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Cox Engine of The Month
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"Bucket-O-Parts Cox TD .15 Special"



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Cox .01 /.02 /.05 /.09 /.15 Speed Planes  - Page 29 Empty

Cox .01 /.02 /.05 /.09 /.15 Speed Planes

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Happy Re: Cox .01 /.02 /.05 /.09 /.15 Speed Planes

Post  balogh on Wed Oct 14, 2020 6:04 am

Thanks, Brad,

yes, exactly as you advised, I chamfered the header entry.

Why do we use 140 for the timing here, instead of the 160 used in the earlier formula? Even if SPI, the exhaust timing remains the same as in a non-SPI cylinder??

I also noted, that the Kyosho muffler may not allow the cylinder thread to fully bottom out in the crankcase, and it may slightly reduce the compression ratio to some extent, albeit not so much that would justify the limping of the engine well below 20k. I did not want to force the cylinder to fully screw in against the Kyosho muffler, but will see if repeated spanning of the cylinder will cause the aluminum header to yield/wear some and the components will finally settle..
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Happy Re: Cox .01 /.02 /.05 /.09 /.15 Speed Planes

Post  1/2A Nut on Wed Oct 14, 2020 6:13 am

That was an example using another engine, you must know timing per engine type.
TD timing is typically 140 degrees, but can vary between 140 - 145

Per post:
1/2A Nut on Sun Oct 04, 2020 10:41 pm

Formula to sort out setting up the pipe example:
- 1675(wave speed) x 160(timing) ÷ 8.5 (pipe length) = 31.53K rpm

Constant:
1675(wave speed) x ___(timing) ÷ ____ (pipe length) = ____rpm

For the cylinder mark location when it seats without the manifold on.
Can very carefully flat sand the manifold - adjusted / small amounts or
you risk loss of a tight seal. Set the manifold tight just before the marked location.
Or allow it to wear in Kyosho did the right thing
to have it a bit off to insure all engines seal the manifold.

Forget your poor results with the wrong prop.

Do you have a 4x4 / 4.2x4 / 4.4x3 / 4.6x3 to properly test the pipe on the bench?

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Happy Re: Cox .01 /.02 /.05 /.09 /.15 Speed Planes

Post  1/2A Nut on Wed Oct 14, 2020 11:29 pm

How many head shims are you using?
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Happy Re: Cox .01 /.02 /.05 /.09 /.15 Speed Planes

Post  balogh on Thu Oct 15, 2020 1:02 am

Thanks Brad. Will check if I have the exact same props hou mentioned. I use 1 shim only but suspect that the cylinder does not bottom out. However I will look at the exact position through the cylinder top before and after the Kyosho is added.
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Happy Re: Cox .01 /.02 /.05 /.09 /.15 Speed Planes

Post  1/2A Nut on Thu Oct 15, 2020 1:11 am

Yes good to know just where the cylinder is at, 1 shim is good to make up for the variance.
With the plug off you can check the deck height with one shim.
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Happy Re: Cox .01 /.02 /.05 /.09 /.15 Speed Planes

Post  1/2A Nut on Wed Oct 21, 2020 6:02 am

Cox Mark II .15 RC with Profi .15 Tuned Pipe:

Painting a picture / with a clean flow, leak free manifold and proper
sealed single exhaust port could become the first TD RC to bust 200 mph!

Cox .01 /.02 /.05 /.09 /.15 Speed Planes  - Page 29 20201013

Cox .01 /.02 /.05 /.09 /.15 Speed Planes  - Page 29 20201014

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Happy Re: Cox .01 /.02 /.05 /.09 /.15 Speed Planes

Post  1/2A Nut on Mon Oct 26, 2020 11:14 am

Kamtechnik Nelson Plug Turbo Plug Adapters has been tested and now
the web site has been updated with new product slots opening up soon
to have stock in hand perhaps by this week.

https://kamtechnik.com/shop/





Kamtechnik Nelson Plug adapter test / Piped 1996 Killer Bee .049
APC 4.6x3 prop / best static 22,609 / 10.4oz thrust / 64 mph PS
.111hp - 82w / if this prop is used to fly it will unload and stage
on the pipe likely boost to unload at 27.5 -28k / 80mph PS
For speed a 4.4x4.5N  120 mph PS expected.

