Moment Exerted on pressure plate by Spring End

[ptunis]

Hi all, I'm new to the forums and am trying to see if anyone can help me with this calculation.

We are designing a larger control valve that uses a helical compression spring with a rate of 2,100 lbf/in. The vale will be pre set to 10" of compress, so the valve will be forced shut with 21,000 lbf (+/- 10%)

The problem we are encountering is that the one end of the spring sits on a plunger, which is currenly free to rotate. We are looking to put guides in to stop this from happening but are looking to see what type of forces we will have to put up with.

I was wondering if any one knew how to calculated a moment exerted on the plunger by the compressed spring which would cause it to rotate when compressed.

Thanks! Any help is greatly appreciated

 

[btrueblood]

There are some equations and graphs in Wahl's Mechanical Springs, amongst other sources. He notes that the theory can differ from practice by 30% or more.

 

[Cockroach]

You know what? You're experiencing wrapping due to relative rotation of ends as the spring is being compressed. I've seen some equations is the Wahl's reference, there are other in spring manuals and website references.

Seen this before, but never really had an issue with it. Interesting.

Regards,
Cockroach

 

[MikeHalloran]

Note also that the axial force exerted by the spring does not conveniently appear along its axis. ... because there's no material there. So the plunger is loaded asymmetrically, just to make things more interesting.

Have you considered a circular array of smaller, cheaper springs, like in an automotive clutch's cover?


Mike Halloran
Pembroke Pines, FL, USA