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Author Topic: Cub .074 diesel 0-rings  (Read 2096 times)

Offline Larry Renger

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Cub .074 diesel 0-rings
« on: June 19, 2010, 12:06:04 AM »
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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Offline Tim Wescott

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Re: Cub .074 diesel 0-rings
« Reply #1 on: June 19, 2010, 10:17:04 PM »
What size?
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Offline Jim Thomerson

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Re: Cub .074 diesel 0-rings
« Reply #2 on: June 20, 2010, 07:43:19 AM »
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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Offline Larry Renger

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Re: Cub .074 diesel 0-rings
« Reply #3 on: June 20, 2010, 12:33:44 PM »
1/2" OD, 1/16" cross-section.

How long do the hardware store o-rings last in a diesel head?
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Offline Jim Thomerson

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Re: Cub .074 diesel 0-rings
« Reply #4 on: June 20, 2010, 02:59:52 PM »
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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Offline GGeezer

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Re: Cub .074 diesel 0-rings
« Reply #5 on: June 20, 2010, 06:33:48 PM »
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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Offline Bill Adair

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Re: Cub .074 diesel 0-rings
« Reply #6 on: June 20, 2010, 10:12:38 PM »
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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Offline Larry Renger

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Re: Cub .074 diesel 0-rings
« Reply #7 on: June 21, 2010, 10:48:11 AM »
I have a Cub .049 diesel, and will measure it.
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DesignMan
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Offline Bill Adair

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Re: Cub .074 diesel 0-rings
« Reply #8 on: June 21, 2010, 12:04:51 PM »
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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Offline Tim Wescott

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Re: Cub .074 diesel 0-rings
« Reply #9 on: June 21, 2010, 08:33:30 PM »
Quote from: Bill Adair on June 20, 2010, 10:12:38 PM
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 problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Larry Renger

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Re: Cub .074 diesel 0-rings
« Reply #10 on: June 23, 2010, 11:02:13 AM »
The Cub .049 uses a 7/16" OD x 1/16" cross-section ring.  I guess they aren't compatible.   :-\
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DesignMan
 BTW, Dracula Sucks!  A closed mouth gathers no feet!

Offline Bill Adair

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Re: Cub .074 diesel 0-rings
« Reply #11 on: June 23, 2010, 01:38:07 PM »
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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Offline Robert Mathison

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Re: Cub .074 diesel 0-rings
« Reply #12 on: June 26, 2010, 02:35:28 PM »
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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Offline Larry Renger

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Re: Cub .074 diesel 0-rings
« Reply #13 on: June 28, 2010, 10:16:12 AM »
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.
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Think S.M.A.L.L. y'all and, it's all good, CL, FF and RC!

DesignMan
 BTW, Dracula Sucks!  A closed mouth gathers no feet!

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