Brushless motor winding class

[donhuff]

haha That makes perfect sense to me Don.

I would think that if you propped to a maximum temperature that you can live with on a 2000kv motor and then did the same with say a 2200 kv motor you should be faster with the 2000kv motor. That 3040kv motor I built makes all kinds of noise but it turns an itty bitty prop doing it.

That's how it seems to be. Especially with those numbers and 4s power. There is a reason that we always suggest keeping the RPM between 25000 and 35000. And all this goes for HEAT RACING! This also seems to hold true for the other voltages too, you just have to change the kv numbers to fit into the same RPM brackets.

For one pass down a SAW, or even one or two laps, more RPM does help "sometimes". Because by going with a higher kv, and keeping the same propeller size, your getting the RPM closer to the motors horsepower PEAK which usually happens close to 50% of the motors unloaded peak RPM. BUT!!!! That's gonna make more heat, a lot more heat. The trick is to get as close to that peak as you can, to accomplish that one way pass, or two laps, then let it cool.

[donhuff]

"I assume this is the case with all the manufacturers and sizes. One less or one more turn."

Yes, that's how it's done, WHEN you are trying to "split hairs" and change the kv only 200 rpm. I guess in some applications that might be necessary, but I don't really think so for a toy boat!

The better way to do it is to change the number of turns on ALL of the coils, but that usually makes a large change in kv on the order of 600- to 1500 per turn. That being less change for the higher turn count, and more change for the lower number of turns.

I explained this in "WINDING CLASS" but I'm sure it didn't make a lot of sense. Maybe now after you've done a few motors, it'll turn the bulb on.

Let's imagine that these dashes are turns around a set of coils on a 4 pole motor. And that the whole line of dashes is one leg. And a 4 pole motor usually has 12 slots, and that means that there are 2 coils per leg, per a "set" of poles (1 north and 1 south is a set). So that will mean that there are 5 turns per each coil.

So lets say that our motor uses 10 turns delta to get 2000 kv. and lets say that looks like this. ___ ___ ___ ___ ___ ___ ___ ___ ___ ___

Now take one turn off of one coil and call it a 9 turn motor, and that strand of wire gets shorter by 10%. As the wire gets shorter, the turn count has to go down, and the kv goes up.

___ ___ ___ ___ ___ ___ ___ ___ ___


But to touch on the other thing you ask about, slot filling for higher copper fill. We see that by doing it 5 Turns on one coil and 4 on the other, were leaving some open space in a couple of slots, actually 6 slots. Because we have three legs and two coils per leg. So to keep the slots full, you'd have to drop 2 turns and make it an 8 turn motor with 4 turns per coil. But when we do that, we can increase the number of strands of wire in our "bundle" of wire.

Lets say a slot will hold 100 strands of #27 wire. For a 10 turn, 4 pole, 12 slot motor, with 5 turns per coil. The number of strands in our bundle to fill the slots to max would be 20 strands. 20 strands times 5 turns equals 100 strands in a slot.

But for the 8 turn motor, which will have 4 turns per coil, we have to up the strand count to 25 to get us back to a full slot of 100 strands.


And to add even more confusion to this. Not all manufactures use the turn count of all the coils on a leg added together. Some or actually most of them refer to turn count as the number of turns on ONE COIL ONLY.

That's why a 4D on motor ABC, might be totally different from a 4D on motor XYZ.

[donhuff]

"So the typical 2000kv Dyno is a 3D. If I leave out one turn on the third coil what does that make it?"

Terry, I'm not even sure that calling the 2000 Dyna a 3D is correct, and they call it a 1.5 delta???. They must have asked a salesman what to call it!

In my mind I call it a 3 delta because you go around each coil 3 times, but............not really. Because of the crazy azz way they do it, going forward and backwards. A straight forward 3 turns is a little easier to understand because the wire goes around and around the tooth 3 times.

That goes back to where I said that the number of time a wire goes through a slot, is the actual turn count.

Some companies like Leopard, would call it a half turn. Even though it's not really a HALF, it's just minus one turn on, one coil, on each leg. And with the Leopards all being 4 pole that sounds ok I guess. But in the case of 6 pole motors, your leaving off one turn on one coil of a set of three coils per leg. Is that really a half???

When I'm writing my notes on a "half wind" I call it a 4-4-3 turn wind. This is for a 6 pole 18 slot motor. That tells me that I have two coils with 4 turns and one with 3 turns. But if you were using the total number of turns per leg it would be simpler to say it is an 11 turn wind instead of 12 turns.

[T.S.Davis]

I followed everything you typed Don. Thank you so much. Still hearing it in yer voice too. haha

I don't know why it didn't occur to me that if I really wanted to make a 3,3,2 I could just up the strand count on the 2 wind coil to 18. Duhhh. Might be a nuisance to wind but keeps the copper content up to maybe control heat better. I did this when I wound a 2y on the standard 2k stator. Hmmmmm thinky pain. I see some mad science in my future. Wish winter wasn't coming.

