let's talk about hydrostatic

[joshuabardwell]

One thing to point out is that small tractor HST systems are happiest when run at high RPM. At middle RPM, my tractor doesn't make much power and bogs easily. I do all my work above 2000 RPM. So the idea of using throttle to adjust power or torque is a bit off, in my experience. Maybe on larger equipment it's different.

 

[Piston]

I'm having a hard time understanding exactly how the torque converter works? How does it multiply the power? I recently read about a new UTV that uses a torque converter transmission, as opposed to Kubota's HST type, and they said they don't need as much power to get a lot of torque because the torque converter increases torque as needed? How's that work?

 

[diesel lover]

I'm having a hard time understanding exactly how the torque converter works? How does it multiply the power? I recently read about a new UTV that uses a torque converter transmission, as opposed to Kubota's HST type, and they said they don't need as much power to get a lot of torque because the torque converter increases torque as needed? How's that work?

If you know how a water wheel works then you can understand how a torque converter works! All automatics use a torque converter for many reasons. They are very strongly constructed.

Imagine two household fans, one is off and one the power is on. What happens when they are both face to face? The air is transfered from the powered fan to the off fan. The powered fan is turning faster than the fan that is being turned like a windmill. So in this way you are building torque. Torque from not moving at all is when the most torque is provided. Its common for cars to have a 2.5:1 ratio and large trucks/ medium duty trucks to have a 3:1 ratio.

Now inside your torque converter your power is being transfered from one assembly to the other by transferring automatic transmission fluid! It can get 10x more descriptive and complex than this but I am trying to keep it simple. When your TC locks up then the entire assembly connects mechanically. This is a 1:1 ratio. Speed from the crankshaft is equal to the speed at the input shaft of transmission for fuel economy. Tc lockup saves fuel by lowering engine rpms

 

[RickB]

Oh so backhoes and pay loaders do use a torque convertor? Must be a very large and strong torque convertor such as large truck allisons

What is the drive train in a payloader/ backhoe behind the torque convertor? Is it made of large planetary gears like an automatic and that's why you are able to shift between 1,2,3 and 4 on the fly at any time you want ?

Most loaders & backhoes use torque converters with manual transmissions behind them. Many use torque converters with powershifts behind them. A few might use hydrostatic transmissions. Without discussing specific brands and models,it's hard to have a meaningful discussion. I'm not qualified to be much more specific than that.

 

[diesel lover]

Most loaders & backhoes use torque converters with manual transmissions behind them. Many use torque converters with powershifts behind them. A few might use hydrostatic transmissions. Without discussing specific brands and models,it's hard to have a meaningful discussion. I'm not qualified to be much more specific than that.

Thanks rick B! That makes a lot of sence because all construction equipment from brand to brand is different.

So can anyone tell me if a 4wd tractor with hst can still be used realistically to pull and push things? I would also be using this to pull vehicles out of the snow and down trees etc. With light pedal application, medium throttle, and lowest range. Light application of forward pedal because that will build most torque

 

[art]

I've watched hydro's pull things that larger gear drive tractors only spun into the ground trying to move. I will say that knowing how to operate the tractors is a big plus.

 

[arlen4720]

Thanks rick B! That makes a lot of sence because all construction equipment from brand to brand is different.

So can anyone tell me if a 4wd tractor with hst can still be used realistically to pull and push things? I would also be using this to pull vehicles out of the snow and down trees etc. With light pedal application, medium throttle, and lowest range. Light application of forward pedal because that will build most torque

A hydro will push or pull just as good as a gear tractor... even better because you will always have the right "gear". If you were plowing all day long, the gear tractor would have better fuel economy since the hydro tranny robs 10% (or so) power.

 

[V1Rotate]

Arlen 4720 Thanks for separating the differences between automotive/ large truck automatics and hydrostatic. I was only com pairing the two with what I know and how they both use fluid to mulitply torque.

Very good explanation guys!!! Everyone that I haven't talked to doesn't know. Well bingo!!!! So the slightest press on the pedal and medium throttle provides maximum torque for pulling power!! I will need to know because I am shopping for a 4 WD tractor for my needs in a year or two. Only have owned manual trans tractors. I'm highly considering a hst tractor after all this cooperation of construction equipment. I want something with a fel and maybe to work in short small spaces completing task.
It makes perfect sence that highest torque is at the lowest spot on the pedal and as speed increases on the pedal torque decreases as will most drive train applications.

I understand hydraulics quite well because we have 115 forklifts at work and their hydraulic systems need repaired. Steering is acomplised by an orbitor- a motor/ rotational valve that transfers the rotational movement from the steering wheel to a hydraulic cylinder that controls steering wheels.

Also our highway plow trucks are hydraulicly powered. Our top kick has a conver belt in the bed that feeds a spredder. Both of these are powered by a fixed displacement motor

If you are going to use that tractor for loader work a HST would be a great choice. It is so much easier when you are constantly going from forward to reverse.

 

[Piston]

If you know how a water wheel works then you can understand how a torque converter works! All automatics use a torque converter for many reasons. They are very strongly constructed. Imagine two household fans, one is off and one the power is on. What happens when they are both face to face? The air is transfered from the powered fan to the off fan. The powered fan is turning faster than the fan that is being turned like a windmill. So in this way you are building torque. Torque from not moving at all is when the most torque is provided. Its common for cars to have a 2.5:1 ratio and large trucks/ medium duty trucks to have a 3:1 ratio. Now inside your torque converter your power is being transfered from one assembly to the other by transferring automatic transmission fluid! It can get 10x more descriptive and complex than this but I am trying to keep it simple. When your TC locks up then the entire assembly connects mechanically. This is a 1:1 ratio. Speed from the crankshaft is equal to the speed at the input shaft of transmission for fuel economy. Tc lockup saves fuel by lowering engine rpms

Thanks for the analogy.

 

[joshuabardwell]

I've watched hydro's pull things that larger gear drive tractors only spun into the ground trying to move. I will say that knowing how to operate the tractors is a big plus.

A hydro will have plenty of power. It's a tractor, after all. The HST loses a small amount of power compared to a gear, but I don't think there's a new tractor sold in America today that won't spin its wheels. So at that point, what difference does it make? You're not getting power to the ground anyway! The part about knowing how to operate it is important, though. Folks who think of the HST pedal as a gas pedal want to go faster and push the pedal down harder. This has the exact opposite effect. The transmission ends up with LESS torque and the engine bogs down more. When an HST is bogging down, the thing to do is let UP on the pedal, not push down. If you have to, shift to a lower gear range. Once you figure that out, you will be fine.