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

Here's an Idea, if you have one of those R/C 4wd toy trucks with independent suspension all round, press down or move it over bumpy ground and watch the bottom of the chassis bottom out. On a solid axle the only way you would get the chassis under the trailer to touch the ground is to bend the axle and splay the wheels out sideways, Regards Frank.

Originally Posted by Vern

I have no idea how the lowest point on the trailer is the trailer in an independent suspension model? Its definitely not on mine, its no different to a solid axle trailer.
Lowest point is the swing arm, even when fully loaded

Ahh there independent suspension is set up dufferent. Swing arms swing the opposite ways, 90degrees difference

On a solid axle the only way you would get the chassis under the trailer to touch the ground is to bend the axle and splay the wheels out sideways, Regards Frank.

Yes that is correct in theory, but the practice with off road trailers is that they are so far off the ground that you never touch the chassis and the suspension travel is not like an RC car, while on the other hand the axle of a solid axle trailer could drag on a high crown track.
Regards Philip A

Some photos of my old Camp'o'matic suspension.

Attachment 90079

Attachment 90080

Attachment 90081

Regards Philip A

Very solid set up! What puzzles me however is that the (45 deg? or is that parallax error?) angle of the shock absorber mounting means that they do not get to operate very far on their stroke unless there is significant displacement of the axle arm ... which means that their damping effectiveness is somewhat reduced compared to a more vertical arrangement

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.

Originally Posted by PhilipA

Yes that is correct in theory, but the practice with off road trailers is that they are so far off the ground that you never touch the chassis and the suspension travel is not like an RC car, while on the other hand the axle of a solid axle trailer could drag on a high crown track.
Regards Philip A

Very solid set up! What puzzles me however is that the (45 deg? or is that parallax error?) angle of the shock absorber mounting means that they do not get to operate very far on their stroke unless there is significant displacement of the axle arm ... which means that their damping effectiveness is somewhat reduced compared to a more vertical arrangement

Yes AFAIK 1997 was the first time they offered Independent and they were probably still learning. But they work well. I don't recall the trailer has ever skipped on a corrugation.

Later ones have the shocks angled backwards, but they all have some type of angle to them so that the bottom of the suspension is not too far from the floor I guess.
The shocks are F100 I beam front shocks so they are heavily valved anyway. They work very well as I found out when I replaced my old ones which had a damaged foot valve from bottoming even though there are large progressive bumpstops ( after 17 years!). Maybe from when I made about 10-15 metres air once on the way to Kulumburu.

Regards Philip A

I had something similar happen on the PRD towing our home made camper trailer south towards Coen... Despite being briefed by eldest daughter who in those days travelled the route regularly and SIL had even prepared a set of detailed 'track notes' for us, I was paying particular attention and sitting on a steady 75-80km/hr ('tradies' were passing at over 100km/hr...) ...the 'rise and dip' was camouflaged in the afternoon sun...it's not an experience I would willingly repeat...