Acceleration ring Cox Tee Dee .010

Actual Max possible window size when in closed position dictates
how big the exhaust sleeves port can be in order to function with
the high rpm TD .010 / you go by the area available where the exhaust
ports are not present not by the exhaust ports themselves.

Hi Mauricio,

in a parallel topic we are just talking about an 010 exhaust throttle system...I know you prefer your own engineered/made components, but may be interested in the PET system as well:

https://www.coxengineforum.com/t12702-dual-balloon-fuel-system-for-010s#163070

Took me three tries to get the idle down low enough for me to be happy with it.
The fit is very important as the aluminum expands more than the cylinder when
hot. Best would be steel.

should be able to do at least 12k idle if set up right.

I do not know, too heavy for my taste and too many parts.
Sport planes will land with a 12k idle with the .010 engine.

Mauricio the inventor of PET claims idle speeds 8k-12k below those with ACE type barrel exhaust throttles are possible: (although the statement below is a bit unclear to me, I guess he claimed  idle speeds 6k-10k were possible)


I have never tached mine but I do remember really low idle speeds.

He does not say directly how low a cox grey and black prop will go.
He compares to .049 engines he compares to a bored out venturi.
No good no answer.

Here is a vid of one running from Andras:

https://www.youtube.com/watch?v=Y-t891Wqy9w


Andras Balogh
Published on Jan 21, 2018

My COX 010 engine with a Proportional Exhaust Throttle device tested under the rudimentary winter conditions of my garage.
The top speed was around 23.3k (near freezing air temperature and only 20% instead of the recommended 30% nitro in the fuel)
and the throttled speed was down around 13k though, due to the short battery in the headcam it was not recorded.

My throttle sleeve is 1/3rd the weight and better results:
Cox TD.010 with throttle sleeve
20% nitro and oil
Cox 3D x 1.25P:
Idle: 11,443 rpm (rechecked with new phone app)
Full Throttle: 28,020 rpm modified for speed



TD .020 stock throttle ring from a Pee Wee
PET design owner avoids comparing to the .020 engines



Idle with a Carbon 3x3 prop: 12.4K
Goes even lower with a stock prop.

TD .049 the PET owners information is not correct.



11.8k idle at the end of the vid.

Thanks Brad I did not even remember this video shot only 1 year ago.

I will repeat the test when warmer weather comes and I am not shivering in the garage

Yes please repeat the test. How cold is it now?
RPM should increase in warm weather.

This weekend the daytime max is expected around 15C so probably warm enough for reasonable testing. I need to also fine tune the PET bolts for a snug fit on the cylinder when cold so as to limit blow-by when hot..

Yes good fit no air leaks should improve the numbers.
How much does the engine weigh with prop spinner and throttle?

1/2A Nut wrote:Yes good fit no air leaks should improve the numbers.
How much does the engine weigh with prop spinner and throttle?

Here is the tonnage Brad: 17 grams

Thank you here is mine.

....heavy equipment....

When you file it down you have to make sure the throttle ring has no play up and down.
I over cut it just a bit and carefully flat sanded it down till it fit perfect with no play.

I don't dare take it apart, the top and bottom cylinder threads have been oil sealed and
holding very good compression. I call it a "maturity seal" since over a year when I rebuilt it
with a new cylinder and new aluminum backplate. The oil in the threads thickens over time.
I fixed the slop at the thrust plate there is no gap it has a hand made thrust washer.



Here is the original photos from 2014 first efforts, note there is a Lip exposed enough to stop the cylinder
from spinning down too far on the crank case. First 3 tries the 3rd one taught me how small I needed to go.
I zoomed in on the photo and highlighted the cut outs for the throttle ring so you can see the size differences more clearly.



First effort only lowered the rpm around 4k / you can vary the cylinder up with a shim (perhaps a TD .020 head shim fits the .010 cylinder?)