Too much emphasis on suspension????

[justinc]

Hello all,

Now some may take umbrage at this, but what is wrong with good quality,(Say, like Ultimate Suspension made ) leaf spring packs and shocks on an offroad trailer, as the all terrain coupling will handle all the 'flex' that could happen off road, and the springs really do little more than carry weight, and shocks valved accordingly to control all that weight during compression/ rebound? I'm making this point to emphasise the glorious simplicity of leaf springs, and whereas they have very little appeal on a vehicle, I can think of very little better to support weight and last a reasonable length of time. Obviously, quality springs designed specifically for the application, maybe even parabolics? and shocks like bilstein , Koni and the like will complement them to last and perform better.
Before anyone screams WHAT??? We took a Cape york trailer on some pretty rough tracks, and at reasonable speeds on corrugations etc, and even with a pair of 'average' shocks fitted, found it to tow quite well, even loaded up. It effortlessly followed the Rangie through some pretty steep and rough tracks near Cloncurry and The Isa, from Camooweal to Lawn hill and Karumba etc. I have two friends ( actually, I have many) one with a T van and one with an Ultimate, they are both awesome pieces of kit, but I can't really see the need for such awesome suspension etc. I know they are well designed and virtually unbreakable, but what is wrong with Simple systems, that have worked well for a long time?

Anyone care to comment?

And be gentle please.

JC

[Discoduck]

I have a Koala c/t that I bought 5 years ago.It was at the bottom of the price scale then.$6200 back then.

It has 7 leaf spring packs on the outside and a 5 pack in the middle.I don't know the reasoning for this setup but after trips to Cape York,the Vic high country and and outback Qld trip plus many 4wd club trips I can not fault the setup.

The only mod I did was to put a set of shocks on it.

I plan on doing an ather Cape trip this year.

Mike

[justinc]

That is one of the reasons for our choice being easier, The Cape York model we are interested in is only $15K, and that includes delivery to Melbourne from Cairns.
We went to the factory, Ahern metal industries, and had a squiz, liked the simplicity and strength, no nonsense design and good build qaulity. I'll be ordering one as soon as funds permit I think.

JC

[incisor]

there is absolutely nothing "wrong" with a good standard leaf spring setup on a trailer.

it is just that the "good" leaf type independant setups are an order of magnitude "better". IMHO a lot smoother to tow and a darn sight less harsh on the contents of the trailer. not to mention they are usually a lot stronger as the load and shock coming back thru from the suspension is fed back into the chassis of the trailer in at least 4 points not 2.

had both and wont be going back to standard leaf suspension on a camper.

never had a coil sprung trailer nor towed one over any serious country so cant comment on them, but i would dearly love to give an ultimate the personal treatment.. love the look and style of them. have followed a few and they seem to tow very nicely as well.

[incisor]

That is one of the reasons for our choice being easier, The Cape York model we are interested in is only $15K, and that includes delivery to Melbourne from Cairns.
good friend of mine has one and he loves it... has been around AU at least twice with it behind his 80 series cruiser.

[Bigbjorn]

A friend built a trailer to carry his Historic race car, about five years ago. He got fed up with trailer repairs on the road. He reckoned going to interstate meetings from Brisbane, he had more trailer troubles than race car ones.

He built a tri-axle using Aeon rubber springs to achieve a low deck, radius rods and Panhard rods, and lever shock absorbers for ease of mounting. The one drawback is that the suspension is not load sharing. He used 2 tonne axles, electric brakes, and 8.25 x 16 light truck tyres. This was not a cheap job but is strong and reliable. He was designing a load sharing suspension similar to a tri-axle Hendrickson but needed the trailer before he nutted it out, hence the non load- sharing suspension as built. The race car weighs a bit over 1 tonne, add tool boxes, spare parts and tyres, drums of fuel, camping gear etc. and you can have some idea of what the gross trailer mass is. It cost him around $5000 plus his time. He says it was worth every cent. He pulls it with a J3 Bedford conversion, with Mexico Chev. truck engine, RTO610 Road Ranger.

