Along with my BIG Ramps I am planning on building a car trailer. I have been looking at some designs as I drive along the road and have a question about suspension.

Does a car trailer need suspension? some look asif the do not have any?

I am assuming that caravan type "bullit proof" tyres would be used.

[Edited on 26/8/04 by ewanspence]

They do have suspension !!!! It would bounce all over the place other wise.

A lot of new trailers use rubber instead of the old leaf springs. Its built into units, compact and light weight. Cant really describe them, cos i've only seen it briefly.

My old car trailer has leaf springs and that bounces unloaded enough, would be dangeous without suspension.

I've wondered about the use of a peugeot 306 rear beam (or 2) for a car trailer. lookng under mine, it doesn't appear to have a normal coil over or spring location, so I imagine it could be cut in half and securely welded to a ladder frame type trailer design?

Ned.

http://www.alstontrailers.co.uk/ these guys supply the rubax units cheap.


And these guys do the stuff as well. But are not manufacturers. more wholesaler little bit more expensive

Thanks for clearing this up for me, the alton site price list is not available now but when I checked towsure a single unit was around £50 and I don't think that that was braked - or should I say broken )

The cost of units from a new source are relatively high and I prefer the idea of making it from recycled parts. I was even thinking about trailing arms from Sierras (most folks don't use them on the Locost build so they are all going spare and probably free) plus the current wheels on my MegaGrip, which will be replaced with nice shinny alloys at some point would also be recycled.

The other obvious source is 2 dead caravans

Got a couple of Sierra trailing arms if you want - but a caravan is probably better - you get a basic chassis frame too.

Thinking further though - why not try to design a trailer so it doubles as a set of high ramps?

Also - a twin axle caravan would be a great basis - save having to find two identical caravan axles, or cutting and shutting one.

Does the design need to have shock absorbers aswell as springs?

http://www.northerntooluk.com/product/search.asp?action=search&k=suspension&i=&s=&page=2&x=0&h=5&g=4&id=281&catId= 0&subCatId=0&x=0&h=5&g=4

I built a trailer for a neighbour this year. I got the indespension units from here. They do braked ones as well with the reverse lock facility. They were the best price I could find.

Thanks Pete, They are now the cheapest I have seen. But I would need 2 pairs which is £140 + vat. and they don't have brakes.

I was wanting to make this along the lines of a locost and use parts available in scrappies.

I could use 4 front struts or idelly 4 rear hubs with drums as they have hand brakes I could modify.

The more I think about it the more I know they will need shocks or they would bounce down the road like a knackered Allegro.

Remember that any towed object ie trailer with a weight of over 750 kgs MUST be braked by law.

I have been looking at Towing dollys, and most of these are not braked. Probably OK for a Locost, but not for getting your Donor car.

Best Regards

GeoffW

I think a towing dolly is only legal for recovery work rather than general towing. Quite how the difference is determined I don't know.

If you use good old leaf springs, then dampers aren't necessary.

The only thing you have to worry about when making a trailer is the police. Apparently they were handing tickets out at the entrance to some show to some trailer owners.

what cars or vans that are in scrappies in abundance used leaf springs and have front wheel drive so the rear axle is a solid bar.

I think a Fiat Panda used leafs at the back but wouldn't take the load, what about vans?

What is it about these places that I enjoy so much.

I spoke with the owner and he said the current choice for trailer makers is a Volvo 440 rear axle. comes with 40mm sq x 5mm wall shaft between the wheels, drums brakes, springs.

For 2 axles and wheels and springs and a couple of shockers £60 and he's taking them off for me.

Will I need to have both axles braked or will 1 do?

I may use the hydrolics for the brakes, not too sure yet.

Single braked is fine, it's hard to have both braked using a cable braking system. Only have both if your gonna go down the hydraulic brake road.

With cable braking it's possible to get in trouble if all the wheels dont brake the same amount. Slamming the brakes on and having 2 wheels on the same side lock up and the opposite 2 not... can lead to major problems, as you can imagine.

nice and low slung with linkage brackets to front and back and a panhard bracket too. Sorry bout the rubbish pic, I will try to take a better one later.




Sq bar across axle is 50mm sq so could be easily cut and shut if required.

I also obtained a 14ft caravan for free so now have tow hitch, a frame/chassis and lights.

Just need to strengthen it, chop off the old suspensions and make up a subframe for the twin axles.

Might make a small box trailer with the suspension from the van and sell it to recoup some of my expenses.

[Edited on 31/8/04 by ewanspence]

er, how where you thinking of operating the brakes and how about making them not operate when going in reverse ( a requirement of the law now , I believe)

If we can build a car from a pile of steel and an old sierra I am sure a simple problem like that can be overcome. But thanks for bringing this to my attention, I tried to dig out info about the law but couldn't find any.

