Chassis blueprints/ irregularities?
Posted: Sat Nov 03, 2018 2:15 pm
Hi
I'm wondering if anyone is aware of blueprints for the SR chassis? Mike Davies at SCCA-E has told me that there are no drawings, which seems odd. To what specifications are major repairs done to frames?
The reason I'm looking for information is that I've discovered some oddities with the front end of my chassis / suspension when comparing (with other cars) the orientation of the front suspension to the main front bulkhead of the frame. There is some evidence of previous crash damage to my chassis (#205) but not enough to explain what I'm seeing. The situation is that the top ball joint on my front suspension is about 20 mm 13/16" further forward than other cars (less caster) . I measured this by putting a straight edge across the front frame bulkhead and measuring back to each upper ball joint. In addition it appears that the old pressed upper control arms locate the ball joints about 1/4" further forward (less caster) than the new tubular rocker arms. This was confirmed by measuring several "thought to be good" pressed rockers. Mike Davies said that there should be no difference....?
I had been having a problem getting enough adjustment to give anything over 3 deg. caster until I discovered that there is a longer version of the lower trailing front suspension link. Although, even even though when this was corrected and I was able to get front caster adjusted to 6+ deg., I still am struggling to tune out poor turn in and heavy understeer. I have tried running 4+ deg neg. to -5 deg neg camber, and 4 to 6 deg. + caster.
I'm not sure if the location of my (virtual ) kingpin location so far forward is a culprit or not, I can see that this would effect the ackermann steering geometry , by moving the hubs forward to the axis of the steering rack.. The location of my front wheels is noticeably further forward in the wheel opening than other cars I see and tires rub on the front wheel arches.
Any thoughts?
Glenn
I'm wondering if anyone is aware of blueprints for the SR chassis? Mike Davies at SCCA-E has told me that there are no drawings, which seems odd. To what specifications are major repairs done to frames?
The reason I'm looking for information is that I've discovered some oddities with the front end of my chassis / suspension when comparing (with other cars) the orientation of the front suspension to the main front bulkhead of the frame. There is some evidence of previous crash damage to my chassis (#205) but not enough to explain what I'm seeing. The situation is that the top ball joint on my front suspension is about 20 mm 13/16" further forward than other cars (less caster) . I measured this by putting a straight edge across the front frame bulkhead and measuring back to each upper ball joint. In addition it appears that the old pressed upper control arms locate the ball joints about 1/4" further forward (less caster) than the new tubular rocker arms. This was confirmed by measuring several "thought to be good" pressed rockers. Mike Davies said that there should be no difference....?
I had been having a problem getting enough adjustment to give anything over 3 deg. caster until I discovered that there is a longer version of the lower trailing front suspension link. Although, even even though when this was corrected and I was able to get front caster adjusted to 6+ deg., I still am struggling to tune out poor turn in and heavy understeer. I have tried running 4+ deg neg. to -5 deg neg camber, and 4 to 6 deg. + caster.
I'm not sure if the location of my (virtual ) kingpin location so far forward is a culprit or not, I can see that this would effect the ackermann steering geometry , by moving the hubs forward to the axis of the steering rack.. The location of my front wheels is noticeably further forward in the wheel opening than other cars I see and tires rub on the front wheel arches.
Any thoughts?
Glenn