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Cox .01 /.02 /.05 /.09 /.15 Speed Planes  - Page 30 Cox_ba12




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Cox Engine of The Month
February-2024
1/2A Nut's

"RC Speed Boat Power Drive TD .020"

More info on this engine!




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Cox .01 /.02 /.05 /.09 /.15 Speed Planes

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Happy Re: Cox .01 /.02 /.05 /.09 /.15 Speed Planes

Post  rdw777 Sun Jun 12, 2022 6:13 am

Nice work Brad,… You put a lot of research and thought into your projects….I really enjoy the videos of the well tuned screamers Thumbs Up
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Happy Re: Cox .01 /.02 /.05 /.09 /.15 Speed Planes

Post  1/2A Nut Sun Jun 12, 2022 7:52 pm

Thank you RDW777,

The fun is making the most out of the engine power on hand per plane type designed, the building of and testing.
The results confirm efforts made and open the door to the next level of extreme performance.


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Post  davidll1984 Tue Jun 14, 2022 7:11 am

balogh wrote:Thanks, Brad,

yes, exactly as you advised, I chamfered the header entry.

Why do we use 140 for the timing here, instead of the 160 used in the earlier formula? Even if SPI, the exhaust timing remains the same as in a non-SPI cylinder??

I also noted, that the Kyosho muffler may not allow the cylinder thread to fully bottom out in the crankcase, and it may slightly reduce the compression ratio to some extent, albeit not so much that would justify the limping of the engine well below 20k. I did not want to force the cylinder to fully screw in against the Kyosho muffler, but will see if repeated spanning of the cylinder will cause the aluminum header to yield/wear some and the components will finally settle..
It is important to adjust this exhaust collector Yes your assumption is correct the cylinder is not able to screw complete in certain cases Depending on the cylinder used, the only one that is direct fit is the cylinder model found on a simple surstart with rc exaust ring or those designed for The different collectors almost all use a machined cylinder for rc ring
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Happy Re: Cox .01 /.02 /.05 /.09 /.15 Speed Planes

Post  balogh Mon Dec 19, 2022 12:36 pm

1/2A Nut wrote:Bit longer tail boom will allow a reduced set of tail feathers, wing loading is
better than needed so 16in x 2.75 30 to 35 Sq. In.

Cox .01 /.02 /.05 /.09 /.15 Speed Planes  - Page 30 Nano_t13

Prop reduction with the new design should hit 120 mph if all goes well.

Cox .01 /.02 /.05 /.09 /.15 Speed Planes  - Page 30 Imag2610

Brad, can you please remind me about the all-up weight of your Nano 010? I am planning to build something similar to this concept of yours with only a square carbon rod serving as the fuselage between the wing and tail section. I will have a SIG 10mm x 100mm wing profile for a full balsa board wing at around 18" span, and want to calculate the necessary taper from wing center to tip.

Thank you.
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Post  HalfaDave Mon Dec 19, 2022 1:44 pm

Hi All,
This is an amazing thread...
Thanks,
Dave
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Happy Re: Cox .01 /.02 /.05 /.09 /.15 Speed Planes

Post  1/2A Nut Tue Dec 20, 2022 4:28 am

Thank you Dave!Thumbs Up

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Post  balogh Tue Dec 20, 2022 4:56 am

Hello Brad,

please see my questions 3 post up regarding the weight of the Nano 010..thank you.
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Post  1/2A Nut Tue Dec 20, 2022 6:39 am

Nano .010 2ch.
3oz RTF - 1st version green fuselage
2.2oz RTF - 2nd version neon pink fuselage

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Post  balogh Tue Dec 20, 2022 6:51 am

Thanks a lot, Brad...I assume mine will be near 3 oz (thanks to my NiMh battery that weighs almost 1 oz alone) and will try to set the wing surface to around 30....35 sq.inch
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Post  1/2A Nut Mon Jan 16, 2023 9:05 pm

Updated vid uploaded to 1440p HD. .. Flying




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Post  getback Tue Jan 17, 2023 5:03 am

VaRooooom Nice run Brad it was really moving out And I could see it much better in 1440p HD . Whats the range on your trans. you look a 1/2 mile away in the clouds RC Plane Very Happy Very Happy This Site Rocks!
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Happy Re: Cox .01 /.02 /.05 /.09 /.15 Speed Planes

