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Old Jan 30, 2016, 07:53 AM
jackerbes is offline
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Jack
USA, ME, Ellsworth
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At the same weight, two motor of different Kv rating use larger or smaller props to adjust the load to the RPM. Any prop increases the load on the motor as it turns faster and reducing the pitch and/or diameter is the only way to reduce the load when that happens.

You mention "maximum pitch speed" as if it were a motor characteristic. Pitch speed is a propeller characteristic and the limit on it would be the prop's RPM limit. And that is usually expressed as something like this:

maximum RPM - APC Thin/Folding Electric = 145,000 RPM / Diameter (inches)

And it relates to the propeller's failure and not the motor. Interestingly enough, APC props are seldom ever used at their max RPM simply because the blades get stalled and inefficient before they get to that high an RPM. Typically, most people don't use them at more than about 2/3rd's of their rated max, you can see that in the testing data at flybrushless.com.

My feeling is that your option 2 is going to call for a smaller prop and that will mean it has less thrust. And that will make it less adept at lifting and hovering and probably slow it down in forward flight. But I defer to your testing the theory.

Jack
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Old Jan 30, 2016, 11:34 PM
manuel v is offline
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Mexico, BC, Mexicali
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Something.

2slipo around 2.5 w/g
3slipo around 3w/g
4slipo closed to 4w/g

high Kv 1700-2200 4-5 w/g
more high Kv 5-8 w/g
in EDF 8-10 w/g
Something in EDF 10-14 w/g

All cases is necessary test.
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Old Jan 31, 2016, 09:07 AM
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Check out the attached spreadsheet compiled by Dave North for different winds of the Turnigy 2730 Blue Wonder motor. The motor tests are listed in order of increasing motor kV. As the kV changes so does the prop selection to match. In general, as kV increases, maximum power increases, pitch speed (not listed) will increase and efficiency decreases.

Interesting to note that static thrust does not drop off at higher kV/smaller props, but costs more power; less efficient.
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Old Jan 31, 2016, 09:33 AM
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Jack
USA, ME, Ellsworth
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Dave North (user timocharis) and Truglodite are just a couple of the real patrons of the rewinding art. Master Man Knitters par excellence for sure!

Dave North / timocharis blog page - http://www.rcgroups.com/forums/member.php?u=31575

Truglodite blog page - http://www.rcgroups.com/forums/member.php?u=142090

Those two blog pages are a gold mine of rewinding info and a history of the art on this forum. If you don't have the M$ Excel spreadsheet software or don't want to buy it, download and install the free OpenOffice.org suite and it will open the *.xls files without any problems at all.

For maximum usability sharing and to spit in M$'s greedy face, keep the *.xls files in the Excel format when you save or use them and then they can be posted here for sharing.

Jack
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Old Jan 31, 2016, 02:06 PM
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Not necessarily reduces efficiency.
The motor work is represented by two things, thrust and propeller speed.

Please read this article, the two sections.
use google translator included.

http://aeromodelismoelectrico.blogsp...000-watts.html
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Old Feb 03, 2016, 02:35 AM
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Hungary, Baranya, Pcs
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friends, sorry to interrupt and to ask some basic questions.

after reading and reading this thread I still do not see clearly what is the big deal about this motors, this is also because I come from gas RC planes have little knowledge about electric stuff at all. but in long winter times and the new multicopter thing I started to build tri- and quadcopters.

my question would be simply that I have 4-5 piece of DT750 , the new version, long, threaded shaft, (I already cut it short..) and the straight magnets, stock copper wire winding.

I want this motors for a simple basic 450 quadrocopter. (I also put it in rotorbits tricopter, liked the response, hated the ball bearing replacement.. tricopter yaw tail motor is being shaked by the servo, DT 750 did not like it)

so, but, I built 450 quadrocopter (so that no motor must be shaken by a servo) and liked the DT750 with cheap plastic 10x4.5 or carbon-mixed nylon props WERY MUCH. on 3S 2200mah lipo, hover was 12-14 minutes, power (torque) was always there. I used them with turnigy plush 25A UNFLASHED esc so the esc was for airplane, no simonK or blheli. the response was slow but okay to basic aerial filming with xiaomi yi camera on a basic 9g servo pan tilt stand.

now I have 4x 20A afro ESC and also 4x30A afros, I flashed them all with BLHELI.

I have great hope in these cheap motors, because I built S500 frame multistar elite 2216-920kv motors and used 4S 5400 multistar and have poor performance and "also" 10, max 11 minutes of hower without gimbal without camera.

so question 1 : generally. where is the truth here? how can a 2216 -920 "underperform" a shaky, vibrating, falling-apart, bendy shaft, poor wound Dt750?

-whats the big deal about re-winding the DT750? what would it bring to me? (power efficiency I am looking for)

question 2: I mentioned my afro 20 and 30A esc with blheli.

-what blheli settings do you recommend for DT750, for most efficient smooth flying around , no aggressive sport flying?
-can I use the 4S 5400 multistar with the DT750? (I promise no aggressive full thr! lipo is also low -C it can not deliver very good...)
what prop would be suggested for the DT750? I have a lot of 10x4,5 cheap plastic "leaf-style", also 11x5 thin electric props.

my current settings BLHELI:

https://onedrive.live.com/redir?resi...nt=photo%2cpng

any good info would be greatly appreciated.
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Last edited by martin555; Feb 03, 2016 at 02:52 AM.
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