Hi ばね初心者sama,
Thank you for your inquiry about conical spring!
The parameter, “RS” means that it is the minimum radius of the coil circle when the parts of coil is contacted.
You can find the answer of “RS” by using the formula that find the solution of “P”.
We think it is the best way to find the solution as a variable from the calculation formula of δ and P.
We hope we can be of any help to you!
Thanks!