What makes a motor hard to spin?

[kazuaki]

I am curious about something I've noticed with my brushless motors. I was used to the stock VXL motors that could be easily spun by hand. When I got my Neu 1112/2D I was surprised at how extremely hard it was to spin. It had the very distinctive 12 notches as it spun and required quite a bit of effort to turn by hand. I figured this is just the way a "high power" motor is. Yesterday, I got my TeknoRC Neu 1512/2D. It is actually very easy to spin by hand. You can still feel the 12 notches in the rotation, but seems much easier to spin than the 1112. Can somebody help me understand what this all means?

[suicideneil]

Its a commonly asked question, and the simple answer is down to the design of the motor- slotted vs slottless.

Slottless motors like feigaos and hackers are much easier to spin by hand compared to slotted stator motors like neus and medusas.

The slots on those motors foucus the magnetic field much more intensly, creating a defined notchyness as it rotates; slotless motors dont focus the magnetic field in the same way, so you dont really feel the rotor (magnets) aligning to the windings inside the motor as you spin it.

The Tekno motors are slotted stator designs, but the slots are spaced differently giving a less pronounced feeling of notchyness.

[zeropointbug]

Yes, precisely.

Also, the difference between the cores of slotted and slott-less motors are:

Slotted: Has coils wound in and around iron 'slots' that run length wise the motor, which creates the defined notch when you turn the shaft.

Slot-less: Has the coils wound in and around themselves, and compared to a slotted design, I believe they use more copper. There is only an iron 'blanket' around the coil to help intensify the field when running, and to shield components around the motor from intense AC magnetic fields.

[kazuaki]

So is the feel any indication of the power of the motor?

[aqwut]

Originally Posted by kazuaki

So is the feel any indication of the power of the motor?

no, I wouldn't think so...

[zeropointbug]

LOL Nope, no sir. It has nothing to do with how much power it's capable of, however, a larger motor will obviously have more 'resistance' than a smaller motor, so in that respect yes; but the power is limited by the stator really, you can only get so much power out of a given amount of copper material, at least according to the design theory of a DC brushless motor.

[BrianG]

kv has an effect as well since it reflects the number of coils there are...

And if you think a motor is difficult to spin, try tying all three phases together and then give it a spin.

[kazuaki]

It never ceases to amaze me how much good info there is on this forum. Thanks again. Hopefully someday, I can be more of a contributor than a consumer :)