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A Mid-70’s engine question. Babe_b10
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A Mid-70’s engine question.

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Post  batjac on Fri Sep 25, 2020 10:53 am

I was just reading the Gremlin 1/2A pattern plane article in the May ’75 issue of Model Builder by Tom Dixon, and it says the plane flies on a Cox “stunt special” engine.  The “stunt special” is a TD .049 with a Babe Bee piston/cylinder and a low compression glow head, a Kirn-Kraft NVA, and turning a Cox 6x4 prop on 5% nitro fuel from a Perfect wedge tank.  Tom says this pulls the 12 ounce model through the entire stunt pattern.  The KK fine needle would be the only thing I would have associated with “performance”.  A low compression head topping a single bypass/no boost cylinder with SPI doesn’t scream “performance”.  5% nitro on a 1/2A doesn’t scream “performance”.  A TD on suction from a standard plumbed wedge tank doesn’t scream performance.  And a Cox 6x4 doesn’t scream “performance” (unless you’re propping for torque).  And we all know Cox TD engines were made to scream.

What exactly am I missing on this?

That 70's Mark
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Post  GallopingGhostler on Fri Sep 25, 2020 12:37 pm

If a CL model, he was basically matching the power to the model, flight environment and run reliability (suction feed, etc.). But then, this was a magazine article intended to sell more magazines and no doubt more Cox Tee Dee engines.  Very Happy

I'm guessing he could have probably gotten away with a .049 Medallion, but those are just my thoughts. Huh... Tired w/ Coffee Read lol!
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Post  Ken Cook on Fri Sep 25, 2020 2:01 pm

A TD runs just as good on a tank as it does on pressure. The problem is knowing how to setup the tank correctly. You also can't run a large heavier pitched prop using pressure. Running a bladder doesn't like a load. What Tom did was turn the engine into a tractor vs a Ferrari. Tom has done some mods to larger engines such as the FP .40 making claims that it runs better than true manufactured stunt engines. I've witnessed them run and I thought they were under powered and ran terribly. Articles written today are no different than years back. Editors will take anything and write about it due to a lack of material to write about. Just because it's in the magazines doesn't mean it worked. Believe what you've experienced. I should also add, the best stunt engines are the most under powered engines. This is what makes the LA engines a good stunt engine. He detuned the engine and overloaded the engine with too much prop. That was the thinking back then. Kinda of like a lugging Super Tiger .60 run. It really doesn't work all that well with smaller engines and it's better to run less pitch and more rpm's to keep it flying at the correct speed then it is to lug it.


Last edited by Ken Cook on Fri Sep 25, 2020 2:29 pm; edited 1 time in total
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Post  Marleysky on Fri Sep 25, 2020 2:14 pm

My first thoughts were, magazine? Sales, add revenue. Get the readers to go out ( there still were some active LHS in the 70’s) and buy some parts. KK, Perfect, Cox, were there any sidebar adds? lol! lol!
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Post  aspeed on Fri Sep 25, 2020 4:56 pm

I picked up a ready to fly plane at a swap meet that had a TD with a single bypass cylinder. Kind of an oldtimer parasol plane. The older owner said it was too much with the twin bypass. I suppose it would be more suited to a reedy or Medallian as mentioned before. Glad I didn't pay too much because I really don't like using the single bypass cylinders even on the reedies.
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Post  davidll1984 on Fri Sep 25, 2020 7:30 pm

Single bypas cylinder is used on cars gtp first modèle wit round rc exaust y use single bypas for park flyer wit exaust dont change mutch of performance use large 6x3  prop plane was made of corflute coroplast balsa mix biplane 670gram plane 4ch tink no8 cylinder is Not si bad Smile
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