Post  balogh Tue Jan 17, 2023 2:58 pm

Great video, Brad,

I see that your tuned pipe connects  direct to the exhaust manifold, and your pipe really steps in at the resonance frequency to boost the engine rpm..Though I use a bit larger prop like the 5x4 COX, I think my silicone exhaust extender between the exhaust manifold and the pipe is excessive...(In fact my tuned pipe has never stepped in to boost engine speed up to the resonance frequency). I use the formula I inherited from you, whereas the TeeDee049 resonance speed in rpm, N=234,500/L where L is the distance in inches between the piston face and the MRP point of the pipe just behind the stinger..

I may be doing something wrong. The distance in the photo below is about 10.0  inches, including the silicone bend, so in principle the tuned pipe should pull the rpm up to near 24k...but it does not... Huh...

Cox .01 /.02 /.05 /.09 /.15 Speed Planes  - Page 30 20220310
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Happy Re: Cox .01 /.02 /.05 /.09 /.15 Speed Planes

Post  1/2A Nut Wed Jan 18, 2023 12:32 am

Thank you Eric, fast n fun!
At 100 mph / 147 ft. per second makes for a small plane fast.

The black scheme profiles best for the eyes to keep it in control.
Best to avoid no sky blending colors or those that fade and blend.
Within a few seconds it can get far out given the abnormal speeds.  
Vertical stab blend pasts 150 ft. neon yellow pops in the passes.
25" span 75 sq. in. wing / 8oz - 226g RTF


Thank you Andras,

Your "a bit larger prop" has a impactful difference - thicker airfoil, wider blades, weighs more, flexes and is not balanced for top rpm.
Post the vid - lets see what the Cox 5x4 prop unloads to in flight not what it benches - we can listen for the pipe to step up the rpm.

Per our previous discussions your set up is more for eye candy / exhaust note / goo control given
the flex tube losses, spinner mass, larger prop and size / weight of plane. Long flex tube soft walls
change in volume percentage and temp - loss of potential better function with tuned pipe pressure.
Coupler at pipe needs matching pipe ID for smooth flow with the flex tube. Insert curved inner aluminum
tube for heat stability / diameter control under exhaust pulses.
  
Based on project viewed and setup - recommend trying for pipe function flight unloaded low weight thin blade: APC 4.7 x 4.2E

MRP - Mean Reflective Point * is well in front of the base of the stinger.
Cox .01 /.02 /.05 /.09 /.15 Speed Planes  - Page 30 Powr_p12

The RC engine tuned pipe formula should always be referenced correctly for on lookers to understand if referencing. :
(Wave Speed - hot gas vapor 1650 ft. per second to 1675) x (engine timing) ÷ (MRP) = Function RPM

Always measure the engine timing of the engine to be used with the formula for best results.

Example:
1650 x (Typical Cox .049 timing - 140) ÷ 10 will sync at 23,100 rpm with a clean flow / sealed tuned pipe exhaust system.
1675 is good for hot / thin air, dry weather with exposed aluminum pipes.

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Post  balogh Wed Jan 18, 2023 5:14 am

Thanks a lot, Brad, for your explanation...yes, I had my doubts with he silicone extender, especially with the bend in it ,that I read somewhere in itself would not hinder the propagation of sound waves...but the flexibility of the silicone extender, i.e. its expansion due to the pressure waves, was indeed overlooked by me...so I will look for a non-flexible extension, and a more sporty propeller than what I currently have on hand..
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Post  1/2A Nut Sat May 06, 2023 6:51 pm

FYI these are now out for sale @ Kamtechnik.com

Less mass on the end of the crank improves rpm and
in turn reduces vibrations / associated heat.

Cox .01 /.02 /.05 /.09 /.15 Speed Planes  - Page 30 20230512

Cox .01 /.02 /.05 /.09 /.15 Speed Planes  - Page 30 20230511

1.4g the hex nut version really shaves off load vs Valentine bullet spinner assembly.

Cox .01 /.02 /.05 /.09 /.15 Speed Planes  - Page 30 20230513


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