TD 09 Glow Head Conversion
 

Hi Ya'll,

Can a Cox TD 09 glo head be drilled and tapped to accept a short reach glo pug? Any hints/suggestions?

Thanks........

$14.95 for a new glow head......OMG!

RE: TD 09 Glow Head Conversion
 

Yes they can-as can all the Cox heads from 049 up-BUT-you will lose a degree of performance from a combination of reduced compression and less optimal combustion chamber shape. You lose volume around the plug threads and the element recess in the plug itself. Optimising the drilled and tapped head will require testing with a variety of different brands and heats of standard glowplug. [how much time effort and money do you want to spend doing this?]Commercial head adaptors to take a standard glowplug are available for a number of engines-Cox 049.09/15, Holland Hornet, Norvel 049/061/074 and Testors-McCoy 049. MECOA makes one for the Cox 09-part # 911-046-price is $13.99 [then you have to add the cost of the plug]. A few suppliers-such as Bob Mattes (www.flyfreeflight.com) will machine your burnt out head to take a Nelson plug, in which case you may not see any performance drop-and in some cases an increase. Ebay vendor cox_hyper_speed lists several adapters for several sizes of Cox engine (and Norvels) for either standard or turbo plugs-but has no listings running at present. Or put another way-there's no such thing as a free lunch-and it may be less aggravation and hassle to buy new 09 glowheads!
IF you are burning out Cox heads on a regular basis then you are doing something wrong..................

ChrisM
'ffkiwi'

RE: TD 09 Glow Head Conversion
 

ffkiwi pretty much sums it up well. I've used both the standard plug and turbo plug conversions he mentioned sold by cox hyper speed on the auction site. They run consistently but with varying amounts of power/rpm depending on the plug style used just as he says. Sometimes a slightly detuned .09 is just what you're looking for on some models. I have a Medallion .09 that has run many hours over the years on a standard plug conversion on an old Randolph-designed Pong Two. For optimum performance, the stock Cox heads have been the ticket for me. A good hot turbo plug conversion is a little bit below that power in my experience. Haven't tried the Nelson plugs.

I tend to run the conversion heads the most since I only have a handful of stock factory units and they are getting harder to come by(as are the great rubber ducky 7x3.5 props). Seems .09 pilots are getting fewer all the time. Parts supply is sometimes a challenge for these. I love their loud, raspy sound!

A video of my Medallion .09 flying at the SMALL fly-in a couple of years ago. Had a stock head on it in this clip, though.

http://www.youtube.com/watch?v=B_MV4PEy6jI

RE: TD 09 Glow Head Conversion
 

Even short reach plugs are getting harder to find now. I would at least try for turbo plugs. They are harder to machine but have a smaller diameter than the Nelson plugs and there are a larger variety of heat ranges and brands available.Henry did kind of retire too, although other guys re making them like Merlin. An OS plug is half way between a short and long and would work but power would be down. I did a few .049 plugs for short reach plugs and they need a counterbore just the right size so the Cox plug wrench still works and you can still get the 5/16" wrench in for the regular plug. I then sanded off a few thou. off the bottom of the plug to get some more compression back. It has to be done very evenly with 400 sandpaper on a plate of glass or machined on alathe and if gone too far it will touch the top of the liner and that should be removed too. I am guessing the same thing for the .09. I just got a tap for the Turbo size (8mm by .75 pitch) after making a bunch for short reach after doing some .049 and Rossi .15 heads. I am holding off on the Tee Dee .09 till it blows. The little ones run better without the regular plugs.AP still makes an .09 real cheap, but the size isgetting less popular with the leckies on the scene now.

RE: TD 09 Glow Head Conversion
 

Thanks Gents for all this great info. I took stock of my parts after I resurrected an old TD 09 I use atop a power pod for an Olympic glider. I noticed I have two glo heads, and while I haven't burned any out, I started thinking of my options should I find myself in need of purchasing one. I enjoy modifying, customizing, tinkering, etc.... and your suggestions will go a long way towards that end.;)

Thanks again [8D]