Cox Tee Dee .049 Throttle Valve Presented here is information on how to convert your 1/2A Cox TD's or Medallions to an R/C throttle valve engine. Using currently available parts and materials I have converted a TD .049 to throttle control and it runs, idles, and transitions very well. In the following you will find photos, text, and instructions to help you convert your engine.

Here is the Completed modifications to a TD .049. One could do the same mods to an .049 Medallion by using the TD carb body. The blue anodized parts were anodizided by me to give the engine a little personality!

Parts to be modifidied.

The carb, available from Hobby Shack (now Hobby People) needs to have the insert base (part that goes into the carb body) machined down to 1/4 inch outside diameter. The Cox carb body needs to be drilled out to 1/4 inch inside diameter so the carb will slide in snugly. Finally the carb body needs 2 holes drilled to accept the carb mounting screws. Do some careful measuring here to be sure you get the holes in the proper place so as the carb will seat nice and snug against the carb "O" ring.

Getting the engine to idle and transition smoothly.

I find the carb must have an air bleed hole in order to idle, have good mid-range, and transition well. The photo shows the angle I drilled the air bleed hole (.040 inch drill bit exiting hole). The size of the hole you drill depends on how rich or lean you intend to fly your model. As you might see in the photo (JB Weld Epoxy), it took me several tries to get the right hole angle and diameter. The air bleed hole must enter the carb throat at the right place or you will not get a good mid-range and transition. My hole is drilled so when the carb barrel is about half closed the air bleed starts to let air in to the carb throat. If in doubt try copying an OS Max .10 air bleed carberator.
Very important is coordinating the throttle barrel with the Ace throttle exhaust sleeve (available from SkyHbby). You can link the two with a simple wire bent to shape as in photo #1. I find that when the carb throttle barrel is about 2/3 closed, then the throttle sleeve must just be completely closing the exhaust ports.
My engine runs, idles, and transitions very nicely. While test running it I took the idle down to about 6,000 RPM, drove around the block, came back, engine still idling beautifully, gave the engine full throttle, it came up to full RPM with no hesitation or sputtering!
Please let me know if you have any luck with this set-up. My e-mail address is < dongarry@webtv.net >. Telephone number is (321)632-9115.

One more item I forgot to specify. I used a Norvel Freedom XL glow plug. Due to high cost of the Cox plugs I decided to use a plug moderately priced and readily available. Cox plugs would work well I am sure. You might try experimenting with different glow plugs.

Big Mig .061 RC Revlite from Norvel

I am adding this photo to show the new Revlite cylinder on the Big Mig and my added anodized colors of purple, black, and blue.
Due to the response on my anodizing I am including a web link to "Anodizing Aluminum", written by Ed Cox of Canada several years ago. This is the article that got me started in the "Art" of anodizing.