Originally Posted by
safe
So we agree then that if you want to increase the top end speed you can switch from Single to Double?
One more time,
no. The number of windings has essentially zero effect on motor speed. Changing the number of turns affects Kv. You are abusing terminology by linking these two concepts.
They are independent.
Assuming that the strand size is the same and you are willing to see an increase in motor rpm. You do this by cutting the "Turns" in half to get everything to fit.
If you have a motor that is working OK, but want a little more speed, then cutting turns in half is a bad idea. Why? Because you won't go twice as fast - you would need to draw 8 times the power you used before (air drag is proportional to the cube of speed) but your motor won't be able to suck that much without increasing voltage. As a result the motor will be lugging, operating less efficiently than before.
As a rule, you want to make small changes to the number of turns.
Now we agree... (this was the idea I was getting at)
"You keep using that word. I do not think it means what you think it means."
The moment you accept the "real world" of imperfection then you start to see the added benefits that rewiring can bring.
Go ahead and rewire your motor with half the turns and let us know how that works out for you. As they say on Slashdot, good luck with that.
As for the "Litz Wire" these guys are actual "winners" in real racing situations and they claim a slight advantage in some situations. I tend to favor the wisdom of those who actually "win" over someone who just claims to know.
I have already debunked the skin effect, which you suggested was relevant, as it applies to our motors. If you really knew what you were talking about, you would have explained the existence of losses due to eddy currents in the wire induced when flux crosses the coils. Litz wire is an effective solution to this phenomenon. The problem is it does not occur to any significant extent in ebike motors. There are two main reasons for this: First, the motors we are talking about are (assumed to be) iron core motors where practically all the magnetic flux is constrained within the core; and, second, ebike motors run slowly (compared to RC motors, for example).
...disputing the "Litz Wire" goes against the entire RC motor community (that seem to all use it as a concept)
You don't frequent the same motor design forums I do, because there is an active debate between the litz and no-litz voices on the ones I read. That's fine, but please don't go around claiming your opinion is the only one out there. Also, let me emphasize that this is a marginal effect on high speed RC motors. As you scale up the size and slow down the rpms, the effect diminishes to irrelevance.
Finally, look at the type of wire used in solar vehicle race winners. Some use coreless motors (with no iron losses) and litz wire, others use iron cores (for a more efficient magnetic circuit) and big fat wire.