VegasJen

hey jim, been kicking around an idea, tell me what you think. we were talking about rear suspension options and i got to thinking about this. what if you were to construct a HD lower a-arm, attatch it to the front pick up point of the third member or the frame where the third member attatches and a rear pick up just behind the spring. the outer portion carrying the bearing would be hinged and then a simple HD adjustable strut rod from the top to a pickup point located above the differential to provide camber adjustments. my intial thought was to have the a-arm hinge solidly located using roller bearings to maintain flexability and proper alignment and utilize factory style cam bolts on the inner pick up point for toe adjustments, however, i'm unsure what that will do to the wheel placement when toe is changed. the relative location of the wheel in relation to the adjustment bolts may shift the wheel fore or aft too much when toe is dialed in. i haven't given up on the idea, since the intial design would be 0* toe but we're only talking about 1/8" maximum toe generally and more likely 1/16". work in progress :banghead: what do you think?

oh, and for all you peeking in who aren't jim. SHAME ON YOU!!!! :nono:
but that's o.k. we're all family here. your input is welcome as well.

71roadster

The lower A-arm is exactly what the transam racecars were doing, but they had a full A-arm on top too, which meant no battery or storage boxes. I think the torque of the wheel would require a full A-arm on top and bottom.

you can see the two legs of the lower arm here.



heres a better one. There is another a-arm just like this one on top.


Both A-arms attach to the back half of a stock trailing arm holding the stock spindle. Of course, the trailing arm was cut in half and welded solid!

Chris

you had to know I would jump in on this one!


[Modified by 71roadster, 10:01 AM 3/5/2003]

VegasJen

the intrusion into the interior was what i wanted to avoid. that's why i was trying to figure a durable way to allow the bearing carrier to hinge on the a-arm without flex or distortion. also, the a-arm i had in mind was more substantial than the one pictured, as it would have to be to support the force and weight it would encounter.
notice in the pictures those guys were using spherical joints on both ends which would allow something like 20* of lateral rotation. this is something i don't want to have at all. both the lower a-arm and the upper strut rod would have some type of solid bushing to positively locate the bearing carrier. what i was picturing for the upper was similar to a 'smart strut' but with a brass bushing or roller bearing instead of a poly or rubber bushing.
the idea is for something somewhat of a compromise between compliant street car and no compromise, full race set up.

norvalwilhelm

Clutchdust. What is wrong with the stock system converted to a 6 link? A six link isn't hard to manufacture of install. It make changing yokes a breeze and toe adjustments require just the upper and lower strut rods rotated the same amount. Camber is sure easy.
You are talking about completely refabricating the rearend.
I often think about going to coil overs and it would be no problem for me to do but I worry about the side loadings on the trailing arm plus extra wear on the pivot point. The 6 link would help the side loading but not the trailing arm bushing.
I think with a lower A arm you are getting into serious design problems.
But if you went that route you could also go for unsprung coil overs laying on their side like indy cars.
We build a new indy car every year and I see dozens of A arm construted yearly. They are not that beefy, just chrome moly tubing. They make alot of backups in case the car slides into a curb and needs rebuilding in the pits.
Good luck if you decide to go that route and I for one will be watching carryfully for some new idea

VegasJen

norval, i'm not sure what all a six link would entail. like i said in a previous post, i want a good compromise for a car that sees lots of duty on both the street and the track. the objective is to get the c-3 on par with a z06 in both ride and performance. needless to say the chassis will need substantial re-engineering to accomplish this but once it's done, the suspensions, front and rear will need to be brought up to the task. i don't believe the front would be nearly as difficult considering how similar the basic concept still is to the design from '63. the rear though, has morphed into a substantially advanced and totally different design. it's also accepted to be superior in nearly every way imaginable.
another consideration i have had is to simply make upper and lower a-arms and locating the rear bearing 3" further out to eliminate the use of wheel adaptors. i can see the possibility of simply welding in a fore and aft pick up point directly above the current bearing carrier location to hand down below the framerail and provide an attatchment point for the upper arm. this would, however, result in a signifacantly shorter than optimal upper a-arm (i estimate an overall length of about 6"). the lower a-arm would have to be shortened as well so as not to induce a similar radical camber change with suspension travel. i was thinking about 9-10" for the lower a-arm.
for my application, i think this would probably be the simplest and most effective solution since i really like the c-4 wheel and the offset would be well suited to this design. it would be totally undo-able for owners who wished to keep the conventional wheels or offset.

norvalwilhelm

A 6 link is just a upper and lower strut rod totally adjustable with left and right ends , parallel to the ground, each other and the 1/2 shafts.
The 1/2 shafts are full floating, no clips and free to move in and out with suspension travel, No binding and the U joints are only to transmit power and not as a suspension component.
The trailing arm is just left alone with it's front pivot point, stock shock location with just an added upper strut rod mount.
Lying under the car without the spring attached , minus the shock also the trailing arm can be put through it's full travel without binding, stays the same camber at all time and you can watch the yoke moving in and out of the rear end.
With a fixed yoke how will the wheel move without a camber change if the yokes try to move in and out throughout the travel.
A 6 link is easy to build other then this one time the rearend must come out to weld to the crossmember. The trailing arms also need a bracket welded to them.
Your upper and lower A arms require total re engineering.
As for ride comfort with softer springs why can't our C'3 give a good ride. With fresh everything our ride can be smooth. I go over railway tracks without slowing down because I will not get the clunk going over them.
Have to admit I am thinking about changing both springs to more performance ones which will kill the ride.
I might take George's advice and turn my car into something that handles a bit better but at what cost to the ride?

PROSOUTH

:iagree: with NORVAL

I think we looked at this sometime ago and decided the 6 Link was the way to go. If I were to scrap the 6 Link I would go with a C-4 style rear asm made to conform to the C-3.

At one time I had a question about using an upper trailing arm such as the the C-4 with the 6 Link. I don't remember if I ever got an answer though. I think this is what you are after is the further stabilization of the rear suspension with another support. Would this aid in traction or handling if a lower control arm was made to coordinate with an upper bar? Similar to the C-4 set-up again? Jim