Das mit der Wendeltreppe war Quatsch von mir, sorry.
Aber beim Googeln nach "one coil of the spring" findet man eine Menge Treffer, z.B. dieses US-Patent
> I claim:
2. A wrap spring couping as defined in claim 1 in which said projecting means comprising a protrusion formed integrally with and projecting radially outwardly from one of the coils of said spring.
3. A wrap spring coupling as defined in claim 2 in which said protrusion projects radially outwardly from the final coil of the spring located adjacent said one end of said spring.
Oder das hier, über die Federung vom Auto:
>I bought some spring clamps for $3.99 a pair. When you shorten springs, it has a twofold effect. [...] Imagine a 10 coil spring sitting upright on a table. You place 200 lbs on the spring. The weight moves the top of the spring down 1 inch. So your spring rate is 200 lbs per inch. Each one of the ten coils has shrunk 1/10 of an inch.