rad and coolant,

[Jeffrey Engel]

I don't think your control would have to be that precise.  How about 
using a PM motor geared down to give the torque required and a 
potentiometer as a position feedback.  You could either use an 'H' 
bridge to reverse directions or regulate one side of the motor to 6 
volts and use only two transistors on the other.  It shouldn't have 
to move often, so effiency shouldn't be a big factor.

=====================================
> Date:          Thu, 23 Oct 1997 08:26:00 -0500
> From:          dave.williams at chaos.lrk.ar.us (Dave Williams)
> Subject:       Re: rad and coolant,
> To:            DIY_EFI at coulomb.eng.ohio-state.edu
> Organization:  The Courts of Chaos * Jacksonville AR USA * 501-985-0059
> Reply-to:      diy_efi at coulomb.eng.ohio-state.edu

> 
> -> Well you could do that, but I was kinda thinking of a ball valve and
> -> a stepper motor, there's gotta be some out there already. It's also a
> -> lot easier from the packaging/plumbing standpoint, and I would think
> -> would afford infinite control within system capabilities.
> 
>  I'd love to find something like that.  All of the commercial valves
> I've seen take more torque than a reasonably-sized stepper can give, so
> it didn't look practical to cobble something up from pieces.
>                                                                                          
> 
> 
je
jengel at fastlane.net

     "I can resist anything but temptation"
                                  Mark Twain