Thread: Car trailer build- brains trust help?

I'm planning on building a car trailer out of a caravan chassis I already have. (see pics) The main part of the frame (minus the outrigger bits which I'll remove) is 4470 x 1750. There's four longitudinal bearers(?) at 100 x 50 x 2 and the drawbar is 100 x 50 x 3. The drawbar A frame runs under the main frame and has a pair of stiffeners which run under the two centre bearers. In between the bearers are inverted channels at roughly 400 centres, 60 x 30 x 2. I plan on decking it with 17mm form ply. I have a box trailer that I built over ten years ago which still has its original 15mm exterior ply floor, despite heavy use and never being under cover. I think the frame will be adequate, especially since I'll probably only use it once a fortnight for only part of the year, but I'm open to suggestions.

Currently there is a single axle, or rather a pair of independently sprung control arms with holden bearings and HT hubs complete with electric brakes. I recently bought a pair of portable traffic light trailers ($190, ebay ) which came with 40mm square axles, 4 leaf slipper springs, new mudguards and electric brakes on each wheel. Now the axles aren't long enough, but I'm planning on buying a pair of new ones at the appropriate size.

I've agonised over this for some time, and the tradesman, do it once, do it well part of me is inclined to go for 45mm axles with new hub/drums to suit, plus heavier springs. Thing is, money is very tight at the moment with so little work around here that I've even been contemplating travelling down to Brissie for work. The trailer will be used to transport my car to race and rally events so it will never make me any money and will not see that much use. The whole car racing game is something I can't really afford or justify too much expenditure on at the moment, hence my budget approach.

I think from what I've read, that a pair of 40mm axles, each braked, will give me a ATM of 2000kg, which possibly is a bit on the light side for a car trailer. It's probably more than adequate for my current 780kg Barina (hell, I've carted over 1000kg of besser blocks in my single axle box trailer) but I'd like more capacity in case I get a better/heavier car in the future.

Questions:
Will this be adequate for a infrequently used car trailer?
How much would the trailer weigh? (ply on top will weigh around 120kg)
I know it sounds crazy, and would probably look weird, but should I make it a triax trailer, using the existing independent set up, along with my two slipper springed axles? I know it would be an absolute pig to maneuver, but most places I would use it would be dirt.

Input and suggestions appreciated

Mick

Anyone?

Mick

Well it's been almost a week now with no replies. Don't know if what I'm a asking is too difficult/simple/stupid or what, but I would appreciate some feedback/input. Am I doing something wrong? Do I need to change my deodorant? Breath freshener?

Mick

Ok, if it was sitting in my backyard and I had the need for a car trailer, this is what I would do.

Using that chassis the way it is, I would build an exo-skeleton frame and turn it into an enclosed motorbike/gokart transporter/workshop.

The sale of this trailer would more than fund all new parts to make a new car trailer.

My main reason for suggesting this is that to setup the suspension properly would require removing that existing suspension (which is Melbourne Trailers Independent Suspension by the way) and setting up a tandem suspension. You could get another single axle setup the same as what's there and turn it into a tandem, but I'd have to get some more detail on that one to tell you what capacity it is. (there's a light series and a heavy series) And as good as they are, they're a little dearer than a standard leaf spring & axle setup.

Hi Mick, didn't see it before this. You can do away with the suspension alltogether if you want. A lot of car floats don't have any because the suspension on the car (on the trailer) takes it up. Check them out many don't have any springs.

Whats happening with rego dare I ask?

Originally Posted by Yonnee

.........My main reason for suggesting this is that to setup the suspension properly would require removing that existing suspension (which is Melbourne Trailers Independent Suspension by the way) and setting up a tandem suspension.............

That's my plan. I have two lots of springs, electric brakes, wheels, and mudguards. I figure all I need to buy is a pair of axles at the appropriate length. Just need feedback to tell me if what I have (see original post) will be okay.

Mick

Originally Posted by Claw Hama

Hi Mick, didn't see it before this. You can do away with the suspension alltogether if you want. A lot of car floats don't have any because the suspension on the car (on the trailer) takes it up. Check them out many don't have any springs.

