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Usingan 049 Medallion for CL stunt Questions... Babe_b10
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Usingan 049 Medallion for CL stunt Questions... Empty Usingan 049 Medallion for CL stunt Questions...

Post  AllSoldOut on Sat Nov 24, 2018 2:40 pm

All,

I have recently acquired, fully stripped, cleaned and test run an 049 from I guess around 1972 (it was very gummy). This one has a single bypass port on the cylinder barrel; I swapped the very old and hard copper glow head gasket for a new one, and put it on the bench.

Initially I felt over compressed, so I now have 3 new head gaskets under the glow-head (I suspect the glow-head that was and still is on it is a high compression one). I was surprised how easy to start and feisty it was - I will run it again in daylight so I can get a tacho reading.

My questions are:
1. Is my fuel too hot for this motor? By the time I have mixed castor into the fuel I am running at 22%-23% nitro.
2. I am running a Cox 5 x 3 prop; any benefit to running a Cox 6 x 3 for CL stunt?
3. What size is the spray-bar C clip? I lost mine on attempting re-assembly; I don't mind paying for it but the shipping costs for small orders are bit stiff.
4. Since I assume the plastic Medallion carb bodies are unavailable; did anyone ever manufacture a Medallion style screw in venture for use with the aluminium/plastic TeeDee 049 carb bodies - I am told the Medallion carb body gives better suction than the Teedee style one.
5. If fitted, do the thrust washers drag/bounce on the prop driver when running? I have ordered a Sullivan Hornet starter (this is really for my PAW 55).

Many thanks.
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Post  ticomareado on Sat Nov 24, 2018 2:57 pm

Oil is good, nitro could easily come down and a 6-3 is definitely worth experimenting with. You didn't mention the stunt plane you plan on mounting it to and that will have considerable bearing on you final set up.
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Post  AllSoldOut on Sat Nov 24, 2018 3:01 pm

Ticomareado,

Thanks for answering, It might go in a KK Radian that I am building - only has a 10cc tank at the moment and TeeDee 051s are a bit thirsty...
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Post  ticomareado on Sat Nov 24, 2018 3:25 pm

Just did a cursory Google on Keil Kraft Radian and see that it was designed primarily for diesels. That being the case, you might even wind up trying a 7-2 or 7-3 prop on it.
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Post  Ken Cook on Sat Nov 24, 2018 3:30 pm

Your nitro is correct assuming your running at least 20% oil. I have used 70% nitro in Cox TD's with no problem.You just need to understand how to prop and shim  the head accordingly to do that. My standard is 25% nitro and it offers decent power without tearing up glow plugs. A Medallion is a timid engine and the standard practice for more power was to add the high comp head. In my opinion, you have too many gaskets and one is all that's typically required even with a high comp head. Leaving them in isn't going to hurt, your just taking a bit of rpm's away. To my knowledge, all of the Medallions I have owned and seen only were a single ported Babe Bee cylinder. Good for fuel economy, low on power. The good thing is, Sure Start cylinders are a inexpensive and readily available if more power is needed.

           The TD unlike the Medallion uses a sprinkler venturi which is unrestricted. The Medallion has the spraybar passing through it taking up volume.  This is where the TD can prove problematic especially when used on a control line  profile plane due to the tank being outboard of centerline of engine. On combat planes using tanks, the engine generally needs to be launched quite rich which defeats the purpose. If launched on the lean side, fuel draw is greatly compromised causing a burp or the engine to shut off due to fuel starvation. A TD does indeed run more consistent when using bladder pressure or crank pressure. I have filled the venturi of TD's with JB weld and re drilled them to smaller sizes in order to utilize the use on profile models. This is a tough procedure which takes a bit of time to make certain you don't fill the jet holes on the perimeter.

        I then started to use old burnt out glow plugs which uses the same thread as the TD venturi. 1/4"-32. I drill out the plug center electrode and drill a cross hole in the plug on the side and install a spraybar and needle. I have unlimited venturi sizes in doing so. This could be done using a TD aluminum body or stock plastic body and implementing this to a Medallion. However, carb bodies are available and come up on Ebay with regular frequency.

            Mecoa offers new replacement bodies,
more info

Part Number: 86-C0502
Old Part Number:
Stock Status: GOOD Price $7.99

EX Model Engines sells spraybars, E clips and needles for the Medallion as well.
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Post  AllSoldOut on Sun Nov 25, 2018 11:17 am

Ken,

Many thanks for all of this information; I will be putting all of it to good use soon.
I tacho'ed the engine today; with 3 head gaskets got 16000 -16300 rpm peak, with two head gaskets about the same. But I suspect my needle valve is a bit leaky making the engine insensitive to needle adjustment (I lost the circlip and have not fitted any fuel tubing over it - I am awaiting a new NV assembly with a circlip from EX Model Engines).

I was expecting 17000 to 18000 rpm with this engine configuration and fuel - am I being too optimistic?

I will probably not change the piston/cylinder from the single bypass since I like the little bit of extra fuel economy. Also whilst the engine starts very easily, I have noticed the increased propensity to run backwards (badly) with less head gaskets, but have improved my 'flick' technique, so no problems.
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Post  Cribbs74 on Sun Nov 25, 2018 11:58 am

Your numbers sound about right. I would go down to one head gasket and see what happens. You can’t get more performance without sacrificing fuel economy. The faster the engines spins the more fuel it will use. So if you want more than what you currently have you will take a hit in economy.

I run my medallions with #4 cylinders and high comp heads. They will pull a 10oz plane easily. I only use 1oz of fuel per run and get about 5-6 minutes of flight per tank.

Ron
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