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Old Jul 17, 2014, 01:49 PM
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United States, NY, Poughkeepsie
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1/2A RC Engines

Greetings Folks,
I am doing a little testing with 1/2A RC engines. First, I love these little guys because they are what I had at about 10 years old to play with. I learned about the bite of the prop pretty early on. That with the soaking of the wound in high nitro fuel - ah, what memories.

I have never run 1/2A's as RC, just wide open screaming FF and C/L use.

I have a used Big Mig .061 on the way to play with, and likely will get a TT .07 which I have heard said on these forums is fairly smooth.

However, I have a lightly used circa 1980 Cox TeeDee .051 and I would like to hear from anybody about the "Cox Canada" carburetor that runs one and has any feedback.

CAVU - Peter from Poughkeepsie
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Old Jul 17, 2014, 02:08 PM
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Might also look into an exhaust throttle ring, if you're not going to/aren't required to run a muffler. Don't believe it is a current production item, but they do turn up now and then. I have one on my TD .051 and it is pretty effective.

You can also look on the Cox engines forum http://www.coxengineforum.com/ for others' experiences with that carb.
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Old Jul 17, 2014, 02:17 PM
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I own an AME 0.061 which has to be similar to your Big Mig. It throttles fine. Just remember that you don't need a 2000rpm idle to slow a plane down being pulled by a 6x3. 5 or 6k is plenty slow and more realisitic with these little guys.
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Old Jul 17, 2014, 02:57 PM
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Quote:
Originally Posted by ahrma_581 View Post
Might also look into an exhaust throttle ring, if you're not going to/aren't required to run a muffler. Don't believe it is a current production item, but they do turn up now and then. I have one on my TD .051 and it is pretty effective.

You can also look on the Cox engines forum http://www.coxengineforum.com/ for others' experiences with that carb.
Interesting - I was planning on bypassing the muffler/throttle but I will watch for a version with it. I am starting a build log here on the RCM 1/2A Basic Trainer - I want to get a few copies of the plane together to put these engines into and compare, for fun. One I will do as foam - DTFB using FliteTest methods - looks fast and easy, with electrics. I also want to do a twin for the heck of it.
Thanks for the good info - Cheers...
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Old Jul 17, 2014, 02:59 PM
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Originally Posted by 706jim View Post
I own an AME 0.061 which has to be similar to your Big Mig. It throttles fine. Just remember that you don't need a 2000rpm idle to slow a plane down being pulled by a 6x3. 5 or 6k is plenty slow and more realisitic with these little guys.
Cool - I was tempering my expectations of throttles on such small engines. I was conditioning myself for more of a "high gear" and "low gear" approach, hence the basis of my original question - how smooth are these different throttles. I'll report out - wish I had more than the cubbyhole where I build to take interesting shots and video of the build.
Cheers -
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Old Jul 17, 2014, 03:31 PM
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I tend to like the old exhaust throttle rings on the Cox engines. The throttle rings work best on the regular Cox engines that do not use sub-piston induction (SPI). What that means is when the piston is at top dead center on the compression stroke, it exposes a opening in the exhaust port to allow a little more air into the bottom of the crankcase.

Now then the Cox Tee Dee and some others do use SPI and with a exhaust throttle it blocks off the SPI from working at low speed and the engine tends to stall out more easily. Bow with that said the throttle still works OK though as a 1/2a engine idling at say 5,000 RPMs is still slow enough to land a 1/2a plane. So it isn't a big deal. The little 1/2a engines because of their size do not have really efficient propellers. So having a higher idle speed isn't normally a problem.

