Another O-ring Discussion

[JFettig]

The reason I am bringing this up is because Im extremely confused. Hara always posts this for O-ring grooves:


Take a look at these links. and they arent the only ones...
http://www.spira-emi.com/mainpages/g...n.htm#standard
http://www.quadion.com/factbook/4-10.htm

They basicly tell me to cut the groove for a 1/8(.139") O-ring with a 3/16"(.1875) EM, .1- .104" deep.

Although Hara's diagram tells me much different
.09313-.0973 for depth
1.6402-1.668 for width

Then I remember measuring .159" for width on the maze3 O-ring. If I dont get any answers that clear things up, I just might have to take that wb out of my system and measure it out.

Thanx
Jon

[N8]

Part of the problem is that 1/8" O-rings are not 0.125", but instead are actually (usually) 0.139". Because of this you must use different O-ring groove dimensions.

The other factor is that there are different O-ring dimensions depending on water vs air vs vacuum.

I just built a waterblock with an O-ring groove and originally used the 0.125" dimensions and the groove was too small. I then remachined the groove width and depth to the dimensions given here on this page and it worked great:

http://www.mhatt.aps.anl.gov/dohn/re...ace_gland.html

You use the groove width for liquids on the chart. Remember that you have to have room for the O-ring to squeeze, and remember to make the depth compensate for any sanding or lapping that you might do to the top side (where the groove is) after machining.

[JFettig]

thanx a ton, thats similar to what I am thinking, same as those 2 links. and yes, I did do .139"

that graph basicly tells me to cut with a 3/16" EM and .1" deep.

-EDIT- By looking at that table, It appears the equasion Hara is spreading around is for vacume and gasses.

Jon

[bigben2k]

Excellent info N8, and good catch Jon!

Bill posted some practical info, based on his many years of experience, in my waterblock thread (see sig).

[Since87]

Originally posted by bigben2k

Bill posted some practical info, based on his many years of experience, in my waterblock thread (see sig).

Only 21 pages to wade through to find it.

[JFettig]

Sean, Delrin is too flexable... It leaks....

http://forum.oc-forums.com/vb/showth...22#post2067722


Jon

[Since87]

Sorry to hear that. The block looks good, and avoiding the whole aluminum/copper issue is a big plus.

[JFettig]

with silicone or GOOP, it works great though! I GOOPed it, Itll be awesome. The gpu block will be great with an O-ring, theres no way that stuff will flex
I couldnt get the 1ft bar to flex


Jon

[bigben2k]

Originally posted by Since87
Only 21 pages to wade through to find it.

and for the benefit of the "search handicapped", here's Bill's advice:

after designing and doing failure analysis of o-ring joints for many years (in both static and cyclic pressure service),
there are several useful guidlines:
- when the component surfaces make contact, as they must, there should be 30 to 40% compression of the crossection
- the o-ring's volume should be between 60 and 70% of the groove's
- using a 30 to 50 Shore A durometer (hardness) material will make the surface finish less critical
- the o-ring's (centerline) length should match the groove's (do NOT stretch)
- the groove must have an outer containment ring to 'capture' the o-ring, else it is functioning as a gasket (different design basis)

do not use a sealant with the o-ring (no need if properly designed, will overfill the groove, make disassembly a pain, etc)

o-rings, properly designed, are FAR more reliable than gaskets