mid-range sweep for calculation length

[makeng]

Good morning, everyone.
I searched in the various forums the solution of a simple problem: calculate the length of a sweep also the different sectors. to better understand I should in fact calculate the length of a cylindrical spiral (molla) by measuring the line of half-work . but how do I get it? definitely (spero) at the solution is around the corner....but I don't even see that!
Thank you.

 

[LuPo_81]

but to create your spiral you didn't use a curve as a path? Can't you measure that?

 

[makeng]

No. in the helical sweep there is no need to create a curve... .

 

[cletus]

hi, usually for the springs I create the helical surface (and not the solid) and the intersection with the curve representing the average diameter; then use the curve as a rif for a variable section sweep (suppressed in my model)