Caravan independent suspension - what do you think?

There is an interesting comment here about a Vehicle Components suspension Cruisemaster

It is the second last post on the page. His other post two above it is also worth reading

Splits, did you post that? :-)

Why? Is there something wrong with it?

I found it years ago and remembered the comment about weld quality. Some of the welds in the photos you posted did not look all that good to me.

Hi splits, sorry - poor attempt at humour hence the smiley. Wondered why you remembered it from 2012.

In the photo, The Vehicle Components welds look great to me, but the ones which weld the suspension to the chassis are from the chassis manufacturer and I agree with you they are not as good.

Cheers
Phil

" but the ones which weld the suspension to the chassis are from the chassis manufacturer and I agree with you they are not as good."

They certainly are not as good. I would be doing them again if it was mine. It looks like they were done with a MIG with the welder lying in an awkward position under the van. Some of them appear to have air bubbles in them. That could have been caused by wind blowing the shielding gas away from the weld before it solidified.

I did a lot of welding back in the late 1970s and early 80s for a major structural steel company in Wagga Wagga NSW. One job was relocating some of the supports for a huge water slide for a park beside the river in town. The manufacturer, who was from out of town, put many of them in the wrong position. I spent two days hanging half upside down from a cheery picker about a mile above the ground while I tried to weld them back on with a big diesel powered DC arc welder. Every weld looked about 200 % better than those ones.

There is no excuse for that when the builders are supposed to be professionals.

The same could be said for a lot of suspension designs that you see under vans and trailers.

What is the difference between a washer & a steel shim, also how & why can the washer twist?
I agree that it it is ridiculous to have that much excess thread exposed to be hammered by rocks, I would prefer to see the use of cone nuts & not nylocs in that situation, as vehicle manufactures do!

Agree. Please post the brand

If you been under another similar unit might have been a Friday or early Monday job read between the lines.

Either way what you have there isn't right or sound looking at welds.

number of threads exposed is excessive this indicates a smaller length bolt in theory should have been used -might have been a engineering decision to use this length but doubt it

i have similar issue with shank on my tregg hitch has a long thread so two nuts fit onto it perfectly prefer it was shorter but way its manufactured to accommodate various hitch thicknesses

cone nuts relatively new item to me,only recently used one for a alko swivel jockey wheel always used nylocks as a single use item -called evolution as with everything

One reason for a longer bolt might be to get sufficient shank for the wearing surface of the bush to work on, instead of working on the threaded part of a shorter bolt. In which case excessive thread should have been cut off.

I was thinking the same Frank, a parallel shank for support, the whole thing is dodgy really. That suspension assembly has been on something else before that van for sure. Michael

I'd agree with everything, except for the MC2 suspension by Track Trailer as used on the Tvan and Topaz - but that's offroad suspension. Designed by an Engineer, the late Alan Mawson.
I'm guessing we could get you going next with caravan wheel bearings and then caravan brakes!!!

" People need to understand and know from the very start, that, trailer suspensions are rough, crude and pretty much made to no standard whatsoever .."

Very true Bantam. Look at the trailing arm suspension under many vans for example. The mounting bushes for the arms are usually mounted in a straight line across the chassis and the arms slope down from the chassis. This means the wheels lean over with the van as it leans. There is also no axle steering assistance coming from this design and the tyre contact patch is being reduced.

Many cars have used the semi trailing arm design but that has been replaced by even better designs on many cars. The centre drawing at the top of this page explains how it works.axle steer

Then we have beam axles. A loaded spring should look like this
It will be flat and the front eye will be down low while the rear eye is much higher. The axle is moving up and down in an arc around the front eye of the spring. As the car leans into a corner the spring will compress even further while the one on the other side will have weight taken of fit. If you follow the path of the wheels it is easy to see that the whole axle is being skewed around in the direction the car is turning.

Now compare the path taken by a much shorter high cambered leaf spring like you see under caravans and trailers with the front and rear mounting points at the same height under a flat chassis. The axle can only be turned in the opposite direction to a car.

This means a swinging van can lean to the right for example and the axle is going to steer it further to the right. The pig trailer design of caravans is unstable enough as it is without that happening.

Does anyone know how you mane photos bigger?

Or the MS suspension on the Vista RV Crossover.
Also designed by Alan Mawson, it is pretty much a refined version of his MC2 but with an extra link to eliminate the bump steer.

Oh hell PhillG ..... don't get me started about caravan wheel bearings, axles and brakes

So much of the problems with caravan trailers and suspension is that most of them continue to try to construct a suspension on a straight beam with little or no attention to the attitude of the spring and it's attachments.

So we have leaf springs that are too stiff, have poor articulation and short travel ...... but worse ... yes the whole of the travel is below the front spring attachment.

when coil spring independent is attempted it suffers the same problems but worse ...... very short trailing links with a savage arc, springs with rediculous attitudes ...... little or no improvement in travel or articulation ... still with overly stiff spring rates.
AND as has been mentioned bad tuck under positive camber on compression.

Sorry I have not seen one single independent suspension on a trailer that even comes close to what would be considered adequate or even competent on a passenger vehicle, commercial vehicle or truck.

When someone shows me a properly camber corrected, long trailing link suspension with a low front pivot point OR a dual wishbone suspension OR a crossover or center pivot axle independent suspension ..... all of which are viable in some form .... I may change my mind.

but in the mean time the easiest, competent suspension is to take the components from a leaf spring sprung vehicle with a similar rear axle loading to the trailer.
Install the springs in the same attitude as the donor vehicle and use the shock absorbers that belong with those springs.

cheers