When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
By 1:30 into the vid, I thought to myself, you are more than mere mortal.
I then proceeded throughout the vid, and by the end determined that you are a jack of all trades and master of all. And also convinced: you are not a mere mortal! What a feat. Simply wow!
Beauty! so on to dynamics.. how do u plan to balance the car with the added weight in the rear? By balance i mean: control lateral forces.. usu this is done by 1) adjusting suspension geometry to alter camber thrust(in turn) for both outside and inside wheels(front back and diagonally eeeek).. and also 2) adjusting wheel rates..
Judging by your thoroughness and passion, dynamics may be in the wheelhouse also.. Have you read Gillespie or RCVD by chance?(you mention roll center adjustments)
Last edited by NotFastYet; 05-17-2021 at 04:36 AM.
Beauty! so on to dynamics.. how do u plan to balance the car with the added weight in the rear? By balance i mean: control lateral forces.. usu this is done by 1) adjusting suspension geometry to alter camber thrust(in turn) for both outside and inside wheels(front back and diagonally eeeek).. and also 2) adjusting wheel rates..
Judging by your thoroughness and passion, dynamics may be in the wheelhouse also.. Have you read Gillespie or RCVD by chance?(you mention roll center adjustments)
Added weight due to the roll bar?
Yes, I'm really looking forward to getting this car on the track and experimenting with suspension settings and alignment. I didn't build that roll bar for looks, ha ha. Actually it was designed to stiffen the chassis.
I did take some weight of the rear bumper (fiberglass), custom made aluminum bumperettes, light weight turn signal housings, lightweight rear glass, lexan quarter windows, etc. Most of those items are behind the axle whereas the roll bar is mostly in front of the rear axle. Hint: Polar moment of inertia.
All really fun stuff, if you ask me. Those books you mention are great. I also have Herb Adams, Chassis engineering and Smiths, Engineered/Tune to Win.
I just got new tires and wheels this week too! Can't wait to start the alignment/setup process video series. Coming soon!
I must have read too fast, i thought you mentioned an engine swap.. from the original.. what engine(year) are u using? thx
Gotcha, this car is confusing because it's a mashup of parts. The chassis is a 1974 911S. Original engine is long gone or at least lost.
The current engine is a 912 engine I had lying around.
The future engine is an 87 3.2L Carrera engine.
The phase 3 engine is the same 3.2L but stroked and bored to 3.5L
Oddly enough Porsche used the same size rear torsion bars on 912 and 911 if I remember correctly. There's a huge difference in weight between these engines!
what i can guess: porsche sets up their cars, geometry, tuned susp, wheel rates/stiffness to some acceptable performance specification... if this is altered by moving weight or adding/removing weight the specs will be off
what i know: textbook and 3d dynamics software dictates that suspension be in “accordance” with com.. mess with the com -> need to make adjustments to maintain performance.. Enhancing performance could be unattainable with some fixed(unalterable) geometry
i need to verify all that first hand(my project) but mathematical models are the starting point(for more math, ha)
Here's a video on brake caliper rebuild. Even though these are for my 356, the 911 calipers aren't that different.
Fun fact, disc brakes were first introduced on the 356B in 1962. Very similar to M calipers which was used until 1977.
Rebuilt door strikers really improve the driving experience without the doors rattling around. Towards the end of this video I explain how I adjusted the door striker for the best fit without any rattling sound when hitting bumps in the road.
Video Link
Not sure how straight youre going for(ive never done an alignment so i really cant speak on it).. but i have been looking into designing a somewhat mechanical CMM for my frame/project.. Ive found that “linear shaft” has tolerances up to .001”, pretty much the straightest metal u can buy.. Lintec has good pricing, after scouring the web and bothering many vendors.. Maybe this is helpful?
Hey Not Fast Yet,
A car CMM would be awesome! For those that don't know CMM stands for Coordinate Measuring Machine and they are typically used to inspect parts in 3D with automatic readouts.
What do you want to measure? Chassis points or wheel alignment or both? Are you only using the cmm bars as a straight edge?
For my purposes a string is pretty straight. If I switch to fishing line, I could measure to +/- .020" most likely. .040" is good enough for car stuff if you ask me. The workshop manual tolerances are +/- 1mm worst case (.040")
I have not measured bump steer yet, but will....so keep watching. (dial indicator on the rotor most likely.) Or maybe a laser pointer projected on the wall, but that's harder to quantify.
Will probably do bump steer later down the road after I change the spindle height in the front. Also once the coilovers go in the rear, it will be a good time to measure rear bump steer.
Suspension travel is another important one. Will probably remove or cut some of the bump rubber in the front given my current ride height, but we shall see. I think the rear has plenty of travel up and down already, but doesn't hurt to check.
Need to add anti-rolls bars too! So, far from done with suspension setup, ha ha. This first go around is just to make the car more drivable for longer trips. I'm scrubbing lots of rubber with crazy toe-in!
Cheers,
Tom
05-03-2021, 02:45 PM