[rovercare]

For the same reason you don't tour in a 60 series or a series rover, they'll do the job quite ample, but the coils are still far superior, you will have trouble with the leaves as they fatique on continous corrugations, as in days in the centre, my old boy has a kimberely, if you didn't notice the weight, you wouldn't know you were towing it

[Pedro_The_Swift]

not that I am trying to advertise leafs,,:angel:
but they do more than just "carry weight" they also locate the axel, probably the second most important thing.
something coils cant do,,
by the time you add location bits and pieces the coil set-up will weigh as much as the leaves,, and be more complicated,,


gawd,, I sound like I own a series:eek::eek::wasntme:

[MT]

I have often wondered about this too. When we bought our trailer we went for the KISS principle - it just has heavy duty leaf and axle. Apart from high clearance and an 'off road' coupling there is nothing too out of the ordinary about it. We have towed it, laden around Australia, dirt, sand and bitumen. Has done GRR, Buchanan Hwy, Gulf Country . Only issue I have had is a rock rebound taking out rear window on the Disco between Lyndhurst and Marree. (hmmm..four hundredth reminder to self - Must get around to fitting a rock boot / sock one of these years....)

Part of my reasoning in going for a simple approach was observing Army half tonne trailers being abused for decades. These are robust, but very simple setups. I could not recall any significant mishaps due to technical failure of the trailer. (quite a few though due to some of the numpties who thought that they could set new land speed records on dirt roads whilst towing a trailer when we replaced the series LR with the Perenties).

I accept that there are some limitations - we never put anything in the trailer that we do not think could tolerate a bit of a shaking. In conclusion, the setup has proven (in our case) to be simple, cheap and effective.

Cheers

Mark

[justinc]

Thanks everyone for their replies. I am a firm believer in the KISS principle, but Incisor makes a very important point (that I hadn't noticed I admit with the one we hired,) that the contents of the trailer will suffer with shock loads and vibrations etc.
But This could be lessened with decent shocks ,and
Tyre choice and pressures will further improve on this situation .
I have utmost admiration for trailer designers that put together something like the Ultimate or the T Van, and their reputation for strength etc is excellent. BUT, not all of us can afford the $$$ tag. I think I'll be sticking with my original idea still, A Cape York full body galv soft floor, with kitchen annexe and uprated suspension. I believe they use Hilux spring packs, which would be very easy to obtain in the out -of- back.
Thanks again for input all.

JC

[Buggerluggs]

JC

One point that has not come out in this thread is the effect of unsprung mass and the direct coupling of the two wheels. A live axle setup will lead to a sympathetic tramp action over corrugations. Every time a wheel hits a bump it takes off very slightly then bites again as it hits the dirt. This bite results in a significant twist reaction directly into the suspension. With both wheels directly linked they tend to do it together in sympathy. This is axle tramp. The heavier the unsprung weight the higher the reaction forces tend to be.

If suspended on a link system such as the LR coil setup tramp is minimised by the links. The four bushes mounted on the Disco arms for example have a small degree of flex and the arms much less. The result is that there is quite a resistance to the tramp action, but it is still there.

With leaf springs the tramp is resisted by the leaf which itself will add to the tramp action. Leaf springs with long travel are usually very long springs. The longer the spring the more it will 'wind up'. The leaf takes a sort of "S" shape on tramp. The axle will twist relative to the ground much more in this situation. Add to this that if you have the shockers mounted on the same side of the axle the spring "S" shape is undamped and will oscillate itself as a function of the leaf. The end result is that tramp action is far worse with leaf springs and either no shocks, or with shocks mounted on the same side (e.g. front only). The solution is to use an anti tramp bar and alternate mounted shocks (one in front and the other behind the axle).

The main advantage of independent suspension is that it reduces unsprung weight if done correctly and also eliminates the direct coupling of the two wheels and hence the sympathetic action resulting in minimised tramp.

Geometry is another aspect of suspension that impacts on how the trailer will handle, but is for another topic/book!

