3000m rear wishbones stance
Discussion
Adrian@ said:
Imagine as this is a clock..If the centre pivots are the swing point and 45min or 15min is level.... then the arms are at 40-41min OR 19-20min.
Adrian@
So with the rear at rest and the car normally laiden the lower wishbones are not level? at the 45min - 15min position) but actually drooping (40min - 20min position) Adrian@
So presumably the drive shafts would be in the level (45-15min position)?
Hi Adrian,
4-5 minutes on a clock represents 24-30 degrees rotation. I'll guess you didn't mean 5 minutes of angle measurement, as that's only .08333 degrees rotation, which equates to less than 1/16" ride height difference, from the wishbones being horizontal.
My measurements show that if the rear wishbones are horizontal, the chassis ground clearance (there) is 7 3/8", whereas the front clearance is 6 7/8", with the lower wishbones horizontal.
I suspect you meant 5 degrees.
When the rear wishbones droop 5 degrees, the clearance is 8 3/8", and with the suspension compressed to 5 degrees, from horizontal, it is 6 3/8".
What are we looking for, a chassis that's parallel to the ground or 1" of rake, front to back? (Something else?)
I am guessing, that the point is to link the front and rear camber curves, in a way that's not completely frightening to the driver.
Starting with the rear lower wishbone in droop at -5°, and compressing the rear suspension in 5° increments,
the first increment yields .75° camber gain,
the second increment 1.04° camber gain,
and the third, 1.38°.
Meanwhile, the same three steps on the front give the following results:
0-5° = .53°
5°-10° = .62°
10°-15°= .73°
Judging by how far apart they are, and adding the front ARB effect, I can't see a 1/2" one way or another making any difference, except to CG, and not much of one there. When we introduce heavier springs, the real world camber gain in cornering is reduced.
Am I wrong in thinking that the ride height matters less as the spring rates increase?
Many thanks,
B.
4-5 minutes on a clock represents 24-30 degrees rotation. I'll guess you didn't mean 5 minutes of angle measurement, as that's only .08333 degrees rotation, which equates to less than 1/16" ride height difference, from the wishbones being horizontal.
My measurements show that if the rear wishbones are horizontal, the chassis ground clearance (there) is 7 3/8", whereas the front clearance is 6 7/8", with the lower wishbones horizontal.
I suspect you meant 5 degrees.
When the rear wishbones droop 5 degrees, the clearance is 8 3/8", and with the suspension compressed to 5 degrees, from horizontal, it is 6 3/8".
What are we looking for, a chassis that's parallel to the ground or 1" of rake, front to back? (Something else?)
I am guessing, that the point is to link the front and rear camber curves, in a way that's not completely frightening to the driver.
Starting with the rear lower wishbone in droop at -5°, and compressing the rear suspension in 5° increments,
the first increment yields .75° camber gain,
the second increment 1.04° camber gain,
and the third, 1.38°.
Meanwhile, the same three steps on the front give the following results:
0-5° = .53°
5°-10° = .62°
10°-15°= .73°
Judging by how far apart they are, and adding the front ARB effect, I can't see a 1/2" one way or another making any difference, except to CG, and not much of one there. When we introduce heavier springs, the real world camber gain in cornering is reduced.
Am I wrong in thinking that the ride height matters less as the spring rates increase?
Many thanks,
B.
Hi Keith,
I assure you, there's A LOT MORE that I'm overlooking*. Thinking about suspensions as dynamic systems is fairly fresh to me. Especially because of that, thanks for the comment. Admittedly, I'm trying to understand it.
By the way, I have no intention of moving the pick-up points. I've always had a desire to find out (prove) just how capable these chassis are.
* I know I have to keep track of yaw moment of inertia, slip angles, Ackermann effect, camber gain, roll centers, mass centroid axes, and more. Still a little overwhelmed trying to imagine all of these effects acting on the system. Easy enough, when you break out a couple, or three, but linking them all together is difficult for me.
Best,
B.
I assure you, there's A LOT MORE that I'm overlooking*. Thinking about suspensions as dynamic systems is fairly fresh to me. Especially because of that, thanks for the comment. Admittedly, I'm trying to understand it.
By the way, I have no intention of moving the pick-up points. I've always had a desire to find out (prove) just how capable these chassis are.
* I know I have to keep track of yaw moment of inertia, slip angles, Ackermann effect, camber gain, roll centers, mass centroid axes, and more. Still a little overwhelmed trying to imagine all of these effects acting on the system. Easy enough, when you break out a couple, or three, but linking them all together is difficult for me.
Best,
B.
. I'll take it off your hands....Gassing Station | TVR Classics | Top of Page | What's New | My Stuff