McCoy .049 Diesel

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McCoy .049 Diesel

Postby jim walton » Sat Dec 22, 2007 6:27 pm

I am in need of a spray bar and needle valvue for my McCoy .049 diesel. The glow McCoy .049 will fit. If you have one for sale, please let me know how much and where to send payment. Thanks, Jim Walton
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Postby Bill Adair » Fri Mar 28, 2008 5:18 pm

Jim,

FYI, Wen-Mac meedle valves fit my McCoy .049 diesels, and should work in yours.

I'm also looking for more McCoy .049 needle valves, so please let me know if you find a source.

Bill
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Postby jim walton » Sat Mar 29, 2008 9:21 am

Bill,

I have a possible source. If it works out I will let you know.

Jim
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Postby Bill Adair » Sat Mar 29, 2008 1:02 pm

Jim,

Nice talking to you on the phone today.

Since we talked about it, I thought I might add info about Atwood needle valves for others to read.

I found that the needle valve from my Atwood Signature .049 is an exact match for the McCoy .049 needle, with only the slightest difference being in spring diameter. Wouldn't surprise me a bit, if Holland .049 needle valves were also the same.

Also found a source for #1 X 72 threaded brass rod, that I think is the size used for these 1/2A needles? Anyone with a lath should be able to make their own needle valves, and brass knobs should be available from watch making suppliers.

Later,

Bill
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Postby loucrane » Tue Apr 01, 2008 10:55 pm

Bill,

There was recent discussion of the NVA for the Sportsman .098, which had the same needle as the larger McCoys. It is possible that the same 2-56 thread would fit the McC .049 diesel...

I had a McC .049 diesel over 50 years ago, and at that callow age, didn't notice such things as thread specs. The .049 needles may have been their own thread, while the rest of the one-piece-spraybar McC needles were 2-56.

(One-piece-spraybar? Yep, for the rear rotor high performance engines, I believe they made a three-piece NVA - (1) fuel nipple threaded into one side of the choke with an open end orifice that the (2) needle entered, after going across the opening bare nekkid, and (3) the threaded side fitting the bare needle oposite the fuel nipple. This made the minimum possible reduction to the inlet area. My count does not include any locknuts needed to hold the two side pieces in...)
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Postby loucrane » Tue Apr 01, 2008 11:04 pm

Jim W,

By the way, I worked on a friend's McC .049 diesel a dozen or so years ago. The O-ring had gone away. I was able to swage the contra-piston to a proper diesel fit in the upper cylinder. It didn't require an O-ring, iow. I never ran the engine, and we lost my friend eternally before he had a chance to.

Leaves me wondering how well it would have served, and how long the shaft would have lasted. (At least the early McCoy diesels had notoriously understrength shafts for diesel loads. Ah, well, so did Cox TeeDees w/DDD conversions until Bob D came out with his 'corrected' shaft.)

Today, it is easier to find O-rings that can withstand the temperatures and pressures... T'wasn't back then...
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Postby Bill Adair » Wed Apr 02, 2008 9:25 am

loucrane wrote:Bill,

There was recent discussion of the NVA for the Sportsman .098, which had the same needle as the larger McCoys. It is possible that the same 2-56 thread would fit the McC .049 diesel...



Hi Lou,

Thanks for the info.

The McCoy .049 needle valves are definitely smaller than 2X56, but I don't have a screw pitch and diameter gage to verify the actual size.

The only non-metric threaded brass stock (smaller than 2X56) that I've been able to locate, is the #1X72 that I mentioned in a previous message. Seemed about the right size for these needles.

The single Atwood Signature needle valve that I have, fits my McCoy .049 diesel perfectly in length, diameter, and taper, as well as the knurled knob on the end. Leads me to believe that one of those early 1/2A manufacturers made the needles and venturi for several different engines.

The NIP Wen-Mac .049 needle I was given is also the correct thread size, but is a different length, slightly different taper, and is apparently anodized to give it that black finish.

I'm considering a membership in MECA, but having a hard time justifying dues in yet another hobby, sport, social organization.

Reports of early crankshaft failures in the original McCoy .049 diesels (with the square cornered crank ports) have been mentioned, but mine never failed. The Brit pen pal I eventually gave mine to (who made a new contra piston to eliminate the rubber O-ring seal), used it for at least another year that I'm aware of, with no apparent problems. I suspect that under size props, hotter diesel fuels (than the equal parts mix I used), and over compressing were the real problems.

Bill
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