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Old Nov 27, 2012, 11:11 PM
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Playing card, thin gasket material from an automotive store, or high temp silicon seal (I have done this one a couple of times).
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Old Nov 30, 2012, 11:01 AM
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I didn't have a playing card on hand, so I used the thin cardboard from a stick-on lead weight package! Sealed it up nicely, no leaks.
Old Dec 03, 2012, 02:49 PM
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My dad wasn't able to make it to the hobby shop when he was out of town, so I just placed an order with SIG for a quart of the Champion fuel that GliderJim suggested. It has 25%nitro and 20% oil (1/2 synthetic 1/2 Castor). I'm really excited to get this engine running! I'm thinking I will build my first balsa plane to put it on, Maybe a Minnie Mambo . . . .
Old Dec 03, 2012, 08:04 PM
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Minnie Mambo would be a good choice for the McCoy .049. Since it also has the radial mount, would make it easy to mount. You might have to use some balsa block with a 1/8" plywood face to space it out, since the McCoy is fairly short. You may not need the spacer if a nylon engine mount is used.
Old Dec 03, 2012, 08:36 PM
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You guys might have noticed that I added "and various questions" to the end of the thread title. I thought it needed it so I added it.

OkiThumper, what do you mean by a "nylon engine mount"? The engine has bolt holes on the back of it, so wouldn't I just use those?

I'm assuming it isn't possible to make this engine throttle-able, am I right?
Old Dec 03, 2012, 11:24 PM
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Originally Posted by PyroMan View Post
OkiThumper, what do you mean by a "nylon engine mount"? The engine has bolt holes on the back of it, so wouldn't I just use those?
The problem PyroMan is the McCoy is 1-1/4 inches (32 mm) from backplate to prop mount. The side cheek cowls on the Minnie Mambo are 2 inches (51 mm) long. You'll need to extend the McCoy from the firewall at least 3/4" + 1/8" (for prop clearance) = 7/8", so that you will have enough clearance between the cheek cowls and propeller. You could use wooden beams also, or relocate the engine bulkhead forward.

Another option may be a cowl-less design such as Hal Debolt's Livewire Kitten.

Quote:
I'm assuming it isn't possible to make this engine throttle-able, am I right?
Around 1971, I had a friend who had a throttle controlled .049 Wen Mac on his CL P-26 Pursuit RTF. It used a throttle ring like the Coxes and a 3rd line for throttle control. Problem would be locating such an engine, as most likely if a throttle ring were available, it would not fit all .049 Wen Mac / McCoy cylinders.
Old Dec 04, 2012, 12:00 AM
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Originally Posted by OkiThumper View Post
The problem PyroMan is the McCoy is 1-1/4 inches (32 mm) from backplate to prop mount. The side cheek cowls on the Minnie Mambo are 2 inches (51 mm) long. You'll need to extend the McCoy from the firewall at least 3/4" + 1/8" (for prop clearance) = 7/8", so that you will have enough clearance between the cheek cowls and propeller. You could use wooden beams also, or relocate the engine bulkhead forward.

Another option may be a cowl-less design such as Hal Debolt's Livewire Kitten.

Around 1971, I had a friend who had a throttle controlled .049 Wen Mac on his CL P-26 Pursuit RTF. It used a throttle ring like the Coxes and a 3rd line for throttle control. Problem would be locating such an engine, as most likely if a throttle ring were available, it would not fit all .049 Wen Mac / McCoy cylinders.
That makes sense. I'll probably do something like that to get the engine farther forward.

About the throttle ring, how does it work? What is it doing to the engine that changes its rpms? I found a picture of one here and a video of one here . I like to tinker with stuff and build things so if maybe someone could explain to me how these work, I could at least try and make something that will do the job.
I'm not all that worried about it being throttle-able, I just think it would be nice.
Old Dec 04, 2012, 06:37 AM
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About the throttle ring, how does it work? What is it doing to the engine that changes its rpms? I found a picture of one here and a video of one here . I like to tinker with stuff and build things so if maybe someone could explain to me how these work, I could at least try and make something that will do the job. I'm not all that worried about it being throttle-able, I just think it would be nice.
I see ExEngines also has a complete engine for $30 US. I've got one such exhaust throttle collar and installed it on one of my Cox Sure Start engines, which is similar to the picture. Only difference is ExEngines is using the die cast crankcase, which was used on the Cox R/C Bee 30 years ago. The crankcase on my is the extruded machined one standard with Cox .049's. I bought 4 nylon spacers at a hardware store, so I could install the Cox Sure Start without cutting a recess into a firewall (attached).

Zenalook of Cox International Canada has similar except for a red anodizes crankcase described at http://coxengines.ca/cox-.049-rc-cruiser-engine.html for $5 more.

Exhaust throttles work effectively. I put over 100 flights on my Sterling Minnie Mambo and R/C Bee engine. The throttle ring rotates. By varying the exposed exhaust slit on the side of the cylinder, it throttles by controlling the exhaust output. It is not as linear as a true R/C carburetor, but you do have control from about 6,000 RPM at idle to 15,000 - 18,000 RPM at full throttle.

