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Old Dec 28, 2012, 09:34 PM
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GliderJim's Avatar
Michigan, USA
Joined Jul 2006
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I'd also recommend the 5x3 safety tip props. Very durable. The old gray Cox competition props were indeed prone to breaking. The ones you linked too say new production, so maybe they're different. They don't look the same as the old gray Cox props that I have.
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Old Dec 29, 2012, 04:28 AM
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Italy, Friuli-Venezia Giulia, Aviano
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+1 for the black (or new yellow) props. I ran the black 6x3 that came on my Eazy Bee II for about a decade on both it's production engine and a couple Black Widows.

They deform a bit at speed and give slightly less thrust, but unless you're pylon racing, life's better with a prop that bounces.
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Old Dec 31, 2012, 04:52 PM
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Here is a link to my Minnie Mambo build log - http://www.rcgroups.com/forums/showt...5#post23672550

I haven't done any work on it yet, just getting some things in order.
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Old Dec 31, 2012, 05:30 PM
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RknRusty's Avatar
United States, SC, Columbia
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Quote:
Originally Posted by PyroMan View Post
Here is a link to my Minnie Mambo build log - http://www.rcgroups.com/forums/showt...5#post23672550

I haven't done any work on it yet, just getting some things in order.
Great, I just subscribed to it. There's never a build I don't learn something from. I've built a bunch of 1/2A kits and a couple of scratch builds from plans.
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Old Jan 03, 2013, 01:59 AM
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United States, KY, Paducah
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I ran a 1/2A engine for the first time tonight!

This morning I got the prop screws in the mail--Thanks a lot Andrew, I really appreciate it-- I wasn't able to attempt to start the engine until tonight because I had to do some work around the house, but about 8 o'clock I went outside and began trying to get it to run. I turned the valve out 3-1/2 turns, primed it by both holding my finger over the air intake while turning the prop and by squirting fuel in the exhaust ports, wound up the starting spring and let it go. The engine started up on the third attempt! It ran for about 10-15secinds and quit. It did this multiple times. I could get the engine started on the prime, but when that fuel was used up it would die. I recorded a video so y'all could see what the problem is, but before I put everything up to come in I thought I'd try one more thing. Since I was unable to get my McCoy to run for very long and seemed to run out of gas and this brand new engine does the same thing I thought there had to be a common denominator. In both cases I have been using an old tin fuel tank that came with my Testors McCoy when I got it. I cleaned it out once with alcohol and pushed music wire through the ports to clean them out, but I felt like the tank may have been the problem. I took the syringe I was using tonight to fill up the tank and for priming and after filling the syringe up with fuel, I removed the plunger. I had my fuel line running from the engine to the plunger-less syringe. I started the engine and sure enough it ran the whole syringe out of fuel! I did this one or two more times with no problems. It makes me wonder if my McCoy engine would've run longer

Anyways, it looks like I need a different fuel tank. I have a 3gallon bucket full of film canisters so I may make a fuel tank out of that. I googled if anyone has done that before and I came across a kind of 'how-to' on how to do that. If I remember right, it was you, Andrew, who wrote that post over on RCUniverse.

So I am very happy! It was pretty exciting getting it running. It amazes me how that tiny little thing runs. Especially up around 18,000rpms!
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Old Jan 03, 2013, 12:22 PM
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Italy, Friuli-Venezia Giulia, Aviano
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Congrats dude. Soon you'll have it flying.

You can make tanks out of film canisters, balloons, all sorts of things. One thought on the tank you have, try turning it over and see if it works better. Some of them only work one way because the tubes don't go all the way to the other side.
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Old Jan 11, 2013, 10:53 AM
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You can buy a small plastic tank with brass tubing, etc. at a decent hobby shop. You will need to attach the "clunk" and flexible tubing, etc., and tighten things up with screwdriver so there are no air leaks. Tank must be mounted so that pickup clunk is level with needle valve so that engine will run out a full tank. Old tin tanks were made by "Perfect" and may be available as old stock in some hobby shops.
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Old Jan 11, 2013, 11:14 PM
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Canada, AB, Calgary
Joined Jan 2013
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I only fly electric rc now. In the late 20th century I balsa bashed Cox .049 TDs on CL.
Back then me and my school mates found we could have the best performance using pen bladders full of 70% nitro boat fuel. We weren't engineers, so we didn't spend hours debating the types of oil (castor, synthetic, blue whale, whatever) in the fuel. All we knew is more nitro = more power and more power is more stress on the con rod. I still have an official Cox piston/conrod reset tool in my old hobby box somewhere.
The bottom line is when you run excessive RPMs on a Cox .049 you must rest the piston ball joint using a Cox piston tool after no more than 4-6 runs. Otherwise you'll see your favorite prop and spinner fly off after a critical event and inside the motor you'll find the con rod wrapped around the crank.
If you want to fly .049 old school style, any modern fuel with 35% nitro will perform with alacrity. This is the exact nitro blend 1/2A motors were designed to run with. Modern synthetic oils are actually better than old school vegetable oils.
Avoid old fuel. Nitro/methane fuels absorb water from air. Check your fuel dates, anything over a month old is questionable.
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Old Jan 12, 2013, 03:55 AM
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Ziroli (of giant warbird fame) designed a 1/2A Mini-Sukhoi that used a balloon for a fuel bladder. I believe he filled it with a 2 oz syringe, by adding fuel, then drawing it out along with any air. By keeping the syringe vertical, bubbles float to the top and can be replaced with fuel.

