Tractor Sizing HP Advice

[rScotty]

An HST transmission is a fluid pump.
The higher you set the engine speed, the more fluid it will pump, and, the more you press the directional pedals, the more fluid will flow from that pump to a hydraulic motor that is attached to the drive system.
The pump works with a swash plate. It's at a 90 degree angle when not moving. You step on the pedal a bit, and the angle changes and it pumps fluid. The more you step on the pedal, the greater the angle of the swash plate, the more fluid it pumps and the faster you go. If you let your foot off the pedal, the swash plate returns to 90 degrees and the tractor stops moving. If you step in the reverse pedal, the swash plate angles in the other direction, and pumps the fluid backwards, which turns the hydraulic motor backwards, which turns the drive system backwards.

Fluid cannot be compressed. So when you let off the pedals, the fluid cannot flow through the system, and it effectively locks the machine in place.

So going down a hill, you want your engine RPMs up as high as they'll go, so you have more responsive hydraulics, which = responsive hydraulic braking when you let off the pedal. It won't freewheel down the hill and it shouldn't pick up speed. You should be able to let off the directional pedals and it will stop itself.


In fact, some machines are kinda brutal as to how fast they'll stop if you whip your foot off the pedals. My old IH2500b had a circuit to soften the hydraulic braking effect.

My current machine is all hydraulic and it doesn't even have brakes; only a parking pin.

Hope that helps explain it a bit. :confused3:

MossRoad, that's a great explanation of a basic single range variable speed HST transmission. And theoretically all any tractor needs is just a basic single range HST transmission. But that's theory. Lucky for us gadget guys, there's there's a lot more that a HST transmission is capable of doing. This may sound like a adv. but it's not; transmissions fascinate me and I haven't seen one yet to compare to Kubota's HST+.

The Kubota HST+ transmission can be operated manually just like MossRoad explains - but it also has a fancy computer aided mode.

Now HST+ doesn't have to be operated in fancy mode. It can be worked all day just using the HST pedal and hand throttle exactly as MossRoad explained. Used that way, the HST+ will stay in a single range & the throttle is adjusted manually. I've done it that way a few hours just to remind myself how HST used to work when it first came out. But HST+ also has some more features.

1. To start with, HST+ has 3 selectable ranges plus a selectable high/low in each range. THe ranges are always manually selected, but the High/Low can be manual, manual override, or let the tractor choose.
2. The tractor will automatically look after itself with varying loads if the operator wants it to. Push a button on the dash, and the HST+ does this by comparing HST pedal position against engine RPM. It will then automatically advance the throttle to match the load, apparently it will even automatically shift between high and low range if needed.
3. Anytime it is in load sensing mode if there is no load, then the tractor automatically returns the engine to idle. I sure like this. On one brand of tractor I had to move a lever to idle every time I let off on the HST pedal. With HST+ this happens smoothly and automatically. All user selectable through that same dash switch.
4. Finally the hydraulic braking effect of any HST tranny that MossRoad refers to is adjustable with the HST+. There is a dial on the dash that allows you to vary the HST response rate from slow to fast. Best to tighten the seat belt before setting it to "fast".

My hat's off to those guys....Kubota made one very clever transmission.
rScotty

 

[jeff9366]

This thread is germane to your search:

http://www.tractorbynet.com/forums/...ons/384070-need-tractor-advice-pics-land.html

 

[Tractorable]

This thread is germane to your search:

http://www.tractorbynet.com/forums/...ons/384070-need-tractor-advice-pics-land.html

"The doggone German's ain't got nothin to do with this!"

- Sherriff Buford T. Justice, Smokey and the Bandit....

 

[terryknight]

"The doggone German's ain't got nothin to do with this!"

- Sherriff Buford T. Justice, Smokey and the Bandit....

hahaha love that movie

Don't you hear good, this is Sheriff Buford T Justice OF TEXAS

I hear perfectly, the fact that you're a sheriff is not germane to the situation.

 

[TomIre]

Can't tell you how much I appreciate all the input and your time here.
I've revisited dealers today. In part based on dealer response and location I've settled on two very similar tractors.
Mahindra 2638 (38 hp) and Kioti CO 3510 (35 hp), in part due to budget, etc. The Mahindra is a slight favorite at roughly 20% heavier (hills again!) for 10% more money. May come down to how much more aggressive the dealers can be on price.