I have a Testors McCoy .049 with Testors tank mount. It graces the front of my Goldberg Little Toot CL biplane (attached).
Old Dec 04, 2012, 01:21 PM
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Thanks for the explanation.
So all I need to do to adjust the rpms of the engine is to constrict the exhaust output? That doesn't seem to hard. I'll see what I can do after I get the engine running normally.
Old Dec 04, 2012, 05:26 PM
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That makes sense. I'll probably do something like that to get the engine farther forward.

About the throttle ring, how does it work? What is it doing to the engine that changes its rpms? .
If building a Minnie Mambo, just move the firewall forward. The plane doesn't care where the engine is as long as you maintain the prop disk in the same location, the same down and side thrust and have the CG correctly located.

Throttle rings must fit tightly to keep exhaust gases from escaping between the ring and the cylinder. Secondly, throttle rings do not work as well on reed valve engines that have a SPI piston/cylinder assembly.

Even though the throttled engine from EX Models is less than the one from COX International, my preference would be the Sure Start from COX Inter. The cast case engines have a reputation of wearing more quickly than the extruded case engines.
Old Dec 04, 2012, 05:31 PM
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Is my engine considered a "reed valve" engine?
Old Dec 04, 2012, 06:05 PM
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Throttle rings must fit tightly to keep exhaust gases from escaping between the ring and the cylinder. Secondly, throttle rings do not work as well on reed valve engines that have a SPI piston/cylinder assembly.
I doubt if the ExModels engine has subpiston induction. The McCoy is definitely not a subpiston induction engine.

Quote:
Even though the throttled engine from EX Models is less than the one from COX International, my preference would be the Sure Start from COX Inter. The cast case engines have a reputation of wearing more quickly than the extruded case engines.
I have over 100 flights on my .049 R/C Bee engine with throttle muffler ring. It has a cast case. Of course, it has always been run on fuel than had Castor oil. Replaced the piston and cylinder due to wear, but crankshaft is still good. Perhaps a bad lot from somewhere, or running synthetic oil only fuel?

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Is my engine considered a "reed valve" engine?
No. Your version of McCoy has a front venturi with intake through the crankshaft.
Old Dec 05, 2012, 11:35 AM
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"Around 1971, I had a friend who had a throttle controlled .049 Wen Mac on his CL P-26 Pursuit RTF. It used a throttle ring like the Coxes and a 3rd line for throttle control."

These were used on the P-26 and not all P-26's. I have only found them recently on used P-26's. There apparently were some used on the Wen Mac Corsair, too. I have four Wen Mac P-26's (one for static, one to fly, two for parts). Two of the four have throttle rings. The return springs are missing from the two that have the throttle ring.

They work quite well, in terms of actualy throttling the engine.

"Problem would be locating such an engine, as most likely if a throttle ring were available, it would not fit all .049 Wen Mac / McCoy cylinders. "

The will fit the later engines (Mk XIII) with the cylinder with uniform diameter over the entire length of the cylinder. The will probably fit the early Testors motors, but not the later ones with the cylinder modification made to fit the Fly'em type mufflers (which appear on late model Testors rotary valve motors (the ones from Wen Mac tooling), even though I do not believe these motors were ever sold with the muffler).

How did that P-26 fly, by the way?
Last edited by Ah Clem; Dec 05, 2012 at 11:45 AM.
Old Dec 05, 2012, 01:15 PM
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These [throttle control rings] were used on the P-26 and not all P-26's. I have only found them recently on used P-26's. There apparently were some used on the Wen Mac Corsair, too. I have four Wen Mac P-26's (one for static, one to fly, two for parts). Two of the four have throttle rings. The return springs are missing from the two that have the throttle ring. They work quite well, in terms of actually throttling the engine.
Thanks for clarifying. I am unfamiliar with P-26's, his was the only example. Interesting that Wen Mac would have ones with and ones without. Circa 1966, My brother had the F4U Corsair, the one with the one piece molded fuselage with wing in chrome finish. It came with a 1957 Chevy dragster that the engine shared. The Wen Mac engine was unthrottled. I am more familiar with the Cox RTF's. Got remnant (donor) engines left over from them (Cox 290's).

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They [throttle control rings] will fit the later engines (Mk XIII) with the cylinder with uniform diameter over the entire length of the cylinder. The will probably fit the early Testors motors, but not the later ones with the cylinder modification made to fit the Fly'em type mufflers (which appear on late model Testors rotary valve motors (the ones from Wen Mac tooling), even though I do not believe these motors were ever sold with the muffler).
Interesting again thanks for clarifying.

Quote:
How did that P-26 fly, by the way?
It flew okay, round and around and around. Never saw my friend stunt it.
Old Dec 05, 2012, 07:52 PM
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If you're interested in throttles I'd personally be looking toward that premade engine from one of the online stockists / manufacturers.

I've ordered through both of them and service seems good - the postage is prompt and engines run well. Currently hotting up a diecast case Surestart (don't like the machined case Cox's!) with a higher comp head, vibe free needle and Mylar reed valve. May also machine the exhaust ports, turn it into a bit of a ripper

- boingk


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