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049 Glow plug conversion perfected

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049 Glow plug conversion perfected

Old 04-13-2003, 02:10 PM
  #26  
AndyW
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Default 049 Glow plug conversion perfected

Andrew,

Deranged, uh, I mean brilliant minds think alike. See my post in this thread.
Old 04-13-2003, 02:21 PM
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AndyW
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Default 049 Glow plug conversion perfected

Oh yes,

I did up a conversion to stock plug for my .074. Throttling was better but power was way down. Have just applied blue Loktite to this one and will see what happens. Next is to make a "tight" version.

Will let you all know tonight, if possible.
Old 04-13-2003, 04:18 PM
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Default 049 Glow plug conversion perfected

Andy... somehow I missed that one post! Doh!

It never occurred to me before I read that article...

AJC
Old 04-13-2003, 06:31 PM
  #29  
PCARROLL
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Default 049 Glow plug conversion perfected

Imalready using a tapered tap I just wont run it all the way through. If you look at the hole in the stock head for the platnium element it is smaller than the hole in the plug for the element there. That gives it more volume which therfore reduces compression ratio. I also shaved the head .005 at a time until i dared not go any more. The starting hole size is also a big factor in thread engagement as well. The smaller the starting hole the more thread engagement you will have. I am currently using a #3 drill bit and get 85% thread engagement according to the tap and die charts If i used a smaller bit by one size i would probably get more thread angagement which equals better sealing properties.
Old 04-13-2003, 09:34 PM
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Default 049 Glow plug conversion perfected

Yes, compression will vary but you usually have to run from one to 3 shims anyhow with the cox's.

Not everyone has a lathe, and some of us who do (like me) dont want to get into the small parts business, so go for it!

I just like to do stuff for myself and friends

AJC
Old 04-13-2003, 10:35 PM
  #31  
AndyW
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Default 049 Glow plug conversion perfected

No sweat Andrew, I kind of pulled a Homer too on the tuned pipe thread we had fun with. Your work on that has got me determined to make one.

I just got back from the flying field. OK. Stock Norvel plug with four washers under head, 16.5K on a 7 X 3.5 Cox prop. Idle, solid 4K minimum, though I fly at 5K.

The adapter I made is flat at the bottom and the threads are cut into the proper sized bore. Then, a 5/16"" round dremel bit is used, and spun till I get a combustion chamber cavity. I made several with the cavity at different volumes. All these adapters gave an average 2K loss of RPM no matter what plug. Best though, was a short reach #3 OS. The last one I made had a very small cavity, obviously too small but the idea was to install 5 to 6 washers and take one out at a time to max the required compression. Final result was two washers giving me15.5K. One washer more and 300 rpm loss. One washer less and same rpm loss. OK. This adapter was taken out and blue Loctite applied to the plug. The result was an extra 500 rpm, or total of 16K. A 500 rpm gain and only 500 less compared to the stock plug. Not bad.

Notable was that my minimum RPM with the adapter, went down to 2.5K. Rock solid idle, acceleration very good. The adapter with a conventional plug reduces top end AND bottom end.

Conclusion is, that the threads of a conventional plug DO interfere, somehow, with combustion and with power output. Nelson discovered this and invented a new type of plug.
Old 04-14-2003, 02:24 AM
  #32  
Red Baron Mike
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Default 049 Glow plug conversion perfected

The Norvel plug adaptor will work in Cox engines. What Norvel
does is they don't drill the hole all the way through the head. The
"small" original sized hole is in the combustion chamber and a few
thousands of head thickness remains before the hole diameter opens up for the standard plug. The standard plug then screws down into a blind hole and bottoms out. If you look up at the plug through the combustion chamber side of the head, all you see
is a hole the size of the coil diameter.

The loss of rpm by opening up the diameter all the way through for the 1/4-32 standard plug is primarily due to the loss of combustion chamber shape and to a lessor degree, the reduction in compression. The Norvel concept seems to be a great compromise.

