Rear suspension redesign, Optimizing a semi-trailing arm suspension Options

[groot]

Finally, I'm actually constructing my rear suspension. This one's been in the works for a long time. I've had the parts, but lacked the mill/TIG time to make it happen. So, I'm starting with the 914 trailing arm instead of the 944 trailing arm (need the TIG for that one since it's alum).

Some background, the SCCA production rules state this under "Unrestricted Suspensions: Suspension Control":

2. Suspension pickup points on the chassis or structure may be relocated and/or reinforced. If such points are relocated to the driver/passenger/trunk compartments, such points and attendant suspension components shall be covered with metal panels.
3. The manufacturer’s original system of suspension, e.g., live axle, swing axle, MacPherson strut, A-arm, etc., shall be retained. The wheelbase of the vehicle shall not be changed or relocated in a fore/aft direction.
4. Suspension bushings are unrestricted. Adjustable spherical bearings or rod ends are permitted on all suspension components.
5. Any anti-roll bar, camber compensating device, panhard rod, watts linkage, and/or other suspension stabilizer is permitted. Attachment points of such components are unrestricted.

So, I can move pickup points, I have to run a semi-trailing arm suspension, but I can add a toe link.

The basic idea is that I can get the camber gain I want by playing with the location of the pickup points of the trailing arm to the chassis, but replacing the bulky semi-trailing arm with rod ends on tubes allowing easy control of static alignment settings. Simple geometry.... But, you're stuck with a crappy toe curve.

What suspension gives an excellent toe curve???? A real trailing arm (no toe change). So, allow the rear suspension knuckle to pivot in toe, but control that toe with an additional link (attached to the chassis in such a way that it mimics a trailing arm). This was the brainstorm that hit me one day.

I gathered all the parts last winter, but spent so much time in AZ for work I didn't get to do the work before the racing season crept up on me.

Here's the work I did this morning. That rectangle stock sticking out will be where I attach my toe link. The semi-trailing arm links will mount on the top and bottom of the knuckle (bearing carrier).

[GTPatrick]

Food for thought on this subject folks. Don't know if the following have been previously discussed or not but here goes.

1) Has anyone given some thought to adapting a Porsche 911 rear trailing arm suspension to a 914 ? Maybe one from a competitive/racing 911 car ? Cost may be high but some of the ideas in this thread ain't cheap either .

2) What about a totally new handbuilt design that completely replaces the 914 trailing suspension pieces ? Maybe even 1 that uses some of the components from either a 911 or possibly a 914 ? Again costs and time for development rears its ugly head here too.

With all of these design modifications, won't some of them possibly have a builtin design flaw/weakness that the original suspension design did not either address or was ever previously conceived of ???

Just some food for thought here. Some of your ideas seem to be really neat but why not take it one step further ???

GTPatrick.