Scorpion 2221-10 3000KV Rewind

[Bladecpnitro]

Hey folks! I'm in the process of rewinding my HK2221 3000KV Scorpion.

I need to keep the KV 3000 stock. I need to get wire ordered and I'm confused a bit on an issue here.

Spec says 13 strands of .21mm wire. 10 turns.

What actually came off was closer to 5 turns

phase 3- 6 4 5
phase 2- 5 5 5
phase 1- 5 5 4
All CW turns
How do they get 10 turns out of that?

Anyhow, the total area of the stock wire sqaures out at .45mm.
21 Aug wire is .41mm sqaure and 20 aug wire is .50 sq mm.

Should I just go with 20 Aug? I need to get the wire ordered and rewind this thing before the 4th of July vacation.

I'm flying my back up Turnigy 2215-3200 KV with an 11 T pinion and it bogs where the Scorpion never let up on the 450 Pro slinging 325's. I've never heard the Scorpion bog. 13T was unusable on the Turnigy it bogged so bad and got my batteries hot enough to darn near catch fire almost.

[ron_van_sommeren]

Turns per tooth versus turns per tooth pair. Spec turns per slot and there cannot by any misunderstanding because that number is the same for equivalent LRK and dLRK winds.

Vriendelijke groeten Ron

[Vinger]

What Ron posted and use the thickest wire that will fit with 10 turns per tooth pair. The stock 2221-10 is delta terminated so if you want to the stock 3000KV you have to terminate the same.

[Bladecpnitro]

This motor has 9 stator arms and 6 magnets. Does that make it a 9N6P?

What exactly are the pairs in this motor? I know each phase travels through 3 post and I thought on these motors that 10 turns meant 10 turns per post


I guess I could order two sizes of wire.

[1BOHO]

Yes 9N6P . In a dual layer it 10 turns per slot.So 5 per arm. Easier to measure from bottom of slot to beginning of hammer then select wire that will fill the bobbin in 5 turns it is ABCABCABC.

[ron_van_sommeren]

Originally Posted by Bladecpnitro

This motor has 9 stator arms and 6 magnets. Does that make it a 9N6P?

Yes.

Originally Posted by Bladecpnitro

... What exactly are the pairs in this motor? ...

Oops, my pole pair remark was about 12statorpole motors. Your motor cannot have pole-pairs.

Vriendelijke groeten Ron

[Vinger]

Even with a 9N6P the wire still needs to fit between two adjacent hammers and you still count the wires in the slot, ie 10wires in each slot, so your choice of wire thickness will depend on what size will fit between the slots.

[Bladecpnitro]

I'm still not understanding why Scorpion calls this a 10 turn motor.
I desperately need to get wire ordered this morning.

I would call it a 5 turn motor based on what came off.

I'll measure the arm and see what thickness of wire will give me 5 turns.

[1BOHO]

Really confusing for scorpion to call it a 10 turn because as Ron said there is truly no "dual layer" or pole pair in a 9N6P configuration.I guess they are counting the wire in the slots anyway. Confusing but based on what you actually pulled off it seems to be the only thing that makes sense. If you check the wind cal you will see no dual layer or single layer option, just wye or delta. Sutty has fit the motor with 5 turns of .85 mm. But terminated in a wye and logged back 2200kv on castle. You may be able to do the math on going from wye kv to what it would be in a delta. Or wind small test gauge and test the Kv before finalizing. Looks to be pretty reasonable fill and he seemed to be really pleased with the result.

https://www.helifreak.com/showthread.php?t=717275

Addendum: This statement was misquoted from Bavaria on rc groups.
http://www.rcgroups.com/forums/showthread.php?t=1394313

"..For the same number of turns and wire thickness:
DELTA gives 1.73 higher power and amp draw than STAR
DELTA Kv (RPM) = 1.73 higher than STAR Kv while the Kt (torque) = 1.73 lower
With a STAR connection, 1.732 more turns need to be wound to get the same power (and Kv) as with DELTA..."

This last sentence is not correct. Here is the actual quote from Bavaria.

"Put differently; with a WYE termination, 1.8 times less turns are needed to get the same Kv as with Delta."

Maybe the reason in the difference of turns you pulled of was an attempt to make 5.5 or 6 turns turns? I get if i take suttys 2200kv using 5 turns in wye X square root of 3 = 3810Kv delta

1 thing I think of is if you make estimates off what the original motor is supposed to be and it is not actually that it throws all your calculations off. If you really want 3000 kv the best solution for accuracy seems to be test winds and an accurate way to measure the kv with the intended controller and settings.

[Bladecpnitro]

Thanks 1OBOH! I don't suppose I can go wrong putting the exact turns back on there that came off if I can determine the correct single strand wire size. After all it was working perfectly.

If Sutty was able to get 5 turns of .85 wire on without issue I guess 'll go with that.

I wonder if your friends KV could have actually been that high though?

