The V8 Owners Forum -

Been looking into Roll centre height effects.
On my MGB the front roll centre is pretty near ground level but at the back with a panhard rod its in the centre of the diff housing. Im thinking that this could contribute to the cars tendency to oversteer.
If I junk the panhard and build a custom Mumford setup I can get the rear roll centre right down.
Anyone know about these things?
Doesnt seem to be a lot of info out there.

This thread is interesting.
http://locostusa.com/forums/viewtopic.php?t=77

Mark

Years since I have heard of the Mumford link, obviously works, BUT, I would think the overly complicated framework involved to support the system on a spaceframe would be a nightmare to fit to a monocoque.
I had the fortune to have a good look around a Alan Mann Mk2 cortina, the whole suspension is quite special and had some lateral thinking applied to fit within the saloon car rules, the watts linkage was interesting in as much as it was fitted to the underside of the diff, the two defing problems I could see would be the bottom mounts must be above the scrub radius and the mounting towers need to be quite long which exerts extra load on the tower body mounts

http://www.locostusa.com/forums/viewtop ... t=0&t=2426
How about that would lower the roll centre too ?

Never heard of a satchel link and cant seem to find any pics of one.
The Mumford will be relativeley easy as I can drop a plate down from the front of the boot floor which would need to be strengthened with a crossmember.
Something like the photo here http://www.british-cars.net/mg-midget-s ... 817406.htm

Try this link, interesting reading too
http://corner-carvers.com/forums/showthread.php?t=18020

Very interesting. Basically triangulated.
I think this setup would put too much stress on my composite springs. I had to be very careful to get the anti tramps right.
Im going to rig up a full size model of a Mumford to see if it will work.

Cheers
Mark

Is your MG on leaf springs or coil overs?

Roll centre with a Panhard should be at the centre of the rod not the diff - centre of diff is usually associated with Watts with a link at the diff centre or with cart springs.- being half way between mounts.

Assuming on cart springs and you retain them I am not sure that the Mumford or Panhard would be of any use other than for lateral location goodness knows where the roll centre would be - in roll the action is for the shackle bushes and the leaf to twist and resist roll and the body roll around the spring mounting points.

The body need to be able to pivot freely on the spring mounts for the Mumfords, Panhards etc to articulate and control the body movement. Hence most of these applications start with a 5 link conversion and coilovers.

Trouble with a lot of leaf sprung systems is poly bushes stiffening the roll up too far which promotes oversteer

Andrew

Satchel horrible thing - dont even think about it unless you want to destroy your axle as it will put twisting loads through the axle tubes between the the upper and lower mounting points.

Andrew

Andrew
my Panhard runs along centre of axle so Roll centre is centre of my diff.

I am using Composite leaf springs which are quite supple so am sure they will work with a Mumford OK.

Will probably convert to 5link and coilovers in the future.

Mark

Is there really much benefit over a Watts linkage? Looks more compicated, more to go wrong and not as strong...

The benefit is that the rear roll centre will be a lot lower. With the Watts linkage the roll centre is fixed where the main pivot is.

Mark

If using a coil based system = Panhard, Mumford, Watt, Wob with leaves you will still have a compromise as leaves have a roll centre as will whatever other system for lateral location you, which one will actually be the dominant system, and where the roll centre location would be an interesting task to calculate - It then also depends if you subscribe to the static, dynamic or force based roll centre location philosophies.

Do you have a rear anti-roll bar and is it adjustable in any way?

Andrew

Andrew
Yes I have a rear anti roll bar. it is adjustable via a slider. It is only 5/8" diameter with fairly long blades. I have tried removing it altogether but this makes the car unstable in fast corners. Stiffening the bar gives more oversteer as does harder bushes.

My main reason for choosing the Mumford is to lower roll centre to hopefully reduce oversteer. If it doesnt work I will revert back to a panhard rod.

Mark

Hi
If your aim is to reduce understeer can you not reduce front end weight transfer? it would seem a better way to achieve the result as you, in theory, will get the result you want and increase overall grip by working both outer tyres less hard. I presume you front end set up is fairley standard MGB so moving the inner upper suspension mounting up a bit would not be too tricky and likewise lowering the lower outer wishbone pivot also though not as easy would be possable, even making up a new upright with the stub axel mounted higher would be doable, or find one you can modify, then reset the front static position so the roll centre is higher.
Just to me it seems a better aproach as on a track car like this you want less roll in a corner not more.
Have you moved everything back in the car as far as you can? and mounted it as low as you can? lowering the engine an inch with new engine mounts would drastically reduce front end weight transfer, shifting it back an inch or two likewise (then move the radiator back the same amount or lower it by mounting it at an angle), where is the battery? can it be mounted lower in the chassis, there are lots of parts that can be moved to improve the local centre of gravity.
Best regards
Mike

I copied this a loonngg time ago from one of the hot rod mags, there's more than one option to help reduce under/over steer
http://www.uk-hotrods.co.uk/v2/tech/tec ... rsteer.php