spring noise 1

[subsearobot]

Hey all!
We are trying to reduce size in a handheld instrument...

One idea calls to use a slender, long travel compression spring riding over a metallic shaft. the problem being noise emitted when the spring buckles and snaps against the shaft. Secondarily, the sound emitted when the buckled spring rubs along the shaft during continued compression.

We need to see 250,000+ cycles minimum. forces are low (couple pounds compression force.) total travel is about an inch.

has anyone used coatings to mitigate audible emissions from spring assemblies? other things to look try?
please help!

thanks

 

[dgallup]

I've used molybdenum disulfide coated springs for wear resistance which it did help. No idea if it was quieter. The MOS2 coating was put on with a dip & spin process which sometimes left blobs that could break off.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[btrueblood]

Put a snug-fitting delrin bushing between the spring and the shaft? "Clipping" it loosely to the spring would keep it centered; then you'd have to see if the 2nd buckling mode happens...rinse and repeat.

 

[subsearobot]

thanks dgallup and btrueblood. good thoughts to examine!

 

[MikeHalloran]

I've used multiple compression springs stacked over a shaft, with a flanged oilite bushing inserted in each end of each spring.



Mike Halloran
Pembroke Pines, FL, USA

 

[btrueblood]

Mike, your example is multiple springs stacked in series (end to end), not one inside another, if I'm following you correctly. As long as the bushing prevents rotation of the spring ends (i.e. is a snug fit to the shaft), this is a good idea too, provided the closed ends of the spring don't take up too much axial length in non-active spring coils.

 

[subsearobot]

mikes idea could work well- the rod is actually a hex rod, so has built in anti-rotation.
problem is that we are tight on length too, but then again, noise could kill the whole thing...

 

[Compositepro]

You could use plastic coated wire for the spring.

 

[3DDave]

You can pre-buckle the spring so that you have control of that and the point of contact.