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MG Midget and Sprite Technical - Anti-tramp bars

I have the competition prep manual and they locate a single bar at the top of the tunnel to the top of the diff housing. Is there an advantage to this rather than a 2 bar system like the frontline one.

Cheers
J White

J

i know the one your talking about and i have not seen it listed in a long time

Id think weight reduction and probably less chance of binding once its over loaded

but i got to think that would only trasfer the inertia to the axle housing shafts tubes themselfs and probably influance some kind of axle drift to the right under hard accelration

it just looks to much like reinventing the wheel just for the sake of reinvention

i personally like the ladder bars in parelle to the leaf springs as it keeps the springs from rolling up and twisting the axle housing

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it'll be lighter...

Not suer how strong the diff housing is for this sort of thing. Used to be done on Lotus 7s with a sort of A frame arrangement that had a rep for breaking off where it joined the diff.
Rob Armstrong

My mates Caterham has the A frame for location to the bottom of the final drive housing and has a significant reinforcement at the back of the Marina axle as that type of location puts the main force accelerating the car through the centre of the axle so subjecting it to bending loads it wouldn't normally see with the normal cart springs at each end of the axle. The anti tramp at the top of the axle is not nearly as bad but the material of then axle casing is quite thin.
David Billington

Thanks all.

I was thinking about the loads involved etc.

The more I think about it the more 2 bars are a better option. With a single bar, mounted centrally it might be possible, depending on tyre grip etc, to have the springs tramp unevenly causing a steering or walking effect of the rear axle. That wouldn't happen with the 2 bars.

Looks like I'll have to not be lazy and just fab up a pair of bars and mounts. As I'll be lowering the car I think it would be better to mount the bars above the axle rather than below it. Anything I need to consider if doing that that I haven't thought of?

Cheers
J White

Whatever you do, you need to go for the geometric centre of the arc made by the mounting point on the axle. Failure to do so results in resistance to the axle moving up and down as the bar tries to make it follow it's own arc. This stiffens the suspension, and results in drastic oversteer. I found this out the hard way many years ago on the fastest corner of the local track ...
I worked out why, found the true arc centre and the problem went away.

It also stresses the mounting points causing them to fail eventually.

The changing chord length of the springs make this arc centre somewhat complex to find rather than a simple one forming a parallelogram with the spring and mounts.
Paul Walbran

I used an A frame on the rear of my modsport frogeye. It was similar to the one used by Keith Ashby on his modsport car. It vital to properly consider the geometry as if not the assembly fails and handling is atrocious. The frame was attached to the diff using a bracket bolted to the existing studs ( longer ones installed). It worked well and certainly settled the car more.
Bob Beaumont

Used a heavy(strong) gas shocky on mine ,mounted on the top of the housing and the other end through the body and mounted on the passenger's bottom seatbelt mount
Using a shock stops all binding up and reduces the strain on the mounting points
Leaf springs, no Panhard bar
Unbelievable traction and not a hint of axle tramp even with full attack standing starts
Heaps better than binding it all up with bars all over the place
willy

William Revit

Willy

that is a great idea... i dont think ive ever heard of anyone using a shock before in that type of set up but i like the concept

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Old speedway trick
shocky on the top and an extra front half leaf under the main leaf of the spring - works every time
I'll see if I can find a pic or two

willy
William Revit

Willy

id appericate that ... thank you

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I don't own this car any more and don't really like posting pics of other people's stuff, but here we go--

Inside the car showing the bottom of the shock--

William Revit

Underneath
With an extra leaf in the front half of the spring,
shocky in the background --By the way that rear body panel that it goes through is a box / hollow section-

And also shows the best mod you can do to a midget in my opinion--which I had forgotten about-- Extended spring mount to lift the front of the spring right up in the body-- Doing this lets you run a 3/4" front bar and decent stiff front springs without any push coming into a turn
Can't remember how tall the extensions were ,it's a few years back now but I'm thinking it was about 40-50mm

willy

William Revit

This thread was discussed between 17/05/2016 and 21/05/2016

MG Midget and Sprite Technical index

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