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by balogh Yesterday at 4:40

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by Ken Cook Sat 14 Jul 2018 - 19:46

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» **VOTE-ON-THE-NEXT-COX-ENGINE-OF-THE-MONTH** (July 2018)
by balogh Sat 14 Jul 2018 - 11:51

Cox Engine of The Month
June-2018
Davenz13's

".049 Bee"



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Cox .01 /.02 /.05 Engines & Mods / Nano Speed Planes

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Happy Re: Cox .01 /.02 /.05 Engines & Mods / Nano Speed Planes

Post  1/2A Nut on Sun 1 Jul 2018 - 13:51

Big improvement with a peaked NV to sing mode good and steady.  Small Cox Logo
Pic shows how much I had the window open for the exhaust breaths
better than with that extension on the muffler, in the field for flying will
have it fully open as shown in the previous post. Beast of a .09 for what it is.

If flown with that prop @ 26k down wind / 80 mph
Serious thrust / 2:1 ratio for constant speed in any direction will pull out
of the hand and bolt away like on steroids. The DART design was around 11.5oz
as I recall a leaner NANO design with a 6.5P speed prop could do 160 pitch speed
with a 1:1 thrust ratio. The pressure tap really woke this one up in combination of
less exhaust restriction. The spring steel ring can be removed if no need for sound
suppression, if left on can close off the exhaust port from air / moisture when not flying.

Static 20,914 rpm / 30.7oz thrust / 1.9lbs / .326hp / 243w / 64 mph pitch speed.



Last edited by 1/2A Nut on Sun 1 Jul 2018 - 14:09; edited 1 time in total
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Happy Re: Cox .01 /.02 /.05 Engines & Mods / Nano Speed Planes

Post  balogh on Sun 1 Jul 2018 - 14:01

Great rpm numbers!
Do you have the top fin milled for the wrench? If not, how do you tighten and remove the cylinder with the muffler covering the access to the exhaust ports?

I have 2 NIB 09- s that have no fins milled so I wonder how I will use them muffled? I tried the rubber belt wrenches wrapped around oldstock COX cylinders with no fins milled but the belt slips no matter how tightly prestressed. I do not and will never use plyers on any COX cylinder!!!
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Happy Re: Cox .01 /.02 /.05 Engines & Mods / Nano Speed Planes

Post  1/2A Nut on Sun 1 Jul 2018 - 14:20

I use a slip jaw wrench and rap the cylinder with leather to keep the fins in mint condition.
You could get a dremel cut off wheel and put some flat spots at the top of the cylinder.
Glow plug did not come loose in this test great little engine. I have two .09 medallions
two TD .09 RC with the mufflers and 2 TD .09. My first one was bought and flown back
in 1996 a TD .09 RC I used a pressure tap on the muffler it was a screamer and flew
a pylon type plane very fast.
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Happy Re: Cox .01 /.02 /.05 Engines & Mods / Nano Speed Planes

Post  balogh on Sun 1 Jul 2018 - 14:29

Thanks fir the tips Brad. Before going to the surgery solution with the dremel - that, given my hand skilss just a tad better than those of the Australopitecus, I have a great chance to cause more harm than benefit with - I will try the slip jaw wrench... lol!

I guess you mean the one with adjustable spanner distance used by plumbers?
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Happy Re: Cox .01 /.02 /.05 Engines & Mods / Nano Speed Planes

Post  1/2A Nut on Sun 1 Jul 2018 - 14:35



Last edited by 1/2A Nut on Mon 2 Jul 2018 - 0:22; edited 1 time in total
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Happy Re: Cox .01 /.02 /.05 Engines & Mods / Nano Speed Planes

Post  balogh on Sun 1 Jul 2018 - 14:39

The 2nd one seems safe without leather if the plastic jaws are wide enough to grab at least 3 or more fins at a time? I will go see in a DIY shop in my area tomorrow.
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Happy Re: Cox .01 /.02 /.05 Engines & Mods / Nano Speed Planes

Post  balogh on Tue 3 Jul 2018 - 5:26

1/2A Nut wrote:.....

Do a weight check on your 7x3 Graupner prop. Compare to the NN glass prop at 6.1g
.....

The Graupner 7x3 is twice heavier, it weighs 12,86 grams...One would assume the prop weight impacts only the time the engine accelerates to top rpm, but it is only the airfoil (width, dia and pitch) of the prop that influences the top speed?