I haven't seen the RJL adaptor, only the Norvel.
Old 04-15-2003, 08:19 PM
  #33  
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Default 049 Glow plug conversion perfected

Wel folks i ran it up today at work with an os plug and got a more consistant run than with the traxxas plug. IT would hold 16.6-16.7 without wavering much. I ran 2 more tanks of fuel through it just to verify these results. Remember now that the engine im using is a 049 tee dee with a KK needle on it and a KK tapped cranckcase cover for fuel pressure. Your results may vary.
Old 04-21-2003, 09:20 PM
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Default 049 Glow plug conversion perfected

Hello again folks. I know that some of you may consider this blasphemus but while I was looking at the threads on the norvel 061 head i saw that they were similar to the threads on my modified cox head. Well VIOLA! it fit . I have attached some pics for your viewing pleasure but I have not run it up yet. Maybe this weekend.
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Old 04-21-2003, 09:25 PM
  #35  
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Default 049 Glow plug conversion perfected

And yet another one
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Old 04-21-2003, 09:26 PM
  #36  
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Default 049 Glow plug conversion perfected

Final one.
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Old 04-22-2003, 01:42 AM
  #37  
ZAGNUT
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Default 049 Glow plug conversion perfected

has anyone tried a turbo plug or a nelson plug in an adaptor? i've got lots of cox engines that i want to start useing again but don't want to buy the EXPENSIVE heads if i can get something else to work good.

dave
Old 04-23-2003, 07:00 PM
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Default 049 Glow plug conversion perfected

I've run the Nelson plugs with the Kustom Kraftsmanship and Galbreath head/adaptors for years with good results on fast reed engines and TD's. I think the Nelson plug magic is due to the good heat transfer characteristics it has, not necessarily because of any compression loss in other setups. This is due to the tapered bottom or "nose" of the plug that seals against a matching tapered lip at the bottom of the threaded hole when tightened. The heat path is far more direct than with plugs that seal with a copper gasket at the top of the threads. My guess is that Henry came up with the system from racing engines which use a glow head "button" with the head clamping it down.

The KK/Nelson heads when properly shimmed were usually good for at least a 1000 rpm and less needle sensitivity to boot, plus lower operating costs. The only problem I had was in trying to use them on my detuned throttled sport TD's. The top end was better as usual but the Nelson plug was (I think) colder which required a richer mixture setting and caused a rich low end and sluggish transition.

The other plug I want to experiment with is the Lite Machines plug which is the same (I think) as the old Glo Bee plugs. They have a "button" style insert with a flat spiral element. They used to work very well way back when on fast engines but I haven't tried one lately. Al Clark reports VERY good results with this plug on his D/Bird TD....an even better top end but still retained good low speed. Gotta try one!
Old 04-23-2003, 11:27 PM
  #39  
Msaint
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Default 049 Glow plug conversion perfected

Im just wondering what cost savings there is in not using a cox glow head. I havent bought anything cox since I was kid so i dont really have any idea to compair the cost of a normal glow plug to the cost of a cox glow head. i do know i used to where out a path to the hobby shop spending my alowance on the cox glow heads tho. Seemed they allways burned out right when all my friends were areound and I wanted to show off my latest slab built control liner.

When I got back into 1/2a I went all norvel and havent looked back yet. Although I would love to do a cox just for ole times sake.
Alltho itll prolly be an .010 on a gnat or a lilest stick. Hmm heh a venturi throttled .010 now theres a thought!
Old 04-24-2003, 12:24 AM
  #40  
Jeff Leavitt
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Default Glo Bee's

Dickiebird,

The only Globee style plug that LiteMachines had that I'm aware of was for the norvel engine. This was a glo head and not a screw in type plug. I talked to "Dave" at LM a while back and he told me that they no longer make that plug, and their stock is gone, and they don't plan on making any more. So, if you stumble across any, buy 'em all and hold on tight. This glohead will produce the most power on norvel's, and if it can be adapted to the Cox it's sure to be a winner. It's not just the spiral element that's responsible for the power, the design and the cut of the chamber helps a great deal too. If you get some of the globee's, the center post is not supported, so fill the center with five minute epoxy and that will eliminate any breakage problems. If you don't do that the center post WILL break off after a few runs, rendering the plug almost useless. Rgds, Jeff.....
Old 04-24-2003, 01:35 AM
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Default 049 Glow plug conversion perfected

Cox glow heads really have only one heat range although they do come in diffrent compression levels. With a glow plug you can run a hot plug with low nitro fuel or a colder plug with higher nitro fuel. The main problem with the conversion heads is the loss of power from the increased combustion chmber volume. What I did with mine was to get as close to stock as possible and I got within approx 300 rpm. Now dont get me wrong but they do good for what they do but I just wanted a little more versatility with my engines. Plus I also LOVE to tinker with things. Just look at Dickybirds engine. I mean this guy has to be one of the master tinkerers out there. I also thing a glow plug converted cox also has a gee whiz factor to it as well. Glow plugs are also about 70% cheaper than glow heads too.
Old 04-24-2003, 02:53 AM
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Default 049 Glow plug conversion perfected

Would anyone be interested in a head that takes Norvel plugs but is hard to distinguish from a stock Cox head? That way you might benefit from cheaper plugs but not be branded a traitor, if no one looks too close.

