TR4A Chassis Strengthening

[The_Doc]

Hello All,

 

In my rebuild of my own TR4A (one with a solid rear axle), I have been doing some reading and it seems that there is some critism over the strength of the chassis. The TR4 appears to have a slightly better chassis in that it is more rigid, which is no real suprise as the TR4A chassis does come in at the back by the breast plates and where the prop shaft passes through it.

 

I was wondering, has anyone else found any issues with the TR4A's chassis and if so is there a good way to provide more rigidity to calm the twisting/flexing of the chassis.

 

I just thought that whilst everything is off this is a good time to do any work rather then thinking of it once the car is assembled.

 

Thanks

 

Adam

[RogerH]

Hi Adam,

I had a crackers idea a couple of years ago but haven't done anything yet.

 

In general it is difficult to add to the chassis. But!!! I have a cunning plan.

 

Attach a bracing strut from the chassis where the TA is attached, to the top of the bridge - rather tight for space

Attach another strut from the top of the bridge down and rearwards to the chassis rail.

 

This would produce a triangular bracing structure that could be very stiff - But!! what will happen.

You will probably transfer the stresses elsewhere.

 

The bracing would not need to betoo strong as the simple rag top Surrey frame or a steel/Ali roof stiffens it up a treat.

 

Probably worth an experiment - that ratling of the doors gets right on my ti.......

 

Roger

[monty]

The rally TR4's & possibly others had their chassis strengthened & various recent 'replicas' have had the same treatment in several cases. Why not contact one of the specialists to see what the standard procedure is?

Cheers.

[Alec Pringle]

Hi Adam,

 

a roll over bar and a rear firewall will do a good amount towards adding rigidity . . . . .

 

Cheers

 

Alec

[RogerH]

Hi Monty,

it is a bendy 4A not a rigid 4.

 

Alec's suggestion would certainly stiffen tio a fair degree.

 

Roger

[Motorsport Mickey]

Fit a towbar whether you decide to tow or not, the triangulation will stiffen up the rear end and the kits have been made with the IRS chassis in mind and so you stand a chance of just enough gained stiffness and not to much. There was a towbar kit for a TR6 on here not long ago.

 

Mick Richards

[stillp]

 

it is a bendy 4A not a rigid 4.

 

 

Lithe and supple Roger, not 'bendy'.

 

Pete

[RogerH]

[MichaelH]

In the eighties i made a rollover bar which was a hoop behind the driver and it had arms which went through the body work past the petrol tank through the boot floor to the chassis. It also had arms that went forward to the front chassis mounting points sort of beside the seats

It also had a transverse bar from behind the drivers head to floor. This made the structure very stiff and it worked

The principle is basically to take a commercial roll over bar (cos then you know it will fit under the hood) and add bars from the hoop back inside the hood down past the petrol tank to the chassis and forward from the top of the B posts level to the front chassis mounting by your feet

This would give the triangulation to make a car stiff

MichaelH

[Geko]

Edited November 3, 2016 by Geko

[The_Doc]

Thanks for all the advice. The weakest point to me seems to be right in the middle, so it seems sensible to try attach something to the outriggers and perhaps brace these to the back of the chassis somehow. Since I don't have IRS, then there is more space around my chassis to perhaps attempt soemthing like this.

 

Adam

[stuart]

I have a solid axle 4A and provided the chassis is sound or properly repaired then the back end isnt any problem as the rear axle is mounted totally different, but you do need to add the stiffening kit to the front lower inner suspension box mountings and also make sure they are converted to 2 bolt fixings from the original single bolt style.

Stuart.