Medallion .15 acquisition

Yes, thanx, looks like almost no running time , cleaned, polished, oiled, assembled...



RGDS

Very nice haul, Pegin, I wonder which model you will fit this engine to?

Upon learning that I did not have .15 size COX engines in my fleet yet, fellow CEF member batjack was generous to send me a fairly used, but perfect .15 Medallion RC and a brand new spare .15 head a year ago, and I am still checking which model in my yet-to-build inventory would best suit this beauty.




Since then I have dressed it up with an engine mount, and another NIB head, then  I also got hold of 2 nice black 8x4 props in a modeler's sale,  that I agree may well fit this powerplant.

Although I have 2 new heads already in my inventory, because  .15 COX heads are rarities on ebay, I ordered a Kamtechnik .15 turbo plug adaptor head too, (https://kamtechnik.com/product/ktk16/)  that also boosts the performance. Unfortunately the Kamtechnik turbo head for .15 engines is currently out of stock, otherwise I would recommend you to buy one.

With all these heads in my inventory I will not have to worry if I can keep this lil monster in service for a long time.-

Thanx Balogh, and great set of Medalion .15 and other stuff you have.
Will check for Kamtechnik head, either new or secondhanded one. Just in case to run out of original glowheads.
I have a lot of ideas, but Medallion will go on one or two i want to build.
Simple TEOSAWKI stunter or some profile scale CL model.
But this will decide durring the winter, to have something to build for spring seasson.
Regards,
Pegin

I bench tested mine with a 8x4 prop, 60/20/20 fuel and Kamtechnik head. A short vid is here, sorry for the non-laboratory environment.



Starts very easy, then peaks above 12k ( with stock head at least 500 less) and idles near 7k.
The combined carb+exhaust throttle responds superbly.
After the bench run I disassembled and found much to my surprise, that mine has a gudgeon pin in the piston instead of the ball socket joint of yours. I went to check which version was made earlier. The 1964 test by Mr Chinn finds this engine - introduced 3 years earlier to the market - with gudgeon pin...http://www.sceptreflight.com/Model%20Engine%20Tests/Cox%20Medallion%2015%20RC.html


It may well be that the balljoint was used only on later production engines...
A very nice sports engine..

Other way round-the ball joint was used on the early engines-and the later ones had the gudgeon....I suspect this came about largely due to the TD 15 (which of course preceded the medallion into production) not being able to hold together when pushed hard with the ball joint conrod-which was fairly rapidly replaced by a conventional gudgeon pin set up. It would not have made much sense to Cox to have continued to manufacture two .15s each of which used a different little end arrangement, so I imagine Medallions gradually transitioned to the gudgeon pin set up as the initial production stocks of ball end piston and rods were used up. If Cox were like most manufacturers they would have built up quite an inventory of parts stock before releasing the Medallion .15 on the market....and since these would not generally be worked as hard as TD's they probably had few if any failures...so the initial ball end units would have lasted several years of production before the newer form began to dominate...and if memory serves correctly the R/C versions did not appear till the mid 60s...so by that time there would have been several years worth of production of the standard Medallion to use up the pre-release inventory of parts. I think it significant that I've mainly encountered the gudgeon pin .15 in RC Medallions and not in standard ones....and again as I recall the Special .15 Mk2 appeared around '65....which is a similar date for the RC Medallions-and several of mine use the same stamped rod as the Special 15-II

ChrisM
'ffkiwi'

Hang on to the burned out head! One of the other sites (RCUniverse, I think) has a thread using hand tools and a low end drill press to convert a Cox head to take turbo plugs. I'll try to find it and drop the link here.

944_Jim wrote:Hang on to the burned out head! One of the other sites (RCUniverse, I think) has a thread using hand tools and a low end drill press to convert a Cox head to take turbo plugs. I'll try to find it and drop the link here.

Thanx for the tip, i searched and looks its this topic,

https://www.rcuniverse.com/forum/1-2-1-8-airplanes-70/4533758-turbo-plugs-how.html

Will try this DIY process just to check my skills, will report success or fail.
RGDS

That's the one!

944_Jim wrote:That's the one!

Thanx, 1/4-32UNEF TAP bought at EBAY is allready on its way to my address.
Hope will do the glowhead modification soon, to catch last nice weather in this year for engine testing.

The tap that you ordered will work ok with a bit less power and it is an easy job. The Turbo plugs have a tapered seal on the bottom and give the same or sometimes better power than the stock plug. They use a 60 degree taper. The Nelson plug is about 118 degrees (or whatever a normal drill angle is.) They take a bit of extra care to prepare compared to the 1/4" 32 tap, but it is worth the time for the performance compared to the standard plug. The turbo plugs do cost a bit more though too. If you go with the Turbo head they area somewhat standard size of 8mm with a fine pitch of 0.75mm. I got a bottoming one. Sretno