Sure would make understanding easier if every manufacturer would follow the same nomenclature for wind counts. Example..... a Neu 1521/1.5D and a TP4060/5D are so similar in performance that I couldn't choose between them. Similar size. Both 4 pole. 50kv between them. Each will push anything 4s. They can't be wound a ton different from each other. Throw in a Leopard version and nobody knows what the heck is what.

[donhuff]

"if I really wanted to make a 3,3,2 I could just up the strand count on the 2 wind coil to 18." ????

I call a "coil" when it makes a circle around a tooth, or set of teeth, Then the wire for that leg hops over a few teeth and makes another coil, and in your case one more time for the third coil on that leg.

Now, your not thinking of winding one leg, with three coils @ 3 turns, another leg with three coils @ 3 turns, and then the third leg with three coils @ 2 turns, are you???

If so, that aint how it works. Well at least that aint what I meant to describe it as being.

All three legs, with 3 coils per leg. Need to have the same length of wire to stay in balance,(I would think). All three legs will need to have the 1 turn less length of wire. And that means that 1 coil on each leg will be short one turn and there will have to be a little bit of copper fill lost on those three coils.

So using one bundle of wires, do 3 turns , then 3 turns, then 2 turns on the last one to finish out one legs, set of coils. Then do the same for the other two "sets of coils".

That's how I have seen it done and I have done it. I don't know for sure that the other way wont work, but I have never seen it done that way.

[T.S.Davis]

That was my thinking and yes I miss understood.

[T.S.Davis]

spit ball'n. Ever done:

2,3,3
3,2,3
3,3,2

[donhuff]

No I haven't. Not that i think it wouldn't work, but because it's easier for me to keep up with it by making the short one last.

And to make it clear, are you saying to do one leg 233, the next 323, and the last leg 332? Or do you mean to do a whole motor as a 233, or a 323, or a 332.

I'm assuming, that you mean to put all three versions in the same motor, with the idea of spreading the "weak coil" evenly every 120* around the stator, rather than putting them all three side by side. Perhaps to make it more "balanced"? That does sound like a good idea, but all the factory motors that I have see lump them together.

[donhuff]

"Sure would make understanding easier if every manufacturer would follow the same nomenclature for wind counts. Example..... a Neu 1521/1.5D and a TP4060/5D are so similar in performance that I couldn't choose between them. Similar size. Both 4 pole. 50kv between them. Each will push anything 4s. They can't be wound a ton different from each other. Throw in a Leopard version and nobody knows what the heck is what."



YES IT WOULD.

If they would standardize on what they mean when they say a motors size.

TP sez a motor is a 4070 for instance. That means it is 40mm in diameter, and the rotor is 70mm long.

Then a NEU is 1530. The OD of the case is 1.5 inches (38.1mm) and the rotor is 3.0 inches long (76.2mm)

Leopard, and a lot of the China motors say it like 4082. That makes it SOUND bigger. The diameter is still 40mm, but on the inside, the rotor is only 50mm long.

I opened up a couple of Hobbystar 4082s a while back. Lots of empty space in the rear of that motor. You'd think it would be the same as the Leopard since it has the same size designation and they "look" like they are sisters. Well not really, the hobbystar's guts are only 45mm long.

Then other companies number their motors buy the diameter and length of the rotor.

[T.S.Davis]

And to make it clear, are you saying to do one leg 233, the next 323, and the last leg 332?

Yes exactly what I was thinking. Balance was the thinking too. I did a stator with the cat 5 just to see where the 2 slots would land. It does spread them about but doesn't quite make a coherent pattern so I don't know if there is really any value in it. Almost need to do it both ways and watch heat. The nature of boats being as they are I'm willing to bet that getting exact real data would be unlikely. Maybe a test jig like Darin was using would tell us something.

I've seen some motors built specifically to comply with the 36x60 rule that had short rotors and short stators leaving just air in there. Would have fit in a 50mm can. There's so much waste in these designs. Especially with the limited motors

I'll likely take some heat for this but........it's as though there is a knowledge disconnect between those that understand the motors and those that have the capacity to get a motor manufactured en mass. I only know enough to be dangerous at this point. I could ask for a motor that is 36mm x 60mm but if I don't really understand what's inside I don't know what to tell them I really want. What I want with my limiyted knowledge is 6 pole, 200c degree wire......fill the damned space! They could be "buy it and forget it" use em forever motors. Oil the bearings and that's about it.

[donhuff]

If you'll go to a DDD wind you can get almost any kv you want AND keep all the slots full. But it's a bunch of trouble to do them that way.


