Re: (ET) linear actuator power steering?

[pieter <pvcl plitch com>]

Good thought.  The converted Yanmar compact tractor I referenced apparently 
uses an on-off-on momentary switch to do the steering.  This is simple, it 
works, no problem.  But I am so based by my thousands of miles behind a 
steering wheel that I would prefer a simulated "normal" steering 
system.  Yes - the idea of using an encoder on the steering shaft to "tell" 
an actuator controller how far to step the screw is far harder to implement 
than a switch and a screw.  But how cool would it be to have a 
"fly-by-wire" ET?

I understand what you are envisioning when you describe a zero turn radius 
ET.  This seems to be a major engineering challenge - way beyond what I 
will undertake!

By the way, my steering gear is worn too.  I have been told that a large 
punchout from a breaker box is almost a perfect fit as a spacer to take up 
the slack in the steering shaft.  I haven't tried it yet.



At 05:52 PM 6/30/2004, you wrote:
> Why not just a toggle switch to control the linear actuator right or 
> left.  If the switch was wired to brake the DC motor when off, the 
> actuator positioning would be pretty crisp (no drift).  Steering would be 
> like on a Dozer.
>
> My E20 has worn steering gears, I have been looking for a linear actuator 
> to replace the steering mechanism with.
>
> The other way to go would be to eliminate the entire drive train and 
> replace the front wheels  with 2 hub motors and 2 PWM motor controllers 
> and replace the back wheels with 2 swivel wheels.  Then the steering would 
> controlled by varying the speed of the 2 hub motors using a 
> joystick.  Essentially "zero steer" control.  No belts, no transmission, 
> no relays, and better steering control.
>
> Jim Leuba
>
>
> Herb Crary wrote:
>
> > A good source for all manner of items, including linear actuators, is:
> > http://www.herbach.com/Merchant2/merchant.mv?
> > This link is to their search page. I have been buying from them since i was
> > in college in the late 1940's. They had lots of WWII surplus then. They 
> > have
> > both new and surplus now.
> > Herb Crary
> > Boulder CO
> > E10M
> > ----- Original Message ----- From: "Pieter" <pvcl plitch com>
> > To: "Elec-Trak Tractor" <elec-trak cosmos phy tufts edu>
> > Sent: Monday, June 28, 2004 2:39 PM
> > Subject: (ET) power steering?
> >
> >
> > > All this discussion of using linear actuators as front or rear lifts got
> > me
> >
> > > thinking.
> > >
> > > My E-15 has a very heavy loader on it, and the steering is a real two
> > > handed job.  I was looking around the 'net for info on linear actuators to
> > > use for a lift and came across an article on an old Yanmar diesel tractor
> > > converted to electric.
> > >
> > > http://www.angelfire.com/ca4/renewables/tracpage.html
> > >
> > > Well - why not do the same thing to an ET??  He used a linear actuator
> > > controlled by a joystick of sorts to steer.  It would be a simple matter
> > to
> >
> > > place a linear actuator between the frame and a steering knuckle parallel
> > > to the tie rod.  I don't think too much force would be required, which is
> > > good because you want fairly fast response (screw travel), so leverage
> > will
> >
> > > be reduced.  There are a number of dish positioners that run on 36 volts
> > > and use a revolution counting circuit to stop at a predetermined
> > > position.  If the steering wheel ran an encoder that "told" the actuator
> > > where you were pointing it, the actuator would then move to that position,
> > > steering the front wheels.  A dish positioner would be very cheap to
> > > try.  The hardest part for me to design is the steering wheel encoding
> > > mechanism.  Any engineers out there?
> > >
> > >
> > >
> > > _______________________________________________
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> >
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