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Medallion 049 & Medallion 049; what is the difference?

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Medallion 049 & Medallion 049; what is the difference?

Post  MauricioB on Wed Mar 29, 2017 10:35 am

Hello, I have seen these two photos, where you can see that an escape is a single slot, while in the other photo, the exhaust gas has two slots, could someone please comment what those differences mean? Different...
Thank you



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Re: Medallion 049 & Medallion 049; what is the difference?

Post  KariFS on Wed Mar 29, 2017 11:03 am

Mauricio, at some point in the early 1980s the exhaust ports were changed to the narrow slot style in almost all .049 engines. At the same time SPI was eliminated.

I am not sure what was the reason for the change. Some say that it was a safety issue, this design will "kill" the exhaust flame somewhat, and eliminating the SPI enables the use of a muffler without losing a lot of power.
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Re: Medallion 049 & Medallion 049; what is the difference?

Post  Marleysky on Wed Mar 29, 2017 1:07 pm

I have a similar experience. Just bought a bunch of parts, pistons,, cylinders and stuff.
Included were these two cylinder/piston sets. Both cylinders have the flats on the top, one exhaust is open, one is dual slits. The dual slit cylinder has a piston with the 051 telltale ring around the skirt. This piston slides up into the dual slit cylinder with compression, as does the the piston in the open exhaust cylinder. If I try to exchange the two, the ringed piston will not fit in the open cylinder, and the other piston slides right through the dual slit cylinder with no compression or resistance. So, my question would be did Cox manufacture TD051s with the dual slit exhaust?  

On closer inspection the open exhaust cylinder has a "1" stamped on the side of the exhaust opening. The other must be a tapered cylinder as the ringed pistion will not go past Top dead center with out force.
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Re: Medallion 049 & Medallion 049; what is the difference?

Post  fredvon4 on Wed Mar 29, 2017 1:37 pm

There are single opening exhaust with and without SPI as well as dual slit exhaust with and without SPI

My understanding was all the dual slit exhaust was an effort to reduce fire

I personally prefer the open single slits, as I find exhaust priming the dual slit version a pain
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Re: Medallion 049 & Medallion 049; what is the difference?

Post  KariFS on Wed Mar 29, 2017 1:53 pm

Rene, that just might be a Medallion .051 cylinder Huh...

Any numbers on it?

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Re: Medallion 049 & Medallion 049; what is the difference?

Post  Marleysky on Wed Mar 29, 2017 5:02 pm

KariFS wrote:Rene, that just might be a Medallion .051 cylinder Huh...

Any numbers on it?


Kari, I can't see any numbers on that cylinder. They both have dual ports neither have boost ports.
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Re: Medallion 049 & Medallion 049; what is the difference?

Post  1/2A Nut on Wed Mar 29, 2017 8:29 pm

Another plus in the change was the plastic around cylinder for models
where no longer subject to melting and deformation issues. It allowed the
designers more flexibility with types of crafts. Small Cox Logo
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Re: Medallion 049 & Medallion 049; what is the difference?

Post  MauricioB on Wed Mar 29, 2017 10:17 pm

Many thanks friends for the answers, I am very clear now with the information they have provided Thumbs Up !.

I leave another question here:

https://www.coxengineforum.com/t10772-what-is-the-average-life-of-a-glow-plug#135920
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Re: Medallion 049 & Medallion 049; what is the difference?

Post  rsv1cox on Thu Mar 30, 2017 6:36 am

In my younger days I found the smaller dual slit cylinders helpful in keeping debris out of the cylinder. Seems like I was always landing in the weeds and wiping or blowing off seeds and grass from the engine.
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Re: Medallion 049 & Medallion 049; what is the difference?

Post  GallopingGhostler on Thu Mar 30, 2017 10:48 am

The dual slit exhaust ports came after my days of prolific .049 new engine purchases and flying. Wonder if the dual slit came about as a result of product liability and potential lawsuits over unmuffled engines. May be someone like Larry Renger could give us insight, if he is still perusing this forum.
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Re: Medallion 049 & Medallion 049; what is the difference?

Post  gcb on Thu Mar 30, 2017 5:14 pm

Marleysky wrote: ...If I try to exchange the two, the ringed piston will not fit in the open cylinder, and the other piston slides right through the dual slit cylinder with no compression or resistance. So, my question would be did Cox manufacture TD051s with the dual slit exhaust?  


Yes, the piston has a groove to indicate that it is for an .051. The groove  was used originally to easily identify an .051 for FF flyers who would swap between .049 and .051 to fly in class 1/2A and A without making adjustments to the aircraft.

When Cox made exhausts with screening and dual slits, at first they forgot to cut flats so you could remove the cylinder or hold the cylinder while you removed the glow head...it was a bear working with these engines without resorting to pliers.

George
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