Yes if I could get with a manufacturer, and get them to make one to my specs. It would be a real MAGNUM of a motor for limited. BUT, BUT, it would be $$$$expensive$$$ because it would require a lot of extra work, to pack it all in there. And they are NOT going to do that for nothing. Plus, the successful build/reject rate would be unacceptable. They have to work at a price point, and I just don't think it's gonna happen for the limited number of motors that they would sell.

[T.S.Davis]

Truth. I forget sometimes what a tiny crumb of the RC industry FE boat racers are. We matter but not when the bean counters look closely. The only way would be if a company like Proboat had the knowledge to design a better mouse trap and then order 500+ of them.

You got some splain'n to do. DDD? Did we cover this and I spaced out?

Edit.....I just noticed this thread has over 5000 views. Holy crap.

[donhuff]

Proboat "tried" to make a better mouse trap with the 2000. And granted, it is a decent motor especially after rewinding with good wire. But instead of taking a GREAT motor, the 1500, and stroking it by making the guts longer, they went with a whole completely different design. The one thing they got right on it was making it longer internally. 1500 is 32mm and the 2000 is 36mm. And that 4mm longer length is the only reason that it can do as well as it does, because every other part on the inside, is inferior to the 1500, when the number one thing we want from a motor is horsepower. The 2000 gave up on all the things that make the 1500 great, so that it could be made CHEAPER!!!

To name a few bad differences about the 2000, that make a horsepower difference. A smaller diameter rotor, smaller magnets, smaller stator slots which means less copper wire, and the big one, almost double the air gap between the rotor and stator. Ever notice how hard a 1500 cogs and most others don't? That's a tight air gap, and and think of it sorta like compression on a internal combustion engine.

Then they made the rotor end caps from cast or MIM, and they have the worst cheapest bearings in them that I have ever seen in anything.

I'm saying all this to say, they made this motor to fit a price point, period. I'm sure that they could make a 36-38mm long 1500, and fit it into a 3660 case, and use parts already being produced, and offer it in a good spread of KVs. And it would cost maybe $150-$200.

[donhuff]

Dang it Terry, yes I have explained the DDs YYs and DDD before. But I know that I have talked abot so many different winds that it's to hard to keep up with all of them.


So for a DD in a 4 pole 12 slot 2000 kv motor for example, what your doing different is your winding EACH INDIVIDUAL COIL with it's own wire bundle. So instead of making up a 2 foot long bundle and winding the stator by winding one coil and then using that same bundle of wire and going the right number of slots around and winding the second coil to make a normal 2D, or 4 total TURNS per leg. For the DD (and for this example let's assume that we want the same kv) we are going to have to keep the LENGTH OF THE BUNDLE the same as on the 2D version. So we'll make a 2 foot long bundle, but it's all got to go around one coil only, sooooo we will have to reduce the number of strands, and since the 2D had 4 total turns we should have to put 4 turns on this one coil to end up at the same length of wire! Wrat the 4 turns and bring the wire bundle out to terminate it like you would with the normal 2D wind.

Now skip around the stator to get to the location for the other coil on this same leg (same place where it would be with the normal wind) and wind it the same way we did the first one with 4 turns and bring the bundle out for termination like before. Now take both STARTS of both bundles and twist them together, and both FINISHES for each bundle and twist them together, now do the same thing for the other two legs. That's a 4 Delta Delta that should be the same 2000 kv as the plain 2D. Mark the starts and finishes for each piece of wire, or you'll be totally lost when you get finished winding, because you'll have 12 leads sticking out instead of the normal 6. And in the case of a DDD 6 pole 18 slot, now you have 18 leads!!!

Why you ask??? Looking at the normal wind like a 2D and having two coils on each bundle. You see that the turn count that will be available are going to be in multiples of 2, right? Add 1 turn to two coils and you get 4, one more and it's 6. And that sometimes makes a big jump in kv.

But by doing a DD you can now wind one coil with 3 turns and it's a 3 turn wind you can do a 5 turn and any odd numbered that wasn't possible before. You can do that with the normal 2 or 3 D, by leaving a turn off of just one of the coils per leg. But then that leaves empty space where copper could be.

And it gets better with the 6 pole 18 slot because their turn count goes in multiples of 3 because there are 3 coils per leg. So then 2 turns 3 turns and say 5 turns equals 6 total turns, 9 total, and 15 total turns. Now we can split the difference even more by doing a DDD. Because with the normal 2 turn =6 total, and 3 turns = 9 total, we skipped 7 and 8 turns completely. With the DDD you can do the 7 and 8 and get two KVs in between what is normally available, AND keep all the slots full at the same time.

Now imagine an 8 pole 24 slot motor!!!

[T.S.Davis]

AHHHHHH!!!

So you could have 18 start/terminations to join? And 15 of them should be inside the can. What a pain in the a$$.

Sorry to make you go through it again Don. It's tough to follow. Probably tough to type it too.