 

[kenmac]

I too use my 52" Ferris IS 750 to mow my 6 acres of pasture sometimes and I can do it faster than I can with my 7 foot bush hog and get everything even right up against the trees. I cant get the tractor in to some of the places with trees. The Ferris is also smoother on the rough ground than the tractor.

I thought I was the only onewith a rough pasture. I understand why they put a seat belt on the z turn. It keeps me in the seat when mowing the rough pasture @ wide open speed

 

[MossRoad]

MossRoad, that's a great explanation of a basic single range variable speed HST transmission. And theoretically all any tractor needs is just a basic single range HST transmission. But that's theory. Lucky for us gadget guys, there's there's a lot more that a HST transmission is capable of doing. This may sound like a adv. but it's not; transmissions fascinate me and I haven't seen one yet to compare to Kubota's HST+.

The Kubota HST+ transmission can be operated manually just like MossRoad explains - but it also has a fancy computer aided mode.

Now HST+ doesn't have to be operated in fancy mode. It can be worked all day just using the HST pedal and hand throttle exactly as MossRoad explained. Used that way, the HST+ will stay in a single range & the throttle is adjusted manually. I've done it that way a few hours just to remind myself how HST used to work when it first came out. But HST+ also has some more features.

1. To start with, HST+ has 3 selectable ranges plus a selectable high/low in each range. THe ranges are always manually selected, but the High/Low can be manual, manual override, or let the tractor choose.
2. The tractor will automatically look after itself with varying loads if the operator wants it to. Push a button on the dash, and the HST+ does this by comparing HST pedal position against engine RPM. It will then automatically advance the throttle to match the load, apparently it will even automatically shift between high and low range if needed.
3. Anytime it is in load sensing mode if there is no load, then the tractor automatically returns the engine to idle. I sure like this. On one brand of tractor I had to move a lever to idle every time I let off on the HST pedal. With HST+ this happens smoothly and automatically. All user selectable through that same dash switch.
4. Finally the hydraulic braking effect of any HST tranny that MossRoad refers to is adjustable with the HST+. There is a dial on the dash that allows you to vary the HST response rate from slow to fast. Best to tighten the seat belt before setting it to "fast".

My hat's off to those guys....Kubota made one very clever transmission.
rScotty

Yes, things are getting pretty darn amazing when you start adding computer control. There are some machines that do it mechanically, as far as adjusting the throttle to the load. Saves a lot of fuel over the life of the machine, as well as wear and tear.

However, we now also have to add up the costs of those features, and can we afford them.... hahaha

 

[Code54]

You want to be in the 40hp-60hp frame size, whatever make and model you consider. Highly recommend HST, just easier all around. :thumbsup:

100% agree!

 

[shaeff]

While I agree with most points in this thread, I will say there are upsides to more horsepower in the smaller frame tractors. May have been mentioned but I didn't thoroughly read every post.

Everyone keeps saying that without the weight of a big frame machine that the extra power is wasted. If you're brush hogging, I disagree. For dirt moving and ground work, yes, weight helps a lot, but if your primary use is brush hogging then extra power to spin a larger unit would come in handy.

More power also lets you get through thicker brush without bogging down.

Just something else to consider. Just make sure you have enough weight out front to keep the nose down!

 

[aczlan]

While I agree with most points in this thread, I will say there are upsides to more horsepower in the smaller frame tractors. May have been mentioned but I didn't thoroughly read every post.

Everyone keeps saying that without the weight of a big frame machine that the extra power is wasted. If you're brush hogging, I disagree. For dirt moving and ground work, yes, weight helps a lot, but if your primary use is brush hogging then extra power to spin a larger unit would come in handy.

More power also lets you get through thicker brush without bogging down.

Just something else to consider. Just make sure you have enough weight out front to keep the nose down!

In the same vein, I occasionally do some brushhogging for the welding shop down the road with our L3830. He also has had someone with a Ford 4000 (or similar size) tractor, there are many of the softer areas where the lighter (and 4 wheel drive) L3830 will float through and but the heavier 2 wheel drive Ford would sink in and get stuck.

Aaron Z