[JDNSW]

JC

One point that has not come out in this thread is the effect of unsprung mass and the direct coupling of the two wheels. A live axle setup will lead to a sympathetic tramp action over corrugations. Every time a wheel hits a bump it takes off very slightly then bites again as it hits the dirt. This bite results in a significant twist reaction directly into the suspension. With both wheels directly linked they tend to do it together in sympathy. This is axle tramp. The heavier the unsprung weight the higher the reaction forces tend to be.

If suspended on a link system such as the LR coil setup tramp is minimised by the links. The four bushes mounted on the Disco arms for example have a small degree of flex and the arms much less. The result is that there is quite a resistance to the tramp action, but it is still there.

With leaf springs the tramp is resisted by the leaf which itself will add to the tramp action. Leaf springs with long travel are usually very long springs. The longer the spring the more it will 'wind up'. The leaf takes a sort of "S" shape on tramp. The axle will twist relative to the ground much more in this situation. Add to this that if you have the shockers mounted on the same side of the axle the spring "S" shape is undamped and will oscillate itself as a function of the leaf. The end result is that tramp action is far worse with leaf springs and either no shocks, or with shocks mounted on the same side (e.g. front only). The solution is to use an anti tramp bar and alternate mounted shocks (one in front and the other behind the axle).

The main advantage of independent suspension is that it reduces unsprung weight if done correctly and also eliminates the direct coupling of the two wheels and hence the sympathetic action resulting in minimised tramp.

Geometry is another aspect of suspension that impacts on how the trailer will handle, but is for another topic/book!

Unless you are either driving the wheels or braking axle tramp is either non-existent or irrelevant, as there is no torque to rotate the axle against the springs (if you have ever driven a car subject to severe axle tramp you will remember how it stopped instantly when you lifted your right foot!).

But your point about unsprung weight is the major advantage of independent suspension on trailers, not axle tramp.

And, as pointed out, the major problems with trailer suspensions are durability (which can be designed into any type of suspension) and ride - which is a lot easier to combine with this in an independent setup.

John

[justinc]

I agree, Durability is one huge factor, but having less moving parts, bushes, arms and anchor points for the aforementioned, means less complex gusseting and 'weight' in the chassis. There are only two mounting points on each side for a leaf pack, and 1 for the shockabsorber bracketry, as opposed to lateral location,( Panhard or watts link, ) upper and lower control arm of some sort, and shocks also ( For live axle).

I still maintain that a properly set up leaf sprung shockabsorbed trailer will be as reliable and as durable as anything, and available parts are important in remote areas. How easy is it to roadside repair a broken leaf spring? a lot easier than trying to reconstruct the set up with a broken panhard rod or trailing arm... As opposed to tying the pack together and/ or turnbuckling the axle in place incase of a U bolt failure. Also, phoning a wrecker for a secondhand hilux rear spring pack would be a whole lot easier than getting hold of the manufacturer for a spare part that has to be 'flown in' because of the lack of local bits.
I'm not poo pooing the major offroad trailer manufacturers here, as most of them won't have breakages anyway, but IF it happens, there is less of a headache to get the holiday/ trip back on the track again.


JC

[walker]

Yep, totally agree.

I have just finished building my offroad trailer and on the recomendation from the MD at Alko I used leaf suspension with shocks. He believes that the only reason many of the "expensive" offroad trailers use independent coils is because thats what people expect...not that it is better.

The important thing is to use leaf springs that are matched to the load you are carrying. Many leaf spring trailers have spring rated to 2000kg + and only carry a 1000kg so they bounce around. Use long springs, have them matched to the load and use good shocks and it should be sweet.

I just towed mine from melbourne to brisbane then around Morton Island and it was great. The suspension worked well and towed fantastically. The real test will be on the corrugations later this year.

