De-Dion rear ends

[thepeter]

Some may scowl at me, but another plus is you could use a nissan center, as they're strong and plentiful.

Also, as Stewart mentioned, shock mounting points are plentiful, and can be chosen depending on how you want the rear of the car to react.

Watts links are great for adjustability, but are a right pain to initially install...

ah, tube-frames get me all giddy.

[oldcorollas]

Roll centres are determined by the locating points of the panhard bar or watts links, whichever you decide to use. So you can set it up however you like.

you would probably go for a watts link as it is easy to attach to the de-dion..

i was meaning compared to IRS... which i guess has a more dynamic roll centre? is that mroe favourable than the relatively static roll centre of a watts link?

inboard discs liek the alfa will make a lot of things easier also...
less unsprung weight (less total than IRS?)?

big pic (front side view)
http://www.transalfa.de/Hinterachse_Alfetta1.jpg

top view
http://www.locost7.info/files/suspen...onSuspPlan.jpg


rear pic
http://www.movit.de/images/alf6ha.jpg

[rick q]

My Fraser Clubman has a deDion rear end in it using the rear from a Series 2 RX7 for the major parts.

Primary advantages as I see them are the low unsprung weight (about the same as an IRS), ease of setting up (about the same as a live axle), but much more adjustability (toe in and camber).

The diff is rigidly mounted to the frame which also means the transmission tunnel doesn't have to accommodate tailshaft movement (helps in a clubman because they're so bloody small anyway!)

I've got a spare deDion tube at home, which I'll measure if that's of any help. I know the English Clubman lads use what seems to be very small tube for theirs - my original one was about 75mm dia - the new one is the same but thicker wall. There's a pretty good photo on Bill Sherwood's site of his Fraser :- http://www.billzilla.org/fraserdedion.jpg

If you're serious about it, look carefully at the availability of LSD's and different diff ratios as it opens up lots of further possibilities - Subaru's and MX5's would be better choices than RX7's for example.

[Ben Wilson]

Subaru's and MX5's would be better choices than RX7's for example.

1.8 MX5 FTW, good for around 250hp or so, factory and aftermarket LSD support and all sorts of different ratios out there...

[oldcorollas]

just thinking about loss of traction etc (hey.. it's a sprinter )

with the de dion in the alfa, since it pivots at the centre front mount bit, if you loose traction on one wheel, then the whole frame will try to move forward at the wheel with traction.. so you need a fairly hefty watts link to keep it in place?

if you have a sudden regain of traction also, surely it will put nasty side loading on watts link or panhard rod?


if you have non-solidly connected lower arms.. and 4 link.. is it harder to control rotation of the de-dion bar? or same?

[Sam_Q]

just to clarify I am after absolute maximum traction, I am not a drift and speed is fun for me.

I did have in mind an MX5 diff because they are a Torsen center which is what I idealy would want. If I was a drifter than a nissan based R200 would definetly be the choice for me.

I would very likely use the original 4 link (3.5 link) system for it and go from there. I will have a look at an alfa setup if I get a chance though.

Thanks for the great info guys

[Sam_Q]

Bill sherwoods setup (very neat)




if anyone can get me dimentions of their rear support tubes then that would be great. Also I cant see how the angles can be adjusted with shims? I mean it looks very much like a through axle design in all these pics? I was personally thinking of just initually welding the wheel axle support in on an angle to get what I want

[oldcorollas]

sorry, that wasn't intended as criticism.. just light hearted spoontah stab

if you are on track, you WILL lose traction at times, albeit from hopping curbs or whatever... system needs to be tough enough to handle that.

biggest advantage of alfa setup is that the "axle" doesn7t roll fore/aft much, as it is all solid.
but being solid it needs to be located at only one spot at the front.

if you use original 4 link, then you still have issues with bush compliance etc changing angles (self steering under power.. roll steering?), in which case the alfa setup is better..ish

later suplah/toyota centres?

there is a yellow hotrod (bretts alfarod) that uses the alfa rear.. easy to set up, few mounting points... it is not exactly a track car but handles well..

[Duk]

I know some of the Alfa guys bend/cut and weld their DeDion frames to achieve desired camber and toe angles. I read on 1 Alfa forum (yeah, I got a Alfa ), 1 guy sugested using a place that does wheel alignments for light trucks because they can litterally bend the front (in the case of a light truck) axle to correct camber angles using special equipment .
What dimentions are you after? I should be able to get track width an a rough idea of overall length.

[Sam_Q]

corollas: ah yes the obligitory ae86 stereotype why would I lose traction everywhere compared to what I have now?

plonka: the thickness and diameter of the bar that runs between the rear wheels, not sure how you would measure that though

[rms]

If you are after traction out of corners or off the line you do not want a De-Dion.
The chassis mounted diff takes away the use of torque reaction to gain anti-squat.
Inboard brakes and you can not use anti-lift.

Bill Sherwood's layout with single top links and a lower 'A' arm for lower and lateral control, when used with a live axle can give large benefits.
Anti-squat and anti-lift can be incorporated and adjustable as to degree. Roll steer can be adjusted as well as biased to roll understeer/oversteer.
The roll centre can be lower and closer to the front roll centre. There is no difference in roll centre movement compared to a panhard bar.

A Watts link with the swinging arm pivoting on the diff or De-Dion has the same roll centre movement as a panhard bar, but with the swinging arm pivoting on the chassis will maintain a consistant roll centre.
A conventional '4 link' rear can be laid out go give anti-squat, but roll steer becomes an issue and the diff housing or De-Dion tube becomes a torsion/sway bar.

So far as camber/toe adjustability goes, the gains would be marginal.

[wa5]

have a look under the back of a Honda HRV (not CRV) as I believe they would be the latest thing to be fitted with a De Dion

[roadsailing]

you can fit proper IRS to a sprinter without too many problems while cutting very little, so dont use that as an excuse.

i'd switch cars before i converted mine to DeDion, and the new car would only get converted to DeDion if i had a very good reason for not fitting IRS.

look up "satchell link" its a bit like bill's fraser setup but a few of the linsk are backwards.

have fun

[Sam_Q]

which irs could I fit without some serious cutting? a trailing arm setup using the original shocker tower with a coil-over type setup?

I will look up that "satchell link", sounds familiar

also I think i better clarify things here, I want maximum cornering traction, and if that means losing my anti-squat due to no more torque reaction then so be it

[Duk]

The horizontal tube of the Alfa's DeDion axle is approx 75mm. That's the largest diameter of the whole axle assembly. Wall thickness is obviously difficult to obtain, but they aren't thick wall tube or anything dramatic. I think your chromolly tube would be plenty strong.