helical springs in compression and torsion 2

[bigTomHanks]

I have a spring that is being put over a bolt and a large nut is tightened over the spring. When I tighten the nut it will compress the spring but it will also turn the spring(creating torsion). I need to find some information on this topic so that we can find out if during operation of the device the spring adjust and straightens itself out. How will this affect the operation of the device. This device is adjusted and if the spring changes any after this adjustment then the device might become out of adjustment.

 

[MikeHalloran]

Relying on friction from a spring load to lock an adjustment is not a winning strategy.



Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

 

[desertfox]

Hi bigTomHanks

Can you provide more information about your application ie:-
physical sizes of bolt and spring, forces involved and how much your compressing the spring and what is the device?
The reason I say this is that compression and tension springs tend to wind up or unwind out during normal peration
but only by a small amount, which is dependant on the physical characteristics of the spring. This winding leads to a term known as ratching. So even if you could tighten the spring down without it twisting, you would probably find during compression of the spring in normal operation that it would wind up and then unwind as the load was released. A couple of suggestions you might try to avoid torsional load during assembly is place a washer with between the top of the spring and nut, if the washer is made with a couple of flats on it so that it can be held still while you tighten the nut to the required position.
Another idea would be to pre-compress the spring to the required length and then just run the nut down to the spring
(if possible).

regards desertfox

 

[bigTomHanks]

Great! Thanks a lot desertfox. I'll look into the winding out during normal operation. I believe that is what is actually happening here. I say this because the spring appears to be rotating exactly with the nut as it is being tightened.