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Cox Engine of The Month
September-2020
sosam117's

"Traded an electric charger for this "Complete" (original) Cox Thimble Drome Olympic .15 engine. Right corner is photo as received."



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Post  balogh on Thu Jul 23, 2020 4:35 am

Mauricio's recent experimental thrust measurements on a NV .061 engine inspired me to do the same on a red postage stamp back-plate 190 reedy, mounted in the nose of my Quickie 100 plane. The engine is not the strongest in my red postage stamp back-plate fleet, the strongest one is that has been with me since 1974, and which revved 23k static and 28k unloaded rpm in the air, when the Quickie 100 plane was  maidened in March.

Anyway, here are the results of my test:

Respect the reedy! Respec11

Respect the reedy! Respec12


I guess 0.305 kg thrust is not bad from this lil engine, spinning an APC 4.5 x 3.5 prop, feeding from a 60/20/20 blend of fuel. The only non-stock part is a Kamtechnik turbo head and plug.
My Quickie weighs around 300 grams when the tank fully filled with fuel, and I noted that the engine hauls the Quickie in unlimited vertical flights, so the 305 gram thrust is realistic.

I am not sure how to post a video other than from youtube, I also wanted to add a short video, but failed with the MP4 format...maybe someone has an advice?
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Post  Levent Suberk on Thu Jul 23, 2020 6:17 am

Andras, I tried to directly post a video but no success. Error sign shown when I tried the post picture button. Perhaps there is another way, but I couldn't find it.
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Post  balogh on Thu Jul 23, 2020 6:22 am

Thanks Levent, will see if others can advise...I am syre rhere is a way other than the youtube link..
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Post  davidll1984 on Thu Jul 23, 2020 11:26 am

very interesting no 1 cylinder up to 21 k rpm Huh... very good for red postage back plate ventury size ? no mod ? cylinder tyming plug wat is use stock engine ? y get same result ilimited vertical wit my a6m5 zero modified reedy my engine run in 22k range plus wit two bypas stock glow plug 6x3 prop my also weight les then 300 g 287 g wit fuel very fast wit 6x4
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Post  balogh on Thu Jul 23, 2020 12:02 pm

Thanks David yes, stock No.1 cylinder with 2 bypass, no modification only the turbo head and plug are extra. Very good little engine.
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Post  MauricioB on Thu Jul 23, 2020 12:22 pm

András, I'm glad that the experience of making these measurements put them into practice, all this generates a lot of learning.
Let me give you some advice, DO NOT USE plastic or other thread to hold the model and the fish scale, use a copper wire with insulation, it does NOT stretch itself, if instead you use an expanding wire, you will be losing part of the real thrust performance of the motor, and can vary from to 5 grams which is not a little !!
Respect the reedy! Andras14
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Post  balogh on Thu Jul 23, 2020 12:38 pm

Thanks Mauricio. In fact this is a strong sewing thread that I used and I would think that once the stretching stops under the impact of the thrust, there should not be any measurement error because the force from the plane  and its reaction force on the scale hook (i.e. in a standstill system where the masses are not accelerating in the direction of thrust ) should be equal, but I will check again with solid wire.


Last edited by balogh on Thu Jul 23, 2020 11:56 pm; edited 1 time in total
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Post  MauricioB on Thu Jul 23, 2020 12:42 pm

balogh wrote:Thanks Mauricio. In fact this is a strong sewing thread that I used and I would think that once the stretching stops under the impact of the thrust, there should not be any measurement error because the forefront theplane  and its reaction on the scale hook (i.e. in a standstill system where the masses are not accelerating in the direction of thrust ) should be equal, but I will check again with solid wire.

Okay friend! ... I'm glad to know that you are experimenting, it is a very entertaining way to have fun and learn with the engines that we like so much! Very Happy I Love This Forum! Hand Shake Clapping Clapping
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