designed for loads applied to the webs (bolts etc.), sometimes it is angles in the corners. I'm not aware of what reinforcement is inside a Defender chassis at the position of the outrigger, and if it is suitable for the additional force from a TA.

In the pic (below) of a TA mount, I have sketched arrows to show how the compressive force in the TA is distributed into the top and bottom flanges of the chassis rail. Note that these particular welds are longitudinal and their length (about 180 mm top flange and 150 mm bottom flange) is far more than that for a body outrigger. Also there is a lip pressed along the long diagonal free edge to stiffen it against buckling. These arrows would reverse direction when the TA's are in tension (braking or reversing direction of travel). There are other forces in the mount, but these are the major ones.

The loads on the body mount outrigger are mainly down at the point where the body weight is supported on the outrigger. On the pic below of a body outrigger I have sketched red arrows to show how the force is distributed to the top flange and web of the chassis rail. The pic doesn't show the bottom of the mount, where the force is directed to the bottom flange of the chassis rail (opposite direction to what occurs at the top flange).

From my sketched arrows you can visualise that with a combined mount there would be forces acting in 2 directions/dimensions. When loads/stresses involve more than 1 direction, we have to use a different failure theory to usual. For ductile materials (like we are concerned with here), and 2 dimensional stress, the failure theory used is called MSS (maximum shear stress theory) – for 3 dimensional stress we use Von-Mises Stress. Both failure theories can be used for 1 dimensional stress, but involve extra effort.

When material is loaded in tension, the principle tensile stress in in the direction of the applied load. As the material is stretched in that direction it gets thinner in the other dimension (it must for its volume to remain constant) – this creates the other principle stress (compressive in this example). Combining these 2 stresses gives shear stress on a plane at 45*.

For external loads loads in 2 dimensions, the induced shear stress is greater and this value is used to determine if the part will be safe.
Although the mount may be sound when subjected to TA, or body loads independently, when the loads act together, but in different directions, the situation becomes more complex and the stresses in the welds will increase.

Normally the failure will occur in the weld or parent metal (mount or chassis) close to the weld. It is not practical to make the welds larger (throat thickness) in this case because we cant easily change the chassis wall thickness. So the option is to make the welds longer in the required direction.

The TA mount in the pic below is on my 110 trayback. When LR built these they stretched the chassis and you can see at the corners of the chassis in front of the mount, how they reinforced the chassis with a pressed C section doubler over both top and bottom flanges. The doublers extend about 50mm beyond where the welds for the chassis extension/splice. The top doubler is about 80 x 20 mm and the bottom about 80 x 40 mm.

This reinforcement method would be very suitable for the location of a mount that was intended to carry both TA and body loads. Extend the 'C' at least 50 mm beyond the extents of the new mount. Saint-Venant's principle is used for good practice and it would dictate about 75 or 80 mm.
It is bad practice to weld at the corners of rolled sections such as C, SHS and RHS because there are residual stresses there from the forming process. It is worse when higher strength material is used. As it is reasonable/prudent to expect residual stresses in the corners of a chassis rail, so it can be considered bad practice to weld there. Toyota go to a great deal more trouble with their 79 series cruiser than LR to keep welds away from the corners of chassis rails.

Edit: pics added now :o

[uninformed]

Thank you very much John.

I can see your pics :)

I am basing my mount on the TA design more so.....or so I thought??? I should have written measurements on it. The top width is the same as TA mount, not the 75mm of the outrigger. The internal gusset is located in the same position as the long diagonal free edge of the TA mount from bush to top corner of chassis rail. But it is full width inside the new mount. I'm am yet to show my added internal piece that is the same as inside the OEM TA mount. Im also thinking to plate the complete bottom of mount with access holes, either dimple died or flanged like the bottom of the OEM RA mount. My mount will also have a couple more gussets in it same as outrigger mount...

I'm at work so will add more later.

Again I need to digest what you have written....

Cheers
Serg

[wagoo]

I recall my old leaf sprung Austin Gipsey, where the chassis designer went to some detail to provide full perimeter welds in addition to avoid vertical welds when attaching crossmembers and outriggers to the main chassis rails. They simply turned rectangular section outriggers/members 45 degrees. Most of their chassis sections were semi oval with large radius corners. A well engineered vehicle I thought at the time, It was a sad day when it tried to clear my property of the biggest ugliest tree on the place.:(
Bill.

[uninformed]

a couple more pics:

http://www.aulro.com/afvb/attachments/modified-zone/51650d1348823590-combined-trailing-arm-mount-body-outrigger-trailing-arm-mount-001-rs.jpg

note the arrows are pointing to a fold. This is a additional plate, 4mm thick that is welded to the mount and chassis. The folds range in size from 10mm up. I was thinking of copying this???

http://www.aulro.com/afvb/attachments/modified-zone/51651d1348823621-combined-trailing-arm-mount-body-outrigger-trailing-arm-mount-003-rs.jpg

[uninformed]

more pics of mock up #1

TA end, showing locations of inturnal gussets. Ignore flap which arrow points to.

http://www.aulro.com/afvb/attachments/modified-zone/51655d1348830383-combined-trailing-arm-mount-body-outrigger-mock-up-004-rs.jpg

mock up of fold for bottom plating:

http://www.aulro.com/afvb/attachments/modified-zone/51656d1348830415-combined-trailing-arm-mount-body-outrigger-mock-up-005-rs.jpg

Top view. Thinking of dimple die holes??? Dotted line is where the internal gusset meets the top corner of chassis rail. It will NOT be welded to chassis, im thinking of a slot in the top of mount to weld to the gusset.

http://www.aulro.com/afvb/attachments/modified-zone/51657d1348830457-combined-trailing-arm-mount-body-outrigger-mock-up-006-rs.jpg

Internal 4mm plate same as LR have inside the TA mount:

http://www.aulro.com/afvb/attachments/modified-zone/51658d1348830484-combined-trailing-arm-mount-body-outrigger-mock-up-008-rs.jpg

[Bush65]

Talk to whoever will be doing the pressing before you start to produce the profiles.

Find out what the minimum flange/lip width they can press with their VEE block. See dimension L3 on the pic below. The flat plate that you start with has to sit across the top of the VEE block and the minimum lip will be L3.

Find out the inside radius that will be pressed with their blade. Bluescope Steel (ex BHP) give the minimum allowable bend radius for the plate thickness. This radius is different if the bend is in the direction of plate rolling or across the rolling direction. You most likely won't know the rolling direction when you get your profiles, so need to know the worst case.

Because you want to press the profiles into 'C' section, with the shortest of the vertical leg lengths of about 180mm (stock body outrigger), if they only have a straight blade, the horizontal flange width will have to be greater than this. See the pic below, where dimension L2 must be greater than L1 so that the toe of leg L2 clears the press blade.

When the thickness is small relative to the width, only the part relatively close to a stiffener is effective for carrying load. Take standard structural section; the to increase the width of a flange outstand from the web (stiffener) they have to increase the flange thickness. Thin wall, cold rolled sections have lips on the flanges to form stiffeners, so the distance from a stiffener (lip or flange) is half of the flange width.

The same principle applies to gussets. Notice on the stock body outrigger the lip (stiffener) that is pressed along the lower, diagonal edge. Without this stiffener the outrigger would be unable to effectively transfer the moment load from the body to the bottom flange of the chassis rail.

I don't understand the need for the dimple die holes. Any weight saving may be less than than the weight of sand, mud and water that they will allow.

Edit: pic added

[uninformed]

I can see your pic ;)

I think I know what you are saying regarding the pressing, that is using a V block and ram? I had not actually thought of that. I had just thought, for the main body/mount, that since it is just a "C" section, that it could be done on a press brake??

I will have to do some more research and speak to potential cutter/benders. PSimpson has had some stuff done locally.

"When the thickness is small relative to the width, only the part relatively close to a stiffener is effective for carrying load." Are you saying that loads will only be effectly carried where folds are or where the addition of material has been added to increase the thickness?

Take standard structural section; the to increase the width of a flange outstand from the web (stiffener) they have to increase the flange thickness. Thin wall, cold rolled sections have lips on the flanges to form stiffeners...... I can visualise a standard thin wall steel stud. They are "C" section but on the ends of the flanges have a small fold (say 2-3mm). Is this what you are calling a "lip on the flange to form a stiffener"?

"so the distance from a stiffener (lip or flange) is half of the flange width"

This part Im not undertanding, what are you referring to when you say "distance"? I see the gussets in the OEM body outrigger have flanges folded on them, no lip stiffeners and the flanges are only approx 10-12mm. I see the small section that is folded along the lower diagonal edge of OEM outrigger....but this is only about 75mm long starting at the chassis rail, which leaves a much larger portion flat, not folded???