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Happy Re: Cox .01 /.02 /.05 /.09 /.15 Speed Planes

Post  Jason_WI on Mon Oct 26, 2020 3:27 pm

All the .020 turbo heads sold out already Sad totally missed out on the first batch.
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Happy Re: Cox .01 /.02 /.05 /.09 /.15 Speed Planes

Post  balogh on Mon Oct 26, 2020 4:13 pm

I guess the out of stock on his website means the stock has not been filled yet...Greg wrote in a post here that he just starts the 020 and 090 turbo head serial production after the prototypes tested well.
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Happy Re: Cox .01 /.02 /.05 /.09 /.15 Speed Planes

Post  1/2A Nut on Tue Oct 27, 2020 1:09 am

Now that the magic dust has been applied to the Cox.020 displacement Greg
is going into mill time and is willing  to sort out an adapter replacement for the VA .020.
Extra power will likely be had by following the current .020 chamber design.
Best rpm sticking to two shims with the APC 4.2x2 each engine will be a
bit different in shim count older engines will only need 1 shim.

Some of my findings during testing:
Compression volume is not the only factor once a given ratio is found,
chamber shape improves and squeaks out further power. The number of
samples tested and those modified helped to sniff out which direction to
go keeping perseverance alive and suitable use of the prototypes around
14 in total. The cox 4.5x2 is a real challenge to hit 19k some engine out
of the box can hit that number, 20k static is possible with further efforts
to improve the timing / deck height of the piston. The crank window can
be sharpened on the rotation side to improve intake.

What mattered beyond compression ratio,
-Proximity of the element to piston face
-Transition shape from shim line to plug face
-Charge concentration across a given percentage of the piston face / what best serves the load of the 4.5x2
-Improvements by sound distinction / variances the adapter shape makes / loud, hollow thru peaky sharp notes.
-Full spread vs narrow concentration of force pressure to piston face, horn, cone and bowl shape diameters all
have their attributes. Providing enough spread to counter the load leaves the rest of blast rate to focus on ramping
up best possible time / rpm.


I am looking forward to testing speed props with the product adapter.
So far with a previous prototype modified for suitable use:




This is J4 the one that has finally brought out the last bit of rpm out of the test
engine. It has been widely used for all the prototypes. A fresh piston cylinder
with good seal will likely hit 19k + Shown with a Cox grey 4.5x2

Cox .01 /.02 /.05 /.09 /.15 Speed Planes  - Page 29 J4_2_s10

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Happy Re: Cox .01 /.02 /.05 /.09 /.15 Speed Planes

Post  getback on Tue Oct 27, 2020 9:45 am

First off The Pipes look really Good for the Mark .15 that should bee interesting ,, The TD .020 was screaming !!! Thats cool the hd. will bee avaible soon Thanks for letting us Know Very Happy Leaves
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Happy Re: Cox .01 /.02 /.05 /.09 /.15 Speed Planes

Post  1/2A Nut on Tue Oct 27, 2020 11:34 am

Thank you Gents looks like the ball is rolling again!
I was given 4 items in the last package sent to finalize, 3 down one more to test.

Some good ole goo control to help keep .020 projects cleaner and it adds a bit of
back pressure for RC carbs. Fit is important for a leak free seal.  I have documented
results with this engine prop and will see what the difference is in rpm with only
the manifold header add.

Cox .01 /.02 /.05 /.09 /.15 Speed Planes  - Page 29 20201015

Some positive tank pressure:

Cox .01 /.02 /.05 /.09 /.15 Speed Planes  - Page 29 Imag7512[/url

Cox .01 /.02 /.05 /.09 /.15 Speed Planes  - Page 29 20201016

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Happy Re: Cox .01 /.02 /.05 /.09 /.15 Speed Planes

Post  1/2A Nut on Tue Oct 27, 2020 4:44 pm



Oct 27, 2020
Kamtechnik Header / Manifold .020 Prototype Testing
Cox TD .020 APC 4.2x2N
Open exhaust: 22.2k rpm 42 mph PS
Manifold and header: 19.9k rpm 38 mph PS
OS P4 Turbo Plug
-Reduces piercing tone
-Adds back pressure for RC carbs
-Single exhaust goo control  
-Can use a pressure tap

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