help choosing trailer for diy camper

There is nothing wrong with your idea. I have built a few multi purpose trailers over the years and one was for camping. It was not like the one you have described though.

Leaf and independent suspensions can both work well but very few of either one that you see under caravans or trailers have been designed properly. It has been well known for about 100 years that vans and trailers have many problems with axle ends shearing off, broken wheel studs, failed wheel bearings and wheels falling off but the cars towing them don’t. It all comes down to design.

You can get some idea of one of the problems in the two posts by Robi on this page. spring rates Hard trailer springs can be fine on good roads because the trailer can pivot freely on its single coupling as wheels move up and down over minor undulations in the road. If you tow them over rough roads though, they can shake the trailer and its contents to pieces. There are plenty of reports on the net of caravans being shaken around with a lot of damage inside.

Trailing arm suspensions in trailers are not designed like cars. They all look like backyard jobs to me but they do look impressive and no doubt appeal to many buyers. This brief description at the top of this page looks at the trailing arm and the semi trailing arm design.trailing arm design I have never seen a car with the trailing arm type but trailers and vans use it. Cars are all semi trailing but that type goes back a few years now and may not be in use any more.

This link explains how the semi trailing design should work.roll steer The centre drawing is how it should be but every trailing arm suspension that I have seen under trailers has been pivoting off a flat chassis and hanging down like the third drawing.

I currently have an 8 x 6 single axle trailer with the rear springs and shocks from a 2004 Hilux 4x4 single cab under it. They are extremely soft making the shocks essential. It tows beautifully and I doubt if it could possibly shake anything to pieces.

This bloke heretrailer plans has a similar set up but he is using Jeep rear springs. Note how the front mounting point is down low and the rear up much higher. My springs are also set up like that. All cars are designed like that to induce a degree of rear wheel steering under load in corners. These two posts, also from Robi, explains it briefly.leaf springs

In your case I would be using a good quality beam axle with ute springs and shocks. If you can find a good hollow axle then so much the better. That will remove a lot of unsprung weight. All of those beam axles under the front of American cars like Ford, Chev etc in the 1930s weighed around 10 to 12 kilos. Unfortunately solid trailer axles are over triple that. All of the big trailing arms under trailers are not much better.

Unless you are going to put a staggering amount of weight into it, you should not need two axles. I have never towed a short dual axle trailer but I have read a few reports that say they are not very nice to tow.

Try and mount the shocks as vertical as possible like cars. The way that Jeep sprung trailer is set up is wrong which is why he had to use four of them to successfully dampen the spring oscillations.

Do not be fooled into thinking those rebound springs are as good as shocks. Trying to create a bit of friction on rebound by clamping the leaves together is no substitute for a good hydraulic shock. Car manufacturers gave up on friction shocks in the 1920s.

You should not need a huge ball weight for something that short. Nothing in it is all that far in front of or behind the axle so it should not swing around of pitch up and down. Keep as much of the heavy items as close to the axle as possible.

The old 10% of total weight on the tow ball rule has been proven to be inaccurate many times. I had my trailer loaded to just over 1000 kg recently on a trip from Sydney to Tumut and it had 48 kg on the ball. It has 38 empty and does not bounce around.

This link goes into the dynamics of caravans but it could be applied to trailers as well.dynamics Note what it says about car rear suspensions and tyre slip angles. Don't start altering factory designs unless you know exactly what you are doing.

Yep...
Independent suspension on a trailer is a waste of money.

Single axle with 'ample capacity'.
Decent size and quality bearings and especially seals on high quality surfaces.
Wheels and tyres identical to the tug.
Identical wheel track to the tug.
Leaf springs of good length and travel.
Decent hangers and pins that are properly located (not splined) and lubricated.
Quality shock absorbers.
Mechanical override disc brakes.
An off road articulating hitch.
An extended draw bar to allow maximum jack knife ability.
GTM 1999kg.

Cheers,
Peter
OKA196 Motorhome

hi shmick
It is important that the axle assembly is well over rated
Refer to Vehicle Components for your application
To get around trailer short commings
eg 12 inch electric brakes 50 or 60mm axle big bearings etc
The combo allows you to fit any wheel size
The larger brakes will also last a long time

The larger the diameter the wheel the lesser the load carrying on say your typical falcon bearings . [derating occurs ]
235/75/15 are common and not a huge diameter wheel

Rate the springs just above tare weight say eg an additional 400kgs . This allows for luggage food water etc etc and still have supple spring pack
Rating the springs excessively will cause a very rigid ride


swampy