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Cox Black Widow - Glow head availability?

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John Falconer13/02/2009 15:39:49
11 forum posts
9 photos

I have just completed a Sig Hummer 1/2a racer (see picture) but all three glow heads for the Black Widow engine are defunct.
I built the model to make use of this engine and an old 2 channel Futaba radio set that were salvaged from my first model which was a Gentle Lady glider. (It got stuck in a tree, soaked by rain, eventually fell out and was trampled by a herd of cows )

Does anyone know where I can get some replacement glow heads in the UK please?

Chris Channon13/02/2009 18:56:00
550 forum posts
Hi, Sussex Model Centre sells them, not cheap , but they are rated at 1.5 volt, if you can use long leads from a 2v cell or turn the glo driver right down on the power panel.
Of course you could use a D type dry cell to energize the plug like we used to !!!!
Chris
ken anderson.13/02/2009 18:59:23
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8683 forum posts
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hello chris-the good old day's with the d cell/cox engine's--we used to think were the bee's knee'ssure i read that someone had drilled out the cox head and tapped for an ordinary glo plug? 
 
                  ken anderson................................................
Engine Doctor13/02/2009 22:30:47
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2511 forum posts
39 photos
Hi john  .You can modify the head to take an ordiary plug but there isn't much material to play with . and you wil probably need an old cox cylinder to hold the head in a lathe so as not to damage the very fine thread. I made one some time ago and it ran ok but I think its worth paying the extra for a proper head.
E.D.
Mark Lubbock17/02/2009 14:06:08
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313 forum posts
13 photos
You can tap out the head-you need a 1/4x32tpi tap, a model engineers thread, available naturally from model engineering suppliers. I think a 1/4 UNEF is also around the same. Unless you do a lot, probably not worth it-try Cox Supplies on Ebay-you can get a complete sure start engine for £8.90 from them, cylinders, complete with piston & head & glow heads etc. all at fairly cheap prices. Take care with the volts as described above & a head should last a long time
John Falconer04/08/2009 10:55:12
11 forum posts
9 photos
Thans for all the suggestions. I have just bought a couple of drilled heads from ebay. Delivered in 2 days by a canadian company. I'll try to do a test flight in the next couple of weeks and post a photo of the results.
Steve Hargreaves - Moderator04/08/2009 22:02:18
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I'd be interested to see how they go......one of the problems of drilling & tapping the head for a standard plug is a loss of compression ratio (adding the standard plug increases the volume of the combustion chamber thus lowering the effective compression) & this reduces power considerably....lets face it at 0.8cc you don't need much of a change to have a big effect.....
Bladerunner18/08/2009 10:29:56
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129 forum posts
Posted by Steve Hargreaves on 04/08/2009 22:02:18:
I'd be interested to see how they go......one of the problems of drilling & tapping the head for a standard plug is a loss of compression ratio (adding the standard plug increases the volume of the combustion chamber thus lowering the effective compression) & this reduces power considerably....lets face it at 0.8cc you don't need much of a change to have a big effect.....

 Good point. Thus an excuse to run higher nitro!

thomas oliver 118/08/2009 22:27:21
96 forum posts
23 photos

Sorry to disagree with some of the previous info.  There is plenty of metal thickness in the head of the Cox.  So much so that the head neads counter-boring to bring the plug through level with the inside of the head. Which of course means there will be no loss of compression.  How do I know - I have just converted an old head - took about five minutes and looks OK to me.  Modolit.
Pat (rActive) Harbord18/08/2009 22:40:35
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634 forum posts
49 photos
I had a sure start off a Canadien company on ebay. No problems at all, I think they bought up as much of the factory stock as they could when cox stopped producing them a few years ago?

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