towbar

Post by **alainmoran** » Thu Nov 06, 2008 1:07 am

I have a towball, and a MIG welder ... does anyone have any advice about how to go about building a towball onto my 2dr?

Right now I'm thinking a large(ish) semi-triangular reinforcing plate to spread the load across the back end and and bolting the towball to it ... the 'point' of the triangle attaching to the towball.

This is all based on supposition about how best to spread the load, but does anyone have any drawings of existing towbar mods?

Post by **kennatt** » Thu Nov 06, 2008 8:22 am

every one i've seen ,and the way i'm going to do it, is an angle iron accross the bumber irons with a supporting strap to the boot floor and the ball coming through a hole cut into the bumper. The only thing I'm not sure about is cutting a hole in a brand new bumper. Might try to weld up some sort of step to bring it under or over the bumper.It all depends on how strong the bottom corners of your boot is.There was a running thread re this a few months ago. Cheers

Post by **mike.perry** » Thu Nov 06, 2008 9:57 am

I would agree with mounting the angle iron to the bumper irons and bracing it to the boot floor, but it is hard work drilling through the bumper chrome, besides it messes the chrome up. I would therefore use a drop plate to mount the towball. This ensures the towball is clear of the boot opening and doesn't get in the way of removing the spare wheel and also means that the trailer normally sits level behind the car and is therefore more stable.
Witter used to make a kit for the Minor. I don't know whether it is still available.
How are you getting on wiring the electrics?

Post by **bmcecosse** » Thu Nov 06, 2008 4:39 pm

My old Minor had a proper DB towbar - it had strengthening angles that ran down and forwards and bolted through the rear 'chassis' members, and was fixed to the bumper iron bolts. You couldn't really rely on the bumper bolts alone unless a very lightweight trailer was envisaged! I towed my racing Mini on it's trailer behind my Minor. The trailer broke away once - but the tow bar survived all manner of abuse!

Post by **morris62** » Thu Nov 06, 2008 7:56 pm

you need to do it off the chassis rails in at least two places either side.
pop down the breakers and pickup a tow bar which has a removable ball that comes up from underneath.

Post by **AndrewSkinner** » Fri Nov 07, 2008 12:02 am

I agree with 'Morris62' all the designs I have seen have had a single cross member spanning across the two bumper bolts and then at least one arm extending from the cross member under the fuel tank to the floor of the boot.

When designing your tow bar just think about the forces involved, the downwards force is actually very small compared to the main forces that come from braking and accelerating which cause a twisting motion. This needs to be stopped by the arm linking the cross member between the two bumper bolts to the boot floor.

If you look on most tow bar websites they will let you download fitting instructions which will let you see how they are designed.

Post by **bmcecosse** » Fri Nov 07, 2008 11:31 am

I disagree - the boot 'floor' has next to NO strength. You must go out to the chassis rails - and most of the forces ARE downward (and upward) forces on the tow ball as the trailer pitches and plunges behind the car! Acceleration and braking forces are relatively low. The trailer should really have it's own brakes anyway!

Post by **246gts** » Fri Nov 07, 2008 3:10 pm

I have a towbar which was bent when a truck rear ended my daughter's car. It still has all the fittings etc but the angle iron is bent.
It is free to anyone who wants to take it away and play with it.
I live near Warrington in Cheshire
Dave

Post by **mike.perry** » Fri Nov 07, 2008 4:32 pm

Provided the back end of the car is in good condition then there is nothing wrong with bolting the towbar to the bumper mounting bars and plating it to the boot floor. That is how the professional towbars are designed and I imagine they have to be rigorously tested before they are sold.
Remember you should only be towing 3/4 of the weight of the towing vehicle max. It doesn't make any difference to the legal weight if you have an 803 or 1275.

Post by **Kevin** » Mon Nov 10, 2008 11:58 am

I'm not sure about is cutting a hole in a brand new bumper.

With a properly designed kit you should not have to do that, and a company that still makes them for the Moggie.
http://www.watling-towbars.co.uk/uk_cars.html

Post by **bmcecosse** » Mon Nov 10, 2008 1:03 pm

I can assure you Mike - my original DB towbar was very well made and took the most ridiculous punishment without slightest complaint - and it picked up from the chassis rails and bumper bolts - there really is NO strength in the boot floor! It's a thin and unsupported sheet of steel. The fuel tank gives it what little strength there is - surely not a great idea to rely on that !

Post by **mike.perry** » Mon Nov 10, 2008 4:41 pm

Maybe the Series MM is stronger then as it has a double skin channel section across the boot well between the fuel tank and the boot opening. The towbar is bolted to this section with 2 plates, strong enough for a 5cwt camping trailer.

Post by **bmcecosse** » Mon Nov 10, 2008 4:45 pm

Ahhh - 5cwt camping trailer is one thing - I was towing a racing Mini on a heavy trailer!

Post by **AndrewSkinner** » Mon Nov 10, 2008 8:17 pm

the trailer shouldnt pitch and plunge! That means the nose weight is wrong. What you are saying is that the force of a e.g. 50kg nose weight is more that the momentum of the trailer tryting to twist the towbar upwards while fully braking????

Bolting to the boot floor is fine, it is how many companies build there towbars. The leverage involved means that the forces are far less on the boot floor and if plated properly will be plenty strong enough.

When I fitted a profesional towbar to my Mums Corsa the plate to hold the weight of the trailer was very small and only required 3 bolts, the plate that went to the floor of the boot however took 6 bolts and 2 big plates. That said the floor of the boot it was bolted to was very thin and could 'pop' in and out by just pushing it! Kinda puts the morris into perspective - its not that weak!