Thread: Is independent suspension that much better than leaf spring?

Originally Posted by Tank

Philip, I know mate, I was using a simplified version to explain to Vern who posted he didn't (and still doesn't) understand the principle.
I like solid axle trailer suspension because the principle works better off-road.
Wheel travels up, so does the trailer body, the ground clearance stays the same loaded or unloaded, the distance to the ground under the centre of the axle stays constant unless you bend the axle. The underbody of the trailer directly above the axle can not change it's distance to the ground once the springs are bound or flat and the trailer is sitting on the axle (Ground Clearance)
An I/S trailer can be loaded to the point where the underbody of the trailer will actually sit on the ground under the inner pivot points or the wheel guards will sit on top of the tyres or the springs bind.
Simple fact if a trailer has I/S when a wheel/s travel up, the opposite end of the swivel/trailing arm travels down.
For every ACTION there is an equal and opposite Reaction, Regards Frank.

I thought that the idea of suspension was that the trailer didnt move and that the wheel did?

Your saying that once the spring are bound or flat like its a good thing?
If you had 200mm of ground clearance and 100mm of suspension travel, once your springs have bound or flattened, you now have 100mm of ground clearance?

Simple fact if a trailer has I/S when a wheel/s travel up, the opposite end of the swivel/trailing arm travels down.

Simple fact is that the swing arm pivots on the opposite end to the wheel. The force is applied to the spring. If it pivoted at the spring mount then the opposite end would travel down.

Dave

Some new laws of physics, you should publish, Regards Frank.

Originally Posted by SouthOz

I thought that the idea of suspension was that the trailer didnt move and that the wheel did?

Your saying that once the spring are bound or flat like its a good thing?
If you had 200mm of ground clearance and 100mm of suspension travel, once your springs have bound or flattened, you now have 100mm of ground clearance?

Simple fact if a trailer has I/S when a wheel/s travel up, the opposite end of the swivel/trailing arm travels down.

Simple fact is that the swing arm pivots on the opposite end to the wheel. The force is applied to the spring. If it pivoted at the spring mount then the opposite end would travel down.

Dave

Wheel travels up, so does the trailer body, the ground clearance stays the same loaded or unloaded

Substitute "axle" for "body " and it makes sense.

This idea of body ground clearance applies to independent front suspension 4x4s where the diff housing /stone guard are the lowest point on the cars Vs a solid axle where the diff moves up and down with the wheel.

LR3and 4 by contrast have the diff tucked up in the chassis rails thanks to Fords Chassis hydroforming techniques and so it is not the lowest point.

So the answer re ground clearance is "it depends" on the design of the independent vs solid.
Same with trailers. AFAIK , no camper trailer has components hanging down to snag if the suspension is compressed.
Regards Philip A

[ame="https://www.youtube.com/watch?v=ADoLPq2L0qE"]Suspension Comparison[/ame]

Originally Posted by Chucaro

Suspension Comparison

Exactly what happens in my experience. I have owned all types and nothing even compares to independent suspension. We just picked up our third camper trailer on the weekend. Its a 2011 Xtrail, with independent suspension and its just fantastic off road.

So you keep your leaf suspension or alko torsion bar etc and I'll stick with my crappy, unreliable, coil sprung, comfortable D2 and camper that matches

I think we have thrown this issue around the campfire a few times previously but maybe it is time for me to chime in once more...

First that cruisemaster video simply demonstrates that poorly chosen leaf suspension rides badly.
What many miss is the terrible uncontrolled left right load shifting in the inde setup.

My two critiques of inde setups are - as above uncontrolled left right control
If you sat in you super special inde trailer you would likely get sea sick pretty quickly
A single axle trailer is a tripod - it needs none or nearly none left right articulation.

My seond critique is unecessary tyre wear / or alignment requirements.


" But why doesn't someone make a solid axle with coil springs"

As Erich intimated this above question is the question and I think you will find a few example of custom made trailers with soft riding either coils or airbag solid axles. This fixes the left right load share and also reduces tyre wear to near zero.

This year I will build another two fixed axle coil sprung boat trailers. Honestly I see absolutely no advantage to inde sprung other than it is commercially available. My triangulated 4link uses twice as many joints as independent swing arms but the benefits outweigh the negatives.

Inde setups are popular solely because they can be made in a jig and then welded into any width chassis. A solid axle linked suspension becomes custom fit and finish. Perhaps overkill for a trailer but pizzles all over an inde setup

Steve

Just to bring a few things together

some links of stuff I have glued together and some opinionated ramblings:

http://www.aulro.com/afvb/trailers-v...x-trailer.html

http://www.aulro.com/afvb/trailers-v...ting-read.html

http://www.aulro.com/afvb/trailers-v...t-trailer.html


ps I have used leaf springs on a few boat trailers - my favourite are 78/79 series leaves super long super supple and nearly unbreakable. Requires a pretty unique chassis to carry leaves that are nearly 1.5m long though!!!!!!


Steve

Well frank we will have to agree to disagree.

The solid axle really performs well in the 3 trailer comparison.

Dave