Assuming my 2221-10 3000KV motor is very close to 3000KV

If my motor has one less turn on one post to get aproximatly 3000KV, that would be 14 turns / 3= 4.66 turns on my motor.

4.66 turns x 3000KV =13980 / Sutty's 5 turns = 2796KV Delta

2796KV x .578 = 1616KV Y termination. I woner if he was actually closer to 1616 KV?

[1BOHO]

I'm not exactly sure because you got some odd wind numbers coming off. Go to radio shack and get a spool of their cheap magnet wire and do the test winds Is what I would do. But if you feel comfortable that it should be 10 turns 5 per tooth you can go with it. I do know if you don't have the right number of poles selected in the esc settings in a castle it will log you back incorrect rpm's so you kv assessment will be off. Dividing the rpms by the voltage. After you wind the motor if you have a D.M.M. hand drill and and you know its rpm with the trigger fully depressed you can approximate the kv of the motor fairly easily. Sutty is a very friendly modeler so I'm sure you can shoot him a pm and get some additional feedback.

Kv = RPM / (Volts × 1.414 × 0.95)

your drills WOT rpm would go into the formula as the "RPM"

Since you measure the phase BEMF with the DMM in ac the voltage will be Vrms so that X the square route of two( 1.414) to get the peak voltage and I guess the .95 is assuming 95% efficiency. If scorpion post the efficiency maybe youll be closer if you plug it in for the efficiency percentage.

You simply divide the "RPM" by the (product) to get the kv.

[Bladecpnitro]

All the radio shacks closed down in our area. I have some 22, 30 and 26 left from a radio shack purchase but I don't think I have quite enough 22 aug to wind this motor. I'll check.

I have all the KV meausuring tools I need as well. This won't be my first motor just the 1st one I've done since last year.

I suspect that if I wind it 5 turns Delta KV will turn out around 2800 and I can live with that.

[1BOHO]

I don't know that it was really just one less turn on one post. I remember Modisc making a mention of a odd backside turn that he found on one of the scorpions. Not to mention it could have been a defect that made it pass QC.I wouldn't recommend rewinding it with one arm out of the bunch with 1 less turns. Id take the 30 ga. or what ever you have enough of and wind the test wind for undoubted accuracy. You can wind the small wire very quickly and run the tests.

[Bladecpnitro]

I have it rewound. I'm gonna do the drill KV test to avoid any risk of blowing my ESC. There are no shorts in it now but without it all glued down a wire could jump out into the can.

I ran 2 phases of 22 aug and the last phase I did with 3 strands of 26 aug which is just a little more square area than the 22.

If I remember correctly all of my past drill meausurements have shown anywhere from 14 to 20 KV higher than ESC and 12'v measurements.

[1BOHO]

I guess that will not hurt things too bad. Let us know what numbers you get back. That 14-20 discrepancy is minimal.

[Bladecpnitro]

Will do! I can't wait to get the Scorp back up and running, I despise that bogging Turnigy. I think the bottom bearing went south in it during its first flight.

I keep shooting the synthetic oil to it hoping it will last until I get this one ready.

Changing the motor out on the Pro 450 is pretty aggravating. The front battery tray has to come off and the two front most servos have to come out to get at the motor screws. So I don't wish to take the motor out to see if I have in stock the correct bearings for it.

[Bladecpnitro]

3400KV seems to be the number

Here is a pic of my Drill KV Test rig. I had to drill new holes to mount my 2221-10 motor. The last one I used it on was the Scorpion HK 111-4020-1350KV rewind.


The average AC voltage came in at .273 and RPM was 1247.

One thing about the drill, it seems the longer it runs the RPM gradually increase but no by much. I took the AC measurements then quickly shot the RPM with lazer tach. Right before I shut the drill off RPM was up to 1259.

If my calculations are correct I come up with 3400KV for the Scorpion HK11-2221-10 at 5 Turns.

[1BOHO]

Was that a wye or delta termination?

I edited out my post about the optical tach and rpm because maybe ultimately it will take you longer to get the voltage seen by the the motor having to upload a log of a wot no load run.
If you have confirmed the drills rpm with the optical tach then your measurements are fairly accurate. I'd think.

[Bladecpnitro]

I used Delta termination. I'm gonna run it on an ESC and power supply this evening and check KV that way as well.

[1BOHO]

If you have the variable supply you may be able to plot some efficiency numbers after the final wind. prototype3a did some very nice work back a while.I don't think anyone payed much attention.I think it was an align thread. I think what he did is at different voltage took idle current readings and plotted them against the voltages then did regressions to get the curve and linear Eq.. Very easy to do if you have the graphing calculator. Once you get the Eq of the line you can put it in an excel cell and plot the curves.Or just look at the calculators screen. He may have done some other things but I'm sure you could ask specifics. A very useful post IMHO.

What I was wondering is if you wound the 2 tooth IN EACH PHASE with an additional turn.
5,6,5, Is something like this what you meant earlier?