Thread: Draw bar lengths and attachment

Follow this link https://www.woodworkforums.com/f184/t...ng-haul-64389/ and the advice contained in it.

Originally Posted by zuffen

follow this link https://www.woodworkforums.com/f184/t...ng-haul-64389/ and the advice contained in it.

And no, it's not quite finished yet...


But the basic points are;
If possible, attach the end of the drawbar to the front spring hanger.
Where the drawbar crosses the front cross rail, DO NOT weld across the grain of the drawbar.

Thanks for the advice, the whole "flex" thing is a new concept to me, can see how it would work though. Have seen heaps of trailers lately with the drawbar welded on "across the grain." Another question I would like some help with, my rear axle is about 40 mm longer then my frount, so therefore the rear tyres are about 20mm wider either side, can you see any long term problems with this or with rego??

Originally Posted by bundydog

Thanks for the advice, the whole "flex" thing is a new concept to me, can see how it would work though. Have seen heaps of trailers lately with the drawbar welded on "across the grain."

Generally by people who don't know any better. Then again, it's not hard to rent a factory, hire a MIG welder, set up a flash website, and call yourself a trailer manufacturer. No qualifications required...

Another question I would like some help with, my rear axle is about 40 mm longer then my frount, so therefore the rear tyres are about 20mm wider either side, can you see any long term problems with this or with rego??

Is it the axles that are different, or different wheels? There was a situation a while ago that one brand of 9" Hydraulic drum had a different offset from the wheel face to bearing journals, and mostly the solution was to make the lazy axle a different length to the braked one. Fast forward 10 years, and people convert these braked axles to Electric brakes, and find they've got two different length axles.
Alternatively, if you have an old trailer with early Holden stud pattern, then a HK wheel and a HT/HG wheel have two different offsets...
As for dramas leaving it the way it is, none... As long as the tyre don't stick out the guards, then it shouldn't effect rego. (I say "shouldn't", because every Roads Authority officer in every state has their own ideas and interpretations of the regulations, if they've even read them at all, so sometimes you get one who's had a bad day...)

Originally Posted by Yonnee

Where the drawbar crosses the front cross rail, DO NOT weld across the grain of the drawbar.

Yonnee, this is one piece of advice that I've gained from this forum that sticks in my mind. The time has come for me to build a trailer so I've been thinking about various trailer related things a bit more lately. In your seminal thread I noticed that you put a vertical gusset that is welded down the vertical of the drawbar. I appreciate this will be way less likely to cause failure than welding across the grain but why do you not instead weld a gusset along the top of the drawbar, maybe in its centre, or along the side of it? Sort of like this expert drawing:

drawbar_gusset.jpg

The gusset along the cross rail and vertically down the drawbar still allows the drawbar to flex, whereas the gusset you've proposed will triangulate the join, making it more rigid than just welding it across the drawbar.

Thanks Yonnee. If that's the case, do you actually weld the chassis lengthwise along the drawbar at all? It looks like it in your old thread but I can't quite make it out. E.g. I'm planning on 50 x 50 x 2.5mm chassis cross rail, so I was planning on welding lengthwise the full 50mm where the drawbar meets the cross rail.

Originally Posted by Legion

If that's the case, do you actually weld the chassis lengthwise along the drawbar at all?

Yep.

For a light trailer (one not requiring brakes) welding along the drawbar at each point it passes a cross rail is all that's required. Once you have a trailer requiring brakes, that's when I like to add the extra gusset, and trailers over 2000Kg capacity, I put a gusset on both sides of the drawbar (4 gussets in all). For all trailers I also recommend attaching the rear end of the drawbar to the front spring hanger so that all the pulling effort is straight on the springs, not via the chassis.