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Home Made Glowhead / Glow Plug Conversion for Space Bug

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Home Made Glowhead / Glow Plug Conversion for Space Bug

Post  Kim on Sat Dec 17, 2011 7:57 am

Well, got one running. It's not gonna set any speed records, but if can make it run, maybe I can make it run faster. At least it will fly a sport plane. Good, steady run to the end of the tank.

Left it slightly rich. Sig 25% fuel / Cox 6-3 Black Prop

I used an R/C long plug (cut off the idle bar) to give me a few more threads.




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Re: Home Made Glowhead / Glow Plug Conversion for Space Bug

Post  GermanBeez on Sat Dec 17, 2011 9:51 am

how does it run its tank dry if its fuel intake is designed for c/l?
isn't it machined into the side of the tank?
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Re: Home Made Glowhead / Glow Plug Conversion for Space Bug

Post  nitroairplane on Sat Dec 17, 2011 10:01 am

Maybe it was sideways and that thing that you think is a wall is the floor Wink
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Re: Home Made Glowhead / Glow Plug Conversion for Space Bug

Post  GermanBeez on Sat Dec 17, 2011 10:13 am

that wouldnt work either because the intake is directly under the needle valve, so it would be on the top Huh... Huh...
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Re: Home Made Glowhead / Glow Plug Conversion for Space Bug

Post  nitroairplane on Sat Dec 17, 2011 10:19 am

Please rephrase that I really don't understand.
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Re: Home Made Glowhead / Glow Plug Conversion for Space Bug

Post  GermanBeez on Sat Dec 17, 2011 10:24 am

ok. the hole, where the engine sucks in the fuel from the tank is machined into the tank case and is positioned level
with the needle valve (the needle valve is on the left side of the engine, that means that the intake is also there),
because it's built for c/l. if the wall would be the floor, then the needle valve(and the intake) would be on top of the engine, and logically, it would just nibble a few dropsof fuel until the fuel level is too low for the intake to reach it.
i.e. the engine would cut after maybe half a second
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Re: Home Made Glowhead / Glow Plug Conversion for Space Bug

Post  Kim on Sat Dec 17, 2011 10:27 am

Well...OK !!!! It ran until it ran out of the fuel it could access!!!! Meaning that it ran smooth and steady until it obviously died of fuel starvation!
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Re: Home Made Glowhead / Glow Plug Conversion for Space Bug

Post  GermanBeez on Sat Dec 17, 2011 10:28 am

so you had half of the fuel left, right?
i figured you did, sry for nitpicking Smile
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Re: Home Made Glowhead / Glow Plug Conversion for Space Bug

Post  nitroairplane on Sat Dec 17, 2011 10:30 am

Beez check you inbox!
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Re: Home Made Glowhead / Glow Plug Conversion for Space Bug

Post  EXModelEngines on Sat Dec 17, 2011 10:56 am

Does the engine have the small diameter thread on the head?

Matt
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Re: Home Made Glowhead / Glow Plug Conversion for Space Bug

Post  Kim on Sat Dec 17, 2011 11:05 am

EXModelEngines wrote:Does the engine have the small diameter thread on the head?

Matt

Yeah...I carefully drilled out the center, threaded and relieved it down to where a Standard Long glowplug looked like it fit about right in the chamber.
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Re: Home Made Glowhead / Glow Plug Conversion for Space Bug

Post  EXModelEngines on Sat Dec 17, 2011 11:22 am

Kim wrote:
EXModelEngines wrote:Does the engine have the small diameter thread on the head?

Matt

Yeah...I carefully drilled out the center, threaded and relieved it down to where a Standard Long glowplug looked like it fit about right in the chamber.

Nice!

Any idea what the thread spec is on that?

Matt
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Re: Home Made Glowhead / Glow Plug Conversion for Space Bug

Post  nitroairplane on Sat Dec 17, 2011 11:23 am

You mean of the plug or the old head?
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Re: Home Made Glowhead / Glow Plug Conversion for Space Bug

Post  EXModelEngines on Sat Dec 17, 2011 12:21 pm

nitroairplane wrote:You mean of the plug or the old head?

Old small diameter head. I would assume the plug is a std. 1/4-32. I was thinking of modifying some of the glow head adapters that I have here, but need to look into the thread.

Matt
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Re: Home Made Glowhead / Glow Plug Conversion for Space Bug

Post  Admin on Sat Dec 17, 2011 12:31 pm

That's great Kim! If I ever need a head converted, I know who to send it to! lol!
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Re: Home Made Glowhead / Glow Plug Conversion for Space Bug

Post  Kim on Sat Dec 17, 2011 3:24 pm

EXModelEngines wrote:
nitroairplane wrote:You mean of the plug or the old head?