I have added a pic of the bottom of the OEM front RA and outrigger area. I can see all the little lips, folds etc and have always took them as being there to "stiffen" those areas due to the thin material used. Note the yellow arrows point to the folds to stiffen the open areas/thin material. The red arrows are pointing to a indent, that has been pressed into the plate material, again I figured this is to stiffen a large thin area?

http://www.aulro.com/afvb/attachments/modified-zone/51666d1348880669-combined-trailing-arm-mount-body-outrigger-ra-outrigger-001-rs.jpg

When I say I will plate in the underside of my new mount, I mean the whole thing. I was thinking of either dimple holes or larger, not uniformly round holes and then welding lip/stifferners to them.... I dont have the advantage that LR etc have of huge manufacturing facilities and building dies to press individual parts out....so back to basics. I would also "fix", that is weld somehow, the bottom plate to the internal gussets. I am open to ideas on this, as I figure welding anything adds some sort of stress?

I was also thinking of putting one dimple die hole in the first 2 gussets and maybe one in the large diagonal one...dependant on your advise. At some point im going to have to have a large enough hole to get socket and nut on the end of the TA, whether this be from the bottom or from the other vertical face of mount???

Why dimple dies? they look pretty :D .... but seriously I have a set (ill dig the sizes out today) I also thought that the more holes the better for the cleaning of mud etc, AND that they would be helping some of which that you have been describing, that is the large sections of thin material, helping by adding the fold in the dimple and stiffening it up.

I had also thought of welding another 3mm plate to the top of the mount, kind of like a large weld washer...because dependant on the design of the mount and its gussets and bottom plating, It may be a bugger to get to the nuts that hold the 2 body mounts. So at 6mm thick I thought I could tap it....plus again, as the top of the mount it now alot bigger than the OEM outrigger, I figured it was more prone to buckling due to the thin material.

maybe Ive looked at to many race trucks :D

You mention cold rolled steel. I was under the impression that standard plate etc was hot rolled? Should I be specifing Cold rolled??

Sorry im not very good at typing my thoughts out

[uninformed]

John, I have not overlooked or dismissed your comments of the strengthening of the chassis rail itself, as in the pic you posted of your 120. I will come back to that. I would rather stay on point with the mount as we are atm.

btw if you ever need a carpenter.....;)

cheers
Serg

[newhue]

very interesting Serg, amazing how much goes into something taken all fro granted by most.

I can understand the outrigger and trailing arm all working from one point, but whats the gain by doing so. Travel? ground clearance? positing of some accessory, .....?

[uninformed]

Hi Jason,

thats not such a simple question :D....something a forum could be dedicated to.

Looking at it from a suspension geometry perspective (rather than a engineering exercise), the TA in our Landrovers of this type, that is parrallel trailing arms and A frame, determine the Axle roll axis and paired with the A frame determine the amount of Anti-squat.

Axle roll axis is described as either oversteer, understeer or nuteral. If the TA are sloping down towards the axle it will be oversteer, if sloping up to the axle it is understeer and if level it is nuteral....A stock LR Defender is about +4-6 degrees of oversteer in the rear and close to nuteral in the front.

When you raise a vehicle on its springs you change alot of dynamics. Depending on the vehicle the amount you can get away with varries. The suspension that the Defender 90, 110 and 130 run was originally designed for the RRC. Designed around its wheelbase, its COG, its wheel size etc...When adapting them to the first coil sprung LR there was some comprimise using the same links and geometry, but it certainly acceptable.

Rasie a defender and you are getting further away from the original package.

For me I want to lengthen the TA so I can mount a battery either side where the current TA mount is. It will also lend itself to better handling and offroad driving, even projecting the TA in the same plane it is in now, which on paper will not change the Axle roll axis or the anti-squat, but it does change the arc the TA scribes and therefore the actual Roll steer. It also tends to drive the chassis forward more on steep climbs rather than drive the axle down and forward.

There is alot more to it than this, pages could be written and discussed very easily, but that will get away from the OT.

things have to be considered when doing this, as with anything, one change can/will affect other things....

[wagoo]

I was just changing a flat rear tyre on my leaf sprung Stage One and had a squiz at the combined body mount/ forward spring hanger,visualising the different forces it needs to withstand, and began to wonder if we really need to get all that scientific here, as interesting as the discussion has been.

The leaf spring hanger/outrigger is a very simple single 2mm thick skin rectangular member that under all the mud on mine, appears to have full perimeter welds at the side rail attachment. there is a bit of overlap at the top, and a couple of light gussets at the bottom of the main rail and that's about it.I'll check a cleaner chassis down in the graveyard later for evidence of internal reinforcement, but from vague memory I don't think there was.

Just like a standard trailing arm mount,the leaf spring hanger has to transmit for/aft thrust, as well as some antisquat force. Unlike a standard TA mount, it has to cope with some vertical down loads imposed by the body and any payload, in addition to vertical up loads imposed by the vehicles weight. It also has to cope with lateral loading, a job that is performed by the A frame on a coil sprung vehicle. Due to the semi open ended construction, these outriggers tended to fill up with corrosive mud, horse/ cow poo etc,which was almost impossible to completely clean out, which tended to rot the outer wall of the main chassis rail. Yet for all that,to my knowledge these combination bodymount/spring hangers rarely if ever gave any problems, including the chassis rail in that zone.

Bill.

PS, My Stage One is/was a station wagon.The forward end of the rear body does use the spring hanger outrigger as a body mount. Utes and trays don't. On utes/hardtops,it appears that most of the body/payload weight sits on platforms above the main side rails anyway. A properly designed tray should bear on all these platforms too but some designs don't, leading to possible chassis breakage.

[uninformed]

good info there Bill. Id rather be prepared with info when dealing with the powers that be so I can half sound like I have some idea and not going to kill innocent families on the road :eek:

I stoped by a couple metal cutting folding places today....both said could not do as they use press brakes (ram and V block like John said) I had my terminology confused....I was visualizing a pan brake...Mal Story has a big old one that would be 2m wide Im sure I have seen him fold 3mm in it with ease. Ill have to try a few more places. The other option that one gave me was to cut slots along one of the fold lines. They would laser cut the whole piece and then fold the TA side vertical, then I could "hand fold" the other vertical side....

btw Bill, I did some chasing up on the paint for you. I have another mob to call tomorrow...PM me your phone number

[wagoo]

btw Bill, I did some chasing up on the paint for you. I have another mob to call tomorrow...PM me your phone number

Thanks Serg. A brief OT, but if I singe the outer skin of the stump with my oxy acetyline torch, would the primer/paint adhere to it?
Bill.

[uninformed]

I'm thinking not...

[Dougal]

I don't understand the need for the dimple die holes. Any weight saving may be less than than the weight of sand, mud and water that they will allow.

Good to see someone else shares my thoughts on dimple die holes. They always seem to be added purely for cosmetic effect and always in orientations that will trap a layer of mud/dirt/sand inside. Like lips being pressed upwards in a belly plate.

I work hard to avoid water/dirt traps in everything I design. These people are adding them in for looks alone.

[wagoo]

I'm thinking not...

OK thanks Serg.

Back on topic. Good luck with DOT, but I'll throw another idea out there if they knock you back.
You may be aware of the after market long arm kit for YJ Jeeps, that retain the standard chassis mount location for the TA, and bolted a 'J' shaped TA to a bracket at the rear of the axle tubes instead of the front?
The result of what I'm suggesting may or may not end up looking a bit homely, but I was visualising using a front axle radius arm in place of the rear axle TA , but only utilising the one bushing on the axle end, sleeved down to accept the standard TA axle bush. A very rough measurement under my hybrid whilst dressed in my best clothes revealed that this may work if the pin end of the RA could be machined back 50mm on a lathe, or 25mm and the chassis bush re fitted to the front side of the chassis mount and spaced forward 25mm.This would give an effective increase of around 150 mm in TA length without changing chassis mount or axle location. The axle bracket could almost be made a bolt on/clamp on affair if your DOT don't like welding to axle tubes.
Of course I don't know how this would work out geometrically with regard to antisquat, under/oversteer etc. I can't find my compass and protractor to draw it out
Bill.

[uninformed]

Good to see someone else shares my thoughts on dimple die holes. They always seem to be added purely for cosmetic effect and always in orientations that will trap a layer of mud/dirt/sand inside. Like lips being pressed upwards in a belly plate.

I work hard to avoid water/dirt traps in everything I design. These people are adding them in for looks alone.

