Extension to towbar - Page 2





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  1. #21
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    Default Re: Extension to towbar

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  2. #22
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    Default Re: Extension to towbar

    It is for bicycles.
    '150MM TOW BALL EXTENSION

    150mm Tow ball extension fits both 50mm and 1 7/8.
    Used for bike racks to clear past rear wheels on 4WD vehicles and comes with a 1 7/8 tow ball attached

    Not Suitable for Towing

    https://www.hamco.co.nz/product/150m...all-extension/

  3. #23
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    Default Re: Extension to towbar

    Tow ball extensions make a huge difference in the forces in the vehicle and towbar structure for the same ball downforce.
    Tow bar and vehicle manufacturers do design and approval testing with standard tow ball position.
    While you are not likely to get a fine in South Africa, it is not good practice to extend tow ball position.
    If you absolutely have to fit something like this, you have to reduce the maximum tow ball downforce to protect vehicle and towbar structure long term.
    New max downforce = Old max downforce X (original lever arm from ball to mounting / New lever arm from ball to mounting)
    (max ball load / downforce is sometimes listed on towbar and normally in owners guide)
    A smaller downforce will affect trailer stability, so all in all not a good thing...

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  5. #24
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    Default Re: Extension to towbar

    Quote Originally Posted by Klaas Vakie View Post
    Dear Rustic. Thx
    Your extension and its design is not under discussion. It look sturdy in fact Mike Oscar Echo Romeo Siera Echo strong and will tow the Queen Mary II would she is be on wheels

    The contraption on my photos is not the same.

    Stay safe and in your shoes!
    All extensions need careful thought before using them, and I don't like them at all. Having said that, I don't think the original extension to be much weaker (if it is) to the "solid" extension discussed in this post. I'd be okay with the original extension on a forged towball as is the original picture, but would loose confidence if this were attached to a bolt down type towball as fitted on the end of this extension. Consider that with the forces in the bolt on type lever off the distance between the bolt position and the bottom of the bracket - so maybe 30 mm if the bracket is a 60 mm high bracket. In the "solid" instance the bolts are under tension and the bottom of the bracket under compression. In the first instance, the entire tube is under tension with it's contact point half way up the ball. The two fixing bolts are under compression and offset a similar amount. I don't think there is much difference in strength between these two.

    Maybe one of the cleverer members can put this into a proper calculation?

  6. #25
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    Angry Re: Extension to towbar

    Quote Originally Posted by Klaas Vakie View Post
    An modification to a standard towbar to increase the ball distance from the vehicle. Probable reason being due to a spare wheel attached to the back door of SUV.I saw it yesterday on a well known beautiful new vehicle. No number plates yet. I covered the dealers IDCan anybody clarify this modification's safety. Two bolts are used on a 45 degree angle to fix the extension to the existing ball .There is no manufacturers label or ID plate on the black extension. The new ball shows 3500 lbs and 50 mm.If this extension is for a bicycle rack, so be it. But I would keep a vigilant eye on those two bolts.If it is for pulling a 3500 lbs (MAX) trailer I am asking:1. How great is the leverage (in all directions)that the extension has on the standard (manufacturer tested) towbar?2. What is the possibility of the two bolts working itself loose and the extension starting to sway Left Right . Or up and down for that matter?So what?I am a fellow road user and I have a forensic interest in the outcome of potentially fatal designs.
    On another camping forum picture was provided awhile back of a similar extension on a standard tow bar that had fatal outcome by which the standard tow bar bolts tore out of the chassis due to increased forces that was a direct result of the levering forces of the extension.I would advise against such an extension for towing.

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  8. #26
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    Default Re: Extension to towbar

    All valid points above.

    Apart from the obvious limitations on loading caused by the increased moment, my biggest concern is the two bolts "locating" the extension onto the factory fitted and marked towbar.

    There is no way that those two bolts will stop any rotating movement around the towball, unless very precise holes have been drilled into the assembly, thus voiding any form of validated capacity.

    Furthermore, two bolts, secured by a reverse lock using a nut, will loosen up quickly, as heat and vibration occurs.

    Sadly, this gizmo looks like an accident waiting to happen, at best a flyaway bike rack, at worst a runaway trailer.

    The manufacturer offers a fully tested towball mounted bike rack option if this is what it is for.

    Click image for larger version. 

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  9. #27
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    Default Re: Extension to towbar

    Quote Originally Posted by Rustic Camp View Post
    Morning,I have this one on me, mounted it due to the same reason.I have been towing my trailer on it since 2013 and till today I still towing with it without any problem.
    I would like to run that setup through some load analysis. No offence but that, to me, is dangerous. With that length the load on the bolts must be quite high. I make 4X4 accessories as a hobby and use Solid Work to design. If I do anything on a tow bar I always run an analysis. I load 500KG on the ball. I know it is high but then I know if it is OK then it is safe. It has to do minimum 1 million cycles. (I am in the motor industry and that is acceptable.)
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  11. #28
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    Default Re: Extension to towbar

    Quote Originally Posted by Disco Smiley View Post
    I would like to run that setup through some load analysis. No offence but that, to me, is dangerous. With that length the load on the bolts must be quite high. I make 4X4 accessories as a hobby and use Solid Work to design. If I do anything on a tow bar I always run an analysis. I load 500KG on the ball. I know it is high but then I know if it is OK then it is safe. It has to do minimum 1 million cycles. (I am in the motor industry and that is acceptable.)
    I agree with you on this.
    The forces exerted on the chassis must be frightening extending the towball attachment.

    For what it's worth, Hanler makes a range of bike carriers for vehicles with reardoor mounted spare wheels.
    But in my opinion, to extend the towball further away from the vehicle to allow the rear door to open is asking for trouble.
    http://www.hanlerproducts.co.za/products.html
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  12. #29
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    Default Re: Extension to towbar

    I have seen a number of Suzuki GV's using the extension - always thought it to be a dangerous practice.



  13. #30
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    Default Re: Extension to towbar

    Quote Originally Posted by Disco Smiley View Post
    ...........If I do anything on a tow bar I always run an analysis. I load 500KG on the ball. I know it is high but then I know if it is OK then it is safe. It has to do minimum 1 million cycles. (I am in the motor industry and that is acceptable.)
    Just to cover yourself, consider getting a copy of the relevant parts of SANS 1505 if you intend doing this commercially, it's not a simple case of applying a conservative vertical load, there's more to it.

    Loading cycles is a minimum of 2 million btw.

    The motor industry has no say, codes of practice and gazettes determine the requirements.
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  14. #31
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    Default Re: Extension to towbar

    The joke about bike racks are the some towbar manufacturers says fitting a bike rack to a towbar negates the warranty on the towbar even if they make the cycle racks themselves. Iknow that
    because I was working at a fitment center until 5 years ago. The sales people don't tell the customers that because most people fit a towbar for their cycle rack, and no clients ask for the fitment literature that comes with the towbar.
    Ignorance is bliss.

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