active coils in compression spring?

[kkg123]

how to measure number of active coils in compression spring? will someone explain

 

[Tmoose]

http://i.ebayimg.com/t/MOPED-SHOCKS...Q=/$(KGrHqN,!k0E+1li8MSQBQPklUlrd!~~60_57.JPG

the lower 5 or 6 coils on these springs on these moped rear shocks are already touching each other, so can't join in any reindeer games. They are not active. The other 6 or 7 coils are active. The upper most coil is pretty much not active, and much of it is ground off to create a flat surface too.
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The coil spacing on these springs varies considerably. As load is applied the closely spaced ones would touch and becom inactive.

http://i.ebayimg.com/t/TRIAL-MONTES...Q=/$T2eC16FHJIIE9qTYI4s)BQW4vK)o)!~~60_57.JPG

 

[desertfox]

Hi
Follow the link and scroll down there are formula for working the active coils out depending on the design of the spring ends.

http://www.roymech.co.uk/Useful_Tables/Springs/Springs_helical.html