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Old 8th April 2010, 10:48 PM
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Default Tow Bar Modifications

I've been thinking recently about making it possible to add a tow bar to my chassis whilst its still in the welding stage. Reasons:

I occasionally go to Greenpower and Shell Eco-Marathon events taking with me the cars I helped build back when I was in the school motor sport team during 6th form. When I went to race meets I used to stick it up on the roof rack of my rover metro but towing seems a neater solution when using a 7 style car

I do a lot of cycling so the idea of carrying two bikes on the back to races/venues is very appealing

Easier way of carrying luggage when planning a 'weekend away'


Has anyone given this any thought? My first ideas are to weld 'L' brackets to the lower inside of the rear suspension framework, one in each corner (with nuts welded to the top side). To this a tow bar style extension could be bolted that brought the tow-mount out the back of the car, or a custom designed bike rack to suit the car. Would it be wise to try and incorporate some sort of triangulation method or would it be strong enough? Perhaps using the roll-bar support tube bolts as an upper chassis bolting point?

My main concern would be to keep the chassis weight as low as possible so a removable design would be best as I want this car to be as multipurpose as possible!

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Josh
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Old 8th April 2010, 10:58 PM
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I,ve seen this discussed before somewhere,

There,s no reason why it can,t be done but I,d suggest you left it till after the IVA test, I can,t remember the precise ruling but there,s something about the Gross vehicle weight that can be affected ( on paperwork side of things as far as VOSA are concerned) if the vehicle has a tow bar fitted prior to the IVA test.

Tho obviously as your Roadster will weigh between 500 to 600kgs approx then you won,t be able to tow something that is heavy etc, its all to do with the "Train weight" of the combined outfit ( tow vehicle / towed vehicle )

cheers
andy
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Old 8th April 2010, 11:01 PM
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Fair enough, but I could always weld the brackets in and leave it at that? Then take it to the IVA minus the actual tow-bar extension from the rear framework to the back of the car.

Or would the IVA man start asking questions about those brackets...
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Old 8th April 2010, 11:05 PM
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If the brackets are there he ( IVA man ) might ask what they are for, depends on the tester on the day,
There is a forum member that has fitted a tow bar , i,m sure he,ll be along soon & give better info than I can ,

cheers
andy
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Old 8th April 2010, 11:09 PM
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All production cars have to be type aproved for fitting a tow bar, if the manufacturer has not gone for type aproval the it is ilegal to fit a towbar to that vehicle.


I guess your best course of action is to try and speak to your local VOSA inspector, or ask Spud to check with his contact.

TT
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Old 9th April 2010, 03:53 PM
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Handy has nailed it as the train weight is greater than the gross weight and you would not be able to tow a trailer and car with your Roadster. A possible way is with an "A" frame fitted to a tow bar like the AA/RAC use.
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Old 9th April 2010, 04:02 PM
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I think the cars he's talkig about probably weigh very little. Considering he's had one on the roof of a metro and usualy the maximum weight on a roof is about 70KG ( on bigish cars ) .

a very light trailer could be built .

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Old 9th April 2010, 07:07 PM
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Yes sorry I should have made that clear, the cars weigh between 30 - 40kg (see photos) so with a lightweight trailer and a few extras it would be below 100kg all up. Whats the deal with train-weight and gross weight ?

What would the IVA say about building a custom bicycle carrier that held the bikes upright across the back? Most probably mounted to the underside of the rear framework and to the roll-bar brace bolts.

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Old 10th April 2010, 02:45 PM
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All makes sense now,if you have to do it, do it later rather than sooner and its less to include in the IVA test. Read the manual and see what it says about axle weights etc. I would think you will need to put the GTW on the chassis plate to please plod if you are unlucky and keep everything legal.
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