Thread: Car trailer thoughts?

Firstly, Welome aboard Dan.

Couple of comments.
Loose half the centre cross rails. They're just adding unnecessary weight without gaining you much.
Use 100 x 50 x 3mm for the drawbar. Mark a point 1500mm forward of the front cross rail, that's where the two pieces touch, and run them all the way back to the front hangers.
The 'T'bar in the middle of the drawbar triangle is also not required. You can run the cross rail to mount the winch post.

Attachment 187158

Thanks Yonnee, I did another redesign earlier this arvo. And I did remove about half of the centre braces.
I'm not quite finished and have drawn it more to scale and on A3 so it's not all crammed together.
I'll do a metal list tomorrow and see how much that's going to cost

Cheers
Dan

Gordo,

I'm also looking at car trailers as my project is now drivable but needs lots of trips for the engineers to sign off on it.

Would it be possible for you to post what you ended up with?

From the looks of it you have it 2600mm wide which is about max width.

I figure no point re-inventing the wheel.

I really like single drawbar. Easier to swing into tight places.

Originally Posted by zuffen

Gordo,

I'm also looking at car trailers as my project is now drivable but needs lots of trips for the engineers to sign off on it.

Would it be possible for you to post what you ended up with?

From the looks of it you have it 2600mm wide which is about max width.

I figure no point re-inventing the wheel.

Nothing further on my end of things, just moved house and have no shed at the moment...

2500 is the maximum width,

2500-3500 needs signs and lights!

Cheers
Pulse

I just re-checked Gordo's "blueprint" and I'd added the width of the chassis rails on the outside when he's actually included them in the 300mm outer dimension.

This makes it 2500mm.

If it's for a Mini and light cars, I'd go with a heavy duty single axle. Will save a lot of money and work, plus be much more friendly to move around in tight spaces (both when towed and hand pushed). Axles that will handle 1500kg single are readily available and a small car plus trailer will come in under that.
I agree that the cross bars are overkill, I'd just put in barely enough to do the job. Expanded mesh will support a car as it is rolled on to a trailer, just put cross braces under where the wheels will sit, to take road loads and stop the floor buckling.
A Mini weighs, what, 750kg? That's only say 250kg on each front wheel and 100kg on each rear.
Having said all that though, price everything up CAREFULLY. A brand new car trailer is only $3500, you'll easily go $2k in materials if you buy new, then there's engineering, rego etc. So consider whether the savings are worth the effort.

While I agree that a single axle trailer is easier to manoeuvre in tight spots, it is extremely critical where the load is placed when loading a car onto a single axled trailer. Too far forward and you exceed the towbar ball weight rating. Too far back and the trailer will want to swap ends with you at highway speeds, usually with frightening and horrific consequences. If you're building a car trailer for one specific car, then you can spend the time in your initial setup placing wheel chocks to allow you to place the car in the same place every time. But a car trailer that can take a variety of small cars, a tandem slipper is a far safer and more forgiving option.

As for a $3500 car trailer, I'd put them in the same league as a $500 6x4 box trailer. Similar quality with similar longevity. I'd happily spend $2-3K on materials building my own, knowing I had a far superior trailer.

If you think a dual axle trailer is more forgiving of load positioning, you're wrong. A dual axle trailer will still have higher tongue weights if incorrectly loaded, with a side benefit of a higher load on one axle than the other. And as an added bonus, if one axle on a dual axle carries a lot more weight, it'll tramline and make things even more scary than a single axle trailer.
How would you know you had a far superior trailer if you built your own? Are you a mechanical engineer? For sure, you'd have a far heavier trailer if you built your own....good engineering and desugn removes unwanted weight, which increases payload.
I wish I had a dollar for every home made car trailer "with all the great ideas mate!' that has been over the weighbridge and punished it at 1200+kgs, as compared to a 750kg commercial trailer.
There are two easy ways to make a home made trailer last forever, get it designed by a professional, and have it hot dip galvanised.

Firstly, a tandem non-load sharing suspensioned trailer is more forgiving of load position than either a single axle or a tandem rocker. Every bit of load forward or rearward of centre is directly transfered to or from the tow vehicles towbar on both single axle and tandem rocker suspensions, and the further from centre this load is, the more impact it has on tongue weight. A non-load sharing suspension allows one axle to carry more weight, reducing the transfer of weight to the tow vehicle. If the trailer is correctly setup, ie, correctly wheel aligned, then it virtually eliminates the "tram tracking" experienced by some multi-axled trailers.

Secondly, having been in the Trailer & Caravan Industry for over a decade, working for the two of the biggest under carriage manufacturers in Australia, running their repair workshops, and being one of a handful of Caravan Industry Roadworthy testers, I think I can safely say I'd build a fairly decent trailer for myself. The handful of car trailers I've built for other people, and that are still going strong after 10+ years on the road can probably attest to that too.

The Trailer Industry around Australia is quite competetive, and therefore you will find very few that have a Mechanical Engineer on staff. Most just copy what everyone else has done in the past and that has been accepted as the "Industry Standard" by the registering authorities. The cheaper ones usually scrimp on material sizes and purchase Chinese sourced rubbish for their components. They're given a stack of number plates and forms by the registering authorities and the rubbish that is put on the road defies belief.