Weight also adds a bit to crankshaft friction, but would that really matter so much?
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Happy Re: Cox .01 /.02 /.05 Engines & Mods / Nano Speed Planes

Post  1/2A Nut on Tue 3 Jul 2018 - 10:07

Through actual use and modifying many props and weighing comparing shapes and airfoils,
flying and recording rpm monitoring ground speeds in relation to my standing position:


- Rpm provides thrust.
- Low weight props can provide more top end rpm.
- Narrow props provide more rpm which increases their ability to provide thrust.
- Narrow props provide less thrust at the same rpm of a standard shape blade.
- Heavy props rob torque and rpm.
- Thicker airfoil robs torque and rpm but can provide thrust.

- Race prop flies faster than a stock prop.
- Race plane flies faster than a trainer plane.
- Narrow cord airfoil allows higher pitch props with the given amount of engine torque to work with.
- Thin airfoil lifts very well at high rpm's and wings lift better at higher speeds.
- Wings are like props reducing drag and weight always increases speed.
- Flying fast increases heart rate and produces adrenaline
- Flying fast retains more memories of those moments
- Flying fast makes you smile at some point during or after the flight.

Posted top vids speeds thus far:
Engine  / Speed / Prop / RPM
Cox .010 / 130 mph / 2.56x4 / 28.86k
Cox .020 / 122 mph / 3.37x4.5 / 28.59k
Cox .049 / 118 mph / 4.1x4.1 / 30.5k
Cox .050 RC / 139 mph / 4.22x5.5 / 26.65K
Fuji .05 / 148 mph / 4x4.5 / 36.75K (tuned pipe)
Sportswerks .05 / 161 mph / 4x4.5 / 37.71K (tuned pipe)
(pitch speed only no viable Doppler pass yet)
Norvel .061 / 108 mph / 4.2x4 / 28.6k (tuned pipe)
(far from done with this engine old data)
SH .07 / 120 mph  / 4.75x4.75 / 26.64k (tuned pipe)
(far from done with this engine old data 36" span wing)
Cox .09 / 144 mph / 5.25x6.25 / 22k


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Last edited by 1/2A Nut on Tue 3 Jul 2018 - 10:37; edited 2 times in total
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Happy Re: Cox .01 /.02 /.05 Engines & Mods / Nano Speed Planes

Post  balogh on Tue 3 Jul 2018 - 10:30

Great summary Brad as always,thanks!

Happy July 4th celebration to all of you CEF mates in the US!
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Happy Re: Cox .01 /.02 /.05 Engines & Mods / Nano Speed Planes

Post  1/2A Nut on Tue 3 Jul 2018 - 10:41

Thank you I hope the information inspires you further. Thumbs Up
Yes Happy 4th time over here thank you my friend, we are all gearing up for Wednesday!

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Happy Re: Cox .01 /.02 /.05 Engines & Mods / Nano Speed Planes

Post  1/2A Nut on Thu 12 Jul 2018 - 17:38

Testing some new custom made bullet spinners for the TD .020
prior to this I would tap out Ron Valentines TD .010 spinners
using a threaded stud to fit the .020.  The dia. is spot on for
.020 props and has enough meat on the bone for an electric
starter to grab onto. Vibrations are knocked out with this type
of centered none migrating spinner with notable top end increase
in rpm over stock.


One of my go to E props makes great thrust 5.3oz and rpm to 95mph pitch speed.


Here shown with the stock grey prop.



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Happy Re: Cox .01 /.02 /.05 Engines & Mods / Nano Speed Planes

Post  Surfer_kris on Fri 13 Jul 2018 - 2:57

balogh wrote:One would assume the prop weight impacts only the time the engine accelerates to top rpm, but it is only the airfoil (width, dia and pitch) of the prop that influences the top speed?

Yes, the weight of the prop itself will of coarse only act as as flywheel and will not affect top rpm. The Graupner props have a much larger area, wider tip-cord, and a much thicker foil profil, and that will certainly affect the rpm.
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Happy Re: Cox .01 /.02 /.05 Engines & Mods / Nano Speed Planes

Post  1/2A Nut on Fri 13 Jul 2018 - 3:55

- Low weight spinners help the engine to turn up more rpm.
- Low weight everything always helps the engine to unload more.

Seen, heard the difference, proved it with my own engines / plane tests / flights and vids.
Only speed flying can clearly show differences, sport designs mask the varibles tried with
only mild sometimes hard to notice improvements tainting perspective.


