I am on to the last 'big make' for the Dauph. Having a swing axle rear end is a bit of a mixed bag, it is not a disaster as it is better for traction than a live axle, has lower unsprung mass and does not alter wheel camber in roll, but the main issue is vertical camber change, or more accurately camber change due to vertical motion. Solution, Limit vertical movement. Well I wasn't taking it into the woods anyway. VW tuners and racers will know about camber compensators, these are another leaf spring mounted on a swinging bracket in the centre of the gearbox, and connected to each axle's outer end. This has no effect in roll as one goes up and the other down and pivots through the centre, but when the car rear compresses under acceleration or lifts under braking the extra spring comes into effect helping to limit the vertical travel. Problems with camber compensators is the centre pivot under the centre of the box loosing you ground clearance, no problem on standard ride height, but when you want it lower than a snake's ass in a wagon rut you have a problem. The super duper deluxe answer is to build a Zero roll resistance rear suspension, and a Guy called Ross in New Zealand did this, but was unhappy with the result and feel of the car. To make this means a redesign of the rear end, and to be honest I think I would have a real issue trying to get that through scrutineering as a historic vehicle, as it means connecting the top spring platforms to a triangular frame which pivots on the top of the gearbox. I personally think the problem with this is that you need some roll resistance on a saloon car as it has a highish centre of gravity. This could be accomplished by adding a 3rd spring and damper between the top of the triangle and the body meaning you having Mainsprings for vertical motion only (fairly high rate) and a roll control spring (low rate) and all 3 can be changed in 25lb/inch steps this would be lodsa fun to set up!!!!!!
I have elected for the 3rd option, based on a device fitted on '68 Beetles (period modification) and touched on in Fred Phun's excellent book 'How to make you car handle' This book is a must read for historic vehicle racers and modifiers, but out of date for Moderns
This is the Z bar which works in the opposite way from an anti-roll bar. The bar is straight, but mounted under the car on an angle with one link going forward to connect to the outer end of the axle at centre, and the other end has the link going back to the same spot on the other side. This means as the car rolls the bar pivots freely, but comes into play if the rear end tries to lift or squat. Last and most important point is that this device is fitted at Zero load when the car is on its wheels and with the rear springs compressed, meaning that it is more effective at stopping lift than preventing squat and is totally adjustable in this respect. Killing the lift under braking is the most important part.
The Mk1 version I used on the 8G used CDS tube as the bar with EN24t blades on each end which adjusted for stiffness by rotating, but the blades were quite short and were prone to snapping. When this happened in a race it was always the same. A loud Bang like a gunshot followed by the feeling that the rear tyres had melted in every braking zone. Proof positive that it was super effective at improving stability under braking and turn in. The MK2 version used Pug 106 (poverty spec) rear torsion bars, the only problem being that I had to spend an afternoon with the burning torch cutting up the rear axle to get the splined mounting points out.
Pic 1 shows the 106 bar with the splined mounts turned into tubes with the ends welded up and then welded in to solid driving links
Pic 2 shows the ends in more detail the mounts are high pressure pipe clamps bored to suit the torsion bar, cheap and easy, I use them for anti-roll bar mounts as well
Now I need to lie on freezing concrete to measure up the carrier frames from the Gearbox crossmember. A job for another day.................