A simple solenoid pushing over a bar to disable the cabled brakes when reverse is selected would do. Or if I use the hydraulic curcuits a simple electronic valve to stop the hydraulics being activated maybe?

how old is the caravan you got given? if it has got plastic windows it is probably fitted with an alko chassis and you should have all you need there to make a single axled trailer. if you need two axles get another caravan, conecting up the cable brakes should be easy. caravan brakes work on the overrun principal, as you brake, the caravan tries to push you, this pulls the brake cables, applying the brakes on the caravan. when you go backwards the brakes are applied but the reverse rotation of the drums applies pressure to the rear brake shoe which is allowed to collapse and pivot out of way and the brakes do not work!
Also if you use caravan axles etc, they will come with required tags saying what load you can carry, this should keep plod happy. one other thing do not use car tyres on the trailer, they will not stand the weight, use 6 - 8 ply tyres.

you could always source a twin axle caravan for your twin axle Trailer

Best Regards

Geoff

Thanks for all the ideas.

Is the axle weight marking a MUST HAVE or just a nice to have. Can I get a list of requirements somewhere? DVLA or Police.

A 4 wheels caravan would be nice to have but not sure I would get 1 for the same price I got this 14 foot 2 wheeler FREE!! and would the weight rating of a 4 wheeled caravan be enough for a car and trailer weight. I guess a caravan will be around 600-700kg so each axle will only be around 350kg.

I want the trailer to be able to take upto approx 1 ton of car. Would the suspension on a pair of axles from a 2 wheeled caravan be enough for a 1 ton car plus 500kg trailer? I would guess they would be arond 500kg per axle if I got a big caravan.

The beauty of using coil springs is that I can uprate them if I need to for a little expence. I am planning on using a set of new sport springs from a Honda Prelude I have aquired so long as the rest of the trailer is able to take the weight. The sring rating looks about right (can't remember what they are off hand).

an average caravan weighs approx 1300 -1400 kgs total pulled weight. other thing is, what are you going to pull the trailer with. it must weigh more than the trailer and load and you must not exceed the train weight.

I am towing it with a c class merc and the spec'd weight is 1675kg. so I want the trailor to weight around 500-600kg max to leave me 1 ton for a car.

I am amazed a caravan is sooooo heavy.

thanks

its not the caravan, its the cooker,fridge,heater, shower, water heater, kitchen sink etc

Don't wish to urinate on anyone's toes here but i thought it was illegal to use car brakes for a trailer. I think earlier in the post you asked about reference material, about 5 years ago i bought a book from my local indespension dealer for a couple of quid that lists all sort of info.

Amongst other things it lists some basic legal info (weights, lighting, good practice etc.) a catalogue of all their products and also plans for different types of trailer. I'm sure that amongst all this it also states that it is illegal to use car braking mechanisms as they are not type approved.

I'm not advocating using Indespensions products, as one trailer builder put it "we stopped using them when the price went up and the quality went down" but this book is useful as reference material.

Hope this helps

Trailer brakes usually have collapsable shoes so that you can reverse. Car's dont; mmmmm

trailer design will now change. I have checked with plod and the they have given me info to help my trailer build.

What I am going to do is build a couple of small unbraked box trailers, sell them and then use the cash towards my big trailer build.

I have just aquired a twin axle horsebox which should be an ideal base for a twin axle car trailer.

I have also now fitted the removeable towbar to my Merc so there is nothing stopping me storming away with alll of my builds (MegaGrip, 2 box trailers, big ramps and a twin axle car trailer....oh except the pending birth of my first born due on Friday but I do get 1 months holidays as parental leave though

Trailers manufactured after October 1982, which require brakes, must be fitted with a braking system complying with EC Directives. Since 1989 only auto reversing brakes comply.

It is vitally important that the trailer coupling and the trailer brakes are compatible.

If brakes are required they must be fitted on all road wheels. Linings must be Asbestos free.

Trailers manufactured after October 1982 must be fitted with a coupling, which includes a hydraulic damper.

Spring overrun couplings can be fitted as a replacement item on Pre 1982 trailers.

All road going trailers/caravans must have a suspension system fitted between the wheels and the chassis frame except for Agricultural trailers used at speeds of less than 20 MPH and trailers used solely for hauling felled trees.

Tyres must be capable of carrying the gross load of trailer Do not mix Radial and Cross Ply on the trailer

Current legislation on tyre wear applicable to vehicles is also applicable to trailers.

Tyre pressures should be as recommended by the manufacturer. A comprehensive guide is given in the Technical Section.

All radial tyres must be `E` marked.

Retread tyres must comply with BSAU1446 and be so marked.

All trailers/caravans must be fitted with mudguards to catch grit and dirt and reduce spray thrown up by the wheels unless the body of the trailer gives adequate protection.

All trailers and caravans must be fitted with an approved style numberplate bearing the same number as the towing vehicle.

If brakes are fitted they must be in working order. Even on trailers where brakes are not compulsory.

[Edited on 10/9/04 by Terrapin_racing]