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  1. #1
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    Default Draw bar lengths and attachment

    Anyone got some photos of drawbar attachment methods?? I am to that stage on my tandem trailer build and am doing a bit of umming and arring.

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

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    Quote Originally Posted by zuffen View Post
    follow this link http://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.
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    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??

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    Quote Originally Posted by bundydog View Post
    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...)
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    Quote Originally Posted by Yonnee View Post
    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

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    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.
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    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.

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    Quote 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.
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    Hi Yonnee
    Could you possibly put up a couple of pics showing what you do for attaching the drawbar to trailers over 2000kg?
    I have one that was welded across the top of the drawbar and of course, it cracked. I am now looking at replacing the drawbar or "plating" the side to repair it.
    Your assistance would be greatly appreciated.
    Thanks
    Ash

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    Hi Ash.
    Once the drawbar has a crack in it, depending on your experience, you'd be better replacing rather than plating, unless you can grind the crack completely out, repair, then plate.

    For trailers over 2000Kg, the attachment to the frame is pretty much the same as all other trailers, it just that the size of the drawbar material gets bigger as the trailer size increases.
    For something around the 2500Kg mark, I'd recommend a 100 x 50 x 3.0mm RHS, and anything up to the 3500Kg capacity I'd then go 100 x 50 x 4.0mm.
    Always attach the spring end of the drawbar to the spring hanger.
    At each contact point with any of the cross rails forward of this, weld both sides of the drawbar to each cross rail ALONG the drawbar (front to rear). I cannot stress this enough.
    I haven't got a picture handy, but I'll try and find something.
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    Hi Yonnee
    Thanks for the advice. I think I will replace the draw bar to be on the safe side. I also have a gap of about 100mm between the end of the drawbar and the spring hanger.
    I can address this with the new drawbar too.
    Do you leave the ends of the drawbar "open" i.e. not sealed with caps?

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    Correct, a new Drawbar will allow you to attach it to the spring hangers. Numerous trailer manufacturers leave this gap as it saves them steel, 100mm per side on every trailer you build adds up to quite a lot of steel in a year. The other reason can be cutting length. You can get Four 2M lengths out of an 8M RHS length and you need minimum of 1.2 out from the front cross rail, so if the other 800mm doesn't reach the front hanger, it can't attach to it, so they don't.
    For yours, generally you'll have to buy an 8M length, so you can make the Drawbar as long as you like, and still attach it to the front hangers. I've always preferred to have a 5ft Drawbar on any trailer I either manufacture or have changed the Drawbar out on.
    Mostly I leave them open so as to not trap water, dirt etc., and it's quicker. But it can be a personal preference. Some Motorbike trailers I've done I've capped front end leaving a 10mm gap at the bottom as it does look a little neater. Plus it's heaps easier to run the wiring cable straight down through the Drawbar without it capped. If you want to be a bit more finicky, you can drill a hole in the front end cap for a wiring grommet.
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    Hi Yonnee
    Thanks for the tips. I will go for a 100 x 50 x 4mm drawbar the same length as what I had. It worked well (until it cracked that is)
    I'll leave it open too.
    Just to confirm, I should put four gussets on the drawbar where the first cross rail comes across?
    Thanks again.
    Ash

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    Yes, correct.
    And the gussets run along the cross rail and down the drawbar.
    The picture above Legion put up shows a gusset running down the cross bar and along the drawbar, which will only stiffen the join, not allowing it to flex, and causing it to start cracking in the future.

    Any chance of a picture of yours where it's cracked?
    It's always good to know the reason for the problem so that you know you're fixing it, rather than making the same mistakes as the original manufacturer.
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