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Cox Engine of The Month
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MauricioB's

"Cox Tee Dee .010"



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Pressure tap back plate 049

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Pressure tap back plate 049

Post  steve thornton on Fri Dec 16, 2016 9:46 am

I recently bought a Tee Dee and aMedallion .049. Both are new and in the Cox Hobbies, Inc original box. Here's my question; the back plate has a mark for a pressure tap & I don't know if that is a "drill here" location or what...none of my other TD's/Medallions have this feature. Should I drill and tap this or just leave it alone? Any advice..
Thanks guys,
Steve
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Re: Pressure tap back plate 049

Post  KariFS on Fri Dec 16, 2016 10:25 am

I think the mark, if it is in the middle, is just a centerpoint or such left by the manufacturing process in a super fast automatic lathe.

The pressurizing point is on the right side of the carb body, you need to take the engine apart and drill through both the plastic part and the crankcase to make the pressure point operational.

Please note, my first point comes from my background in engineering, the second from the engine manual Smile I have no personal experience on pressurizing, but I know some people have drilled the backplate too.
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Re: Pressure tap back plate 049

Post  gcb on Fri Dec 16, 2016 2:05 pm

steve thornton wrote:I recently bought a Tee Dee and aMedallion .049.  Both are new and in the Cox Hobbies, Inc original box.  Here's my question;  the back plate has a mark for a pressure tap & I don't know if that is a "drill here" location or what...none of my other TD's/Medallions have this feature.  Should I drill and tap this or just leave it alone?  Any advice..
Thanks guys,
Steve
 
Steve, I would leave it alone. If it is just a mark, the material in the back plate is not thick enough to support a pressure tap.
As mentioned, the pressure tap on a TD is on the side of the crankshaft housing.
Unless you have a specific need for crank case pressure, you would be much better off using a bladder setup. Using any type of pressure requires you to get a fine-thread needle valve setup.
BTW, here is a back plate made for pressure tap:  
 

George
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Re: Pressure tap back plate 049

Post  steve thornton on Thu Dec 22, 2016 12:36 pm

gcb wrote:
steve thornton wrote:I recently bought a Tee Dee and aMedallion .049.  Both are new and in the Cox Hobbies, Inc original box.  Here's my question;  the back plate has a mark for a pressure tap & I don't know if that is a "drill here" location or what...none of my other TD's/Medallions have this feature.  Should I drill and tap this or just leave it alone?  Any advice..
Thanks guys,
Steve
 
Steve, I would leave it alone. If it is just a mark, the material in the back plate is not thick enough to support a pressure tap.
As mentioned, the pressure tap on a TD is on the side of the crankshaft housing.
Unless you have a specific need for crank case pressure, you would be much better off using a bladder setup. Using any type of pressure requires you to get a fine-thread needle valve setup.
BTW, here is a back plate made for pressure tap:  
 

George
Thanks for the advice George and Kari. I have decided to leave it alone. From what I have read, the benefit to back plate pressure vs the crank pressure is an increased and more consistent pressure. My machine skills are even more undeveloped than my inverted flight skills, so these pretty little engines will remain original.
Thanks again for your help!
Steve
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