I was adding them for a few reasons.

#1 to stiffen the large thin top surface.
#2 to reduce some weight.
#3 more access for hosing/cleaning out as the gussests form compartments.

My bottom plate will have any dimples or flanges down not up.

I am happy to not dimple the top if they will not be functional.

[wagoo]

Hi Jason,

thats not such a simple question :D....something a forum could be dedicated to.

Looking at it from a suspension geometry perspective (rather than a engineering exercise), the TA in our Landrovers of this type, that is parrallel trailing arms and A frame, determine the Axle roll axis and paired with the A frame determine the amount of Anti-squat.

Axle roll axis is described as either oversteer, understeer or nuteral. If the TA are sloping down towards the axle it will be oversteer, if sloping up to the axle it is understeer and if level it is nuteral....A stock LR Defender is about +4-6 degrees of oversteer in the rear and close to nuteral in the front.

When you raise a vehicle on its springs you change alot of dynamics. Depending on the vehicle the amount you can get away with varries. The suspension that the Defender 90, 110 and 130 run was originally designed for the RRC. Designed around its wheelbase, its COG, its wheel size etc...When adapting them to the first coil sprung LR there was some comprimise using the same links and geometry, but it certainly acceptable.

Rasie a defender and you are getting further away from the original package.

For me I want to lengthen the TA so I can mount a battery either side where the current TA mount is. It will also lend itself to better handling and offroad driving, even projecting the TA in the same plane it is in now, which on paper will not change the Axle roll axis or the anti-squat, but it does change the arc the TA scribes and therefore the actual Roll steer.( IT ALSO TENDS TO DRIVE THE CHASSIS FORWARD MORE ON STEEP CLIMBS RATHER THAN DRIVE THE AXLE DOWN AND FORWARD.)

There is alot more to it than this, pages could be written and discussed very easily, but that will get away from the OT.

things have to be considered when doing this, as with anything, one change can/will affect other things....

( IT ALSO TENDS TO DRIVE THE CHASSIS FORWARD MORE ON STEEP CLIMBS RATHER THAN DRIVE THE AXLE DOWN AND FORWARD)

You are basically describing anti squat forces there Serg, which I assume is another thing you desire to reduce? I wonder if the A S geometry of the standard arrangement is all that high.The way I visualise it, Anti squat is performed by the axles torque reaction lifting the rear of the chassis via the pins on the chassis end of the trailing arms. Yet on RangeRover Classics at least, those pins (5/8'' dia) are almost as soft as licorice sticks. If the A S forces of the original set up was significant, those pins would bend on just about every RangeRover, except possibly the one driven by Grandma. Yet bent pins aren't that common except on vehicles with raised suspension, where on suspension droop the chassis end bushes of the TA exceed their limit of compliance.

Bill.

[Bush65]

My opinion hasn't swayed from when I said:

The problem I see with the proposed mount, is that it is based upon the LR design for the body mount outrigger, modified to accept the TA. IMHO this outrigger design doesn't lend itself to adequately transferring the loads from the TA to the chassis. I believe it would be better to base it upon the design for the TA mount, suitably modified for the additional duty as a body mount outrigger.

The dynamic load from the trailing arm can and does vary from very high compression (in some circumstances equivalent to the vehicle weight), to fairly high tension. The magnitude of the load fluctuation is the difference between the two extremes, i.e. it is much greater than either the peak compressive or tensile load. It also undergoes an enormous number of load cycles and both of these factors lead to fatigue failure, unless the maximum fluctuation in the stress is below the endurance limit.

I have pointed out the issues of welds where fatigue is involved and attempted to explain how the load was transferred from the TA to the top and bottom flanges of the chassis within the stock TA mount.

Avoiding fatigue is not about adding material, gussets, etc. all over the place like “belts, braces and nappy pins”. It is all about attention to the details that matter, such as minimising the effect of stress raisers, minimising residual stresses, and eliminating defects/flaws where cracks can start. For example the fatigue strength of axles/half shafts can be increased by waisting to the root diameter of the splines.

Loads will always (without exception) take the stiffest route in their general direction. This is where material is used efficiently, where stiffeners play a great role even if they might look insignificant and where stress raisers should be avoided when fatigue is an issue (stress raisers are not an issue with static loads).

In your modified body outrigger design you have added a gusset between the vertical legs to transfer the TA load. The great majority of the TA load must be transferred through this gusset and the plate that you intend to weld underneath. Have a good look (based on pics that I posted before) at how the path of these loads through the gusset and bottom plate. Now compare this with the stock TA mount design.

How many welds can you count across the path of the load in each of these designs?

The welds connecting the stock mount to the chassis are unavoidable, but their location, direction, length are fit for the purpose.

Welds, even those executed perfectly, reduce fatigue strength. The direction of the weld has a large effect, as I indicated in an earlier post. Defects in welds are not acceptable where fatigue is a concern. Fillet welds are worse than butt welds.

Because you don't have good access to weld both sides of your gusset and bottom plate, you will not be able to make a good weld and prevent defects - backing strips would help, but IMHO the design is flawed and this is what should change.

Have you considered access for welding the mounts to the chassis and the difficulty of welding in positions other than downhand?

The body load on the outrigger is smaller than the TA and always in the same direction, so the load fluctuation is much less than that from the TA.

IMHO it is better to give priority to accommodating the major loads, i.e. TA load in this case. Quite often the design for the major loads will be untroubled by the minor loads or only small changes or tweaks are required. This is why I made the statement at the top of this post. You have done the reverse and exposed your design to considerable difficulties, including fatigue failure, access for welding, and access to the bolts for the TA bush.

My preference would be similar to what Slunnie suggested, using Patrol TA bushes. However if I were to stick with the LR TA to chassis bush I have used an old cardboard carton to show how I would base it on the design of the LR mount – see pics below.

Bend the 3 mm thick plate as shown in the pics by the cardboard mock-up against the LR TA mount.
Now take your modified outrigger mock-up which is wider (horizontal direction) where it joins to the chassis rail. The rearward vertical leg stays as is and welds (use virtual welds for cardboard) to the new TA mount. The chassis bush for the TA bolts to this as per your earlier pics. It should also have the same doubler plate.
The forward vertical leg of the outrigger needs to be shaped to fit against the new TA mount – see dashed line in second pic. The TA mount can be trimmed back to leave a stiffener as shown by the solid line in the second pic.
Finally add the proposed bottom plate from end of outrigger to underside of TA mount.

IMHO a better design for the outrigger is to press up 2 'L's instead of a 'C' plus bottom plate. Joining the 'L's together to form the box section involves no more welding but they are simpler to press than a deep 'C' section.


"When the thickness is small relative to the width, only the part relatively close to a stiffener is effective for carrying load." Are you saying that loads will only be effectly carried where folds are or where the addition of material has been added to increase the thickness?
Take standard structural section; the to increase the width of a flange outstand from the web (stiffener) they have to increase the flange thickness. Thin wall, cold rolled sections have lips on the flanges to form stiffeners...... I can visualise a standard thin wall steel stud. They are "C" section but on the ends of the flanges have a small fold (say 2-3mm). Is this what you are calling a "lip on the flange to form a stiffener"?
"so the distance from a stiffener (lip or flange) is half of the flange width"
This part Im not undertanding, what are you referring to when you say "distance"? I see the gussets in the OEM body outrigger have flanges folded on them, no lip stiffeners and the flanges are only approx 10-12mm. I see the small section that is folded along the lower diagonal edge of OEM outrigger....but this is only about 75mm long starting at the chassis rail, which leaves a much larger portion flat, not folded???

All of you questions pretty much relate to understanding the same issues. Think of it this way: load is carried by the stiffest part.

For example take two coil springs of identical length, but one is soft and the other is stiff. Say the load to compress each spring 1 mm was 1 Newton for the soft spring and 100 Newton for the stiff spring. Now if the springs were arranged one inside the other so that a load compressed both springs simultaneously, by an identical deflection. If the load was 101 Newton you should clearly see that both springs will compress 1 mm and the soft spring will only carry 1 Newton while the stiff spring carries 100 Newton.

If we want to increase the load capacity of a structural member, one way is to add material where the stress is most severe, but we can only achieve the desired result if the material is added where it is sufficiently stiff.

Take roof sheeting. The thin sheet can carry considerable load (compared to flat sheet) because the material is stiffened by the ribs.

Material too distant from a stiffener is not capable of carrying as much load as it can close to a stiffener. The thicker the material the further the distance it can be from the stiffener. Stiffeners can take many forms, such as ribs, webs, flanges, corners in LR chassis rails, pressed lips, virtually anything that constrains the element from flexing (flex is the opposite to stiffness – recall what I said about loads and stiffness) to in thin direction and forces it to remain straight while subjected to the design load.

