goeduck
Super Star Member
Except when on a hill and the engine dies or is shut off. Then terminal velocity of the slope.
Traction Hydrostatic trasmissions and braking. (Hills)
- Thread starter rsl360
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MossRoad
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Not exactly. If the engine dies, the pump doesn't turn and it acts very much like a brake. The machine will roll slowly, very slowly.... unless a hose breaks!
Then it's back to ZOOM!
goeduck
Super Star Member
Not exactly. If the engine dies, the pump doesn't turn and it acts very much like a brake. The machine will roll slowly, very slowly.... unless a hose breaks!
Right by definition this would be terminal velocity for that tractor on that slope. Whatever the maximum speed is would be its terminal velocity? Yes? No?
MossRoad
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I think terminal velocity is the speed an object can attain while falling through a fluid.
This would exclude hydraulic braking and ground resistance, I think.
This would exclude hydraulic braking and ground resistance, I think.
4570Man
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In low range my tractor rolls a couple feet an hour shut off in a slope. Not exactly rolling rapidly out of control.
goeduck
Super Star Member
Well this link would seem to take into account slope and drag. I am not going to pretend to have followed the math.
Is there a terminal velocity equation for a slope instead of free fall? If there is, what is it? - Quora
MossRoad
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That formula is for sliding, not rolling and being held back by the hydraulics.
goeduck
Super Star Member
Sliding, rolling, let’s not stop to split hairs when a tractor is rolling down a hill.
VroomVroom
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Has anyone had a hydrostatic transmission slip into Neutral on a hill?
OP
rsl360
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I thought one thing we figured out here was that hydrostatic transmissions don't have neutral. Seems like you can look at them like a speed control, (and zero is a speed, which they will attempt to meet), or just look at it for what it is, an infinitely variable transmission system that cannot be taken out of gear. Of course, it's true that some hydrostatic transmissions have a gearbox connected to them. And it's common to call the whole assembly between the engine the rear axle a transmission. But this is really a hydrostatic transmission plus a gear box. And while virtually all gear boxes have neutral, a HST does not.
What are the takeaways here?
-If you have a tractor that has a HST, and no brakes, always keep the drive train in top shape. Failure of a coupling, or a hose, could have you sailing down a hill.
-Terramites have a parking brake, keep it working. Although it might not be the best way to stop a runaway, it's better than nothing.
-If you do have a gearbox somewhere in your drivetrain, don't disconnect your your drive train on a hill. (Neutral)