Minimum speed?

boogs · Aug 10, 2012

I just received my 3039h with a tiller, mower and box blade. Is there a minimum speed you can go with a hydrostatic transmission without it heating up?

LittleBlueTractor · Aug 10, 2012

I'm a gear guy, but I assume the slower you go the less the pump (and hydro system) is working, so the less the amount of heat generated. But I don't know nuthin' about HSTs. Looking forward to somebody that knows to give us the scoop on this one. You may have to post it up in the Hydraulics forum though.

jpm1 · Aug 10, 2012

Well boggs first of all welcome! I have 2 HST's, a Kioti DK35SE HST and a Mahindra 2810HST which are used hard. I mow a lot of acres a week and do mowing for others in my local area and last Saturday with temps near or at 100 degrees i mowed with my RD finish mower for 7 hours in low range with the cruise set at a creeping speed doing some heavy mowing with no problems. Kioti has 1560 hours and the Mahindra has 1200 hours with no trans. problems. Use them on a 72" brush hog tiller the same way. Keep in mind now, you might have different results but this has been my experience. . . .good luck . . .John

Guesseral · Aug 10, 2012

I am a gear guy also but. I think the HST being hydraulicly driven will heat up the same fast or slow because as you use the hydraulics the pump creats heat no matter what and that heat transfer to the metal housing, no different that the heat of using a gear driven trans transfers to the metal housing. Well that's my take on the matter, because it just makes sense to me. :confused2:

boogs · Aug 10, 2012

Thanx for the replies.

Gary Fowler · Aug 10, 2012

I have an HST and gear and I think that the faster you go the more pressure that is put on the pump hence the engine stalling if you put the pedal too far down where as just creeping only uses a little pressure. Flow might be the same coming out of the pump but the high pressure is what produces most of the heat. I would compare it to a gear drive in this way: Which puts more pressure on the engine pulling a load, running in high gear or low gear. I think the same is true of the hydrostatic, faster= more strain which means more heat buildup. You are likely to get more heat from turning the tiller than from moving the wheels.

CJONE · Aug 16, 2012

Gary Fowler said:
I have an HST and gear and I think that the faster you go the more pressure that is put on the pump hence the engine stalling if you put the pedal too far down where as just creeping only uses a little pressure. Flow might be the same coming out of the pump but the high pressure is what produces most of the heat. I would compare it to a gear drive in this way: Which puts more pressure on the engine pulling a load, running in high gear or low gear. I think the same is true of the hydrostatic, faster= more strain which means more heat buildup. You are likely to get more heat from turning the tiller than from moving the wheels.

Gary is correct, but the faster you go the more volume you put through the hydrostat assembly. Flow is speed, pressure is force.So the faster you go the more flow is required, the pressure is a result of resistance and the only way you will generate excessive heat is to go over the relief or if the unit is worn when going slow. Now where everybody seems to mess up is they don't run the engine rpm up and it is not good on the hydrostat to run under a heavy load at low rpm. Higher rpms 1800+ gives good charge pressure and more cooling. CJ