HST Power Consumption

[xtn]

The difference there is that the geared tractor would still be able to spin its tires if they were 4 loaded AGs and he hung enuf extra weight to more than double normal tractor weight. The HST would pop its relief valve and sit there.
larry

Whoa there. How much power are you assuming? Given more traction than power the hst will eventually open a relief valve, while a gear unit will eventually stall the engine or spin the clutch. No tractor in the world will just keep spinning the tires regardless of traction level.

 

[John_in_TN]

What you just stated about parking made me thing of a factor where gear has a real advantage: If you run your battery down on a gear tractor you can pull it with another vehicle and get it started that way. Or it can be towed by putting it in neutral or pushing in the clutch. HST, now...forget about pulling those to get started. When my Deere was about 2 years old, the OEM battery failed (shorted) when I was 500 feet from the barn, and a rainstorm was heading this way. Had it been a gear tractor I could have towed it to the barn, but because it was a HST I had to replace the battery to get it started. Hmm this gives me an idea for a new thread.

Dosn't your tractor have a Neutral position on the Range selector? I agree you can't tow start it, but you should be able to tow it all you want to in Neutral.

 

[JDgreen227]

Dosn't your tractor have a Neutral position on the Range selector? I agree you can't tow start it, but you should be able to tow it all you want to in Neutral.

Good point, and when I had that situation I dug out my owners manual, QUOTE:

"IMPORTANT: Avoid damage. Push or tow machine for short distances only. MFWD remains engaged on eHydro and ePowrReverser models when the engine is turned off"

Further down in the steps you should take before pushing or towing, it lists "disengage the MFWD if equipped"

I would have had to make a number of turns on hard surfaces when towing the tractor that 500 feet, and that warning "MFWD remains engaged..." worried me as I didn't know if I could disengage it without the engine running. My interpretation may have been wrong, but I didn't want to risk any damage.

 

[Redneck in training]

Doesn't your tractor have a Neutral position on the Range selector? I agree you can't tow start it, but you should be able to tow it all you want to in Neutral.

That is correct. There are two neutral positions between each stage.

 

[SPYDERLK]

The difference there is that the geared tractor would still be able to spin its tires if they were 4 loaded AGs and he hung enuf extra weight to more than double normal tractor weight. The HST would pop its relief valve and sit there.
larry

Whoa there. How much power are you assuming? Given more traction than power the hst will eventually open a relief valve, while a gear unit will eventually stall the engine or spin the clutch. No tractor in the world will just keep spinning the tires regardless of traction level.

What 2 points are you extrapolating between. The 1st point is 1 in our test. All gear and most HST will spin at that weight multiple. I dont know the typical weight multiple for gear [we could figure it out since Gear HP has nowhere to go but ground and traction coefficient with AGs is ~1+/-]. I know from experience on several gear tractors that a 2+ muptiple is supported. It may be above 3 since I have never been able to overcome the HP in 1st gear regardless of 4loaded AGs, heavy counterweight, Loader lifting and pushing.
larry

 

[xtn]

What 2 points are you extrapolating between.

Well your previous statement was open ended.

If your conditions are such that an hst will relieve while a geared unit will spin the tires - as you set up in your example - then I don't see how one is any better than the other. Either way you're sitting still.

 

[IndyIan]

Well your previous statement was open ended.

If your conditions are such that an hst will relieve while a geared unit will spin the tires - as you set up in your example - then I don't see how one is any better than the other. Either way you're sitting still.

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.

 

[slowzuki]

I use my L5030 to jockey haywagons down the road several miles when haying, its not a speed demon with 8 tons behind it in high range, but it will hit its top speed fine. I also have a 100 hp tractor with a 25 mph road gear. It also feels very sluggish doing the same job, because even with my lighter, 300 hp pickup pulling the same wagons, its sluggish. Its just a lot of weight to get moving, and keep moving up hills.

Yes, a gear tractor could be slightly faster, and I'll agree, if it has a synchro transmission, is a better pick for this job.

Re underpowered cars and towing, I have to say, if its a good transmission cooler in it, I'd rather heat up some transmission fluid than burn up a clutch if there is a lot of starting/stopping to be done. Our Matrix is a 4 banger and first gear is setup for fuel economy, not towing. Trying to start on any kind of grade with a load just roasts the poor clutch. Once moving its fine.

In mid or high range though, you can put all the HP to the ground. But how many guys are running hay or grain wagons with a tractor like mine? Not many but there are some situations where 5-10% more in driveline losses would get annoying. Kind of like towing with an underpowered car, its easier on a manual trans than an automatic.

 

[slowzuki]

I can tell you what happens in a gear tractor when you overload it. Our previous MFWD had a nice slip clutch on the drop box output to the front axle. Most of the time this would slip and let the rear tires spin when you overloaded it, but sometimes it would strip the splines out of the driveshaft yoke. (IH 584, ZF front axle)

Our current "big" tractor, a MF5455, the previous owner tried to get up a steep hill in the winter with a bale of silage on the loader, tires loaded and implement on the back. It does not have a slip clutch for the front axle. It stripped the splines off the front input shaft to the front axle (Dana AG85 front axle).

The point is you can't just ballast a gear tractor until it spins.

What 2 points are you extrapolating between. The 1st point is 1 in our test. All gear and most HST will spin at that weight multiple. I dont know the typical weight multiple for gear [we could figure it out since Gear HP has nowhere to go but ground and traction coefficient with AGs is ~1+/-]. I know from experience on several gear tractors that a 2+ muptiple is supported. It may be above 3 since I have never been able to overcome the HP in 1st gear regardless of 4loaded AGs, heavy counterweight, Loader lifting and pushing.
larry

 

[MHarryE]

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.

 

[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.