Track Report 50 F Vacuumed water off. Track green but clean-
The car is hooked up well. The new porsche body was planted on the straight and the sweeper. I have increased front shock oil to 37.5 weight from 35. I increased the rear to 35 weight from 30. The car was a bit twitchy. Increasing the shock oil weight took some of it out, but it is still just a bit twitchy. I may play with the droop next. I can adjust it with spacers inside the shock under the piston. No breakage yet.
Spring Rate
I have a collection of VCS Microshock springs which are about 10 mm Id and 12 mm OD from two sources. Associated and
MurdockRC. The spring rates don't match the labels very closely and in the case of the Associated springs are way off. Here is a formula that you can use to calculate the spring rate using measurments from your dial caliper. All of my springs have 6 active coils to start with. I have cut my red and blue one down to about 3.5 coils.
Spring Rate = (G x d^4)/(8 x N x D^3)
G = Torsional modulus for steel = 11.25 x 10^6
d = the diameter of the spring wire in inches
N = the number of active coils (full coils)
D = the mean coil diameter (the average of the spring OD and spring ID
8 = a geometric constant for all coil springs
This formula works for full size cars also.
So here are the results it may help you if you use this type of spring or if you are Marty and need a spring for your prototype front end.
Associated Blue = 13.5 lb
Associated Copper = 13.7 lb (this was supposed to be my new 16 lb spring)
Murdoch RC Gold 14.1 lb
Murdock RC Copper 14.6 lb/in
Associated Red 18 lb (this is supposed to be a 14 lb spring)
Note that IRS sells springs for The RC18 as well as shocks for this minitruck.
John