Send me a nice new, but burned out Cox plug and I'll make one up for you. All I ask is a spare for me and maybe also a newish but burned out Texaco plug. Need the extra cooling fins for an in cowl installation.

I'll pay the freight back to you.
Old 04-24-2003, 03:03 PM
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Default Re: Glo Bee's

Originally posted by Jeff Leavitt
The only Globee style plug that LiteMachines had that I'm aware of was for the norvel engine. This was a glo head and not a screw in type plug. So, if you stumble across any, buy 'em all and hold on tight. If you get some of the globee's, the center post is not supported, so fill the center with five minute epoxy and that will eliminate any breakage problems. If you don't do that the center post WILL break off after a few runs, rendering the plug almost useless. Rgds, Jeff.....
Thanks for the tip Jeff. I have a few old Globees left from the old days....guess I better use them wisely! They are a steel "head button" style plug with a screw on aluminum outer portion that clamps it down.
Old 04-24-2003, 09:24 PM
  #44  
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Default 049 Glow plug conversion perfected

I have enjoyed following this thread and I have set up my lathe and made three threaded heads.

I have two questions.
Are you using the copper gasket under the glow plug?
Does any one know of an inexpensive sorce for the copper head gasket (spacer)

Walt
Old 04-24-2003, 09:30 PM
  #45  
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Default 049 Glow plug conversion perfected

since you allready have a lathe, make your own

I use copper grounding bar (pure copper) and just turn it to the right diam. and drill a hole, part off as many as you wish.

AJC
Old 04-24-2003, 09:31 PM
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Default 049 Glow plug conversion perfected

I assumed youmeant the copper glow plug (not glowhead) gasket. The thin glowhead gasket/seal would be too hard to part off!

AJC
Old 04-25-2003, 11:53 AM
  #47  
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Default 049 Glow plug conversion perfected

Walt,

Yes, copper gasket under the glow plug. Even if you make the threads real tight, they'll leak, at least a bit.

For the Cox head gaskets, call 1 800 451 0339 and ask for
Cliff Cotton. He's always been a lot of help to me for unusual or even usual requests. I've got a lifetime supply of gaskets for all the Cox engines.

You can also get gaskets from Norvel/Sig. At least I did when they were still just Norvel.

Also, you can get extremely thin gaskets for adjustment purposes from Kustom Kraftsmanship but I haven't used them in a long time and can't find their address or phone number. They have custom Cox stuff for the free-flight guys. Do a Google for them.

Hope that helps.


Hey Andrew,

That's a great idea. Making various heads, I've always had trouble with the stock gaskets just not quite giving me the proper clearances under the glow plug. Will give that a try. Thanks.

Here's an idea. Using a Fox miracle plug, bore out the head with a step so that the smaller diameter end of the Fox plug is a squeaky, sealed fit. The rest of the bore would be sized to suit your tap for the plug. Of course, you'd need to get yourself a bottoming tap and, you might need to use a Texaco head.
Old 04-27-2003, 02:56 AM
  #48  
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Default 049 Glow plug conversion perfected

Hi everyone,
I live in japan where it takes a while to get norvel parts. I am making a 1/2A(actually a .074) ducted fan. as my plug recently died, and because of modifications to the engine meaning i have to run it with 7 shims on 10%fuel, i decided to make a adapter head with corrected volume to take the new o.s turbo plugs(these are nelson plug copys with a taper seal at the base)
Has anyone tried this?
J.M
Old 04-27-2003, 11:43 AM
  #49  
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Default 049 Glow plug conversion perfected

I was unaware OS had a new type of plug, with a Nelson taper. Any chance of a picture?

If they are not available in North America yet, I would trade you a few norvel head buttons for a few of the new OS plugs just to see them!

Andrew Coholic

if you are interested let me know:

[email protected]
Old 04-27-2003, 02:34 PM
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Default 049 Glow plug conversion perfected

ajcoholic: I would be willing to bet OS has a engine now or in the works that that plug is being made for. Check with Bill Baxter & see what he can find out . Bet it is for a car engine. Might be cheaper freight. >>>>>>>>>>>big max 1935>>>>>>>>>

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