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Old May 04, 2014, 11:31 PM
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Since this is a new engine I'm running rich 40% nitro / 25% caster blend. I recorded two video's with an audio tach 25.2k rpm ran for about 2 mins break mixed throttle then dialed in a little more fuel to richen it up further as the engine warmed up to running temp. The second run I left the needle as is and used a photo cell tach. On the low end I had 9,570 rpm and the top end with a stock 3 x1.25 black flexible cox prop 19,110 rpm. The aluminum sleeve can obtain a 50% reduction. Some carbon steel would be best or stainless tube - will have to order. For now the aluminum sourced for the project is thick walled 10mm OD x (apparent) 8.5mm ID. Using the photo cell tach on the second run I had varying readings a DC light behind the prop would be best. I might add the sleeve has no play up or down sits snug between the lower cooling fin and the crankcase. The expansion is just enough for the engine to breath through the vents is most likely the key source of loss - perhaps a little castor oil is helping to hold the seal somewhat. I have some reasonable reduction in rpm to work with for now and the sleeve should make a difference in flight duration, load control on the ground to allow safe use modded props and a broad flight envelope in the air. Once I lean out the engine more I would imagine the percentages will stay near the same. 14k low 29k high with the stock prop.

No flight yet looks like next weekend will have to do for now a pic n throttle observation vid to wet your appetites

Cox TD 010 Lil Speedy 2014 (3 min 54 sec)
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Old May 05, 2014, 04:41 AM
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I decided to fabricate another throttle sleeve this to be my third try with 0 slop up down and snug fit over the cylinder I have achieved steady idles 4,600 to 5,200 rpm on 40% nitro. Will post a vid Monday evening.
Took a transition pic the 3rd one was not finished at the time of pic.
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Old May 05, 2014, 08:04 AM
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Nice. Can you detail the fabrication of the sleeve please ? I am considering building one for my Golden Bee. Do you need special tools? Lots of photos if possible. Thanks a lot.
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Old May 05, 2014, 09:42 AM
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For 1/2A engines you can buy new here is a link:

http://coxengines.ca/throttle-ring-f...49-engine.html
You can fab one up out of your own materials if you wish. Mine is this basic design.
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Old May 05, 2014, 11:09 AM
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Thanks for the link.
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Old May 08, 2014, 01:43 AM
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Here is the new vid showing the results
Cox TD .010 Throttle Sleeve 3rd Gen Sleeve Test, note I had it set for 3 blade so will have to divide by 3 and times by 2. Most of this was in the 4k to 6k range.

Cox TD .010 Throttle Sleeve 2nd Gen Sleeve Test (2 min 51 sec)
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Old May 10, 2014, 11:11 PM
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She flies:
Flew 3 flights recorded continuous 3.15 GB file / will have to take a section and post.
I will need to edit this is a continuous large file for now I took a cell phone vid of the 1080p version of one of the flights that had some fast up close fly by's just after 2.45 mins (perhaps someone can give me a doppler reading) - I saw about 25.7k with an audio tach.

I was flying in 13 -15 ish mph winds and around 93 degs and used the 2.8 x 2 prop.
Total average flight times for all three flights was around 3.2 mins each.
I was running tad rich to insure the engine would'nt die and left it at full throttle do to wind


TD .010 on a 2.8 x 2 prop (3 min 26 sec)
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Old May 10, 2014, 11:25 PM
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Very cool!

It is such an immense feeling of satisfaction to create something and see it work, huh? And work well, at that!
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Old May 10, 2014, 11:43 PM
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Congratulations! A sweet little mosquitoe.
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Old May 11, 2014, 12:19 AM
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Yes thank you, this was a tricky project as the lil TD .010's just don't make much power. To achieve any speed out of the wee engine without going with a very small airframe as the solution makes it difficult. So I just kept things slim, lanky and light to help me still have enough plane to see from a reasonable distance. The plane is big enough to handle a TD .020 but want to try a few props yet. One goal is to use the throttle if there was no wind I could have but needed max power today. So I have a solution more dia and pitch with a very light weight / paper thin composite prop by Gemfan. It is a 4 x 3 cut on the back side to make it slim cord wise the prop can handle 35k rpm but only if its tugging along a sub 7oz plane. Graupner makes one like it that can do 40k rpm. Here are the stock props and one mounted modified. This prop gives me the thrust I need to go vertical with enough speed to cut through a typical windy day.
stock Gemfan 4x3 prop weighs 1.6g
mod prop with thinner cord 1.2g
stock cox 3 x 1.25 / 1.8g
stock cox 4.5 x 2 / 3g
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Last edited by Amp Abuser; May 11, 2014 at 12:48 AM.
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Old May 11, 2014, 04:39 AM
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Did additional cut like a APC pylon prop. 3.6 x 3
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Last edited by Amp Abuser; May 11, 2014 at 01:53 PM.
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Old May 11, 2014, 06:33 AM
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Congratulations! Looks great
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Old May 11, 2014, 12:05 PM
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Used my wavscope program and have these results and pitch speed calculator in conjunction with my audio tach to determine some mph data.
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Old May 11, 2014, 12:14 PM
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Need to source a transmitter strap so I can hold my bushnell radar gun in my left hand while running the head cam.
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Old May 11, 2014, 11:25 PM
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I hope this little map will help you find a nice flying field not to far away from your place.
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