Question about Hydraulic Pump Control

[Wyatt Williams]

I'm very new here and don't quite know the rules, so my apologies if I break any of them, but I was wondering if any of you guys could help me with a couple questions I have.
1) What sort of joystick would you use to control this pump to allow the two piston pumps to control 4 wheels kind of like a 360 turn lawn mower?

https://www.surpluscenter.com/Hydra...Pump-Casappa-Hydraulic-Triple-Pump-9-7705.axd

2) Using that pump I want to power four hydraulic pumps to spin 4 wheels and so far I have picked this pump to use

https://www.surpluscenter.com/Hydra...Hydraulic-Motor-276090W3114AAAEG-9-8837-B.axd

do you think that this pump and motor combo will work well to power a four wheel drive lawn mower?
Thanks for any answers that you are able to give. I am a total hydraulics noob and any help goes a long way.

 

[waross]

Study up on hydrostatic drives for a serious vehicle.
For best control use two hydrostatic pumps, direct connected.
The control sticks will be connected by linkage to the control levers on the pumps.


Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[tombezlar]

Thanks!
It works for me too!

 

[Wyatt Williams]

We have been looking at hydrostatic drives and that is why we were thinking about using that dual pump setup linked.

https://www.surpluscenter.com/Hydra...Pump-Casappa-Hydraulic-Triple-Pump-9-7705.axd

That pump setup has two pumps on it so we were planning to link one to the right drive side, and one to the left drive side. We are now trying to find the best way to link a individual servo control style joystick to drive the unit.
We cannot use linkage drive similarly to most zero turn mowers because it has to be controlled by one single joystick for driving.

 

[SwinnyGG]

Planes were flown using a single joystick to control multiple degrees of freedom well before electronic servo control existed.... That requirement does not eliminate a mechanical system.

 

[Wyatt Williams]

So how would you suppose I connect both linkages to control the two different pumps with one joystick? Also, looking at the pump that I linked, do you know of a specific single joystick to control it?

 

[waross]

Some skid steer loader use a "Tee Stick".
Forward is forward on both, backwards is reverse on both, twist to turn.
Old school:
Near the bottom of the control stick is a spur or pinion gear.
On each side of the pinion gear is a rack gear.
Moving the stick forward or back moves both rack gears forward or back, operating the pump controls.
Twisting the stick turns the pinion gear and one rack moves forward and the other moves backwards.

State of the art:
The joy stick has two variable resistors, one for and aft and one side to side.
The for and aft resistor generates a signal that controls pulse-width-modulation of both hydraulic valves.
The side to side resistor generates a signal which adds a positive bias to the signal for one side and a negative bias for the signal for the other side.

For a straight joy stick, the pinion is free to turn on the stick shaft, but is extended and also engages a fixed cross rack gear.
Moving the stick from side to side causes the fixed rack gear to rotate the pinion gear with the result that the other rack gears are moved in opposite directions.
Hint, position the fixed rack at the pivot of the stick.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[SwinnyGG]

So how would you suppose I connect both linkages to control the two different pumps with one joystick? Also, looking at the pump that I linked, do you know of a specific single joystick to control it?

The goal of being a student is to learn - we aren't going to design this thing for you.

You aren't going to be able to just buy something off the shelf; you'll need to design and fabricate.