1302

[evilC]

Hi, Nice work but a couple of queries:

1) Front suspension. Why control the caster from the top of the strut? The anti-roll bar controls the caster and locates the TCA via a squidgy bush that doesn't allow any anti-dive to be built in especially if you lower the suspension. With the accuracy that you are initiating with the inner heim joint having the bottom of the strut potentially moving around via the AR bush seems counter productive. The classic way of adjusting caster and tightening the whole assembly is to use a tension or compression strut. I prefer the idea of a compression strut as the inner pivot can be adjusted to amend the anti-dive. The AR bar can then be detached so that it can become adjustable. Its a win-win system.
2) Front suspension. Are the front struts Golf or is it just the inserts?
3) front suspension. Are the top mounts solid?
4) Front suspension. I think you should consider a brace bar and then look to cross brace the front of the hammer head to stiffen the whole body and therefore the suspension pick up points.
5) Front suspension. Consider dropping the inner pivot on the TCA to lower the roll centre to increase the roll couple.
6) Front suspension. Whilst lowering the tank lowers the front weight distribution I have kept ours as the standard tank in situ to improve the roll couple and keep the weight within the wheelbase to help with polar moment of Inertia. Similarly the battery remains in the VW position for the same reason.
7) Rear suspension. Are you intending to run a full coilover suspension i.e. removing the torsion bars?
8) Are you fitting a full cage? Its worth linking the cage to all the suspension pick up points as well as multi-pointing it to the body to increase the torsional rigidity.

Clive

[1302 S]

Hi, Clive
Many questions you got. Realy nice to get responce and share thoughts.

Coilovers are homemade. Lower mount from 944T. Thinn wall pipe and threaded end from a 944N/A. Shockabsorber is golf inserts. The spring and threaded sleeve is bought separately.

As I wrote the TCA rebuild is only a part of a larger plan. I will build new towers for a adjusdtebly pillowball top mount. Adjust the basic angles, so they better fits a lowered car. To be able to increse caster. The top mounts will include supports for a brace bar.

I will also look at the inner mountings for the TCA. They looks very weak and mounting point is not adjustebly.
Droping the inner pivot on the TCA is not a good idea. Dropping it would cause the angle between TCA and strut to increse.
On MacPherson strut-equipped cars, the wheel will gain negative camber under roll as long as the lower control arm is positioned
less than 90 degrees relative to the strut axis. Beyond 90 degrees, the suspension will gain positive camber instead of negative
as it compresses, significantly compromising grip.

I see that you and I have different oppinion about weight transfer. In my experience and what a learnt, I try to minimise the weight transfer.
I try to place parts as low as possible and they should be as light as possible, all to reduce the influence of the torque arm (both lenght and strenght) that that virtally apperes between the gravity of center of the car and roll center when the car turns. I also have increased the tracktion-width to decrease the weighttransfer (the main reason I choosed P-parts for chassie). This make the suspension work in a smaler range and the weaknesses of the MacPherson design could be less.
To adjust the couplung between front axis and rear axis I will rake the car in different degree.

Rear suspension. The rear end bushings will be replaced with the parts you see. Its practically the same change Wally made but I have constructed the kit myself. I hade to make a outer plate to hold the bushing in place. I hope that the bushings and balljoint will decrease the friction and give better response.
I would nerver use alu arms in a full coilover solution. The reason is that the alu arm isnt made for it and you change the stress points in the chassie.
First all the rear weight of the car from the torosionbar (spring) via springplate mount is moved to the to the lower coilover mounting point.
Now the lower point of shockabsorber mounting, has to deal with both the force from damping forces and the weight of the rear end
of the car. The lower mount is single sided and the increased load will sooner or later breake it due to overload and/or fatigue. In the upper
end of the shock the unsupported mounting have to take all the added force. On 911 p-cars they brace and reinforce the upper mounting points to avoid cracks and deflection.
If I do a coilover mount I should mount the steel arms (compare the lower mounting points, both sides) and connect the upper mountings to a
to a multi point brace or even better rollcage.
In my case I will see how far I could take the "standard solution" due to make it more exact and smother and it will be combined a 5 point brace.

I probably end up with a full roll cage. Its true as you said that it will improve the handling the chassie could never be too stiff.

//Anders

[oasis]

Impressive work. Nice presentation for us, too.

[evilC]

Hi Anders,
I'm enjoying this debate.

I appreciate that the caster can be controlled at the strut top but the range of adjustment is limited by the body shell. A compression strut has the advantage of potentially more adjustment. Also, the loads are fed back into the strongest part of the chassis and it gets rid of the anti-roll bar locating the axle.

I agree the inner mounting for the TCA looks weak but having looked at the forces involved they are well up to the job. I would only beef them up for rallying where inpact damage was a possibility. The inner TCA mounting bracket on ours has a lower pair of slotted holes that I used to provide the pivot point.

I agree in general with what you say about camber change but my reason for doing it was that the roll couple was increased that then loaded up the outer front wheel in the turn to improve grip. Also, the front roll centre was lowered by doing this so that the couple in dive was increased to again load up the front especially under braking in the turn. the actual camber change is relatively small with mine being set statically at -1.5* that should give a 0*- (+)0.5* at full roll.

I understand now your rear suspension however, don't dismiss the strength of the alloy arms as Porsche used the same technology and layout in their 935 long distance racers with a uniball rear and coilovers. The coilovers were racing spring rate with their heavy 6 cylinder rear end. My concern was not with the lower bolt, which is M14 high tensile but with the top mount in the beetle which is only M12 and desperately needs the cross bracing afforded by the 5 bar cup brace

The rear end bushings are now explained for me - thank you.

Keep us all up to date with progress.

Clive