I been around for a long time but I am just beginning to look seriously at 1/2 A.  What is the difference between a Cox TD and a Medallion.  I see red cases and black cases.  Are they basically the same and all of the parts interchange.  I have a black case rotary shaft Cox with a Black Widow jug. I also have the bottom end of a red case rotary shaft Cox that I plan to put a product engine jug on. I have a LH crank comming. Will it work in both?  Everything seems to mixes and match so what's the dif in a TD and a Medallion and how can you tell them apart?     

PS I was just looking on ebay at a Medallion .049.   It appeared to have a molded in venture.  My two have screw in venture.  Is this the differance?  If so why is one of mine black and one red?

Quickest way to tell them apart is the needle valve location. The needle valve on a Medallion goes through the side of the venturi like most c/l engines, while the needle on the TD goes into a housing around the venturi, and is alongside the venturi tube.

There are other differences such as cylinder/piston assy, glow head, crankshaft, and carb housing.

The red or black carb housing was usually used to identify the .049 from the .051 TD, black being .049.

Bill

Thanks bill.  That all makes sense.  is the crank interchangable between the TD and Medallion?

Don't know for sure John, but I would think the crank has different timing, and/or inlet port size. The TD cylinder has different porting, and is also tapered.

Warren Leadbeatter has a great article on Cox engines in Wikipedia. He explains the different cylinder porting, and shows photos of the cylinder flutes. Here is the link.

http://en.wikipedia.org/wiki/Cox_Model_Engines

It's a great read.

Bill

As always you guys know it all or know where to look.  The above link is a great read. And besides it had the answer to my question.

Quote from wikipedia.

"On the Tee Dees and Medallions the cranks are also interchangeable but quite different. The Tee Dee has a large square hole at the intake end of the crank whereas the Medallion has a smaller round hole. The timing is also different."

This tells me that my LH crank is Medallion but will work with my TD bottom end.  I am not looking for big HP - rather easy start and good runs.  I will be using it as a pusher on a scale DO335.  In a few weeks (months) I will start a new thread on the scale BB.  Lots of problems to overcome but if it all works I will have a one of kind. And that, as they say, makes the effor well eorth it.  Thanks for the help!   

John,

Found some of the aluminum carb bodies on Ebay. Different colors available. Here is the link.

http://cgi.ebay.com/Cox-049-Tee-Dee-Alum-Intake-Housing-replaces-carb-body_W0QQitemZ260310359152QQihZ016QQcategoryZ34056QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Bill

Just a heads-up.  If you use a muffler, be sure you have a piston/cylinder set that does not have any sub-piston induction.  (that's where there is a little gap under the bottom of the piston when it is at top-dead-center as seen through the exhaust port).  If you keep your eyes out, there are pressure tap backplates out there.  And, look at the TD Venturi size thread in this section to see how to use the built-in crankcase pressure tap you already have on the engines.

Hi Ty,

Perhaps Warren will see this, and comment?

He tries to keep the Wikipedia article as accurate as possible, but some facts are difficult to verify. I'm sure he will appreciate your input, on the Conquest.

Thanks,

Bill

Right again, Mike!

Don B, to your post #9...

The magic number for reversing rotation on an engine with a detachable front end (bearings, shaft, inlet) (that has a symmetrical bolt pattern allowing rotation by 90° either way) IS 90°. Which way doesn't make any difference.

The intake port in the case gets turned 90° and the shaft port meets it the other 90°, earlier or later. If you turn the front end counter-clockwise, you could call the change later in the stock direction of rotation, and vice versa: CW could be called earlier... Either way adds up to 180°.

One problem: the shaft port timing is often 'biased' to run better in the originally designed direction. Reversing the sequence in which the ports open will reverse that 'bias' opposite to what the mfr intended. For mfrs who offer either CW rotation engines (e.g., ENYA for several engines) or CW shafts (e.g., FOX), it is safe to presume that the mfr mirrored the port timing bias to get the same advantage as the original CCW rotation shaft in CCW operation.

BTW, I've never seen a COX engine with a front end suitable for this trick...

I HAVE seen COX reed valve engines run happily, and equally well either way - occasionally when you DON'T want them to... Reed induction is "controlled" by pressure changes in the crankcase, not by carefully timed ports cut into the metal (or plastic). Most reed COX engines don't have the power of a decent Medallion, or anywhere near the power of a TeeDee, but a reed at the back of that Do-335 could be a simpler way to do it.

The "product" engine - as installed in the department store plastic ARFs - isn't as bulky as the "integral tank" reed engines, and you'd use a separate tank. That could make fuel feed easier to tune in for an engine flying "backwards."

The old side port (usually spark) engines could run either way equally well, except that spark timing prevented reverse running...

...The magic number for reversing rotation on an engine with a detachable front end (bearings, shaft, inlet) (that has a symmetrical bolt pattern allowing rotation by 90° either way) IS 90°. Which way doesn't make any difference.

I think the correct front-end rotation is 90 deg CCW for running the engine in a CW direction. To turn it either way would, to me, seem like saying for normal CCW running, the intake can be either up or down...but then, I haven't tried it. As long as the intake opens while the piston is going up, I guess.

George

John,

If you know anyone who is into model boats you might find a good U-joint...and perhaps a shaft. 

George

True, the The Medallion Intake is round and the TD is rectangular.  The LH Medallion crank came in and it does have a round intake hole. However power is not an issue. With the Medallion crank and a product engine jug I am hoping for a easy starting mild manner engine.

I used to race fast electric boats. I still have a collection flex shafts etc. The problem is that they don't adapt well to a 1/2 air prop. Anyway the rigid shaft design and fabracition is well under way. If that doesn't work I will look at u-joints.

Wow, Larry...that's a little shaky. You may be right but it sure seems counterintuitive to me. I wouldn't try it myself.

John,

A stuffing tube is usually used to keep water out of a boat, I can't understand why you are using it on an airplane when a simple shaft would work and be much lighter?

BTW, plastic fuel tubing was used as a "U" joint on 1/2A boats back when parts were not as accessible and engines had less power.

George