I'm sure you would have observed when building a roof, that when the trusses are first stood up they can't carry large loads but as purlins are added, the load capacity increases because the purlins keep the top chord of the truss straight. In this case the purlins “stiffen” the chord in the direction in which it was previously able to flex.


You mention cold rolled steel. I was under the impression that standard plate etc was hot rolled? Should I be specifing Cold rolled??

Thick steel sections and plates are rolled by a “hot mill” - the steel is red hot while it is rolled.

Sheet and strip is first rolled on the hot mill and further rolling, to produce thinner sheet, or to form it into sections such as hollows (shs, rhs, chs), 'C' or 'Z', etc. is performed in a cold mill (sheet and strip) or in a roll former (a series of rolls where each set of rolls produces an incremental change in the section shape from the flat strip to the finished section).

[isuzurover]

I recall Ralph Posch and Sam Overton both did this mod (On a S1 hybrid with a disco chassis and a RRC and ) respectively. Both were happy with the result, however I have no pics of the mounts. I can't recall any failures. Sam's RRC is probably long gone - and has been through multiple iterations. Ralph's S1 is still in daily use on Flinders Island.

[uninformed]

OK thanks Serg.

Back on topic. Good luck with DOT, but I'll throw another idea out there if they knock you back.
You may be aware of the after market long arm kit for YJ Jeeps, that retain the standard chassis mount location for the TA, and bolted a 'J' shaped TA to a bracket at the rear of the axle tubes instead of the front?
The result of what I'm suggesting may or may not end up looking a bit homely, but I was visualising using a front axle radius arm in place of the rear axle TA , but only utilising the one bushing on the axle end, sleeved down to accept the standard TA axle bush. A very rough measurement under my hybrid whilst dressed in my best clothes revealed that this may work if the pin end of the RA could be machined back 50mm on a lathe, or 25mm and the chassis bush re fitted to the front side of the chassis mount and spaced forward 25mm.This would give an effective increase of around 150 mm in TA length without changing chassis mount or axle location. The axle bracket could almost be made a bolt on/clamp on affair if your DOT don't like welding to axle tubes.
Of course I don't know how this would work out geometrically with regard to antisquat, under/oversteer etc. I can't find my compass and protractor to draw it out
Bill.


Very interesting Bill, I was not aware of this style for Jeeps. I quickly threw my tape measure on mine and I think the RA would have to reduced by more than 50mm to work in length....The front and rear axle tubes are pretty close for OD so that side of things would be ok. As, you I cant quite guess the result of geometry without drawing it and I also wounder if there would be any change to the axle end loading from changing the bush from front to rear? As the rear end flexs more than the front, the cup in the RA that goes around the axle tube may be to close and bind during cross axle articulation.

At this stage I think it wouldnt really be worth the hastle and would not give me the room to do the battery trays etc where the TA mount already is.

[uninformed]

( IT ALSO TENDS TO DRIVE THE CHASSIS FORWARD MORE ON STEEP CLIMBS RATHER THAN DRIVE THE AXLE DOWN AND FORWARD)

You are basically describing anti squat forces there Serg, which I assume is another thing you desire to reduce? I wonder if the A S geometry of the standard arrangement is all that high.The way I visualise it, Anti squat is performed by the axles torque reaction lifting the rear of the chassis via the pins on the chassis end of the trailing arms. Yet on RangeRover Classics at least, those pins (5/8'' dia) are almost as soft as licorice sticks. If the A S forces of the original set up was significant, those pins would bend on just about every RangeRover, except possibly the one driven by Grandma. Yet bent pins aren't that common except on vehicles with raised suspension, where on suspension droop the chassis end bushes of the TA exceed their limit of compliance.

Bill.

Yep, and Im still trying to figure out how, if you extend them along the same plane as OEM, that it changes. I was told this by Sam Overton, that he found better hill climbing with his extended arms, I figured they had lowered them.... As Ben noted, Sam had extended his and some others forward to the body outrigger, in the same plane as stock......I also asked how he did the mounts and he said he just cut the OEM mounts off and moved them forward. :confused: I had touble visulaizing the actual end result without it being absolutely booty fab... I never saw any pics and new that I was missing something as Sam is pretty switched on.

Ben, maybe Chucks truck is done also???

FWIW, the main chassis rails are still sweeping donw between the TA and the body outrigger. If I make my mount the exact same as the OEM one, the arm will mount 20mm lower at the body mount location. This with the added length will change my TA angle from 13.65 degrees to 8.79 degrees...

And, the AS will change simply by wheelbase and tyre size, so even with the same spring height, My 110 wheelbase and 32 inch tyres will have more AS than the 100 Rangerover on 29's....of coarse this based on the same COG height, which wouldnt be true...but you know where im coming from.

food for thought.

But lets stay on the mount before we get all geometric :D Im struggling with the simple stuff here and I think John may feel like he is dealing with a special needs kid.

[uninformed]

See bold responses:


My opinion hasn't swayed from when I said:

I got the impression that the main reason you thought I was modding the body outrigger was the top plate width, looking at my original pics it was hard to tell that the top, at chassis, is the same width as TA mount. You now know this and have elaborated.


The dynamic load from the trailing arm can and does vary from very high compression (in some circumstances equivalent to the vehicle weight), to fairly high tension. The magnitude of the load fluctuation is the difference between the two extremes, i.e. it is much greater than either the peak compressive or tensile load. It also undergoes an enormous number of load cycles and both of these factors lead to fatigue failure, unless the maximum fluctuation in the stress is below the endurance limit.

I have pointed out the issues of welds where fatigue is involved and attempted to explain how the load was transferred from the TA to the top and bottom flanges of the chassis within the stock TA mount.

Avoiding fatigue is not about adding material, gussets, etc. all over the place like “belts, braces and nappy pins”. It is all about attention to the details that matter, such as minimising the effect of stress raisers, minimising residual stresses, and eliminating defects/flaws where cracks can start. For example the fatigue strength of axles/half shafts can be increased by waisting to the root diameter of the splines.

Loads will always (without exception) take the stiffest route in their general direction. This is where material is used efficiently, where stiffeners play a great role even if they might look insignificant and where stress raisers should be avoided when fatigue is an issue (stress raisers are not an issue with static loads).

In your modified body outrigger design you have added a gusset between the vertical legs to transfer the TA load. The great majority of the TA load must be transferred through this gusset and the plate that you intend to weld underneath. Have a good look (based on pics that I posted before) at how the path of these loads through the gusset and bottom plate. Now compare this with the stock TA mount design.

How many welds can you count across the path of the load in each of these designs?

none on the OEM mount, edit, 1 on the OEM mount if you count the weld were the inner 4mm plate is welded along the lower fold to the 3mm main body:

4 on mine:

#1, the bottom plate to vertical face
#2, the bottom plate to bottom of internal gusset
#3, the gusset to vertical face
#4, the guesset to top plate through slot for welding

One thing I was thinking of doing is using one peice for the gusset and the added internal plate on inside face of vertical leg. This would be 4mm and a simple 90 degree fold. This would reduce 1 of the welds...

The welds connecting the stock mount to the chassis are unavoidable, but their location, direction, length are fit for the purpose.

Welds, even those executed perfectly, reduce fatigue strength. The direction of the weld has a large effect, as I indicated in an earlier post. Defects in welds are not acceptable where fatigue is a concern. Fillet welds are worse than butt welds.

Because you don't have good access to weld both sides of your gusset and bottom plate, you will not be able to make a good weld and prevent defects - backing strips would help, but IMHO the design is flawed and this is what should change.

Internal gusset can be welded both sides. I can fit my MIG gun in there with good angle and this would be welded on bench before fitting to chassis as the gusset is not weled to the chassis rail. The top and bottom of gusset would be welded via a slot cut in top and bottom plate, this would result in a edge to egde weld.

Bottom plate would be fitted last, in postion on chassis. I have looked closely at the bottom plate at RA and front body mount, both of these are only welded on the outside, not internally.

Have you considered access for welding the mounts to the chassis and the difficulty of welding in positions other than downhand?

Yes, as a carpenter I am use to dealing with pysical limitations over those of a simple pen stroke in a design. I have thought all along about the fabrication process and fitting of mount and one of the reasons I have made a full size mock up. I know that vertical down is not considered ideal in structural welding, but have been lead to believe it totally acceptable in welding materials 3mm thick.

