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).

[Thorshammer]

Okay boys!

I have heard some of the limited prep guys running the cantelever slick at higher pressures than normal, I can't run them that high. My normal starting pressure is near 17lbs which gives me a 24.5-27 psi hot pressure. As for qualifying with 250's. Good call, my budget does not allow for that. I have been using tire warmers and qualifying on the 430's. As for running 600's in the rear. I don't think thats the way to go. But you have to do what you have to do. I think Kevin is driving the car very well, and very hadr trying to make up for his lack of power. He ran 139's? at MO and I ran 1:36's (I think) and I probably had 30 or better hp on him. Once he gets his new MOTOR. He'll be fine, btu I do agree that the rear triling arms can be improved. All the rest of us are doing is working with the existing trailing arm, Where as Kevin is attempting to correct some deficiencies (sp) with all semi trailing arm designs, adn apply them to the 914 within the constraints of the rules.

BTW Kevin, Sargis car has a similar type deformable bushing and toe link for his trailing arm swingaxle spitfire. Many of the front running spits have now developed something similar. It has been through two protests and been declared legal, so I think you are fine.

I don't totally agree with you in one way, I really don't think EP is just a HP class, I think both of us can run at or near the front with the right engine and chassis combo. With the way my car is set up now, I think I can run with Pratt or any of those guys. Lowshaks Honda IS fast. it will be interesting what my car will be able to do against him with the new motor. Building a Runoffs only motor.

I think if you have yours (come on JAKE buddy, I think I can, I think I can) (just kidding, I know your working hard at it) you will have a good shot.

I really think one of the only drawbacks to what we have is getting fresh air to the carbs/airbox, legally.

Erik Madsen