Sandy sir, have you finished rewinding the motor? I'm really eager to see it work!

Thanks for reminding me buddy  .

I was caught up with business at work. Then had a great time with VC yesterday.

Though from here after the application of epoxy and curing for smoothness of the corners, it is just 1/2 to 1 hours effort but it is still eluding me.

will complete and update.

Great! I had a question bothering me. Will the rewinded motor have the same kv as before? Also, will the stall current rating change?

KV Though is mainly dictated by the number of poles and number of Magnets for optimum wattage. However it varies based on the number of turns and the wattage by both number of turns and gauge of the winding.

Sir, what I intended to ask was, have you made any changes to the no. of turns and guage (as compared to the original)?

I have not yet started winding the motor. But yes there is going to be marginal changes. because the winding  though will be same turns but will slightly vary in gauge and number of strands.

And that won't drastically affect the kv, will it?

it was a 1400 KV it will be plus minus 100.

O.K. so I guess it will still have the same prop range (approximately)...

I have a similar issue now with a 2826 motor, i couldnt reach to rewind as the bottom aluminum frame cannot be removed.
Bell motors are kind of different it was very easy to remove and rewind a towerpro motor.

Send it to Sandy sir! 

Bearing are now removed and was sucessfull loosing the stator from the alluminium plate.
It took 2hrs of heating with soldering iron for the glue to release the stator. Now its freely rotating but still is not coming out.
Followed  the last few posts in http://www.rcgroups.com/forums/showthread.php?t=1079423

finally was able to seperate stator and alluminium base!! A drop of oil did the trick.

Well all that effort is surely worth it if you are able to get the pole shoes core out without damaging it and the bearings without  damage. Though all that heating did not damage the varnish and insulation of core?.

If you are able to remove core shoes out then it surely makes your life easy while rewinding.

Now back to Swapnil's motor, in preperation for its winding it has been given a thin coat of eppoxy on the core to smooth the edges to prevent damage to enamel wire while rewinding. It will set over night then it will be ready for rewinding.

wow, very good going sunder sir .

Quote from: sundaramvelar on July 08, 2011, 11:29:11 PM
... It will set over night then it will be ready for rewinding.

Sandy sir, when you rewind the motor, is it possible to increase the kv to 1700-1800? I was hoping to use it with 5-6 inch props as they do non break easily.

For Increasing KV I have to reduce No of turns per pole and increase the Gauge of the winding which will also increase the wattage.
let me see how much I can do it without over loading it.

Oh yes, I forgot about the increase in wattage with kv! I only have a 30 Amp ESC.
How much will the wattage increase with turns and guage? Is there any mathematical relation for that?

KV has no relation to the wattage. All KV Range is available for all wattage.

Wattage is purely = Volts x Amps. and Amps is dictated by the Resistance of the coil of the Phase And Impedance for the coil in rotation. Impedance is also dependent on Resistance in addition to various other factors like flux, load (resistance to motion in the field), number of turns of the coil, core properties, air gap, frequency, and may be I am missing out some.

However When you increase the thickness of the gauge of enamel wire and reduce the number of turn. Surely you are reducing the length and increasing thickness and the resistance is bound to fall drastically. Which will increase Amps and hence the wattage increase.

Some of the relations I am posting just for Knowledge sake

Watts per pound of airplane weight.
100w/lbs = trainer/sport
150w/lbs = 3D aerobatics
200w/lbs = extreme

And wattage is calculated as
Watts = volts * current
7.4v * 10amps = 74watts
11.1v * 25amps = 277watts
22v * 50amps = 1110watts

Motor Kv: Kv = RPM / (Vin - Vloss), Vloss = Iin * Rm

Torque constant: Torque constant: Kt=Kb x 1.345, Kb = Voltage constant (Volt/1000 RPM)

Doubling the number of winds halves Kv (rpm/volt) and doubles Kt (torque/Ampere),
Doubling stator height halves Kv, doubles Kt and (roughly) doubles maximum power.

Higher the dia of the Motor Lower is the KV Higher is the Torque.

6 cycle step sequences needed to complete 1 revolution of the magnetic field.
A to B / C to B / C to A / B to A / B to C / A to C

Examples of gearing of the Motor because of No of Stator and No of Magnet:
10 magnet
   360deg / 10 mag = 36deg || 36deg / 3 phase = 12deg
   (12deg / step) x 6 steps = 72deg. Sequence
   360deg / 72deg = 5  or 5:1 gearing

14magnet
    360deg / 14 mag = 25.71deg || 25.71deg / 3 phase = 8.57deg
   (8.57deg / step) x 6 steps = 51.42deg. Sequence
   360deg / 51.42deg = 7  or 7:1 gearing

Higher the Gearing ratio Higher is the Torque and lower is the KV and Vice verse. In other words higher the number of Magnets lesser is the Number of KV - higher is the torque due to Gear Ratio.

A, B, C are the Three Phases. When it is in Capital it is Clockwise winding and When in Small it is anticlockwise winding.

9-pole stator can only be wound using ABC wind
ABC - ABCABCABC

12-pole stator can be wound either ABC, LRK or DLRK.
ABC – ABCABCABCABC (easy, need more magnets)
LRK – A-b-C-a-B-c (high wrap count per tooth, less to wind)
DLRK – AabBCcaABbcC (low wrap count per tooth, more to wind

In Delta system of connection it gives 1.73 times more KV than the Star system of connection whereas gives 1.73 time less KT (Torque).

Since it was 12 Pole and 14 magnet Motor applicable winding was DLRK The picture posted earlier. Posting in-spite of repetition for closer reference.

The photographs of the three phases wound.

Since Swapnil wanted a little Higher KV it is now 8 Turns per pole in place of 10 Turns but Gauge is I think almost same.

I could not get the correct thinner strand for multi strand winding which would have given a smoother winding, less noisy motor and some say cooler winding.

I have used a single strand of thicker winding which was comfortably filling up the pole shoe without crowding and enough space for cooling air too.

Leading end the the trailing end are protected from nic at the corners with heat shrink wrap.

If it was 16 magnet Motor the recommended ABC as the picture posted below.

And a 9 Pole Shoe is always ABC Winding as below Which is also an example of Delta for of connection.

Example of star connection is the second picture.

The Delta Connection for the Swapnil's Motor is as shown in the picture.

Here you have to be very carefull for DLRK and LRK with the sequence unlike an ABC winding.

In ABC winding the Start end  and finish End of two different phases have to be connected and the six ends have to be paired to three sets by connecting the starting end and finishing end two diff phases in any sequence (Just don't connect ends of same phase  ). Since all winding is Clockwise it can be done in any sequence without any effect on the motor only the direction of the rotation will change.

However since in DLRK and LRK the winding are alternating Clockwise and anti clockwise the sequence have to be strictly maintained as per the sketch for Delta.

For star just connect and solder all the ends and give three phase supply to the three start ends.

Swapnil,

Till now I thought the bearings were OK since when rotated with Hand it is not giving any noise. But when powered up it has a small rumbling at low RPM i think one of the bearing towards the Clip side is dented and is slightly damaged.

You can still use the motor without any worry only it is more noisy. earlier I thought because of thicker strand but it is distinctly rumbling at low RPM like play in the bearing. Otherwise it is spinning at good RPM.

Earlier I did not doubt it now I can feel it when in free rotation with hand also. Now only since I know it I can make out it is that light.

I will load test it and post photos and video with wattage and temp results.