The body load on the outrigger is smaller than the TA and always in the same direction, so the load fluctuation is much less than that from the TA.

IMHO it is better to give priority to accommodating the major loads, i.e. TA load in this case. Quite often the design for the major loads will be untroubled by the minor loads or only small changes or tweaks are required. This is why I made the statement at the top of this post. You have done the reverse and exposed your design to considerable difficulties, including fatigue failure, access for welding, and access to the bolts for the TA bush.

My preference would be similar to what Slunnie suggested, using Patrol TA bushes.

I went back and re read Slunnies post, though I was a bit confused when he mentioned not overlaping top and bottom of chassis rail, but then said weld it to the sides, making sure it contacts the top and bottom, plates....now without overlapping, this would mean the corners, which we have already discussed as not being a good idea.




However if I were to stick with the LR TA to chassis bush I have used an old cardboard carton to show how I would base it on the design of the LR mount – see pics below.

Bend the 3 mm thick plate as shown in the pics by the cardboard mock-up against the LR TA mount.
Now take your modified outrigger mock-up which is wider (horizontal direction) where it joins to the chassis rail. The rearward vertical leg stays as is and welds (use virtual welds for cardboard) to the new TA mount. The chassis bush for the TA bolts to this as per your earlier pics. It should also have the same doubler plate.
The forward vertical leg of the outrigger needs to be shaped to fit against the new TA mount – see dashed line in second pic. The TA mount can be trimmed back to leave a stiffener as shown by the solid line in the second pic.
Finally add the proposed bottom plate from end of outrigger to underside of TA mount.

IMHO a better design for the outrigger is to press up 2 'L's instead of a 'C' plus bottom plate. Joining the 'L's together to form the box section involves no more welding but they are simpler to press than a deep 'C' section.



All of you questions pretty much relate to understanding the same issues. Think of it this way: load is carried by the stiffest part.

For example take two coil springs of identical length, but one is soft and the other is stiff. Say the load to compress each spring 1 mm was 1 Newton for the soft spring and 100 Newton for the stiff spring. Now if the springs were arranged one inside the other so that a load compressed both springs simultaneously, by an identical deflection. If the load was 101 Newton you should clearly see that both springs will compress 1 mm and the soft spring will only carry 1 Newton while the stiff spring carries 100 Newton.

If we want to increase the load capacity of a structural member, one way is to add material where the stress is most severe, but we can only achieve the desired result if the material is added where it is sufficiently stiff.

Take roof sheeting. The thin sheet can carry considerable load (compared to flat sheet) because the material is stiffened by the ribs.

Material too distant from a stiffener is not capable of carrying as much load as it can close to a stiffener. The thicker the material the further the distance it can be from the stiffener. Stiffeners can take many forms, such as ribs, webs, flanges, corners in LR chassis rails, pressed lips, virtually anything that constrains the element from flexing (flex is the opposite to stiffness – recall what I said about loads and stiffness) to in thin direction and forces it to remain straight while subjected to the design load.

I'm sure you would have observed when building a roof, that when the trusses are first stood up they can't carry large loads but as purlins are added, the load capacity increases because the purlins keep the top chord of the truss straight. In this case the purlins “stiffen” the chord in the direction in which it was previously able to flex.



Thick steel sections and plates are rolled by a “hot mill” - the steel is red hot while it is rolled.

Sheet and strip is first rolled on the hot mill and further rolling, to produce thinner sheet, or to form it into sections such as hollows (shs, rhs, chs), 'C' or 'Z', etc. is performed in a cold mill (sheet and strip) or in a roll former (a series of rolls where each set of rolls produces an incremental change in the section shape from the flat strip to the finished section).

I will re read, and re read. Please dont think I am disagreeing with you in any way. It would be all to easy just to say ok and how would you do it....in which case I could have just said "John, please design this for me"

Im sure you are seeing large differences between my mount and the OEM type with regards to the TA and its forces. Im just not seeing that great a difference and am trying to understand.

BTW, I spoke to another sheet metal mob and they said it would be no problems folding up the main body "c"....his words were as long as the web was greater than 100mm then they generally can fold the toes, legs etc longer than it is.

With my current design, and it may be hard to see, but the front vertical leg is not as tall as the rear where TA mounts, this along with the width change, creates a compound angle and would be a bit more difficult to fold in 2 seperate L shapes...

again more food for thought for me.

feeling pretty dumb right about now :(

[Dougal]

I was adding them for a few reasons.

#1 to stiffen the large thin top surface.
#2 to reduce some weight.
#3 more access for hosing/cleaning out as the gussests form compartments.

My bottom plate will have any dimples or flanges down not up.

I am happy to not dimple the top if they will not be functional.

For access and weight reduction any holes will work. But I'm not overly convinced of the stiffening properties of round flared holes. Creases or cross-breaks work well to stiffen sheetmetal and provide support over a whole length. Any hole pattern results in lines of no reinforcement.

Crease in a hotrod floor:
https://www.aulro.com/afvb/images/imported/2012/10/1540.jpg
1968 Pontiac Firebird - Floors & Firewalls (http://www.hotrodscustomstuff.com/OLD_SITE/1968-firebird-23.html)

Cross break in sheetmetal:
https://www.aulro.com/afvb/images/imported/2012/10/1541.jpg

But back on topic. I second John's comments about designing it as a new trailing arm mount and incorporating a body mount second.

[uninformed]

For access and weight reduction any holes will work. But I'm not overly convinced of the stiffening properties of round flared holes. Creases or cross-breaks work well to stiffen sheetmetal and provide support over a whole length. Any hole pattern results in lines of no reinforcement.

Crease in a hotrod floor:
https://www.aulro.com/afvb/images/imported/2012/10/1540.jpg
1968 Pontiac Firebird - Floors & Firewalls (http://www.hotrodscustomstuff.com/OLD_SITE/1968-firebird-23.html)

Cross break in sheetmetal:
https://www.aulro.com/afvb/images/imported/2012/10/1541.jpg

But back on topic. I second John's comments about designing it as a new trailing arm mount and incorporating a body mount second.

You may sitting on the fence regarding dimples, but others clearly are not :D

Structural beams used to stop large concrete wall panels breaking when being lifted off the ground in a horizontal postion, to there final vertical resting place:

http://www.aulro.com/afvb/attachments/modified-zone/51837d1349334167-combined-trailing-arm-mount-body-outrigger-dimple-001.jpg

http://www.aulro.com/afvb/attachments/modified-zone/51838d1349334377-combined-trailing-arm-mount-body-outrigger-dimple-002.jpg

Tread plate on the scaffold stairs I walk up and down about 38 billion times a day...

http://www.aulro.com/afvb/attachments/modified-zone/51839d1349334418-combined-trailing-arm-mount-body-outrigger-dimple-003.jpg

Yep Im familiar with the concepts in the pictures you have shown, and as you used the term "Sheet metal" I have really only seen them in 2mm thick and less....mostly less.

It gets to the point of being the absolutely best design would probably mean a whole new chassis :eek:. Alot of good designs require a more complex shape than can be simply folded....then its the turn of many 100's of tonnes press and dies to "stamp" or "form" the part....the LR OEM TA mount is such a part...not just simply folded.

So with out expensive production line machinary Im back to a more simple design and maybe some compromise with welding.

BTW, I thought you said I was on the right track....whos side are you on anyway????





















Im guessing the side of better, proper design ;)

[Dougal]

The precast slab supports, the holes are there for weight reduction and to provide very convenient fixing and lifting points. The rolled edges (not just dimpled) mean they won't cut into lifting slings.

The tread-plank of that design I personally don't like. They flex a lot because there is no continuous path of metal across to carry the load. I have used similar designs (but without the open raised perforations) for slider beds in fruit dewatering conveyors. But I put cut and folds through them to add stiffness across and stop them sagging.
But for a lightweight portable tread or plank they do the job.

I don't think you'll need a new chassis just for this (but feel free). Plating the rail for reinforcement and a plate wrapped mount with a body mount bracket will do the job.
Exactly the geometry and size that will work the best is always the hard part. That eats the most time in all design jobs.

[uninformed]

The precast slab supports, the holes are there for weight reduction and to provide very convenient fixing and lifting points. The rolled edges (not just dimpled) mean they won't cut into lifting slings........


weight reduction yes, lifting and fixing, no. There are no fixings through these large holes (say 100mm dia) and while there may be the odd time a lifting sling is thrown through the hole of one or 2 of these NOT attached to any pannel, they are NEVER used as a lifting point.

As you said earlier, any hole will provide weight reduction...and the 4mm or so material these are made from wouldn't really trouble a true lifting sling as far as abrasion.