The new Cox carburetor is quite interesting and it does work, but with 1/2a engines you want to have lower expectations as to how well they work. So you may or may not like it. With the Tee Dee engines you can't really use mufflers on the engines because of the SPI, so the idle speed isn't quite as good as with a engine that does not use SPI so you can put a muffler on it.
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Last edited by earlwb; Jul 17, 2014 at 03:32 PM. Reason: typo correction
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Old Jul 17, 2014, 04:57 PM
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Small diesel is the way to go !
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Old Jul 17, 2014, 05:08 PM
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Years ago, I used the RC Bee, Dragonfly and QRC engines for RC flying and I had a lot of fun using them too. The RC Bee worked really well on a Airtronics Q-Tee plane too. I used to shoot touch and go's with it and even fly it at night using the Cylume light sticks at the time. The QRC wasn't as good as the fuel tank was too small and the flight times were too short for me.
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Old Jul 18, 2014, 12:17 AM
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Originally Posted by LittleRock View Post
Small diesel is the way to go !
I never used diesel - reading up on it I was intimidated by buying the fuel.
Do you buy it ready-to-go or mix your own?
Cheers
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Old Jul 18, 2014, 06:00 AM
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It seems that the term, 1/2A has lost its meaning among the majority of people. None of the engines mentioned in the original post are 1/2A! http://www.modelaircraft.org/events/...reeflight.aspx
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Old Jul 18, 2014, 07:50 AM
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Originally Posted by GeoffinIN View Post
It seems that the term, 1/2A has lost its meaning among the majority of people.
Well, that's an enlightenment - I've seen references while I have been hunting around for used engines that 1/2A referred to any engine up to .15 - not sure where that came from. Thanks for "going to the source" for accurate info on this one.
Cheers- Peter
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Old Jul 18, 2014, 10:54 AM
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Well originally originally we had "A" class competitions that used engines of .051 cubic inch displacement or larger. Later they made the "1/2A" competition class for engines .049 or less in displacement. Cox had the .049 Tee Dee and made the .051 Tee Dee engine so you could bolt on a different engine and use the same plane in 1/2A and A class events.

1/2A was relatively new and was .000 to .049 dispplacement engines.
Class A was originally .000 to .20 cubic inch displacement and was changed to .051 to .20 later on.
Class B was .201 to .300 (which is why they make .29 engines too)
Class C was .301 to .500
Class D was .501 to .65

You still hear people use the 1/4A (.020 engines) and 1/8A (.010 engines) designations for micro engines too.

Thus one could use a Cox Tee .049 for 1/2a and bolt on a tee Dee .051 for A class events using the same airplane.
For Class B events they used a .29 engine and bolted on a .35 or .36 engine for those C class events. This is why you see .29 engines that were made using a .35 or .36 engine design. This was quite common to do in the past and probably is still being done today.
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Last edited by earlwb; Jul 18, 2014 at 11:04 AM. Reason: add more info
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Old Today, 07:13 AM
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I have a mig .061 and .074, they are really tight engines. On both when new, I had to warm them up with a hot air gun first and hit them with a Sullivan 1/2A starter. Hand flipping just didn't work since they were so stiff at the top. Once they had been run for awhile, I didn't need the hot air gun any more. What was said about the trying to get a low idle is true, it's kind of relative considering how high these things rev. They were good little engines. I just didn't like the plug that was used. It was hard to find sometimes and was expensive.

Are Big Migs still sold?
Edwin
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Old Today, 07:27 AM
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http://www.nvengines.com/index.php?o...mart&Itemid=65 Not sure how Russian sanctions affect the imports. The .074 is a great example of good engineering. Powerful, idles nice. I have a couple nice .06 Big Migs that are good too, and one that doesn't idle too good. Maybe it needs more break in time. The 1/2A term has lost it's meaning lately. Few people compete any more, and a .46 motor is considered small nowadays. Then there is the electric takeover.
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Old Today, 10:44 AM
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Haven't run 'em in many years but Cox Tee Dee's with RC carb throttles worked to lower rpm to where model would creep along but seldom would sit still for scale-like taxiing, etc. Things got lots better with OS-10's and on up the size range. Hot glow fuel always spattered on scale model windshields making them milky. 1/2 A glow was better for sport models.
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