.051 groove ring lowers power?

I am incredulous. The power output difference of .002 CI is pretty low to start with. I see no reason to deliberately lower the power.

Phil

I tend to believe the groove was there only to mark the 051 design. Because the groove connects the outside atmosphere with the by-pass flutes in the cylinder, it may have a very small SPI-like effect i.e. allowing some fresh air into the crank before the piston hits the TDC.

But, given the groove's incomparably smaller cross section than that of the SPI gap, I doubt this will have any practical SPI impact. The manufacturing tolerance between two 051-s with a tiny difference between their SPI gaps would probably have an impact more noticeable than that of this groove.

The compression pinch occurs well above the ring in the skirt. It has zero effect. I agree with others. Visual only.

Well, the difference in CID is only 2% 4%, probably less than the average difference between seemingly identical engines.

Theoretically, as the piston travels downwards, the groove will let a portion of the fresh charge escape from the bypass ports directly to exhaust ports, so that may reduce the power. Probably exactly 2%  4%

But given the possible differences in power output between individual engines with the same specification, to verify this would require extensively testing with at least 10 NIB units of each kind...

"If I were a rich man,
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All day long I'd biddy biddy bum.
If I were a wealthy man.
I wouldn't have to work hard.
ya ba dibba dibba dibba dibba dibba dibba dum.
If I were a biddy biddy rich,
Yidle-diddle-didle-didle man."

How about something achievable like testing 10 unmolested, otherwise original or returned to original, .051 engines with the same intake, NVA, and prop against 10 unmolested, otherwise original or returned to original, .049 engines with the same intake, NVA and prop.

I have an .051 engine and an .049 engine I would be willing to volunteer as long as it gets returned in a timely manner...although they have aluminum intake bodies on so that may not be close enough to "stock"...

The tester would have to provide fuel, shared intake and NVA...

Phil

Is That Warren Leadbetter's Wikipedia page? I wonder if he wrote that. Maybe it should have a "Needs Citation" note next to it.
Rusty

The Cox Tee-Dee .051 was basically an .049 with a slightly larger bore. (Bore: 0.410", Stroke: 0.386") compared to the 049. (Bore: 0.406", Stroke: 0.386").

The groove was put in the piston to stop the unscrupulous passing it off as a 1/2 A engine by exchange the red plasticky bit for a black plasticky bit. The Tee Dee 049 was at the upper limit for the American 1/2A size.

So I am not really sure why they made the 051 but I very much doubt that the groove affects performance and may even be beneficial as an oil carrier.

ian1954 wrote:...may even be beneficial as an oil carrier.

If you stretch the imagination with that thought, it could be said to help prevent piston slap. I'm sticking with the "just for identification" crowd. Any power modification could have more effectively been done to the #5 cylinder.
Rusty

I just stretched my imagination and thought that perhaps the machinist measured wrong when he went to part off the piston. He stopped just in time but thought it looked nice and then produced every one the same way.

My TOTALLY unscientific experience is....

I have 7 .049 TeeDee engines and 5 .051 TeeDee engines all with various configurations of venturi size, crank shaft design, and plastic and aluminum carb bodies

NOT one of my .051s is any more or less powerful from a RPM bench run perspective with the same fuel and propeller...all my bench testing shows that the biggest power adder is Nitro and venturi size....up to a point

I did this last year after buying several of the so called high performance crank shafts and muddled the experiment with 4 different aluminum venturies that had been over bored and polished, so my experiment can not in any way determine if or if not the groove ring has any effect

Logic tells me, based on the groove rings location, that it an NOT have an effect--- and logic also tells me that even at similar RPM given a particular fuel and propeller the .051 produces some measurable torque gain that would only be found with a true engine dynometer

I am NOT an well enough accomplished flier to say the .051 or the .049 TeeDee in the air is any more or less powerful and the truth is I have so many different weight and constructed combat planes it is not an easy to determine in flight.

I am not that interested to take each engine and swap it into a particular plane, fly it with same fuel and prop to see which one is the best....I generally can tell by ear which ones need to be on my heavier planes

I just thought the wikki guy seemed to insist that the goove for identification purposes was Secondary to deliberatly lowering the power output, and I contend this is FALSE until at least one of the original designers weighs in and confirms this was indeed a design goal

The Killer Bee .051 has two rings, leads me to believe they were for ID only.

Well, anyone can write what ever they want on wikipedia, you can't trust anything that you read there...

My The .051 displacement simply places the engine in the "A" category. Detuning for "trim-purposes".. could have been accomplished in plenty of other ways. I always understood the groove in the piston-skirt to be for ID purposes only.. as most of us here would agree on.

In this case the wikki page for cox engines is really well written and this is the first time something funky grabbed my attention

Between the wikki and MH aerotool page on cox engines and toys there is a lot of agreement and I am generally impressed that someone went to the trouble

I have never relied 100% on any non documented source

Last night I just happened to work on my newly acquired Tee Dee .051. It's the first .051 I have ever seen "in person", and now that I saw the groove I have to agree that it most likely has no effect on the performance of the engine.

So the "A" class had a minimum engine displacement limit as well?

Warren L. is a member on the Facebook page "Control Line Enthusiasts".. as well as myself and a few other CEF'ers. Check it out if you have a FB account. There's always something interesting happening there.

KariFS wrote:Last night I just happened to work on my newly acquired Tee Dee .051. It's the first .051 I have ever seen "in person", and now that I saw the groove I have to agree that it most likely has no effect on the performance of the engine.

So the "A" class had a minimum engine displacement limit as well?

Yes. I believe the "A" class to be .051 thru .1525 cubic inch size. I've heard .020 and smaller to be referred to as 1/4A.. but the official range for 1/2A is .000 to .050 cubic inches. The actual #'s go into the 4th decimal point in displacement, between 1/2A, A, B, C and so on.

Here's an example that I found.

Wiki-model engine classes