I do how ever agree with you (and John) regarding my design.

Am I correct in saying the major difference (and flaw) between my design and the OEM TA mount would be the welding?

breaking it down:
The vertical face is the same design and thickness, so this is ok.

The diagonal free face/edge that goes up and overlaps the top rail is one peice, stiffer and has no weld at the top where mine would, to the top plate in my design.

The diagonal bottom plate that goes from the vertical face to the inside bottom corner of rail, is folded from the main face, thus no weld?

what else am I missing?

Since my vertical face is the same, and also includes the same 4mm internal double plate, it seems to me the main problem is my gusset, which is acting as the diagonal free face....but lacks the ridigity and has welds at vertical and top plate rather than one single peice.

Im thinking the bottom diagonal plate is not quiet as a problem as LR have no stiffener or fold etc on it....I would have thought my bottom plate, attached to the inside corner in the same manner as LR, be up to the same task.

[uninformed]

Bill, having a think about the TA length and relocating it in the same plane, IE not changing the AS. I think what is happening on hill climbs is, with the stock length, when you climb and the axle goes into droop, the AS increases quickly, which in turn wants to drive the axle further down and foward, AS gets higher again and this gets worse....With a longer link, my thinking is the AS wont increase as rapidly (due partly to the arc is scibes compared to the shorter link) therefore the axle is now less prone to driving under the rig and instead wants to push it forward

does this make any sense :confused:

[uninformed]

Bill, having a think about the TA length and relocating it in the same plane, IE not changing the AS. I think what is happening on hill climbs is, with the stock length, when you climb and the axle goes into droop, the AS increases quickly, which in turn wants to drive the axle further down and foward, AS gets higher again and this gets worse....With a longer link, my thinking is the AS wont increase as rapidly (due partly to the arc is scibes compared to the shorter link) therefore the axle is now less prone to driving under the rig and instead wants to push it forward

does this make any sense :confused:

[Dougal]

does this make any sense :confused:

Yes.
Consider AS at ride height level as well as ride height climbing (rear compressed more) and descending (rear extended more). Longer will give less change, but overall it may be dictated more by the length of the upper link than the lower.

A side on drawing, some ice-cream sticks and thumb tacks can be very good for seeing how it's going to run.

[rick130]

Yes.
Consider AS at ride height level as well as ride height climbing (rear compressed more) and descending (rear extended more). Longer will give less change, but overall it may be dictated more by the length of the upper link than the lower.

A side on drawing, some ice-cream sticks and thumb tacks can be very good for seeing how it's going to run.

I used to plot wishbones out in half scale on huge sheets of cardboard with thumbtacks and string just to see where changes in camber curves and roll centres would end up.

Quick and easy to get a visual on what's going on.

[uninformed]

Yes.
Consider AS at ride height level as well as ride height climbing (rear compressed more) and descending (rear extended more). Longer will give less change, but overall it may be dictated more by the length of the upper link than the lower.

A side on drawing, some ice-cream sticks and thumb tacks can be very good for seeing how it's going to run.

Since AS is a combination of link geometry, wheelbase and COG....everything changes on a climb.

Climbing as you say may compress the rear, which on level ground would decrease AS, but as the COG has shifted on a climb, it will increase. Throw into the factor real world wheeling and rutted tracks etc, plus the axle wanting to crawl down and forward due to higher AS.

I think it can be controlled alot more with the TA than the A frame. as the A Frame and ball joint will change the pinion angle, but the TA control the axle arc.

at the end of the day, it is the relation of the A frame to the TA's...the more parrallel they are to each other the less the AS.

[uninformed]

I have submitted my 1854 form to Qld DOT for vehicle modification.

PSimpson was generous enough to give me some of his time and chat about doing some CAD for the cutouts and folds. I will supply him with full scale tech drawings to the best of my abilites. I have started drawing Version 2.0, but looking at the end elevation of TA side, im not happy with the size of this thing.

Im going to source a used TA chassis bush and cut the rubber off so I have the physical part that bolts to the mount. I can place this on my drawing and see where it fits and what can be done. All of coarse, keeping in mind the TA height....

This whole project is not going to be a quick process. I am greatful for anyone that has and will help along the way. The knowledge and experience of some of you guys is invaluable to me.

Thanks

[Dougal]

Since AS is a combination of link geometry, wheelbase and COG....everything changes on a climb.

Climbing as you say may compress the rear, which on level ground would decrease AS, but as the COG has shifted on a climb, it will increase. Throw into the factor real world wheeling and rutted tracks etc, plus the axle wanting to crawl down and forward due to higher AS.

I think it can be controlled alot more with the TA than the A frame. as the A Frame and ball joint will change the pinion angle, but the TA control the axle arc.

at the end of the day, it is the relation of the A frame to the TA's...the more parrallel they are to each other the less the AS.

The COG when climbing only moves due to compression/extension of the suspension. Climbing a hill and accelerating are exactly the same thing to suspension. The force vectors move in exactly the same way.

Accelerating at 1g (fast landrover) and climbing a 45 deg slope give exactly the same forces and suspension reaction.

[uninformed]

The COG when climbing only moves due to compression/extension of the suspension. Climbing a hill and accelerating are exactly the same thing to suspension. The force vectors move in exactly the same way.

Accelerating at 1g (fast landrover) and climbing a 45 deg slope give exactly the same forces and suspension reaction.

hang on a second.....are you saying that all the geometry is the same if the vehicle is sitting on flat level ground, or flat 45 degree incline?

lets say both parked and both at 7km/h???

From what I have read, or thought in my head I would have said different. To me gravity does not act perpindicular to a surface. So if its mostly in a vertical plane then there has to be a difference between the 2. If your wheelbase is 110 inch on level ground, does it not become 78 inches at 45 degrees (no the wheels dont get closer togther but the points ploted do..the engine and tranny is now much high than the rear axle than on level ground.

I would have said that COG definitely be different from level ground to 45 degree incline, even with suspension at same postion relitve to vehicle....

[Dougal]

hang on a second.....are you saying that all the geometry is the same if the vehicle is sitting on flat level ground, or flat 45 degree incline?

lets say both parked and both at 7km/h???

The geometry isn't the same, as the suspension extends/compresses at each end due to the load shift. Accelerating at 1g on the flat will give the same load shift and same geometry as 45 deg incline.

The load shift from being stationary (or at steady speed) on an incline is the same as the load shift from acceleration.
Squat/Antisquat and force vectors are exactly the same.

The reaction on the tyres is perpendicular to the surface, weight isn't just gravity, it's gravity plus acceleration.
Gravity acts downwards, acceleration acts forwards (in this example). The result on a flat surface is the weight/inertia vector swinging backwards with acceleration.
The result is exactly the same as being stationary (or at steady speed) on an incline.

I started down this path 15 years ago nutting out mountainbike rear suspension and climbing vs acceleration. It is a mind-bender and it might take a few years to accept.

[uninformed]

Is the COG the same for level and inclined?

[Dougal]

Is the COG the same for level and inclined?

Generally yes. It will move a little as your heavy axles move on their suspension, but this could be ignored with no great harm.

[uninformed]

hmmmm......then why do I need a handbrake on an incline and not on flat level ground.

I think im going to struggle with this one :eek:

[Dougal]

hmmmm......then why do I need a handbrake on an incline and not on flat level ground.

Because the acceleration reaction has a component pointing backwards.


I think im going to struggle with this one :eek:

Nah, just accept that they're the same, optimise your suspension for the flat acceleration and it'll climb well enough.

[uninformed]

problem is, flat ecelleration is more forgiving than hill climbing rutted tracks. For a good launch on flat you just need AS so it gets power down and goes forward...go up a hill climb, and the same AS, if high, will launch but straight away try and drive the axle under the rig instead of pushing the chassis forward. Yes there is throttle control, but with the response of the LR throttle it may be more forgiving to have a little less AS....but not so little the bum squats AND that the front end does not get loaded by the rear (think weight in tyres type of thing)

[Dougal]

problem is, flat ecelleration is more forgiving than hill climbing rutted tracks. For a good launch on flat you just need AS so it gets power down and goes forward...go up a hill climb, and the same AS, if high, will launch but straight away try and drive the axle under the rig instead of pushing the chassis forward. Yes there is throttle control, but with the response of the LR throttle it may be more forgiving to have a little less AS....but not so little the bum squats AND that the front end does not get loaded by the rear (think weight in tyres type of thing)

Which is why you are putting in longer links in the first place. Minimise change in AS with suspension motion?

