Post questions and info about safe and unsafe materials that can be or should not be used to construct a launcher. Also post things about different universal accessories for your cannon (breech loader, muzzle break, etc.)

Postby An Apple Pie » Sat Dec 16, 2006 11:08 pm

I am working on a piston valve with o-rings at the moment. I just went to Home Depot and Lowes, and neither of them have o-rings large enough.

What I need is one that will seal between the ID of 2" PVC Pipe(sch. 40) and about halfway between a 1 1/4" End Cap and the OD of some 1 1/4" PVC Pipe(sch. 40).

Any ideas on what size I would need and where I could get them:?:

Yes I know where to get the ID and OD of pipe although I do not know if you need to add anything to get the o-ring size, because it needs to seal.
An Apple Pie
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Postby np0405 » Sat Dec 16, 2006 11:36 pm

Ace Hardware or McMaster maybe?
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Postby An Apple Pie » Sat Dec 16, 2006 11:39 pm

Okay, any idea on what size:?:
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Postby crashtestdummy » Sun Dec 17, 2006 12:37 am

Does the O-ring need to seal on the 1.25" fitting --> 2" pipe or does it need to be on the 1.25" pipe (next to the fitting) and seal from there to the 2" pipe.

I believe that Ace has them up to 3/16" width and around 2" in diameter. I may be slighly off, though. The best thing would be to just take your fittings to the store and test the o-rings for the best fit, because Ace usually has them in little zip-loc bags.
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Postby An Apple Pie » Sun Dec 17, 2006 8:31 am

Yeah, I will just do that. Oh, and the o-ring is going to be is a groove cut into a 1.25" End Cap.
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Postby Navigator7 » Sun Dec 17, 2006 12:50 pm

Get an O-ring Repair Kit.
O-ring kit's I've bought are around $30.00.
Make your own o-rings!

Kit includes:
o 3' lengths of various o-ring sizes. (1/16 on up to 3/8)
o A fixture to assure 90º cuts.
o A sharp razor to cut the o-ring
o Super glue.

Throw away the instructions, the super glue and find the sharpest cutting tool you can find. Keep the box and write in big bold letter: O-RING REPAIR KIT. USE FRESH SUPER GLUE!

Having used these kits many many times....find the o-ring material you need instead....and cut it your self.

These glued o-rings work in all but the highest pressure applications....and then, even a few work fine in high pressure application anyway.

The trick is to use clean o-ring material, minimal super glue and make a square cut.
I shoot the 0-ring end with starting fluid or brake cleaner and let it dry and never touch the end after that. Don't use a rag...just let the pieces dry.
Same with the razor.
I make sure there are no twists in the o-ring and cut through both o-rings at once.
Just a hint of glue on one end of the o-ring. Bring the ends together perfectly and then become a statue for a while as the glue cures.
I've tried to pull my work apart and the o-ring has broken elsewhere.
If you get sloppy....IE dirt or oil on the o-ring or a contaminated razor.....the joint won't hold as well or at all.

For spudding...it's the only way to go.

The kits offers many o-ring sizes...That's the worse part. You don't need a kit, you need o-ring material of the size you want, a very sharp and clean razor and super glue.

The other thing is....Superglue...or cyanoaclate.... or whatever it's called...seems to have a shelf life. I think the glue in a kit is too old when you buy the kit. There is nothing like fresh superglue. I've been on projects costing $100.000.00/day stopped for want of a suitable o-ring and going again because of these $30.00 kits and fresh superglue.

For small o-rings...say under 1.25"....it's not worth the effort unless in an emergency.
Buy an O-ring kit for small o-rings.

Don't be afraid of the idea...it works.
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Postby Mr.Plow » Sun Dec 17, 2006 12:53 pm

You can also get O-ring kits, which contain several hundred O-rings of varying dimensions, at Harbor Freight and the like for very cheap. I got a 400 piece one for ten bucks.
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Postby sgort87 » Sun Dec 17, 2006 2:40 pm

I was interested in what Plow was talking about and discovered exactly what Navigator was talking about, and for a 6th of the price!

http://www.harborfreight.com/cpi/ctaf/d ... mber=30958
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Postby Navigator7 » Sun Dec 17, 2006 3:26 pm

Gort...Yes...you nailed it!

I believe o-rings are universally not understood by most and are often mis-used in an attempt to hide the sins of poor craftsmanship.
<img src="http://www.applerubber.com/library/src/tolstackupchart.gif">
As a machinist...I learned tons about o-rings and o-ring tolerance.
I'd get this....."Just give me some grooves for o-rings." (A misguided belief on the part of the customer o-rings fix leaks.)

The biggest lesson was this:
"Few customer never have enough time to do it [$]right[/$] but they all have enough time to do it over!"
So the lesson is...take the time and do it right in the first place!
<img src="http://www.applerubber.com/sdg/guide2/oring/src/31.jpg">

Everybody should "Bookmark" this website:
<a href="http://www.applerubber.com/library/techofail.cfm">O-ring Troubleshooting</a>
This website is full of good stuff about o-rings.

OH! BTW....Register. Inside there are tons of calculations for 0-rings. Very informative website!!!!

If you don't have a Mac...get one!
Get it? Apple......
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Postby An Apple Pie » Sun Dec 17, 2006 3:32 pm

Will rubber washers work as O-rings?

I am using them on a barrel sealing piston valve, and I just went to ACE, and that was the only one they had that was the right size. It seems pretty mush like a normal o-ring except it is square. Not like the whole thing makes a square, just if you were to cut it and look at it from the side it would be square.
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