Jump to content

Unofficial Home of Old Simplicity & Allis-Chalmers Garden Tractors

Hydro 101


Guest

Recommended Posts

Upon digging into the hydro-transmission of my Powermax I was struck by the simplicity (no pun intended) of the design. Are all garden tractor hydros basically the same or do some use other methods to generate hydraulic pressure?
Link to comment
Share on other sites

I'm talking about the hydrostat unit. Sunstrand calls it a hydro-transmission. So that's the name I used. I suppose one way to generate hydraulic pressure for the motor side of the hydrostat unit would be to use a gear pump. Are these ever used?
Link to comment
Share on other sites

Gear pumps are good for decent flow, up to around 20 GPM. Any gear pump is only good for around 2500 psi working pressure. The positive displacement pumps used on these tractors, and any other aplication, uses between 4500 and up to 6000 psi to operate. A gear pump would NEVER hold up under this pressure. There are lots of operateing principles and advantages to useing the positive displacement pumps/motors like this. The best one is the fact that the flow rate doesn't fluctuate depending on pressure like a gear pump and motor would.ie, when you go up hill at a certain amount and turn and come down hill the ground speed stays relitively the same. On a gear type system, like the older Cases used, it takes great amounts of oil flow to go up a hill and reqiures pulling the directional lever into slight reverse to keep it held back so it doesn't run away. Almost forgot, to answer your orriginal ?? yes, a lot of manufacturers use this type of setup for their mowers/tractors. It's very simple to combine the pump with a self contained piggy back motor. This elliminates lots of extra plumbing and hoses. This works a slong as only one motor is needed to drive some sort of transaxle setup. On a lot of industral and ag equipment mutiple motors are needed to drive 2-3-4-6 wheels independently. All off 1 pump.
Link to comment
Share on other sites

Guest
This topic is now closed to further replies.
×
×
  • Create New...