[uninformed]

thats it :)

not sure if I should trust the word of a cyclist atm, in light of everything :D

[slug_burner]

you would need the handbrake on flat ground to stop your vehicle rolling away if it was subjected to a force equal to one G in the horizontal direction.

[uninformed]

you would need the handbrake on flat ground to stop your vehicle rolling away if it was subjected to a force equal to one G in the horizontal direction.

yep, but park it and it will stay put with no brakes, park it on a incline and it will roll.....my point was that I feel that the COG must change from flat to incline due to this among other things....that is the same things happen differently

im probably very wrong, but it doesnt really matter as the point of my new TA is to deal with the physical limitaions of what can be done. As Dougal pointed out, all Im doing is reducing the change in stock set up, static height is important but changes as soon as you drive. If I can keep the changes less, then in THEROY it should be better

[uninformed]

I recieved a very friendly phone call from Qld Dot yesterday. I have been informed that as of Nov 1st, the new vehcile code comes into play here in Qld. They advised me to wait till after that and then contact a approved ENGINEER (read not just a blue plater). Saying that the new code is more flexable :confused: and that it will be up to the engineer to deem whether the idea is doable: that is, safe and within the new code.

So it sounds like its a good chance (at this stage) But I have that sinking feeling, like most things in life "if you want to play, you's got to pay" Its sad its should cost so much to do something by the book and safe, but such is life.

I asked for a list of approved engineers in my area:



Queensland

Clinton Harry
38 Blackwood Road Geebung Qld 4034
0438 738 454

Alan Marburg
P O Box 9385,
Wynnum Plaza Qld 4178
0410 669 075

Len Emerick
LW Emerick & Assoc.
PO Box 1609
Hervey Bay Qld 4655
4128 6867

Darren Dakin
Altra 9 Pty Ltd
PO Box 5570
Brendale Q 4500
0431 382 789

Richard Larsen
101 Lochinvar Road,
Upper Kedron Qld 4055 3851 1066

Werner Ihle
3/28 Activity Cres
Ashmore Qld 4214
0418 551 331

Garry Bow
PO Box 120,
Strathpine Qld 4500
3881 1355

Timothy Bartrop
9 General Macarthur Place
Redbank Qld 4301
3280 8202

Kevin Walsh
Walsh Engineering Solutions Pty Ltd
478 Boundary Street
Toowoomba Q 4350
4634 3344

Bruce Hartwig
Sapid Pty Ltd
25 Raven Street,
West End Qld 4101
32551621

Graeme Presley
115 Radford Road
Manly West 4179
3348 2211

Bruce Johnson
4 Colworth Street, Sunnybank Hills Qld 4109
0413 137 201 / Sunnybank 3344 1803; Cairns 4097 6731

David Blythe
DB Autotech
26 Nicholson Avenue
Salisbury Qld 4107
0407 756 870
www.dbautotech.com.au (http://www.dbautotech.com.au/)

Maxwell Evans 42 Lincoln Green Drive,
Forestdale Qld 4118 3800 8636

Willem Saarberg
24 Slatter Court, Brendale Qld 4500
3396 6033

Trent McMahon
OS Imports,
2 Solander Street, Carina Qld 4152
0437 126 853

Earl Gilchrist 4/70 Redland Bay Rd Capalaba Qld 4157
0417 229 723
John Allen
P O Box 80,
Thuringowa Central Qld 4810
4788 8864

Phillip Harris
Pipers Glen
315-331 Hein Road, Buccan Qld 4207
5546 3126

Timothy Gregg
813 Upper Ormeau Road,
Kingsholme Qld 4208 5547 5879

David Turner
Vehicle Safety Certifications & Heavy Vehicle Certifications GPO Box Brisbane 4002
0434523282

Raymond Miller
6 Coughan Street
The Gap Qld 4061
3300 4700

Lindsay Stone
Livingstone Automotive
36 Coates Street,
Mount Louisa Qld 4814 4774 8807

Christian Arendt
4 Progress Road
Rupertswood Qld 4817

if anyone has used or knows of any of the above listed, please pm me with good or bad info

cheers
Serg

[Slunnie]

you would need the handbrake on flat ground to stop your vehicle rolling away if it was subjected to a force equal to one G in the horizontal direction.
True for more and less than 1G also.

[wagoo]

problem is, flat ecelleration is more forgiving than hill climbing rutted tracks. For a good launch on flat you just need AS so it gets power down and goes forward...go up a hill climb, and the same AS, if high, will launch but straight away try and drive the axle under the rig instead of pushing the chassis forward. Yes there is throttle control, but with the response of the LR throttle it may be more forgiving to have a little less AS....but not so little the bum squats AND that the front end does not get loaded by the rear (think weight in tyres type of thing)

Serg,I know that Antisquat has been discussed to death on the Pirate Forum, but not so much here.So I picked this post at random mainly to ask if you have calculated the position of the converging imaginary lines of the rear links otherwise known as the 'Instant Centre (IC')? The position of the IC in relation to the for/aft centre of gravity (COG), I would assume would determin the degree of antisquat (AS) that the system can generate.
Just looking at my old standard Range Rover, and without crawling around underneath to measure link placement points, I would guess that the IC is probably forward of and below the COG.
Now for the sake of the mental exercise, if we disregard the links and replace them with a Unimog style 'Torque Tube' that pivots from the chassis at the same location as the IC, and then twist the rear axle around the halfshaft axis, a lifting force would be applied at the IC, which being in front of and below the COG would cause the front of the body to rise and the rear to squat, would it not? This is not taking in to account the positive squatting forces that the front axle radius arms (RA's) impart.
To clarify the reason for my question. I have never observed the rear of a RangeRover Classic squat or jack up under accelleration or on hill climbs.
Another question. Is the climbing performance of a Discovery 2 inferior to that of a Disco 1 or RangeRover Classic? Presumably the rear radius arm suspension would give higher antisquat characteristics than the 3 link arrangement of the D! and RRC.
Bill.

[uninformed]

Bill, from what I have read, you need to:

Draw 2 wheels representing front and rear (wheelbase)

Draw a horizontal line representing the height of COG

Draw the 2 lines through the rear upper and lower links, where they meet is the IC

Draw a line from the rear tyre contact patch to meet the IC

Draw a vertical line through the center of the front wheel.

the height of the line from tyre contact patch to IC, at the front wheel vertical line is the point that represents the amount of anti-squat. If I am correct, if the tyre CP to IC line was to disect the front wheel vertical line AT the height of COG, this would be 100% anti-squat, above is more below is less....

I cannot comment on D2 at all.

I have read and seen pictures of LR with A frame rears hill climbing where they want to "pig root" or have the axle start to drive under. Throttle control can help but not the best answer.

Im guessing a RRC on 29's and stock springs would climb pretty well, but throw 32's, 34's or bigger on and a spring lift and you have change the geometry alot

[uninformed]

True for more and less than 1G also.

but gravity isnt applying it horizontally.....

I must be missing the point :confused:

or confused (very likely)

but gravity doesnt change (well much unless you start talking about the mass of the surface materials in the earths crust), so if you change every thing else but gravity, my gut tells me the COG must change.....

[slug_burner]

No, CoG does not change. Ignoring the change of the position of the mass of the axles/wheels due to suspension travel.

The CoG is the point around which all other points moments cancel out. Therefore it does not matter if you place the collection of components on a horizontal or inclined surface the CoG is the same.

The change in CoG due to the suspension travel would be small and for most applications probably ignored.

Then again I am not an automotive or mechanical engineer.

[uninformed]

As I have said, looking at a static vehicle to keep the variables out. This is NO suspenion or acceleration movements.... Just the same vehicle on flat level groun and then on a 45 degree incline.

Im not saying that it definitely does change....no way, just trying to get my head around it

[wagoo]

Suspension dynamics are definately not my forte,so can someone correct me and demonstrate where I am going wrong with this admittedly simplified example of what I understand antisquat forces to be?
Without getting too down and dirty under my vehicle tonight, I am estimating the instant centre of the RRC 3 link is about mid wheelbase and top of chassis rail. This would give an effective equivelant torque tube/radius arm length of about 4 ft .If you sunk the rear tyres in concrete and the rear axles were transmitting 4000ftlbs of torque, the lifting force at the front of the radius arm,mid chassis would be only around 1000lbs.
An unladen RRC has around a 50/50 front/rear weight distribution, and weighs around 4000lbs,Delete weight of axle assemblies, lets say sprung mass of 2800lbs. The radius arm/torque tube applying a lifting force at mid chassis is attempting to lift the whole 2800lbs with a force of only 1000lbs.
Seems to me that 1000lbs is insufficient to provide any antisquat at all.
Bill.

