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  1. #1
    Join Date
    Jul 2006
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    QLD
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    56
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    Default Telescopic extension to Trailer drawbar

    Hi All, I need to extend my 7x4 Box trailer drawbar by around 1000mm. This is to allow me to carry a long Kayak on the trailer. As I only need the long drawbar when the Kayak in on the trailer I am going to make the drawbar telescopic.

    The current drawbar is 75x50x3mm RHS that extends from the centre of the trailer to the coupling. So What I am looking at is getting a length of RHS that will side inside the current drawbar and use some pins (like the ones that hold my Hayman Reece towbar in) so I can extend the drawbar out and lock it in place.

    Anyone see any major problems?

  2. #2
    Yonnee's Avatar
    Yonnee is offline Trailer Bloke & Mild Mannered Moderator
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    May 2007
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    Tooradin, Vic.
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    Default

    Only in finding a length of RHS that measures 67 x 42.
    65 x 35 wil be about the closest you'll get, and that will be a pretty sloppy fit inside the current bar.

    The only other issue will be a legal one, and the interpretation of ADR 62/01 Clause 14.1 "The ‘Drawbar’ must be securely attached to a substantial portion of the trailer." and whether a couple of pins are enough to convince the authorities that it's 'securely attached'. Also, if the trailer is registered, the RTA will have it on record the overall length of the trailer. All this only really comes to a head if the trailer is involved in an accident and questions are asked as to the integrity of the trailer.
    Too many projects, so little time, even less money!
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  3. #3
    Join Date
    Jul 2006
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    Default

    That's a bugger about not getting something that will slide in the current drawbar.

    I just had a chat to my mate who is in the steel business, and he reckons to cut the drawbar out replace it with 65x65x5mm one and then have 55x55x5mm for the extension. He will do mates rates for me which is good.

  4. #4
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    Other options I have used are to weld strips of flat of the right thickness to two sides of the insert - the other is to cut two angles to the right width and weld them together into a rectangle.

    Joe

  5. #5
    Join Date
    Nov 2004
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    Millmerran,QLD
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    JohnH

    I think I would be looking at cutting off the existing drawbar and using that to slide inside a larger section RHS. I appreciate that there is probably not a lot of weight in the Kayak, btu there would be a lot of bending moment in a bar that is probably 1.8m long. Doing it that way you would not have to refit the coupling either.

    If neccessary go with jhovel's suggestion of some suitable flat bar welded to the old drawbar to bring it up to the internal dimensions of your new drawbar. One problem I have had in telescoping steel sections is that there is normally a seam internally which tends to get in the way.

    If two pieces of flat bar are welded in either side of the seam that problem is also removed and a reasonably snug fit could be achieved. It is also possible to get seamless pipe, but that may only be in pipe not RHS.

    Regards
    Paul
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

  6. #6
    Join Date
    May 2009
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    Hobart
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    Default

    John H,

    I urge you to take note of Yonnee's advice re ADR compliance and you should check out your proposed modification with your local motor registry authority.

    If you are involved in an accident and your lengthened trailer is implicated, you may find yourself with an insurance company that declines to support you, or even worse if there are public liability issues.

    Your choice, just be mindful of the advice.

    Cheers, Cameron.

  7. #7
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    you must be able to do it legally because you can get boat trailers that have it
    ....................................................................

  8. #8
    Join Date
    May 2009
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    Hobart
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    Default

    Quote Originally Posted by Harry72 View Post
    you must be able to do it legally because you can get boat trailers that have it
    Yes, but for launching and retireving on a boat ramp.

    On the highway? I doubt it.

    Cheers, Cameron.

  9. #9
    Join Date
    May 2011
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    Murray Bridge S Aust.
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    Default

    Hi,
    I've done a couple of setups like you are looking for, it was behind Pajeros, so that they could open the back door with out unhooking the trailer which had a tinny on it. Re 55X55X5 there is no such size, 65X65X6 on the outside and 50X50X5 as a slider which is basically the same as "Hayman Reece" type towbars, there is about 3mm slop inside which is why towbars have the antirattle bolt fitted. If this size is not satisfactory then use what ever size you are comfortable with, the slack can be taken up by welding thin plates on the inside of the outer RHS at the front, and at the rear of the inner RHS. You are better to over engineer something than under. If there is a seam it is only a matter of grinding a V on the plate where the seam is. I personally would NOT weld a flat bar along the the side/bottom as it will bend, warp or twist if not all of the previous, making it extremely difficult to move either in or out.
    Another thing I would do is to find/wrap a strap around the outside of the outer RHS as per a towbar, to give extra support MINIMUM of 6MMX40MM.
    Hope this helps
    Kryn

  10. #10
    smidsy is offline 21 with 19 years experience
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    Default

    John,
    Have you thought putting carry bars on the trailer, as if you were going to carry timber or steel.
    Depending on what car you have you might be able to make them high enough that the canoe can sit over the tow car which would negate the need to lengthen the draw bar.

    Cheers
    Paul

  11. #11
    Join Date
    Nov 2011
    Location
    Canberra
    Posts
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    Default

    Hi
    I have done exactly what you propose to do for exactly the same reason and it has worked beautifully for over a decade. I don't know about the legality, but my trailer went over the pits recently here in the ACT and it wasn't even mentioned.

    Matt

  12. #12
    Join Date
    Oct 2012
    Location
    Perth
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    3

    Default Hi John

    I'm keen to see how this project turned out for you. I'm looking at doing the exact same thing, extending the drawbar on my 7x4 so that I can carry a kayak. If you have advice, pics etc please post.
    thanks

  13. #13
    Join Date
    Nov 2010
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    not quite Adelaide
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    Default

    hey , thats exactly what I had in mind as well, please put up some shots, I'd like to know how it went before I take the angle grinder to my trailer..
    cheers
    Matt

  14. #14
    Join Date
    Oct 2012
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    Perth
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    Default

    Quote Originally Posted by surfmat View Post
    hey , thats exactly what I had in mind as well, please put up some shots, I'd like to know how it went before I take the angle grinder to my trailer..
    cheers
    Matt
    Me too, I'm tempted to take the angle grinder to the A-frame this weekend but would hate to regret it

  15. #15
    Join Date
    Oct 2012
    Location
    Perth
    Posts
    3

    Default I've done it

    Okay, I took the plunge and converted my 7x4 box trailer to telescopic drawbar.

    I used:
    100 x 100 x 3mm for the fixed section (1300)
    90 x 90 x 3mm for the telescopic section (2000)

    The telescopic section will be pinned with two 16mm high tensile steel bolts (130mm) and nuts. The bolts have holes drilled on the end of the threaded section with R clips to prevent the bolts from falling off....should they come lose When in fully retracted mode the trailer is not much longer than it was before the mod.
    Attached Images Attached Images

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