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Medallion .049 Exhaust Throttle Muffler RC Conversion
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Medallion .049 Exhaust Throttle Muffler RC Conversion
Please note, this thread may take a longer time in developing, as it will be done on a time available basis.
Back in May 2018, I won a bid on a used good condition Cox .049 Medallion, earlier one with no spanner flats at cylinder top. Only obvious defect was plastic engine pressure nipple by the venturi was broken off, minor scratches, and engine was stiff and gummy from being run on 100% Castor oil based fuel.
CEF: Woo Hoo Won Bid on Medallion 049
I'm in the process of converting my earlier version Medallion to RC throttle. Here's the exhaust throttle muffler setup I got from Cox International back in mid-July:
Throttle ring slot width compared with cylinder between exhaust slits.
Throttle ring slot width compared with cylinder slits.
Throttle ring slot width other side (with idle exhaust dimple each side) compared with cylinder slits.
Cox installation instructions, Tee Dee and Bee tanked engines shown. Please note, Spacer ring "A" is not required if a starter spring is installed.
Now starting disassembly for any additionally needed cleaning and reset the piston con rod ball and socket joint. Back was on tight enough that simply using the Cox spanner did not budge it. To remove the back, I followed the golden rule: Don't force it, get a bigger hammer. With needle valve removed, wooden blocks to protect the engine and C-clamp to hold together, a tap or two broke loose the back cover without damaging or marring the engine.
Back in May 2018, I won a bid on a used good condition Cox .049 Medallion, earlier one with no spanner flats at cylinder top. Only obvious defect was plastic engine pressure nipple by the venturi was broken off, minor scratches, and engine was stiff and gummy from being run on 100% Castor oil based fuel.
CEF: Woo Hoo Won Bid on Medallion 049
I'm in the process of converting my earlier version Medallion to RC throttle. Here's the exhaust throttle muffler setup I got from Cox International back in mid-July:
Throttle ring slot width compared with cylinder between exhaust slits.
Throttle ring slot width compared with cylinder slits.
Throttle ring slot width other side (with idle exhaust dimple each side) compared with cylinder slits.
Cox installation instructions, Tee Dee and Bee tanked engines shown. Please note, Spacer ring "A" is not required if a starter spring is installed.
Now starting disassembly for any additionally needed cleaning and reset the piston con rod ball and socket joint. Back was on tight enough that simply using the Cox spanner did not budge it. To remove the back, I followed the golden rule: Don't force it, get a bigger hammer. With needle valve removed, wooden blocks to protect the engine and C-clamp to hold together, a tap or two broke loose the back cover without damaging or marring the engine.
GallopingGhostler- Top Poster
-
Posts : 5214
Join date : 2013-07-13
Age : 70
Re: Medallion .049 Exhaust Throttle Muffler RC Conversion
Today, I mounted the Kamtechnik radial mount for my Medallion .049 engine. When tightened, it precisely aligned itself where I can insert #2 sheet metal screws evenly spaced into a plywood bulkhead. However, I did notice something, and I think this may have to do how through time, various .049 engine crankcases have their backplate threads cut a little different than others. This is why he drilled so many holes (12 total) in the mount area, so one could successfully mount the engine no matter what Tee Dee or Medallion one owns.
However in my case, once it tightened it up, the two screw holes are slightly blocked by the crankcase, so one would screw the backplate in place, but not snugged up yet, insert the two top screws, then tighten the back down. There is sufficient room for a small screwdriver or Allen wren to snug it down, just not enough for screw to cleanly be inserted into the mount hole if back it tightened down.
It is just one of the minor sacrifices in having a mount compact enough to fit nearly every fuselage firewall situation. Otherwise, the Kamtechnik backplate mount is an extremely well made precision part that perfectly replaces the stock backplate and provides an excellent solution for a convenient and compact mount for these Cox front venturi engines. I also bought one for my .09 Medallion muffled R/C.
I attempted to remove the cylinder, so I could mount the later non-SPI cylinder and throttle sleeve muffler, but the cylinder is on very tight. I will have to partially disassemble to remove the plastic venturi carb body, then gently apply heat from my propane torch. This should swell the aluminum a tad enough so cylinder then unscrews easily.
I plan to salvage and reuse the Babe Bee style single bypass SPI cylinder and piston after resetting the socket, on my "Bumble Bee" custom yellow powder coat, cast crankcase and 8 cc non-stunt plastic venturi tank that recently arrived from Bernie. With his brass prop thrust plate or Killer Bee thin stainless thrust plate washer (have both), I can use this "Bumble Bee" engine as a pusher, too.
However in my case, once it tightened it up, the two screw holes are slightly blocked by the crankcase, so one would screw the backplate in place, but not snugged up yet, insert the two top screws, then tighten the back down. There is sufficient room for a small screwdriver or Allen wren to snug it down, just not enough for screw to cleanly be inserted into the mount hole if back it tightened down.
It is just one of the minor sacrifices in having a mount compact enough to fit nearly every fuselage firewall situation. Otherwise, the Kamtechnik backplate mount is an extremely well made precision part that perfectly replaces the stock backplate and provides an excellent solution for a convenient and compact mount for these Cox front venturi engines. I also bought one for my .09 Medallion muffled R/C.
I attempted to remove the cylinder, so I could mount the later non-SPI cylinder and throttle sleeve muffler, but the cylinder is on very tight. I will have to partially disassemble to remove the plastic venturi carb body, then gently apply heat from my propane torch. This should swell the aluminum a tad enough so cylinder then unscrews easily.
I plan to salvage and reuse the Babe Bee style single bypass SPI cylinder and piston after resetting the socket, on my "Bumble Bee" custom yellow powder coat, cast crankcase and 8 cc non-stunt plastic venturi tank that recently arrived from Bernie. With his brass prop thrust plate or Killer Bee thin stainless thrust plate washer (have both), I can use this "Bumble Bee" engine as a pusher, too.
GallopingGhostler- Top Poster
-
Posts : 5214
Join date : 2013-07-13
Age : 70
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