HST Power Consumption

[SPYDERLK]

I guess in theory you could add more weight [or chains etc] to the geared tractor and either push more or break it... I know if my hst started "relieving" itself in low range under almost conditions and I was stuck, I wouldn't be a happy camper.

Exactly. I run into that sometimes pulling a heavy load with the BX - not stuck, just wont go up the hill or spin ... all power thru the relief into the sump. Frustrating.
larry

 

[beppington]

My Kubota Grand L brochure says that for every model that offers both HST & gear transmissions (3240, 3540, 3940, 4240 & 4740), the PTO power is 1.5 HP less in the HST model than the gear model.

So, if I'm interpreting it correctly, for Kubota Grand L's it appears that the HST power consumption is an additional flat 1.5 HP more than the gear model, rather than a percentage.

(The 3 other Grand L's offer: 5040 = GST only, 5240 & 5740 = HST only)

 

[schmism]

Exactly. I run into that sometimes pulling a heavy load with the BX - not stuck, just wont go up the hill or spin ... all power thru the relief into the sump. Frustrating.
larry

Thats a function of the poor design (or designed capability) with your model. My 3 ranged HST in low has spun the tires or the engine has bogged down before the main relief has started to open. I only hit my relief in med and high range. (ie my HST gearing is designed as to never hit the relief in low gear, something else is the limiting factor, either engine power or traction)

But your complaint is common among 2 range HST owners across various brands.

 

[slowzuki]

Our MF has a wet disc clutch, it goes to released state after about 5-10 minutes of the tractor being turned off. No pull starting it like you say. There are a few wet clutch tractors without reversers, can't name one right off, but they might be able to pull start?

Most Kubotas need power to shut off, like bigger ag tractors.

I am a bit curious how the tractors with wed disk clutches are capable of being pull started while a hydro can't. Seems like the came conditions apply. You need hydraulic power to engage the clutch and if the tractor isn't running, you don't have hydraulics unless the engine is running. Okay, granted most of the CUTs have old technology dry clutches. So hydro's like my L5740 has a pump locked by hydraulic pressure when stopped so unless you shift to neutral or hold down the dry clutch pedal, it will only move what leakage allows. Our power shift Deere's free wheel when the engine is off so they have a PARK position on the shift control just like a automobile automatic. But even if I got my L5740 to turn over I need power to the injection pump because I do believe I have a power to run, not power to stop, FIP control.

 

[RaydaKub]

If you run your battery down on a gear tractor you can pull it with another vehicle and get it started that way.

Our yard had a small road ditch on one side of the driveway. We used to park our old Model A JD on the top slope and leave it in road gear if the starter or battery were acting up. Let it roll 1/2 way down, jam the clutch in (hand clutch) and it would be running by the time you hit the bottom.

 

[Redneck in training]

My HST will spin wheels in low gear even at 1800 rpm, in mid gear it will also spin tires but at 2300 rpm, below 2200 the engine stalls, never tried that in high gear. I have never noticed my HST going to relieve. All while the tractor has 450# box blade on 3PT.

 

[SPYDERLK]

Thats a function of the poor design (or designed capability) with your model. My 3 ranged HST in low has spun the tires or the engine has bogged down before the main relief has started to open. I only hit my relief in med and high range. (ie my HST gearing is designed as to never hit the relief in low gear, something else is the limiting factor, either engine power or traction)

But your complaint is common among 2 range HST owners across various brands.

My HST will spin wheels in low gear even at 1800 rpm, in mid gear it will also spin tires but at 2300 rpm, below 2200 the engine stalls, never tried that in high gear. I have never noticed my HST going to relieve. All while the tractor has 450# box blade on 3PT.

I doubt that would be the case if you doubled the weight of the tractor. My 7520 with FEL but unloaded AGs would spin at 800 rpm idle. Add 5000# and it needs about 1800rpm to hold a spin - but would even still spin a little before it stalled at lo idle.
larry

 

[Redneck in training]

The point is that HST is easy to use, it is hard to abuse, beats gear in mowing around obstacles, FEL work and anything that requires varied speed while maintaining PTO speed. When I need to plow my fields I will need much bigger tractor anyway. For what I do HST is hard to beat.

 

[xtn]

I guess in theory you could add more weight to the geared tractor and either push more or break it... I know if my hst started "relieving" itself in low range under almost conditions and I was stuck, I wouldn't be a happy camper.

A clutch has some limit of torque that it will transmit before slipping, and a hydraulic drive system has some limit of torque it can transmit before relieving. Although the component costs and efficiency are different, either system could be designed to transmit just as much as the other before giving up the ghost.

There is no inherent reason an hst must give up sooner than a clutch as was previously implied by Spiderlk. It may be the case in his BX and some other machines, but it is not an inherent quality.

xtn

 

[DK35vince]

A clutch has some limit of torque that it will transmit before slipping,

Which should be well above the HP the engine can produce.
A properly working clutch should never slip before the engine runs out of power.