RE: (ET) Solid state controls

["Elie, Larry (L.D.)" <lelie ford com>]

Hydrostatic transmissions are 75 to 80% efficient.  Hydrodynamic 
(automotive type automatic) is 90%.  Gearbox is 95%.  So are belt drives.  
E20/I5 is very close to the feel of a hydrostatic transmission.  
Solenoids, switches and TrenchFET's are very nice controls to produce 
efficient motor control.  Most 'modern' controls do use FET's or 
TrenchFET's, but require a higher control line voltage to close the FET.  
I have a patent in a simple control without the higher voltage 
requirements.

Larry Elie


-----Original Message-----
From: SteveS [mailto:ssawtelle fcc net]
Sent: Monday, July 22, 2002 8:52 AM
To: elec-trak cosmos phy tufts edu
Subject: Re: (ET) Solid state controls


It probably was hydrostatic, many higher end mowers use it and they are
nice. I've been wondering what it would be like to couple the ET motor to a
hydrostatic transmission. I don't know much about them, though - I fear the
hydrostatic isn't very efficient, since I assume it must 'dump' pressure
when you are at less than full speed. I bet one of you can enlighten us on
this.

On solid state controls, what kind of electronic control would be
appropriate for the motor type we have (compound, right?).  Do you PWM the
armature current, or what? 'Course, as has been mentioned, the present
arrangement is real efficient - when the throttle is full on.

SteveS
E12S



----- Original Message -----
From: "Phil Trice" <pctrice purdue edu>
To: "Elec-Trak List" <>; <jbc_shop coate org>; "Christopher Zach"
<czach computer org>
Cc: "Phil C Trice" <pctrice purdue edu>
Sent: Monday, July 22, 2002 8:22 AM
Subject: RE: (ET) Solid state controls


> Chris & all,
> I have a data point to offer in this area. When I was in school, I worked
> for the city's parks dept, and had the opportunity to use a Toro
> Groundsmaster tractor. This machine was targeted for mowing around
> obstacles. It utilized a single pedal that controlled speed and 
> direction.
I
> think it utilized hydrailics, but gave very smooth control over the speed
of
> the machine, and made it very easy to change direction (to stop going
> forward, press the pedal as if going in reverse).
> I'm trying to think of a way to to replicate that efficiency of control 
> in
> my electric tractor. The real attraction for me is that there was no need
to
> stop the tractor to shift gears, no clutch, and no need to press a
separate
> brake. It was actually kind of a kick to drive, as I recall.
>
> -Phil Trice
>
> -----Original Message-----
> From: owner-elec-trak cosmos phy tufts edu
> [mailto:owner-elec-trak cosmos phy tufts edu]On Behalf Of Christopher
> Zach
> Sent: Friday, July 19, 2002 10:19 PM
> To: jbc_shop coate org; Elec-Trak List
> Subject: Re: (ET) Solid state controls
>
>
> Hm. I've thought about this, and for a tractor, I don't see any advantage
to
> an infinately variable speed control. In fact, I would consider it to be
> somewhat of a disadvantage.
>
> When mowing I like to set the speed to a quantum level and forget it. 
> With
> an infinite speed control, you never quite know if you're at the best
speed
> for mowing. Or plowing. Or tilling. With 8 motor speeds plus four gears
you
> have a range of 32 speeds between 0 and 9 mph. The greatest thing on the
E20
> IMHO is the cruise control lock-in.
>
> Then there's the efficiency. Running full field/full armature is the most
> efficient way to go with the elec-trak motors. Use the gears to modulate
the
> speed; don't lose 5%-10% of the power thru a controller (the relays and
> solenoids are probably >99% efficient).
>
> Also would need to make sure that any controller could *fully* support
> regen. The elec-trak does have significant regen, and dumpstering it is
> going to decrease your range and put a significant load on your brakes.
I've
> dropped regen on hills; the brakes have to work very very hard.
>
> Chris
>
>
>