The TD .010 with the least amount of torque showed me the proper path most clearly during
the variables I imposed on it a few years back. The TD .020 has been the second best teacher
which continues to challenge me to this day pushing for ways to improve the top end.

Will be bench testing this prop next and the new TD .020 bullet spinner.
Spinner and stud weight is 1.9g / the tapped out TD .010 bullet spinner is 1.4g
a tapped out stock TD .010 spinner 1.3g / stock TD .020 spinner and hex bolt 1.6g
I need to cut the thumb screw off the NV and put a thin / leaner nyrod extension on it.  
Forced perspective with the prop / spinner closest to the camera lens.



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Happy Re: Cox .01 /.02 /.05 Engines & Mods / Nano Speed Planes

Post  MauricioB on Fri 13 Jul 2018 - 7:37

1/2A Nut wrote:Big improvement with a peaked NV to sing mode good and steady.  Small Cox Logo
Pic shows how much I had the window open for the exhaust breaths
better than with that extension on the muffler, in the field for flying will
have it fully open as shown in the previous post. Beast of a .09 for what it is.

If flown with that prop @ 26k down wind / 80 mph
Serious thrust / 2:1 ratio for constant speed in any direction will pull out
of the hand and bolt away like on steroids. The DART design was around 11.5oz
as I recall a leaner NANO design with a 6.5P speed prop could do 160 pitch speed
with a 1:1 thrust ratio. The pressure tap really woke this one up in combination of
less exhaust restriction. The spring steel ring can be removed if no need for sound
suppression, if left on can close off the exhaust port from air / moisture when not flying.

Static 20,914 rpm / 30.7oz thrust / 1.9lbs / .326hp / 243w / 64 mph pitch speed.


Very interesting!!
Friend have you tried making a pressurizer for this muffler?
Reference: corresponds to Cox .049 / .051

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Happy Re: Cox .01 /.02 /.05 Engines & Mods / Nano Speed Planes

Post  getback on Fri 13 Jul 2018 - 9:30

The prop spinners look Fantastic !! 4th of July Flag
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Happy Re: Cox .01 /.02 /.05 Engines & Mods / Nano Speed Planes

Post  1/2A Nut on Fri 13 Jul 2018 - 21:19

Thank you Eric it is a perfect fit for the .020 engine.
Mauricio I have not tried that muffler trick on the .049 muffler should work though.

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Tested the new spinner and prop the engine ran very smooth no vibrations
centering of the prop and spinner was perfect! 102 mph pitch speed static!
Also used some nyrod tube as a exhaust diverter it seems to be griping
enough to stay so far. Muffler design needs a bit more barb on the end of
the exhaust tip to hold silicon tube. Added a bit more back pressure to the
tank engine was rock steady running. So far best speed in the air has been
122mph I hope this prop can bust the 130 mph barrier. Typical unloading
in the air with speed props is over 5 to 7k with the TD .020

Note at the end it runs steady then stops clean no erratic stop due to pressure in the line.





Previous test without the exhaust deflector:
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Happy Re: Cox .01 /.02 /.05 Engines & Mods / Nano Speed Planes

Post  1/2A Nut Yesterday at 6:35

Will try this modified 5x5E prop next cut down to 3.88x5N
Need to hit 3oz thrust static to pull out of the hand on windy days.
I decided to leave the thumb screw alone on the NV since it's in
front of the muffler still dirty but atleast a bit cleaned up the ridges on
the nyrod makes it easy to grip.


Comparisons of whats been tested vs this more proportional cord prop.


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Happy Re: Cox .01 /.02 /.05 Engines & Mods / Nano Speed Planes

Post  1/2A Nut Yesterday at 18:53

Per pic: 4.23oz of thrust at 96 mph pitch speed looks like the effort
to sculpt the prop to 3.88 x 5 has paid off well. Prop was well balanced.
20.1k to 20.45k: 95 to 97 mph pitch speed. Enough thrust to go vertical
out of site. Sorta looks like a APC prop now. Would be nice if APC made
a 3.75x4.75 proportioned like this for the TD .020 good for 21k static.
Took about 30 mins. to make this prop, sanding the cut side back into a
airfoil on the top side of the blades and balancing. Tough prop at the hub
will handle some not so good landings.

Duplicated out of carbon would be most worthy.






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