Smooth or notchy????

[yoodoo]

I have a few different motors and all go well but, a Castle I have is really hard to turn on the magnets (by hand) and a Toro is pretty smooth.all of them turn either notchy or smooth,all are new or ran once so I know they are good.

Question is,why are some smooth and others differcult to turn?

J

[Oh How Original]

Quality of magnets really and strength.

My understanding is, the more torquey it has, the stronger it will be to turn.

Imagine for example a highly tuned race engine, it would have lots of compression and be difficult to turn over.

At least, that's the impression I have gathering from my info.

One thing I've always found (by pure coincidence) is motors that are harder to turn, tend to cog a lot more.

My Castle ones cog bad but my HobbyWing don't.

Yet the HobbyWings perform better.

 

[turok007]

ok i have used castle items and they work well   but the lipos took a beating because of the very powerful magnets.  but i also used a novak setup that was more powerful but the motor turned very smooth.  and i got a lot more run time and power from the novak.

[Si Coe]

Technically speaking when switched off the only magnet in the motor should be the rotor. The coils shouldn't be magnetic (since no current is flowing) and whilst they are wrapped round an iron core the field ought to be quite weak. 

 

But in the real world I've had smooth and notchy motors that worked great, and smooth and notchy motors that didn't. I guess that there are a lot of other factors in motor design that matter much more. 

[Fly In My Soup]

The way understood it is

 

The more poles and slots a motor has, the more resistance ( notchy ) feeling a motor will have, since every time a pole on the magnet crosses over a slot it creates resistance.

 

So a 4 pole 18 slot motor will have more resistance than a 2 pole 10 slot, as more magnets pass over more slots in one rotation of the motor

 

At least that's my understanding of it, lmao

 

 

Edited May 14, 2017 by Fly In My Soup

[Fly In My Soup]

I also know that cogging will be increased if the stator windings are laid out in a distributed fashion as opposed to normally wound

 

Cogging torque in dc brushless motors comes from variations in magnetic field density around a rotor's permanent magnets as they pass the nonuniform geometry of the slot openings in the stator.

 

In applications such as servo systems and spindle drives, the pulsating speed that cogging generates can blemish machined surfaces or reduce position accuracy, thus making the issue worse with more usage

 

Also, other major factors affecting cogging torque include magnetic wave shapes, air-gap length, slot opening, number of stator slots and rotor poles, skewing, copper fill, pole pitch, flux distribution or density, magnet volume, and material weight.

Edited May 14, 2017 by Fly In My Soup