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Old Oct 03, 2013, 04:22 PM
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Yeah, the Cox .074 QB seems to be a paradox, aspeed. Thanks for the tip, I'll try that later. Others seem to really like the Thunder Tiger GP07, not a super strong motor, but stronger than your reedies, a good sport motor with good throttling characteristics and decent power for the larger half-A aircraft.

OTOH, I replaced the Norvel .061 Big Mig CL with Mecoa Texaco glow plug head with Enya .09-III TV. Was expecting more power on my 40" Sureflite foam Cessna 180, but having some teething problems. Some were corrected with muffler pressure. At the time had a really mild APC 7x3 prop on it, at full throttle was slower than with the Norvel, which surprised me. Am going to try an 7x4 next time. The Enya is milder an .09 than I thought.

At least I verified that for a next build, 1959 Berkeley Impulse 46" single channel pylon racer, a Gilbert .11 Thunder Head would be marginal. Best would be a .15 sized cross scavenged or .10 Schneurle sized motor.

I've got one McCoy .19, an E-Bay buy, a little rough cosmetically (tool drawer wear), but never run. I like the way it pulls a 9x4 prop. Am targeting it for a slow combat 33" span Midwest P-40 profile, with wings increased a rib panel both sides for 38" span.
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Old Oct 03, 2013, 06:37 PM
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flyinglog's Avatar
Deutschland, Berlin
Joined Aug 2011
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Hello !

The 7x3 Prop is too small for the Enya, because it have an Iron Piston which is too heavy for high revs and just Plain bearing Crankshaft. The 7x4 is the right Prop for this engine.

Regards, Sebastian
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Old Oct 03, 2013, 11:08 PM
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Yes, you are correct, Sebastian. 7x4 and greater props are suited for the engine.

The 1966 Enya .09-III TV will run a 7x3 prop. Peter Chin did it in his 1966 report, but pointed out that props smaller than 7x4 were of no real advantage. The .09-III CL turned it 1,000 RPM more. It worked, because the Gilbert .11 Thunderhead typically runs a 7x3 prop comfortably. The Enya is a mild .09 engine, a good simulation for the Gilbert. Also, it was the only prop I had at the time.

I'd like to give an 8x3 or 8x4 wood a shot, too, once I have them on hand. Peter ran up to a 10x3.5 wood on the Enya. Instruction sheet gives 7x4 to 8x3 for FF, 8x3 to 8x4 for RC. Here's Peter Chin's report:

http://www.sceptreflight.net/Model%2...-III%20RC.html

Update: Yesterday, my Top Flite 7x6 wood props came in from Penn Valley Hobby Center. Today with winds of 10 - 15 MPH with gusts of 20, had 3 successful flights from the Enya .09-III TV with Tatone Peace Pipe universal muffler. It was well within its power band, moved out very spiritedly. This engine doesn't seem to like the plastic props, needle setting was critical, just couldn't get it run consistently. With the 7x6 wood, only 1.5 turns on the needle, several flicks of the chicken stick and it started right away. Problem solved.
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Last edited by GallopingGhostlr; Oct 04, 2013 at 02:53 PM. Reason: Updated Info.
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Old Oct 04, 2013, 03:02 PM
gcb
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Quote:
Originally Posted by aspeed View Post
Wouldn't it have been nice to have had CNC stuff back then? All the piston/cyl sizes would have matched and they maybe would have worked more consistantly. I remember the Supertiger .15 motors were pretty inconsistant too, most cylinders had no taper, and some were too tight to start with, while others were almost to loose.
Even without CNC some companies like Dooling were able to assemble their engines without using gaskets. I believe the secret was hand fitting. Expert assemblers were used to get good fits.

George
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Old Oct 04, 2013, 07:12 PM
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Yes, there was a lot of time spent lapping, cleaning, remeasuring, lapping again... Time and money. The CNC's for the most part can be set for a taper, and with a good toolbit keep the size and not wear much if roughed out with another tool. The operator can just load a bar, check parts once in a while (hopefully) and run three machines if things are going well.
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Old Oct 04, 2013, 08:14 PM
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Wasn't there a way that LMCox was able to precision machine the half-A pistons and cylinders, back when there were no computerized numercial control, and yet have that fit to fit accuracy?
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Old Oct 05, 2013, 09:03 AM
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I am guessing they used automatic bar machines. I ran a few of those too, they are kind of a lost art. There were single spindle and multi spindle automatics. Kind of tricky to set up with cams and things, but were pretty accurate depending on the machine. I am sure Cox had nice stuff because their tolerances were one of the best. I am sure that is how they remained so competitive, because their designs were so simple and geared away from castings and extra operations, and they worked good too for the times.
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Old Oct 12, 2013, 04:18 PM
Balsadustus Producerus
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I was told by a former Cox employee those engines, especially the TeeDee series, were machined and finish-ground at the anticipated operating temperatures of the engine. That's why the ad of the "Temp-Trol" manufacturing process in the magazine ads.