[JDNSW]

Another point in favour of leaf springs - coils, rubber torsion members or torsion bars carry the entire weight of each side at a single point, which means that the trailer frame has to transfer all the weight to these two points. Leaf springs carry the load divided between two widely separated points, so that (unless carrying a single fixed, concentrated load such as a motor or genset) the trailer frame is simpler and lighter -, which however, does not help the unsprung weight problem! If the independent suspension trailer frame is no more complex than the leaf spring trailer frame, it is either weak near the spring mount, or unnecessarily heavy away from the spring mount.

The same comments incidentally apply to cars, and taking the case of the coil spring 90/110 compared to the leaf spring Series - I suspect the coil spring chassis is significantly heavier than the leaf spring chassis, certainly the vehicle as a whole is, although there are other reasons for this as well - heavier engines and a lot more equipment.

John

[Buggerluggs]

Unless you are either driving the wheels or braking axle tramp is either non-existent or irrelevant, as there is no torque to rotate the axle against the springs (if you have ever driven a car subject to severe axle tramp you will remember how it stopped instantly when you lifted your right foot!).
You are right John. I was getting ahead of myself. It is the unsprung weight and the fact that the two wheels are attached that have the greatest effect.


Another point in favour of leaf springs - coils, rubber torsion members or torsion bars carry the entire weight of each side at a single point, which means that the trailer frame has to transfer all the weight to these two points. Leaf springs carry the load divided between two widely separated points, so that (unless carrying a single fixed, concentrated load such as a motor or genset) the trailer frame is simpler and lighter -, which however, does not help the unsprung weight problem! If the independent suspension trailer frame is no more complex than the leaf spring trailer frame, it is either weak near the spring mount, or unnecessarily heavy away from the spring mount.
When it comes to load sharing into the chassis, there are three load points per side on a leaf spring. Each end of the spring and the shocker mount. The loads are different in nature. The ends of the spring input loads in three planes. The ends of the shocker input loads in the verticle plane. On a coil sprung suspension the coil input is in the verticle plane and depending on what the geometry actually is, other points input in two planes or one plane e.g. the panhard rod inputs on one side in the transverse plane, a watts link is similar but on both sides and half the magnitude. At the end of the day it all comes down to how much of a compromise you make in designing the total system and how good your stress anaylysis is.

Back in the late 70's the Ford Falcon went from leaf to coil sprung rear end. Part of the design criteria was to ensure that it could tow as heavy a load and carry as much luggage in the boot. The end result was a lighter vehicle, but with a better use of the structure. It did all it was designed to do. The rest is history. At about the same time (earlier from memory) Holden introduced the Commode which had a propensity to bend at the rear spring mount when used at design limits and driven over good old Aussie outback roads. This required significant strengthening and alteration to the vehicle in its early years.

In summary, I like the simplicity of the leaf spring. It needs to be long and soft, hence closely matched to the vehicle weight characteristics. It needs to be damped with double acting shockers. The axle needs some carefull thought. The concept of a solid square bar is wrong in my opinion. The most significant aspect ot the axle is to resist bending. A solid anything is not the strongest method of achieving this. A tube is! A tube of say 75mm od and suitable wall thickness can be much stronger than a solid bar of 50mm, yet much lighter for the same duty. As unsprung weight is the critical factor then a tube would be the better alternative. At you reduce the unsprung mass you reduce the requirements of the shocker and therefor the loads transmitted into the chassis. This allows the chassis to be refined and be made lighter, which means the springs can be smaller etc....

My one concern with a leaf spring is the quality of manufacture. As it is both a load suspension and location device should it fail you are totally up the creek. Leaf springs are a relatively low technology to make, but to ensure high quality they need more than a blacksmith approach. If you get a product made for the high volume automotive market then the manufacturer will have quality levels of a high degree of confidence. If you get one made up by a smaller operator then you take your chances. There are a hell of a lot of things that will influence the durability of any spring, but more so the leaf spring. If a leaf spring fails at the eye there is little you can do (hence the military wrap). If a coil or air bag fails you can block it up and still get home.

