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Old Dec 05, 2012, 10:57 PM
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On the Coxes, engines don't have to be manufactured with the throttle sleeve already installed, if one knows what they are doing. Ace R/C used to sell the rings separately. I've installed them on Black Widows. One needs to make sure that they have the right cylinder diameter to fit. I've put the same on my Sure Start and it fits perfectly.

Of course, if one doesn't feel comfortable removing the cylinder and installing the sleeve, they are better off buying one already made that way.

Bernie at Cox International Canada came up with a choke tube throttle, which I hear is very good. It costs a little more than the exhaust throttle version engines, but I heard the throttling action is more linear. Not having tried one myself though, can't say specifically.
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Old Dec 05, 2012, 11:42 PM
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Well I couldn't wait. . . . I took a break from studying for my math final tomorrow to begin a throttle ring!

While out today, I ran by my local hardware store and picked up a sheet of .010" brass. When I got home I cut a strip of it 3/8" wide and curled it into a circle around the engine exhaust ports and marked where to cut and solder the metal together. I cut the strip and soldered the ring just barely smaller than what I had marked so it would be a very tight fit on the engine. After soldering the ring together, I soldered on a piece of brass that a servo will eventually be attached to. I then started to put the ring on the engine. It was very tight like I wanted. It was hard to get back off, even though I could only get it on like 1/8"! I than began sanding, smoothing, and polishing the inside (and a little bit of the outside) of the ring. It now will go onto the engine with little effort, but is still a tight fit. I can rotate it around the engine a little, but it's not super easy. I think for now I won't sand it anymore and I'll just see how it goes. I feel like it will wear itself in within just using it barely.

If you look at the pictures it is obviously not finished. I have yet to put any exhaust ports in. I didn't have time because I got back to studying. But I'm happy with the way it's going so far and it only took about 30-45minutes.

I won't try the throttle ring until I run the engine for a bit and get it all tuned up. Then I will try 'er out and see what she does.

Here's a picture or two . . .
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Old Dec 05, 2012, 11:55 PM
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There was one person selling some time back Sure Starts with his custom machined throttle rings on E-Bay. He simply drilled or milled a hole in the ring on each side for the exhaust slit. He had videos, it seemed to work effectively.
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Old Dec 06, 2012, 08:32 AM
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Quote:
Originally Posted by PyroMan View Post
I won't try the throttle ring until I run the engine for a bit and get it all tuned up. Then I will try 'er out and see what she does.
Have you decided on the location of the exhaust hole on your ring yet?
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Old Dec 06, 2012, 10:46 AM
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I like PyroMan's improvising a ring out of brass. This may be a solution to other engines with round steel cylinders with exhaust slits cut into the cylinder.

Brass does wonders. I accidently broke the thin aluminum exhaust outlet on my A.C. Gilbert .074 Thunderhead. Attached is how I fixed it. I used brass shim stock, bent it until I had a good fit. Drilled a hole in the muffler mount bracket; used a 3-48 tap and screw to mount it. Second picture is a close up of the break. A spot of solder was used to strength where a tear developed in the thinnest part during cutting. Engine is a little gritty with dust from sanding the plane. I'll clean it up when I reinstall it in the finished CL Beginner's Ringmaster 'Gee Bee Z' variant (in my build blog). The brass covered up the ugly broken out exhaust port.
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Old Dec 06, 2012, 11:32 AM
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Originally Posted by Andrew0820 View Post
Have you decided on the location of the exhaust hole on your ring yet?
Yes. Here's a picture of where I plan to put the holes at. I lined up one of the lines on my cutting mat with the center of the holes on both sides of the ring that way you can visualize where the hole will land on the other side of the ring. (I hope that makes sense) …Name: ImageUploadedByTapatalk1354811500.023930.jpg
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Old Dec 06, 2012, 03:17 PM
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Since your investment is very low, Pyroman, that you could easily remake it from learning lessons from the first.
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Old Dec 06, 2012, 03:24 PM
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Yeah, I think if I had to do it again (and I may) I would not have soldered it slightly smaller than I marked. Although it's a very good fit, it's just barely smooth enough for a servo to push it. Right now I'm in the middle of honing out and polishing the inside a bit smoother and making it a tiny bit bigger.
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Old Dec 06, 2012, 03:26 PM
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Also I would solder the servo linkage piece on the same place where the band meets itself for both extra strength there and so there would be one less obstacle to plan my exhaust holes around. How big should my exhuast holes (more like ovals) be? Right now they are about 1/8" wide by about 3/32" tall.
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Old Dec 06, 2012, 08:12 PM
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I just measured the Ace R/C throttle ring, it has 1/4" (6 mm) long slots. However, the one on E-bay with his machined ones appeared to have smaller round openings. I guess you could try it and see how it compares with non-throttled, if you have a tachometer.
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Old Dec 06, 2012, 08:57 PM
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I have a tach, but it's not a non-contact. I'll see if I can get a good reading with that. I'll post a picture of the holes I have cut now in just a bit.

