Cox Glowhead questions

Roddie, Cox produced the high compression head and the standard head for both the .09 and the .15 as they did for the .049's. I've never checked, but I believe the .020 is the same knurled head or plain. Truthfully, I have had two of the same .049 catalog# glow heads and while the same, they offered slight differences in the squish band. There's no mistaking a high comp head from a standard. I hopefully have enough TD .15 high comp heads left as they're quite rare. I don't use the TD much but I just built a plane for it.

I own two .074's, one new in the box and one with about 4 runs on it. I quickly put it back due to it's turd like performance. My buddy Dennis insists I put the TD .09 plug on it because that's the problem with the .074 engine. It doesn't surprise me, standard plug adapters absolutely suck and they lose too much performance. It's a known fact that you lose compression in the cavity of the plug and around the threads.

Thanks Rene and Ken. The Cox Medallion and Tee Dee engines are "new to me"/my engine stock. I'd never owned either type FRV engine until a few years ago. I'm just starting to learn about them.

My concerns for future operation (parts availability) lie with my Tee Dee .09's, of which I now have two examples in good/complete condition. I have bench-run my first one. You both may remember that this engine somehow developed a bent conrod.. which I managed to tweak-back straight enough to run.. after I put it back together.



Ken, That's the "Kap-Pak" head-clip you sent me a while back..  
The 7 X 3.5 prop (and a spare head and gasket..) were sent from Bob Dickerson..  



.. and Ron Cribbs sent me a pair of wrenches which enabled me to work on the engine..  

Hey Ken. Would love to know what you're building for your Tee Dee .15....

Roddie, hopefully I can get some pics up later. One of my club members Bob Klausse was the chief designer at Sterling Models. He moved to a condo with his wife and they couldn't take all of their belongings. He showed up in his wagon one afternoon with what appeared to be every kit that Sterling made. My son pulled out a Ringmaster JR Flash. Bob said make a donation to the club and it's yours.

Still in the cellophane wrapper, I took out the components last month. To my surprise, this is one of the nicest Sterling kits I have ever laid my hands on. No die crushing pieces in this one as every rib and former cleanly came out. I will say it was a real joy building this kit and I know Bob would appreciate seeing it completed. Nothing fancy here on the build other than keeping it straight. I just brushed on a dope finish as I didn't feel like dragging out the spray equipment. One solid color and no trim colors.

The plane is designed for the Fox .15X. The Fox .15 steelfin would also fit but the TD shares the same bolt pattern as well. The steelfin is the least powerful and would probably require a bit shorter lines to fly as well. The .15x is the lightest out of the bunch. I have a MVVS .15 somewhere which I think would fit as well.

roddie wrote:These are probably dumb questions.. but I'm going to ask anyway. Are the Cox .09 Medallion and Tee Dee glow-heads the same.. or does the Tee Dee use a high-compression head, as the Tee Dee's .049/.051 do?

Then there's the .15's; Medallion and Tee Dee. Do they use the same glow-head?

Does the Tee Dee.020 use the same glow-head as a Pee Wee .020?

I've heard that the Cox .074 Queen Bee engine's glow-head (and head-gasket) are interchangeable with the Cox .09 engines. Is this true.. and if so; will Cox .09 glow-heads interchange with the .074 Queen Bee's?

Thanks in advance for your responses.

Some of this has been answered already, but

(1) no-the Med 09 and TD 09 heads are quite different-the Med being hemispherical, the TD having the classic trumpet shape once common to the whole TD series...BTW the TD 09 head is not the same style as the TD 049-the latter being more of the 'cone and squish band' variety than the true 'trumpet'

(2) there are actually three Cox 15 glowheads (excluding the later Conquest engine 'button' type)-the Medallion has a hemi shape, just like the Med 09, the TD 15 a trumpet shape like the TD 09-but there is also the Special 15 head-which was also high compression-with a conical head shape and a heavier element.  Genuine TD 15 heads are VERY thin on the ground-not the least because TD 15s when fed lots of nitro and propped for their peak rpm had a ravenous appetite for glowheads...partially due to the element being just a little too thin to cope with the conditions-and to compound the situation, people-in Europe in particular-discovered around 1964-65 that if you machined a TD 15 head down and turned it into a button-your Super Tigre G15 went even better-so demand for the heads went through the roof. Finally-when the FAI banned nitro for FAI speed and FAI FF events a redesign on the TD 15 head produced the very high compression Special 15 head to facilitate running on straight 80:20 fuel-along with a heavier element to improve durability..

(3) Pee Wee 020 vs TD020 head has been covered already.

(4) Yes the QB 074 head and the 09 heads interchange-in terms of thread-but the 074 head on the TD 09 requires a bit of fiddling with head shims to get the appropriate head clearance-which of course depends on the particular plug fitted-and the fuel used...what it does allow of course is a way of optimising your TD or Medallion that was not possible with the standard Cox 09 head [though in the 90s there WERE some alternative heat heads produced for the 049s by non OEM producers-one in Canada and one in Australia...]

ChrisM
'ffkiwi'