I started flying 1/2A at 13, and in the vacuum of any outside influence, flew them trouble free, mostly on 15% nitro, without ever resetting a ball joint, until I was 19. If you run 30% nitro (or 70%), yea, you’ll probably need to pull them apart on a regular basis. But 15-25%, with a recommended prop… just fly it.

As for old fuel, again I just kept the container sealed and never had a problem... The worst I got away with was probably the 30% buggy fuel can I've been milking for the last year... My Cox 0.049's and the Norvel in my heli don't seem to mind yet.

But if you do have problems, a new glow plug and fresh fuel are a good start.
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Old Jan 12, 2013, 10:26 AM
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I've put probably 8-10 ounces of fuel through the engine now and I'm curious on when I should start noticing the "tightening up" a couple people mention earlier in the thread. Is this something I should feel when turning the prop by hand? I haven't yet noticed anything that feels tight. (except for when I get too much fuel in the cylinder and its slightly more pressure to turn over )

I'm waiting for my cox international order to arrive to try out one of there commercial starter springs. To get it started at first I wound my own starter spring from some thin music wire, but after about a couple dozen wind ups it started to give me some problems. It helped to get the engine started the first day or two, but now I just use my hand and a glove.
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Old Jan 12, 2013, 03:44 PM
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Like I mentioned, I ran them for 6 years without tightening a piston rod or removing varnish from a cylinder... Just run them, and if they start giving you trouble or sounding odd, then check back and find the fix.

Could be your modern fuel is helping too.
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Old Jan 12, 2013, 08:59 PM
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It might not varnish up enough to bother it. You can look at the cylinder walls with a bright light, and if they're noticeably brown, that's varnish. If it was a loose fit when it was new, then it may be beneficial to maintaining good compression. Sometimes they'll fall on their face if de-varnished needlessly. If you need top speed for racing or serious aerobatics, then you could worry about the varnish. But if it doesn't seem tight at all, I say leave it alone.

If you want to test the fit, take the piston and cylinder off and completely clean and de-grease them. Don't get fingerprints on the piston either. Insert it from the bottom and push it towards TDC and feel for tightening just barely before or right at TDC. That's a good fit and the piston should hang there by itself, and with a tiny tap of your pinky it should fall out. If it's any tighter than that, take a little of the finest steel wool wrapped around a dowel and wet it with... people will tell you 27 different things to wet it with. I start with de-natured alcohol for a few passes and then use 10w oil. Singer sewing machine oil, air tool oil, MMO, etc. Don't get aggressive and wash it all out thoroughly. Squirt some oil in the ball socket and put it back together with oil on the piston and cylinder.
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Old Jan 13, 2013, 04:13 PM
Two left thumbs
Muncie, IN
Joined Sep 2006
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The OP asked what 1/2 A engines were in current production. Besides the NOS Cox engines, NV (formerly Norvel) is back in business. Kinda pricey, but nice engines. http://www.nvengines.com/ Brodak also has a couple of .049s: http://brodak.com/engines/brodak-mk-ii-049-engine.html Annnnd, if you wanna spend lotsa money and go fast, you can buy a Cyclon: http://www.rusengines.ru/
(Hope you read Russian!)
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Old Jan 13, 2013, 05:16 PM
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The Norvels really aren't too pricey considering what you have when you buy one. They are fast, friendly(after break-in) and tough. Just use a large prop the first time you fly one... or make sure your name and number are on the wing.

The parts are available and the heads and plugs are interchangeable with Coxes.
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Old Jan 28, 2013, 08:24 AM
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Hi,
I have a Testors Fly em' Spitfire plane missing half the elevator. Does anyone know where I can get a replacement or parts plane. None on E-Bay.
Thanks,
Dave
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