Also I got my fuel today! I should be able to start the engine either tomorrow or Saturday!
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Old Dec 07, 2012, 06:20 PM
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I read that to start a Cox engine that you need to turn the needle valve out 3 1/2 turns. Do ya'll agree with that for this engine? Also do ya'll have any tips for starting the engine?

I may start the engine tonight when my dad gets home from work or tomorrow afternoon when I get home from taking the ACT.



Warning: shameless plug for my website
I don't have a normal glow clip for a 1/2A engine so I improvised one with a clothespin and some brass pieces. If you want to check it out here's the link to my blog post about it.
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Old Dec 07, 2012, 06:51 PM
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I like your glow clip. I would keep it disconnected from the battery when not in use. It wouldn't take much to short that thing out. Things would get pretty hot pretty fast at that point. Otherwise keep it clipped to something to prevent contact. I have one I keep clipped to the wooden handle on my flight box when not in use.

As far as the needle valve goes, 3 to 4 turns out is probably a safe starting point.
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Old Dec 07, 2012, 11:32 PM
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So I tried to start my engine tonight…

So when my dad got home from work I told him that I would be setting up stuff on the front porch to start try and start the engine. So I set up a table, vice, shop lights, video camera, etc… on the front porch. As I was out there I grabbed my chicken stick (just a wooden dowel) and began flipping the prop for practice/fun. Well I'm an idiot. So I was flipping the prop when my chicken stick came down and hit my needle valve and bent it! In the shape it was in it was pretty much unusable because when rotating it the handle would hit the prop if the engine was running. When I first got the engine the needle valve was bent a little; last week I fixed that bend by just bending it back straight easily. So I thought I would just do that. Wrong! As I began to put pressure on it, it broke clean off!! Now keep in mind the the needle valve is screwed in fully and it has now sheared flush to the engine so it is impossible to grab with tweezers or something. After being extremely mad at myself for like 2 minutes, I brought the engine to my work desk to sort things out. I couldn't get the needle to rotate by pressure of a screwdriver or awl, so I took my smallest file and filed an extremely shallow notch in the needle valve for one of my precise flat head screwdrivers to just barely catch on. I was able to get the needle out this way. I still wanted to start the engine tonight so I began working on a quick fix. I cut a very thin piece of brass sheet and with a tiny, tiny bit of solder I soldered this brass strip (more like a flattened brass wire) to the end of the needle valve. At this point I could screw the needle valve in all the way just fine because it broke off when it was fully screwed into the engine which was 'good'. I will fix this better over the next few days, but it worked for tonight.

So after remounting my engine to the piece of plywood and filling up the tank, I went and got my dad so we could start the engine. I primed the engine by covering the air intake and turning the prop two or three turns and then tried to start it. The short story is it wouldn't start. I played with the needle valve a bit ranging from 3-4.5 turns out. It popped a few times but never really sputtered. Well I think if I remember it did do like three full rotations on its own once. So then I got my electric starter. On about the third go with the E-starter the engine ran for like maybe 2 or 3 seconds, then no more. I took the glow plug off, and sure enough, my glow charger battery was almost dead. The glow plug glowed a very dim red. So the I spent the next 30minutes trying to find a way to power the glow plug. 2 D batteries didn't make it bright enough, only a very dim red. So I'll charge up my glow charger tomorrow and try 'er again! Quick question, is a 6v lantern battery too much for the glow plug? Will it burn it up? I refrained from using one tonight because I didn't want to blow my glow plug and then be screwed. I knew if that thing burned up it would be a long time before I locate a new one.

Anyway, that's my story for the night! I'd upload a bi of the video, but I have no time to fool with it right now because I'm tired and I have a big test tomorrow sooo, yeah.

Thanks for all of the help so far guys,
Nicholas

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P.S. it may look like in the pictures that the broken needle valve sticks out a little so I could grab onto it…that's not the case
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Old Dec 08, 2012, 12:17 AM
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Sorry to hear about the needle valve. As far as the starter battery goes, 2 D cells in parallel (1.5 volts total) should be plenty. That's what I've been using for my Cox engines. You don't want to use 6 volts.
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