O-ring as an extension spring?

[Glenn Gordon]

Hello,

I have an application where I would like to use an o-ring as an extension spring.

It is not a heavy duty application and it is not subject to any cyclical loading.

This o-ring in this mechanism is to hold tension between two pins whose center to center distance are infrequently adjusted.

Can you recommend what o-ring material would offer the best longevity in this application?

Thanks,
Glenn

 

[JohnRBaker]

That would depend on the environmental conditions.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
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[Glenn Gordon]

The o-ring is in contact with two stainless pins and the ambient air (room temperature).

Glenn

 

[Compositepro]

From experience, I would recommend EPDM.

 

[dgallup]

If you look at the ASTM D 2000 and/or SAE J200 spec for rubber there are a few materials that have ultimate elongation as high as 600%. Given the minimal stated requirements, one of these would be "best". However, I suspect in this case the "best" would be whatever the local building supply has on hand.

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[Glenn Gordon]

Thanks for the replies

 

[btrueblood]

Nitrile would probably work fine too, and be a bit cheaper than epdm. It would also relax less (maintain a more constant tension over time). But, epdm will stand up to a lot more stuff (ozone, uv) that might be coming through your "ambient air". We use a "bungee cord" to hold a lid on a product that sits in a potentially ozone filled, potentially moist environment, we fabricate the cord from some 1/8" epdm cord stock.