[Vwdiesel] OT: Joystick hydraulic control

[lbaird119 at aol.com]

Nothing much diesel about this other than it's surrounded by diesels on the orchard!  :-)
  We have 4 1/2 Groenig Orchard Apes.  They're a 14' vertical reach, boom, man lift with 3 wheels (two drivers) that are independently driven by Sunstrand "transmission" hydraulic pumps and motors.  Currently, two boat control type cables run to each pump volume control from a basket mounted joystick.  Each controls forward and backward for each wheel, allowing one direction, slow turn, rapid turn all the way to one turning each way to spin.
  The cables attach to a lever which is on the shaft.  There is really no center other than exact position so "creep" is a problem most of the time.   40 years of wear, old cables, weakening return springs and stiff cables have me at a point of repair on most of these.  
  I got to thinking that we have the technology, I can rebuild them...  This time with fly by wire, using a joy stick, controller and servo motors (I assume, since I know NOTHING about this area of  expertise.)  
  Anybody here know of something I can borrow from or scratch build?  I just don't know where to start, what I'd need etc.
  I don't think the motors would need a LOT of pull since most of the resistance is the centering spring (about 1/4 turn of a 1/4-28 bolt goes from forward to backward) and the cables.  The joystick would need to be fairly indestructible or be able to attach something to the existing, steel one.  It'd definitely need a slow movement and either progressively faster as the stick is moved or two speed ranges.
  Fun project if I can get the right parts the first time.  Next is replacing the 3 chains and reduction gears with a gear reduction unit.  That's a bit more major modification and a good, non creeping controller would make that less of a necessity.
   TIA!!!
    Loren