Re: [CAD_CAM_EDM_DRO] Re: Why gecko drives don't support DC brushless servo ? do they ?

On Mon, 09 Oct 2006 03:00:18 -0000, you wrote:

>There was some discussion some months ago about optimizing motors by
>offsetting the armature or brushes or some such to allow the motors to
>run better at some speed and/or direction.

>do you know if this is the case with these R/C type motors ?

Hi Dave

There are two types, both brushless, of the type we are discussing.

The most common and cheapest are not constructed like the motors we are
used to. The windings and stator are fixed, and the outer case, with
several magnets rotates driving the shaft! (like a PC cooling fan or CD
drive motor on steroids ;) They are known as outrunners. There's
hundreds on ebay.

The other, which is more expensive, is of conventional construction, the
majority of these seem to be six pole motors. The prices for some of
these are horrific. The windings vary to get anything from 600-6000+ rpm
per volt and commonly cost $200 upwards!

Most are "coggy" by design, to stop the prop freewheeling, or to allow a
folding prop to fold.

On the ones I've seen none had skewed armatures/rotors and it would be
very difficult to modify them. They tend to run equally well in either
direction so a gearbox can be used to drive a bigger prop at slower
speeds.

There are people who custom build motors, and no doubts they do motors
which are more efficient in one direction.

Steve Blackmore
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