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Post  Yabby Mon Nov 13, 2023 6:00 am

what sort of revs are people getting from a standard TD 049. Not a hotted up one. but one running a standard Cox head or maybe a TD head, and say 20% nitro with a 5x4 yellow safety prop or the black 5x4 prop, and the standard TD needle and NVB. and assuming an SPI cylinder without a muffler. Ive got a tch on order and Im interested in what revs people are getting from engines they fly. Flying
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Post  GallopingGhostler Mon Nov 13, 2023 9:49 am

I'm not in a position (moving) currently to repair and run my .051 Tee Dee that I acquired from an on-line auction and parts from Cox International and Ex Model Engines, but the Sceptre Flight Tests provide some numbers from off-the-shelf Tee Dee .049's.

I suppose these ancient produced numbers to be old hat to you, and in camaraderie you are seeking comparative numbers personally experienced by our modelling community. But, these have enlightened me to seek my own results when time and opportunity permits. Only familitar with sport reed valves, these are quite good.

Dec. 1961 Model Aircraft: 30% nitro, 0.145 BHP @ 21,000 RPM.
Top Flite 6x3: 18,300, Tornado 5.5x3: 19,800, 5x3 KK nylon: 21,900.
https://sceptreflight.com/Model%20Engine%20Tests/Cox%20Tee%20Dee%20049.html

The sport reedie is around 0.065 to 0.085 BHP (Babe Bee to Black Widow), the Medallion around 0.11 so the Tee Dee does distinguish itself quite nicely.
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Post  Yabby Tue Nov 14, 2023 4:16 am

Thanks George Thumbs Up great website.
yep, I was looking for other flyers experiences as I remember the bikes back in the 70s and 80s that could do 100mph in a magazine review, but from real life we kinda figured they did the test downhill, tail wind and small japanese test rider. lol! I raced a yamaha RD 250 G model for a seaon that had the engine built by yamaha mechanics from individually measured and selected parts and it never did 100mph as claimed in magazine test rides. and I was only about 5ft 8inches and 9 stone back then. hence my interest in peoples experience.

The info from the link you provided is quite interesting though as to how big a props they were able to use. I imagine you can use different props for different purposes. I was surprised by the 7 inch prop.
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Post  Ken Cook Wed Nov 15, 2023 3:24 am

My experience is that Cox 4pitch props when used in control line for Cox engines does nothing more than create poor performance when stunting. It loads the engine too much. This results in losing speed in the top which causes poor line tension and instability of the plane. The plane now struggles to recover when entering the bottoms due to loss of speed. I've also found that safety tip props are not the same as the standard props in terms of performance. I personally avoid them myself. On TD's, I use one particular prop which is the APC 4.5 x 3.5. This prop works quite well for me. It's quite difficult to offer prop suggestions when so many factors go with it such as plane weight, line lengths, engine condition and fuels used.
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Post  Yabby Wed Nov 15, 2023 3:44 am

thanks Ken @Ken Cook Thumbs Up cheers you have described exactly how my planes behave at times. I will try some different prop sizes and pitches as you have suggested. Flying
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Post  balogh Wed Nov 15, 2023 10:29 am

Screenshot of my youtube video with my Toucan RC pulled by a TD049 with a COX 5x4 black prop, spinning near 24k in the air.



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Post  Ken Cook Wed Nov 15, 2023 3:05 pm

I've never flown r/c. A 4 pitch prop is probably not a problem. When your dragging the plane down with two lines, this now becomes a issue.
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Post  balogh Wed Nov 15, 2023 3:12 pm

Ken the COX black 5x4 prop is flexing unlike the stiff APC props, so the COX 4" pitch prop is like an APC 3" I guess.
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Post  Ken Cook Thu Nov 16, 2023 4:09 am

One important factor I left out is that you must listen to your engine. Make certain throughout the maneuver that the engine isn't bogging down. While a prop change might cure this, it's not going to overcome a plane which is too heavy or controls which are moving too fast combined with too much deflection. This too will cause the plane to seemingly feel as if it's falling out of the air.

I believe of the setups that I've seen you using, your using a standard vent tank. This can be somewhat problematic for 1/2A maneuvering. You have to find the happy balance between early on in the flight vs halfway and to the end of the flight. Early on, your probably too rich to do any type of overhead maneuvers whereas halfway through as the fuel load burns off, things are going well. Your experiencing 2-3 minutes of successful flying. At the end of the flight your probably nearing supersonic which can offer confidence but it's difficult to handle. You should try a uniflow tank which will allow almost consistent rpm's throughout the entire flight.
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Post  Yabby Thu Nov 16, 2023 4:39 am

thanks Ken. Thumbs Up some really good advice that matches up with what seems to happen at times. I will give a uniflow tank a go. lots of little things add up in getting a good setup.
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