[DiscoDan]

WOW what a good read, I was going to fit the ALKO independent to a trailer that I have plans of building (gunna) ;)

However after this read I may be reconsidering this. Don't know if i would put in Yota parts as they shook you apart in the ute and would prob do the same in to the trailer. :o

The Army 1/2 tonne trailers were over sprung, I remember Mortors loading one up when I was in and from memory it weighed in at over a tonne and the springs hadn't sagged at all. Use to bounce over the road when empty as well. Tough though.:D



Back in the late 70's the Ford Falcon went from leaf to coil sprung rear end. Part of the design criteria was to ensure that it could tow as heavy a load and carry as much luggage in the boot. The end result was a lighter vehicle, but with a better use of the structure. It did all it was designed to do. The rest is history. At about the same time (earlier from memory) Holden introduced the Commode which had a propensity to bend at the rear spring mount when used at design limits and driven over good old Aussie outback roads. This required significant strengthening and alteration to the vehicle in its early years.


Ford introduced the coil spring with the XE which was released in 1981/1982. It may have been on the plans for the XD (1979) but didn't make it, couldn't even fit a decent esky in the boot.I do remember the bending Commodores from towing one of the main things my boss looked for when trading them.

[Buggerluggs]

Ford introduced the coil spring with the XE which was released in 1981/1982. It may have been on the plans for the XD (1979) but didn't make it,

Splitting hairs, but it was designed in '79 and released in '80. I know because I did the original design. The last job I did for Henry.

[Bigbjorn]

Holden went to 4 coil suspension with the Torana in 1969, and the HQ in 1971.

[numpty]

The Army 1/2 tonne trailers were over sprung, I remember Mortors loading one up when I was in and from memory it weighed in at over a tonne and the springs hadn't sagged at all. Use to bounce over the road when empty as well. Tough though.:D .

Too true. That's why when I fitted the camper top on my army trailer, I removed some of the leaves to soften the ride. Think I took out 2 maybe 3 leaves, can't remember. Also my setup is not that heavy and that helps.

[Reads90]

Keep it simple
I have just leaf springs (no shocks) on my camper trailer and found them to be find on our trip around Aus. And we did all the mayjor tracks and gave the trailer death, as i am a ruff ar*e:) . We dragged it at 110kph over corrigations with no problems and off roaded it will no problems at all. We also think i over loaded the trailer too with all our crap but that did not seem to matter to it performance. I am a coil person and was a bit worried at first with having a trailer with Cart springs but they were fine. And my trailer does not even have shocks. But nothing got damaged or brocken in the trailer on the trip. Even the TV.
The company i bought the trailer off and a later article in 4wd said that the set up i have is alot better in the feild as little to go wrong, and easy to fix if it does
To sum up i will not be going out and up grading the surtpension to some fancy stuff, moto is keep it simple stupid

[Utemad]

Splitting hairs, but it was designed in '79 and released in '80. I know because I did the original design. The last job I did for Henry.
The sedan may have had coil suspension since then but the wagons and utes which are more for load carrying than the sedan still have rear leaf suspension in the current model.

I just recently bought a camper trailer with leaf springs and no shocks. I was a little concerned when I towed it home from the factory as it bounced around a lot. However when I loaded it up for its first trip it towed beautifully. No bouncing at all. I might put shocks on it one day but if I did I would take it to a trailer suspension place and get them to tell me my options first considering how little I know about trailer suspension design. The springs that are on it now I think are designed for use without shocks. They have those weird things strapped to the top of the spring packs. Two for each spring with one mounted in front of the axle and one behind on each spring. So not sure how just adding shocks to these springs would go.

[mcrover]

I spoke to a trailer builder a while ago about this very subject and I put him back in his place when he started going on about axel ground clearance and crap like that.

I just told him that if the tow vehicle will make it through, granted the trailer has the same sized tire package as you should in that situation and wheel track is similar then the trailer axel will have clearance and that wouldn't even be a consideration.

This was at a camping show and he was trying to sell his suspention on that grounds only really.

The main thing is matching load, stopping suspention hop with shocks and reliability.

There is no real substitute for leaves and coils, rubber or what not is more something just as a sales pitch than a nessesity.

