Hydrostatic VS Fixed Displacement for a Zero Turn Mini Excavator

[cnicholls]

I have a surplus mini excavator (TMX Lineman) I picked up with no engine or pumps basicly its a rolling chassis with 2 hydraulic motors in the front and giant caster type wheels in the back.

I have the hydraulics figured out for the digging and auxiliary circuits so we wont get in to that in this discussion.

The original design used 2 pilot operated hydrostatic pumps (one for each motor). However, I have a surplus of large John Deere Gear pumps from a local combine/tractor grave yard. I have quite a few on hand along with several hydraulic directional control valves.

Is there a huge disadvantage to using directional control valves in a skid or tank drive configuration? Is there any equipment out their that drives this way?

I know hydrostatic system have less pieces, however would a system like this work?

 

[oldnslo]

two main problems with using fixed displacement pumps on hydrostic drives
1) speed control: Controlling the track or drive speed with varying loads is a real challenge. Also braking becomes a problem unless some form of brake valves are included in the circuit.
2) HP & heat generation: Since you are running a constant flow it has to go some where. At slow speeds and heavy loads this consumes a lot of HP and turns it into heat.

Answer is yes it will work, just will require some careful thought on circuitry and components to ensure that you don't have any run away potential and will climb & push with the force required.