Would any here have an idea or comment about that? How would you do it? Might that be Bill Atwood's idea?

And to keep on topic, I have a McCoy .29 from the mid-Sixties on a Goldberg Little Toni that still runs well. Lost the Golden-Glo glowplug on the first run, though Burned right out.
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Old Oct 12, 2013, 10:26 PM
gcb
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Quote:
Originally Posted by Balsabird View Post
I was told by a former Cox employee those engines, especially the TeeDee series, were machined and finish-ground at the anticipated operating temperatures of the engine. That's why the ad of the "Temp-Trol" manufacturing process in the magazine ads.

Would any here have an idea or comment about that? How would you do it? Might that be Bill Atwood's idea?

And to keep on topic, I have a McCoy .29 from the mid-Sixties on a Goldberg Little Toni that still runs well. Lost the Golden-Glo glowplug on the first run, though Burned right out.
Manufacturers gave names to make their products appear special. I believe the Tee Dee series and later some other high-performance Cox engines had tapered cylinders so friction would not increase as the parts expanded at operating temp. VECO called this TCC (temperature controlled clearance).

George
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Old Oct 13, 2013, 09:21 AM
BWA
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The last Triumph TR6 motor I built, I designed and had made the Intake and exhaust valves. The exhaust valve stems were taper ground for exactly the same reason.

As they heated up, they became less tapered and, a better fit in the valve guide. It allowed closer tolerance (used less oil) in the valve guide when hot.

It's a fairly standard procedure nowadays when designing hot running parts.
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Old Oct 16, 2013, 12:24 PM
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Here's my best shot at a use for a McCoy .35 Red Head, a 1950 Sterling S-1 Ringmaster (thanks to Plowboybill at Brotherhood of the Ring forum.)

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Old Oct 16, 2013, 03:45 PM
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I flew a S-1 kit built Ringmaster for about six years. Engine was a good one and fed it right. good tank and filter and engine held up. Old McCoy ran fine. I used uniflow and had to set engine rich on take off. After few minutes power was normal. That was ok for sport flying. Controls were so worn that i gave plane away.
I just finished my new scratch built R/M and this time put a good engine in it. OS . Max 35 S. With Jetstream muffler. It will run pressure to uniflow vent. Covered in poly-span all natural with colored silkspan trim. McCoy was sold to new owner Down under. McCoy's and OK Cubs were made with sub-standard metals. One bad run and toast. Some Cubs were ok just luck of draw.
Only decent McCoy's were pre-testos engines. They had rings and some ball bearing. The Testors engines were designed by Dick McCoy and if they had used better materials would have stuffed Fox. The McCoy .40 R/H had perfect timing for Vintage stunt, much like the Great ST G-21 .46.
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Old Oct 16, 2013, 10:20 PM
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Originally Posted by dankar04 View Post
The McCoy .40 R/H had perfect timing for Vintage stunt, much like the Great ST G-21 .46.
I've got it's cousin, the Testor McCoy .40 Series 21 Black Head. It's got a Dykes ring. Some have taken parts from the Series 21 line and used them in the Red Head's, which make for a better hybrid Red Head.
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Old Nov 19, 2013, 07:35 PM
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Since no one is currently producing McCoy Red Heads, who would I get the blueprints from? Just curious for no reason!
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Old Nov 19, 2013, 09:01 PM
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I don't know where, I guess you'd have to trace the history and people who played a significant part. The Testor Corporation is still in business, as far as I know. They still make model paints and a few other things.

Those who have machining skills can template from existing engines and make their own parts, AFAIK. There are some aftermarket parts, like the Dykes ring for example. Some know how to recondition the piston to restore compression and fit.

Recently I've acquired several Testor McCoy .35 and one .19 Red Heads, and a .049 also to add to the one I already have. These are in good condition and should do me well in CL, possibly the .049 in a small RC vintage aircraft.
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