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.
\----------------------------+----------------------------+ o_,
O_/ \ Ken Muldrew, PhD | Voice: (403) 220-5976 | <\__/7
<\__ \ Dept. of Cell Biology | Fax: (403) 270-0617 | | /
"\ L | University of Calgary | kmuldrew ucalgary ca | / /
< +-----------------------+----------------------------+ / /
Morning coffee recapitulate phylogeny L/
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