Old small diameter head. I would assume the plug is a std. 1/4-32. I was thinking of modifying some of the glow head adapters that I have here, but need to look into the thread.

Matt

Hey Matt!

Sorry for not responding sooner...all this high-powered machinist work is rough on an old guy...I had to take a nap! Yes, the plug thread is the same ole 1/4 x 32 we all know and love.

Using my newly purchased MATCO Thread Gage Set (you people are costing me money!), the threads look to be 40--inch:




Looks like they've got a diameter of .434" on the outside of the threads---you'll just have to take a W.A.G. to convert it, but I think it was pretty close.



Yeah Jacob, I'd give it a shot! As long as you understand that delivery times can vary wildly, and the general quality of the work is a direct function of the crankiness level of the machinist!

Later Dudes !!!!
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Re: Home Made Glowhead / Glow Plug Conversion for Space Bug

Post  EXModelEngines on Sat Dec 17, 2011 3:35 pm

Sounds like a 7/16-40 then? Then again Cox liked odd sizes lol.

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Re: Home Made Glowhead / Glow Plug Conversion for Space Bug

Post  Kim on Sat Dec 17, 2011 5:57 pm

EXModelEngines wrote:Sounds like a 7/16-40 then? Then again Cox liked odd sizes lol.

Matt

Wonder if there's a die that size somewhere?
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Re: Home Made Glowhead / Glow Plug Conversion for Space Bug

Post  nitroairplane on Sat Dec 17, 2011 6:35 pm

Thermal be one somewhere.
What happened to the cox ones?
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exactly??

Post  Jaspur_x on Sat Dec 17, 2011 8:23 pm

nitroairplane wrote:Thermal be one somewhere.
What happened to the cox ones?

Bernie or Matt may have the best of notions there
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Re: Home Made Glowhead / Glow Plug Conversion for Space Bug

Post  andrew on Sat Dec 17, 2011 9:38 pm

McMaster-Carr

Part No. 26005A132
Price: $56.56

It ain't cheap, but it ain't common either.
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Re: Home Made Glowhead / Glow Plug Conversion for Space Bug

Post  EXModelEngines on Sat Dec 17, 2011 10:19 pm

I'll have to see if I can borrow one and try it out.

Matt
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thread die

Post  Jaspur_x on Sat Dec 17, 2011 10:26 pm

andrew wrote:McMaster-Carr

Part No. 26005A132
Price: $56.56

It ain't cheap, but it ain't common either.

Cheap no, lucky to find yes.
Also , its not like you have to replace tools of this kind from use/wear, more like from misplacing lol Tools are always a wise buy Rolling Eyes
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Re: Home Made Glowhead / Glow Plug Conversion for Space Bug

Post  andrew on Sun Dec 18, 2011 11:54 am

The companion tap for the 7/16-40 die is part no. 2595A234 . Plug that into the search box at McMaster's site to find it. Tap price is $27.53. This is a bottoming tap. They also carry a taper and plug tap in the same size, but for chasing threads in the top of the cylinder, I think a bottoming tap is probably better.

McMaster uses a javascript search applet, so frame URL's aren't easily located.

Matt --
If you can verify that the thread is indeed a 7/16x40, a tap and die combo might not be a bad investment for anyone planning to refurbish a number of engines. Because the glowhead/upper cylinder threads and the lower cylinder/crankcase threads are the same, you would get double duty from the combo.

A little shopping around can find the same sizes for lower pricing -- Model Engineering in the UK seems to be a little less expensive (but you know how it is dealing with those Brits!! Very Happy )

andrew
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Re: Home Made Glowhead / Glow Plug Conversion for Space Bug

Post  EXModelEngines on Sun Dec 18, 2011 2:43 pm

andrew wrote:The companion tap for the 7/16-40 die is part no. 2595A234 . Plug that into the search box at McMaster's site to find it. Tap price is $27.53. This is a bottoming tap. They also carry a taper and plug tap in the same size, but for chasing threads in the top of the cylinder, I think a bottoming tap is probably better.

McMaster uses a javascript search applet, so frame URL's aren't easily located.

Matt --
If you can verify that the thread is indeed a 7/16x40, a tap and die combo might not be a bad investment for anyone planning to refurbish a number of engines. Because the glowhead/upper cylinder threads and the lower cylinder/crankcase threads are the same, you would get double duty from the combo.

A little shopping around can find the same sizes for lower pricing -- Model Engineering in the UK seems to be a little less expensive (but you know how it is dealing with those Brits!! Very Happy )

andrew

Andrew,

Yes, that is probably a good idea. For now I will probably see if I can borrow one to confirm the thread matching. Hopefully sometime in January there will be time to look after this project.

Matt
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Re: Home Made Glowhead / Glow Plug Conversion for Space Bug

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