[uninformed]

Bill, I think I can visualise what you are describing, but I dont think its that simple....because if the upper and lower arms were parrallel to each other, there would be no IC, and in your example create a huge lever....but in reality the AS is lower in this case.

It must have to do with the IC AND its relation to tyre contact patch, front axle line and COG...so while the 2 links make an imaginary lever, the pivot point is the front axle...so maybe its the distance from the front axle reward to the IC...the longer this distance (which would mean the IC being closer to the rear axle, which would be achieved by greater angle between upper and lower links) the greater the leverage ie higher AS....

I think thats about as clear as mud :angel:

[uninformed]

2nd go:

what im seeing in my head is the forces from tyre, pushing the end of the lever which is the IC, but the lever is from the front axle center rear to the IC....

[Dougal]

Bill, I think I can visualise what you are describing, but I dont think its that simple....because if the upper and lower arms were parrallel to each other, there would be no IC, and in your example create a huge lever....but in reality the AS is lower in this case.

It must have to do with the IC AND its relation to tyre contact patch, front axle line and COG...so while the 2 links make an imaginary lever, the pivot point is the front axle...so maybe its the distance from the front axle reward to the IC...the longer this distance (which would mean the IC being closer to the rear axle, which would be achieved by greater angle between upper and lower links) the greater the leverage ie higher AS....

I think thats about as clear as mud :angel:

If the links are parrallel, then the IC is at infinity and the effective swingarm is one acting from the tyre contact patch forwards parrallel to those links. The point of most interest is where that point passes over your front tyre contact patch.

The below site is a bit dated and needs an overhaul (parts of it are 12 years old), it's also about mountainbikes where the drive is taken by a chain rather than axle reaction. But the pictures and diagrams may help you.
Dougal.co.nz (http://www.dougal.co.nz)
browse through "suspension", then "pedalling effects"

I have to say. Suspension dynamics gets VERY complicated very quickly.

[uninformed]

Thanks dougal,

Btw you were and others were right about COG....bloody pea brain of mine.

[Bush65]

True for more and less than 1G also.


but gravity isnt applying it horizontally.....

I must be missing the point :confused:

or confused (very likely)

but gravity doesnt change (well much unless you start talking about the mass of the surface materials in the earths crust), so if you change every thing else but gravity, my gut tells me the COG must change.....
Gravity is an acceleration and has an approximate value of 9.81 m/s2 on earth's surface. Being a vector quantity, it also has a direction - toward centre of earth for our purposes.

Weight is a force derived form mass times gravitational acceleration.

G denotes a magnitude of acceleration equivalent to gravity on earth's surface but often in some other direction, such as how Slunnie used it. It gives a feel of the effect of acceleration in comparison to weight. For example when changing direction (which is acceleration because vectors have direction), pilots of high performance aircraft experience high G forces.

[Bush65]

My explanation of anti-squat starts with what squat is.

When a vehicle accelerates (level or inclined surface) inertial forces (force = mass x accel and every force has an equal but opposite reaction) act in the opposite direction. The sum of all of these reactions is resolved to the height of the centre of gravity. During forward accel, this causes an increase of the load acting on the rear springs, compressing them, and a reduction in the the load on the front springs, extending them.

When the rear suspension geometry is designed to produce anti-squat, the force in the suspension links create forces that have a vertical component to lift the vehicle apposing the squat forces. If anti-squat is equal to, but opposite direction, this is called 100%. It can be less or greater than 100%.

If the rear, lower links are parallel to the ground, they will not create any lift (0%), if they are very steep, anti-squat will high.

Squat and anti-squat both change the suspension geometry, and if anti-squat is greater than 100% the change in geometry leads to even greater anti-squat, which leads to unstable change in geometry/anti-sqaut and hopping during hill climbs. This is what Serg is most concerned with here.

[uninformed]

John has simply and clearly stated what I was trying to....this is the sign that he really knows it and I just feel it.

For me it is not only AS that im looking at, But roll/bump steer and geometry change through Bump and Droop. There are alot of comprimosies though, as Im not starting with a clean sheet of paper. For example, as im not changing the A frame links I am limited to the length chnage of the TA's otherwise there will be some funky pinion angle changes through bump and droop due to the different arcs the uppers and lowers will scribe....

IMO the stock RRC on 29s probably has it bloody good for a mass production vehicle...but as soon as you change one thing, it all changes. Example, change the wheelbase and the AS/AD changes. Fit larger tyres AS/AD changes....and if you fit longer springs it changes more things, Roll axis angles, roll center (in the front due to Panhard)

I have in mind many things I would like to do...but feel it can only be tackled one item at a time. Consideration has been made to the final set up, but any effect that only doing one item will cause.

[wagoo]

Thankyou John, Dougal and Serg, but my head really hurts now from reading the replies and I think I will retire from this vehicle modification hobby. It's getting too scientific for my feeble old brain to keep up with.:confused:
bill.

[slug_burner]

The guys that can model all these suspension setups and play the compromise game to get a particular outcome aren't necessarily much more knowledgeable than someone who has a gut feel approach.

It is often the combination of an internal sense, an understanding of the science and access to resources like modelling software than can make some breakthroughs. I would therefore not throw it in Bill, it takes all kinds. All the better when shooting the breeze.

[Dougal]

Thankyou John, Dougal and Serg, but my head really hurts now from reading the replies and I think I will retire from this vehicle modification hobby. It's getting too scientific for my feeble old brain to keep up with.:confused:
bill.

Says the guy who's built more than all of us.:D

[Bush65]

Says the guy who's built more and achieved more successes than all of us.:D
Fixed it for you!

[Bush65]

Suspension geometry, relies upon solution of triangular geometry (i.e. trigonometry involving sines, cosines and tangents, etc. of angles).

As such it is easy to solve by graphical methods and, with some knowledge of these constructions, can be visualised by simply looking at the relative positions of the ends of the links relative to the tyre contact with the ground and a good guess of the location of the centre of gravity. Some people don't need to do any more than this.

What I find a little missleading is that some people think that these theoretical lines through certain points are lines of force that cause squat/dive and their anti's, etc. In fact they are only a graphical method to resolve the resultant of a bunch of forces and solve the vertical/horizontal components of them.

The other thing which missleads is that the suspension geometry and forces constantly change when our vehicles travel over obstacles.

[Dougal]

Suspension geometry, relies upon solution of triangular geometry (i.e. trigonometry involving sines, cosines and tangents, etc. of angles).

As such it is easy to solve by graphical methods

That's it exactly. It's a geometry problem (like ~90% of mechanical engineering), the complicated maths is just there to describe the geometry.

[uninformed]

Suspension geometry, relies upon solution of triangular geometry (i.e. trigonometry involving sines, cosines and tangents, etc. of angles).

As such it is easy to solve by graphical methods and, with some knowledge of these constructions, can be visualised by simply looking at the relative positions of the ends of the links relative to the tyre contact with the ground and a good guess of the location of the centre of gravity. Some people don't need to do any more than this.

What I find a little missleading is that some people think that these theoretical lines through certain points are lines of force that cause squat/dive and their anti's, etc. In fact they are only a graphical method to resolve the resultant of a bunch of forces and solve the vertical/horizontal components of them.

The other thing which missleads is that the suspension geometry and forces constantly change when our vehicles travel over obstacles.

the only reason I can visualise the small amount I can, is because I play with BASIC trig. most days and constantly looking at angles etc for work...

The forces would have to be transmitted through the physical components would they not??? I cant see force shooting out from the tyre contact patch through the point of IC and over the front axle.......dissapearing into the eather :D

But that imaginary line is still a very important one IMO

Suspension change is the whole reason I want to change mine....at static height it is fine and drives ok on flat level ground, but when you go around cornes etc things change rapidly....

[uninformed]

Thankyou John, Dougal and Serg, but my head really hurts now from reading the replies and I think I will retire from this vehicle modification hobby. It's getting too scientific for my feeble old brain to keep up with.:confused:
bill.


Bill, the science has been there from the begining of exsistance, its just that now the internet is here it has opened up the web wheelers (me!) to bang on about something that I know VERY little about...

I would not be able to learn were it not for the very knowledgeable, like John, nore without the workings of guys like yourself (that is not to say you are not very knowledgeable as well)

You can have my theroy(ill write it all down on a grain of rice) if I can have your pratcial experience and unique designs :)

[wagoo]

Thanks guys, but it's true, my comprehension abilities are diminishing at an alarming rate lately. It's either a product of age, or a result of one too many welding sparks sizzling down my ear hole. One sizzled right through and fell out the other side yesterday I think!:)
Bill.