Leading/trailing arm suspension

[Pedro_The_Swift]

Theres probably a correct name for it,,
anyone have an engineering problem with this?

[Tombie]

Interesting.. similar to the front and rear of a Discovery suspension

[Tombie]

I can see some potential to rip underneath if it's not adequately controlled

[Surrufus]

I can see that there might be an issue with one leading arm one trailing arm?
I don't know enough about the geometry and suspension in general to know whether "leading arm" as opposed to "trailing arm" is better or whether you can use them in combination like that.

[justinc]

The similar issue exists with the differences between front or rear hung leaf springs. Landcruiser etc front leaves are fixed at the back and during compression the axle wants to move forward which is a crime against physics. The humble landrover series is however a far better design where the axle follows the natural movement of the forces involved during suspension compression 😍

Jc

[BigJon]

It isn't load sharing. There is a similar design which uses a rocker leaf spring instead of coils to allow for independent and load sharing.

[justinc]

It isn't load sharing. There is a similar design which uses a rocker leaf spring instead of coils to allow for independent and load sharing.

Sinplicity suspension. Used on some New Age vans etc.
Can't say I am a fan. ..

Jc

[Graeme]

I prefer mine's 2 trailing arms with 2 cross rails taking the weight rather than a single cross-rail, without considering the leading arm debate.

[Pedro_The_Swift]

gotta pic Graeme?

[Pedro_The_Swift]

How can this possibly work?
the trailing arm cannot be connected to the leaves surely?


https://www.aulro.com/afvb/images/imported/2017/03/559.jpg

[Graeme]

Mine has the standard twin trailing arm arrangement, unfortunately only with 1300kg (per pair) stub-axles and bearings although should be adequate for its 2.5T ATM.

119467

[BigJon]

Sinplicity suspension. Used on some New Age vans etc.
Can't say I am a fan. ..

Jc

Dad has had two vans with it. He is happy with how it works. Dirt road capable, but not proper off road.

[Johnno_p]

One of the issues are the shocks being on too much of an angle. The closer to vertical they are the better they work.
Also with the angle of the shock there is quite a bit of side load on it and the seals will fail earlier

[Pedro_The_Swift]

You may have read this recently--- [bighmmm]


I reckon the main reason for the laid over shocks is the modern requirement for "no holes" through the floor,
and the only way to control the spring travel is with a laid over shock.
My old Golf has four shock towers through the floor and vertical shocks,, you dont exactly trip over them--[bigsmile1]
mind you, you cant exactly walk under it either--

[Johnno_p]

You may have read this recently--- [bighmmm]


I reckon the main reason for the laid over shocks is the modern requirement for "no holes" through the floor,
and the only way to control the spring travel is with a laid over shock.
My old Golf has four shock towers through the floor and vertical shocks,, you dont exactly trip over them--[bigsmile1]
mind you, you cant exactly walk under it either--

To have laid over shocks is a very poor design. The shock won't work properly which is why some run double shocks.
The Alko off-road set up is better but the G&S Chassis is far superior. I think Kedron Caravans also have a nice system.

[cjc_td5]

With the leading & trailing arm design, if both droop at the same time, the tyres are going to get very close together.

[Johnno_p]

With the leading & trailing arm design, if both droop at the same time, the tyres are going to get very close together.

Wouldn't they travel in the same arc and stay the same distance apart?

[bee utey]

To have laid over shocks is a very poor design. The shock won't work properly which is why some run double shocks.
The Alko off-road set up is better but the G&S Chassis is far superior. I think Kedron Caravans also have a nice system.

VW Beetle front shockers are ideal in this application as they are very short travel, being designed to work at around 50% of the wheel travel (mounted half way down the swing arm). I've built a few trailers with these shocks canted at 45° and they give excellent control.

[Slunnie]

My opinion on the leading / trailing arm suspension is thst it isnt an appropriate setup.

I think that as a rule of thumb it really should be setup as a trailing setup for both axles.

The crossmember that has the suspension points looks, unusually, like it has been engineered well to take the forces from both axles.

The front suspension will be prone to be rough when offroad as it drives the axle forward rather than rearward when it hits bumps

The front may be prone to driving under (I cant think off the top of my head what the correct term is) when traversing steps, mud etc, especially when unloaded

The front produces antisquat under brakes and the rear will lift which may make it more prone to locking rear wheels under brakes with that braking setup. You'll notice that 4WDs have really long and flat radius arms at the front to help with this problem. Those ones are short and have a lot of angle.

The trailer requires more engineering and weight to provide strength at the right points to prevent failures and fatigue.

The shocks as stated need to be perpendicular to the suspension travel - the more the shock is needed the less they work due to geometry.

To prevent airation from the shocks being so flat you can run monoshell or remote res shocks which will get around that problem.

[Slunnie]

Wouldn't they travel in the same arc and stay the same distance apart?

Very roughly when articulating (ie 1up, 1 down), but not when loading and unloading the suspension. When unloading (ie over a crest) the wheels will come in closer.

[Homestar]

How can this possibly work?
the trailing arm cannot be connected to the leaves surely?


https://www.aulro.com/afvb/images/imported/2017/03/559.jpg

Can't see why that wouldn't work. Just using leaves instead of coils. You'd just need to make sure the leaves are rated so they actually flex and aren't rock solid all the time which would be pointless - and what a lot of people do when building trailers themselves. Not sure how much more effective it would be than a solid axle though apart from giving extra ground clearance between the wheels.

[Pedro_The_Swift]

While I do agree Slunnie, Trailing arms were used on the front of Off Road buggies for many many years,, then someone built triangulated fronts , and now full A arm which are straight across, so the newer systems do handle the rough.
https://www.aulro.com/afvb/images/imported/2017/03/556.jpg

https://www.aulro.com/afvb/images/imported/2017/03/557.jpg

https://www.aulro.com/afvb/images/imported/2017/03/558.jpg

with this front end you can see why the yanks like desert racing... ;)

[Pedro_The_Swift]

Can't see why that wouldn't work. Just using leaves instead of coils. You'd just need to make sure the leaves are rated so they actually flex and aren't rock solid all the time which would be pointless - and what a lot of people do when building trailers themselves.
what i mean is, when the leaves flex the 2 arc distances would be different,,
drawing an arc from the mounts on the square tubing and one from the leaf end,,

[Homestar]

The pivots look like they are set at different distances so I would assume the pivot point is where it's attached to the spring.

I am looking at this and typing this out while lying on an ER bed with a drip in my arm so not saying I couldn't be wrong.

long story which I'll save for another time.

[Homestar]

I don't think my last post made much sense, but there looks like another hinge arrangement on the top of the spring that may be there to cope with that.