Whats happening with rego dare I ask?

I'd rather have suspension as I assume not having any would tend to stress everything else more. The roads up here aren't all that good either. Rego shouldn't be a problem, I've rego'ed a home built trailer before. I'll present it as a newly built trailer, rather than a modified caravan.

Mick

Is the Barina the race car or the tow car?

Originally Posted by surfin

Is the Barina the race car or the tow car?

It's the "race" car, such as it is. Tow vehicle is a diesel 4wd Rodeo ute.

Mick

Originally Posted by journeyman Mick

Just need feedback to tell me if what I have (see original post) will be okay.

Mick

Fair enough. The chassis will be fine... all-be-it on the heavy side. Car carriers are usually alot simpler than that, and therefore lighter.

I was dangling a different carrot by suggesting that rather than putting a heap of time into tearing half that chassis apart to turn it into something else, use that effort in building on what's there, and the funds from it's sale would allow you build a car trailer from scratch with rocker suspension and 45mm axles.

Originally Posted by Yonnee

..........I was dangling a different carrot by suggesting that rather than putting a heap of time into tearing half that chassis apart to turn it into something else, use that effort in building on what's there, and the funds from it's sale would allow you build a car trailer from scratch with rocker suspension and 45mm axles.

Thanks, yeah,I got that, but money is very tight in this region at the moment, so selling a trailer for carting toys is not a great proposition. The current suspension set up is mounted on an angle frame which has about half a dozen welds holding it in place. I was just going to remove the whole frame, which shouldn't be too much trouble. I hadn't planned on touching the rest of the frame.

Mick

Mick

Depending on how much you "prune" the chassis, how much strengthening you put in the sides, spare wheel, ramps etc, I would suggest it will weigh around 700kg possibly more. Tyres may be your limiting factor, but you can use light truck tyres if you want a little extra capacity.

As you have electric brakes you are allowed over 2T aggregate weight. 3T is probably practical as the towball is a standard rating. As you go up in weight rating really you have to make sure everything elase is compatible. Springs for example.

2T is easily enough your Barina and probably most race cars which themselves are stripped down for lightness. However even a road going falcon or commodore would go over the 2T mark if my estimate of the trailer weight is in the right ballpark.

I made a single axle 3.6m trailer, albeit with 16" wheels and huge drum brakes and it weighed 500kg without the spare wheel, plywood floor, tailgate and front gate all of which I added later. It was about 600kg all up.

Regards
Paul

Thanks for that, I did some sums and worked out that the chassis itself, without springs etc should weigh less than 200kg. Ply top should weigh around 100kg. Axles, springs, wheels, guards etc will be the killer for weight. I'm not planning on any sides, I figure the chassis should be stiff enough as is. I'll just weld on tie rails.

Mick

Originally Posted by Bushmiller

As you have electric brakes you are allowed over 2T aggregate weight.

I'm going to clarify this by adding that the trailer can be registered to Gross over 2000Kg provided the trailer has breakaway fitted, and brakes on all wheels.

Originally Posted by Yonnee

I'm going to clarify this by adding that the trailer can be registered to Gross over 2000Kg provided the trailer has breakaway fitted, and brakes on all wheels.

I've got electric brakes for both axles, but my limiting factor is the axles. Two composite axles on slipper springs = 1830kg.

I gather that when you have two axles on slipper springs you subtract one third the capacity of one axle from the capacity. What about 3 axles, how does that work?

I've got the Melbourne trailers indepependant set up, it's either got LM or composite bearings in it. I could, at no extra cost, have a triaxle set up. It would be a bit of a hybrid, but if I fitted a breakaway unit I'd get more than 2000kg capacity. It wouldn't be pretty and tight turns on bitumen would be a pain (but could mostly be avoided). But I would have a trailer that I wouldn't soon grow out of and which would have ample carrying capacity.

I could even chain one (or more) axle up if running lightly loaded or unloaded.

Mick