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Building Tips and technical articles. => 1/2 A building. => Topic started by: Larry Renger on June 19, 2010, 12:06:04 AM
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Smallparts.com being who they are, I had to order 100 o-rings for my Cub .074 diesel to get one. They are Viton elastopolymer, and resistant to heat and chemical stress.
If anyone wants one, a self-addressed, stamped envelope will net you one (or more, let me know) in return. The 100 only cost $8 with shipping, so this is a freebie!
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What size?
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I use the black O rings from the local hardware store. They seem to work fine, and they will sell you as few as you want.
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1/2" OD, 1/16" cross-section.
How long do the hardware store o-rings last in a diesel head?
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I don't know. I've never had one fail or leak. If I have occasion to take the contrapiston out, I replace the O ring because it is compressed looking. Crossection D instead of O. :o
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I use standard nitrile "O" rings on the contra pistons in my home-made diesels. They seem to work fine in these long-stoke cool running engines. I haven't tried them in my hotter engines (Cubs & McCoys) where I use the Viton versions.
Orv.
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Hi Orv,
I'd like to try Viton O-rings in my McCoy 049 diesels, because the hardware store Bunna-N rings don't seem to last very long.
Do you happen to know what size rings the McCoy 049 uses? I just took my engine to the hardware store, and found the rings that fit about right. Should have paid more attention to the sizes.
Bill
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I have a Cub .049 diesel, and will measure it.
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Thanks Larry,
Just found measurements that I jotted on the back of the ACE small parts envelope, so I did note the size after all.
If my McCoy .049 takes the same size rings as your Cub, we could split a bag of Niton rings if you like.
Measurements are: (Dia X ID X O/D)
1.6mm X 7.1mm X 10.3mm, or 3/32" X 1/4" X 7/16".
Bill
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I'd like to try Viton O-rings in my McCoy 049 diesels, because the hardware store Bunna-N rings don't seem to last very long.
Do you happen to know what size rings the McCoy 049 uses? I just took my engine to the hardware store, and found the rings that fit about right. Should have paid more attention to the sizes.
O-rings come in even-inch sizes (unless they're metric -- let's not go there). They're probably either 3/8 (0.375") OD 1/16" thick or 7/16 (0.437") OD. Measure the bore that they go into (or a fresh hardware store O-ring) with a ruler and see.
If you know what size, both Smallparts (www.smallparts.com) and McMaster-Carr (www.mcmaster.com) stock many different O-rings in many different materials -- don't get lost and chances are you'll find what you want.
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The Cub .049 uses a 7/16" OD x 1/16" cross-section ring. I guess they aren't compatible. :-\
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Larry,
Thanks for checking the Cub O-ring size. Looks like they are much thinner than the McCoy rings, but about the same outer diameter.
Bill
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Larry,the O K cub diesel's came in two sizes , .049 & .075 and the .075 was a very good diesel we used the one we had for years.
Bob
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Oddly, Cub never turned their .099 into a diesel. Wonder why.
Oh, yes, looking in my diesel box, I found I have a couple of extra .049 0-rings in Viton that I picked up years ago. I went to an aviation O-ring supplier, and asked to buy one or two rings. The guy laughed (You want 1 or 2 THOUSAND, kid?) and gave me several for free.