(ET) (Fwd) Re: Ariens AMP Mower

["Ken Muldrew" <kmuldrew ucalgary ca>]

On 14 May 2009 at 11:28, David Roden wrote:

> However, an electronic motor controller is effectively a continuously 
> variable transmission without the inefficiency of hydro drive.  The
cost
> of 
> a small DC motor controller adequate for a garden tractor is certainly
> not 
> prohibitive, and much less today than it was 30-35 years ago.

Unless I'm misunderstanding the product description, the Ariens mower uses
a brushless DC motor (a three phase armature with permanent magnets on the
rotor and hall sensors for sequencing). It can't run without a controller
so variable speed and reversing are available at the outset with no 
significant additional cost. The torque vs. speed trade-off could be 
managed through dual windings in the armature or switching from WYE to 
DELTA configurations, but given the limited needs of a riding lawnmower, 
even this seems unecessary. I don't understand why the hydrostat is
there.

Ken Muldrew. 
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