Re: (ET) Ariens AMP Mower

["David Roden" <etpost drmm net>]

> I do 99% of my work with it in two speeds ...

Not here!  My property is hilly, uneven, and broken up in to little 
islands 
of grass.  I appreciate being able to creep the machine at times.  Am I 
typical?  Probably not, but I'm sure I'm also not the only one.

When you're designing an electric tractor from the ground up, I agree that 
the cheap way to go is to bolt the motor into an existing design.  There 
are 
advantages to using mass-produced, proven components.

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.

> just reverse the armature with big contactors instead of fiddling
> around with the field. 

I don't understand why you suggest this.  Reversing the low current field 
in 
a shunt motor is almost a trivial task, requiring only a small relay or 
small semiconductors. It makes much more sense to reverse the field than 
to 
reverse the armature. This is one of the advantages of a shunt or sep-ex 
motor over a PM or series motor.


David Roden - Akron, Ohio, USA

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