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RGT52
06-02-2008, 10:16 AM
I am about to start rewinding my first motor. In preparation for that, during the past several days I have been reading lots of posts & articles on the subject so as to get familiar with it. While reading, I noticed that most people determine the “new” wire thickness & number of turns based on the “old” values and the intended use of the rewound motor (i.e. higher/lower Kv, etc…).

Question:

Is there any “generic” calculator available that will not require the use of reference data taken from a specific(base) motor ? (i.e. purely based on formulas and/or empirical data contained in a database)

I am looking for something that will take input values such as:

- Stator diameter, length, nbr of teeth.
- Number of magnetic poles.
- Wire thickness.
- Number of Turns.
- Termination (Star / Delta)
- Input Voltage.
- Propeller (Diameter & pitch)

… and will then estimate motor performance (i.e. Kv, current, RPMs, thrust, efficiency)

Any assistance/comments will be highly appreciated.

Moxus
06-02-2008, 02:24 PM
SI units.
The SI unit system got units for pretty much all of these factors, and the good thing with SI is that all the units are derivated from the others, so they are easy to calculate in between.
Voltage, current and number of windings gives you magnetic field strength, rpm and permanent magnet field strength gives you counter ems.
Counter ems and input voltage and rotor diameter gives you rpm per volt, og kv. back to magnetic field strength: this lets you calculate torque at a specific rpm with a specific input voltage.
Its a bit of a headache, but it shouldnt be impossible.
Wikipedia, wich i usually dont take for its scientific value, its actually quite good on its overview and description of SI units, if you are more familiar with the empirical ones.
You might not see why SI units is so goot for this purpose yet, but when you see that you can measure amps in weight, distance and time, then you realize how versatile the system is. And this versatility makes for very easy calculation between otherwise unrelated units. Like for eksample input watts, and torque out of the engine.

ron_van_sommeren
06-03-2008, 01:50 AM
... Is there any “generic” calculator available that will not require the use of reference data taken from a specific(base) motor ? ...Alas, no.
http://www.gobrushless.com/shop/index.php?app=ccp0&ns=display&ref=rotorcalc
http://www.rcgroups.com/forums/showthread.php?t=587549


Excellent motorbuilding articles by Brian Mulder,they cover the all the basics, a must read:
http://www.southernsoaringclub.org.za/
-> Articles by SouthEasterners.
-> Electric Motors - part 1-5

Do-it-yourself motor homepages, manuals/tutorials, checks and tests in this motor builders tips and tricks thread. The checks and tests may save you from frying your controller or motor. Thread is active, bookmark it for future reference and subscribe to it:
http://www.rcgroups.com/forums/showthread.php?t=240993 (sticky thread, at top of that subforum)

The ‘bible’
http://translate.google.com/translate?u=http%3A%2F%2Fwww.powercroco.de%2F&langpair=de%7Cen&hl=en&ie=UTF-8
http://www.torcman.de/peterslrk/index_eng.html (LRK)
http://www.torcman.de/motoren/manuals/anl_eco_200e_scr.pdf ((LRK: assembly, magnet glueing, winding)

Two instructive cd-rom motor winding/assembly videos, 14 & 10Mbyte respectively (note!!! cd-rom and lrk have different winding diagrams!)
http://www.youtube.com/watch?v=iHYlWKICkqc&e http://www.youtube.com/watch?v=Ybb0Ysh0FRE
Vriendelijke groeten ;) Ron van Sommeren
• brushless motor building tips & tricks (http://www.rcgroups.com/forums/showthread.php?t=240993)
• diy brushless motor (http://www.yahoogroups.com/group/lrk-torquemax) discussion group
• Drive Calculator (http://www.yahoogroups.com/group/D-calc/) download & discussion group

RGT52
06-03-2008, 08:20 AM
Moxus: I find your hint interesting. I had a quick look at SI units in Wikipedia and could see its potential. I would not mind the headache ... unfortunately, what kills me is the lack of time to pursue so many interesting projects !

Ron: I appreciate the suggested links (I have read several of them already. Very informative !). Too bad no such calculator is available.

Anyways, thank you both for your answers !