I towed caravans commercially for a couple of years and the only suspention failiers I ever had was 1 U bolt that I noticed while stopped at a truck stop and a broken stub axel on a rubberised viscount that was not meant to be towed where the hirer towed it.

Brakes and stuff like that fail all the time on trailers but the old simple leaf springs are the most efficient and cost effective way of keeping a trailer off the ground.

[blitz]

I built my trailer over 17 years ago and have skull dragged it every where my Series IIA could take it, the rangie and now in my Disco. She has HG Holden Monaro leaf springs of christ only knows load capacity (got them off a rooled car and nice and long) bounces a bit empty but with a bit of weight in it rides beautifully.

i would love to be able to justify buying one with coils and all the fruit but my old trailer is still in exellent nick so she stays.

Blythe

P.S. To true about the unsprung weight

[wardy1]

WOW.... what a thread!
One of my clients actually builds the trailers for a fairly big ff road camper mob and he hs been telling me that all the hype around indpendent coils is just money for jam to him. He can build a leaf susp with shocks for less than half an Alko and he has laid $10,000 on the table if I can break his suspension!!!!
The point of a 75mm tube axle is well founded according to my mate, just he reckons everyone asks for a solid axle so thats what they get.
I've been researching all this for about a year now and reckon I've heard/read it all but this thread has been fantastic!!!!

[noddy]

We dragged it at 110kph over corrigations with no problems

:eek: :eek: That is way too quick for me with a trailer! What was the rush?

[loanrangie]

Just to add to the flaming, i have never seen an XD falcon with coils in the rear and that goes for sedan/wagon/pvan/ute. I'm 99 % sure it was the XE that had coils.

[Reads90]

:eek: :eek: That is way too quick for me with a trailer! What was the rush?

Nah no rush just the 90 loved to sit at that speed and floated across the top of them and made the ride so much more pleaseant

[BigJon]

Just to add to the flaming, i have never seen an XD falcon with coils in the rear and that goes for sedan/wagon/pvan/ute. I'm 99 % sure it was the XE that had coils.

I am with you on that.

[Buggerluggs]

Just to add to the flaming, i have never seen an XD falcon with coils in the rear and that goes for sedan/wagon/pvan/ute. I'm 99 % sure it was the XE that had coils.Not too sure about the model, but it was definately released in 1980/81. (Age affects the brain...so does the alchohol!) I used to work for Ford in the Advanced Engineering group and the coil sprung rear was the back off as the original was an independent suspension but the Granada diff would not take the torque of the 5.7 V8. We designed and built a hell of a lot of specials during those days.

Some more food for thought. Springs are designed based on some simple stress/strain criteria, but the manufacturing method has a dramatic impact on their durability. Leaf springs are very simply a flat bar in simple bending (not, but will do for the argument). At the surface of each leaf under certain conditions the stresses reach their maximum, this is the determinant of the spring strength and durability (assuming suitable steel selection...steels aint steels!). As part of the manufacture the leaf is heated to very high temperatures. During this process as it is exposed to air and you get what is called decarburisation. In effect the carbon contained in the steel in leached out into the surrounding air. As a result the effective strength of the steel at the surface is reduced. This is usually catered for in the design of the spring. However as you reheat a leaf as in the case of getting a spring reset, you take more carbon out of the steel. End result you reduce its surface strength and it will eventually fail, sooner rather than later. The same principle ocurs in coil springs. I have seen springs reset by a spring maker several times and then had it tested for fatigue only to see it fail well short of its design life, just because it was exposed to air while above a certain temperature for too long during its manufacture. Why is this important? Anyone with a simple forge and furnace can make a spring, but not everyone can make one to last the distance we put them through. The moral being 'go to a reputable spring maker, preferably one who makes springs for the motor industry and get quality product'. And another is NEVER get a spring reset (especially a coil spring), you could reduce its life quite significantly.

[Pedro_The_Swift]

I would think if you are getting a spring reset,, its life is already over---


but the rest all makes good sense Ian:D