o-rings

8-Ball · 01-20-2003, 01:52 PM

How big a groove do you need for an o-ring.

Would 1mm deep be sufficient?

How wide would it heve to be? would 2mm be enough or would you need 2.5, to go with the depth of 1mm.

8-ball

Cathar · 01-20-2003, 02:02 PM

It all depends on what O-ring you choose.

There are numerous books on the correct use of O-rings. Pretty much any metak-working machine-shop will have such documents handy. Other than that, Google is your friend.

chewyboy · 01-20-2003, 07:22 PM

you want some compression and a good fitting. I'm doing mine with 1/8" dia o-ring material because i have about 500 yards laying around and dont have any 1/16" :P anyway i'm doing a 1/16" on the bottom plate and a 1/32 cut on top so there is a bit of compression. but go with what your o-ring material asks for, all are different.

bigben2k · 01-20-2003, 07:32 PM

Quote:

Originally posted by chewyboy
...but go with what your o-ring material asks for, all are different.

Really? That's not what I read...

I'll be using a 1/16 o-ring, in Radius. BillA posted some excellent specs, based on his years of experience:

Quote:

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)

If you need any help, let me know.

chewyboy · 01-20-2003, 08:08 PM

I'll admit he is an expert i've only used it for maybe 10 projects (which by no means makes me an expert) but from my experience go with what the o-ring manufacturer calls for. they all are different. some are harder rubber that do not like compression as much and some are softer and like more compression. so yeah i am disagreeing with him a little bit :P but not enough to start a flame war.

bigben2k · 01-20-2003, 08:49 PM

...and I've never used it, but my readings indicate a 20% height compression. (gotta find my print-outs...)

Since the materials have a durometer rating, I had a hard time understanding your statement, but it makes sense now.

I've opted for silicone, as a material, because it's cheap, and will resist the chemicals I'll have in the coolant. Bill suggested EPDM, but that first price quote scared me off of it. It's actually cheaper than I thought.

Neomoses · 01-21-2003, 01:58 AM

www.efunda.com is your friend when it comes to this. It's quite possibly one of the best engineering reference sites available.

LiquidRulez · 01-22-2003, 12:26 AM

gotta love efunda !

Lt.Dan · 01-22-2003, 11:31 PM

Great Site Thanks!

01-20-2003, 01:52 PM	#1
8-Ball Cooling Savant Join Date: Feb 2002 Location: Oxford University, UK Posts: 452	o-rings How big a groove do you need for an o-ring. Would 1mm deep be sufficient? How wide would it heve to be? would 2mm be enough or would you need 2.5, to go with the depth of 1mm. 8-ball

01-20-2003, 08:49 PM	#6
bigben2k Responsible for 2% of all the posts here. Join Date: May 2002 Location: Texas, U.S.A. Posts: 8,302	...and I've never used it, but my readings indicate a 20% height compression. (gotta find my print-outs...) Since the materials have a durometer rating, I had a hard time understanding your statement, but it makes sense now. I've opted for silicone, as a material, because it's cheap, and will resist the chemicals I'll have in the coolant. Bill suggested EPDM, but that first price quote scared me off of it. It's actually cheaper than I thought. __________________ WBTA (Water Block Testing Alliance) Nordic Hardware WC 101

01-20-2003, 02:02 PM	#2
Cathar Thermophile Join Date: Sep 2002 Location: Melbourne, Australia Posts: 2,538	It all depends on what O-ring you choose. There are numerous books on the correct use of O-rings. Pretty much any metak-working machine-shop will have such documents handy. Other than that, Google is your friend.

01-20-2003, 07:22 PM	#3
chewyboy Cooling Neophyte Join Date: Dec 2002 Location: us Posts: 75	you want some compression and a good fitting. I'm doing mine with 1/8" dia o-ring material because i have about 500 yards laying around and dont have any 1/16" :P anyway i'm doing a 1/16" on the bottom plate and a 1/32 cut on top so there is a bit of compression. but go with what your o-ring material asks for, all are different.

01-20-2003, 08:08 PM	#5
chewyboy Cooling Neophyte Join Date: Dec 2002 Location: us Posts: 75	I'll admit he is an expert i've only used it for maybe 10 projects (which by no means makes me an expert) but from my experience go with what the o-ring manufacturer calls for. they all are different. some are harder rubber that do not like compression as much and some are softer and like more compression. so yeah i am disagreeing with him a little bit :P but not enough to start a flame war.

01-21-2003, 01:58 AM	#7
Neomoses Cooling Neophyte Join Date: Nov 2002 Location: Rolla, MO Posts: 51	www.efunda.com is your friend when it comes to this. It's quite possibly one of the best engineering reference sites available.

01-22-2003, 12:26 AM	#8
LiquidRulez Cooling Savant Join Date: Sep 2002 Location: In Hell Posts: 322	gotta love efunda !

01-22-2003, 11:31 PM	#9
Lt.Dan Cooling Neophyte Join Date: Jan 2003 Location: Northern CA Posts: 14	Great Site Thanks!

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