HST Power Consumption

[CJONE]

OK so I finally get enough money together to buy the 45HP tractor that is recommended for the range of jobs on my size acreage.

Then I find out that 9 to 13.5 HP will be consumed by a HST transmission.

That's OK ; just spend even more cash to size up to a 55 to 60 hp to accommodate that loss of power.

But wait there, that size of machine ( HST or Gear) is, for me, just too large to work in those tight places: the narrow creek crossings and tree plantings that separate large open fields.

Firstly, I want the HP I need but I also want a size machine that can be operated efficiently and conveniently in a fair range of conditions.

If you run the HST at lower flow/pressure the efficiency increases so don't sweat it. I was just tring to make a point that a HST will use more than 1.5HP. CJ

 

[CJONE]

I'd love to see some proof of this.

See post #51. Also why is there either a dedicated HST cooler or a larger one with a HST equipped tractor. Simple answer, something has to be done with the added heat generated by the HST, The heat was generated by lost HP. With all this being said give me a HST over gear anyday. CJ

 

[CJONE]

I don't know if anyone else has noticed this but with my HST when I start the engine and it's running at a fast idle 1200~1400 rpm) if I move the loader or raise the 3pt and put a load on the hydraulic pump the motor will load down. It doesn't matter how slow I try to raise the loader it still loads the motor. But when you use the HST it doesn't unless you push the HST pedal to the floor (which would be like trying to drive in top gear at idle in a gear tractor. Just an observation.

Cold fluid in the hydros takes more hp to raise a implement. A hydrostat will only use as much HP as needed to get the job done. Put the hydro in high range and it will lug the engine with just a little bit of pedal. CJ

 

[SPYDERLK]

The hst pump/motor combination, separate from any geared range mechanism, is infinitely variable within it's own range. So if you push the pedal down 1/3, for example, you are getting an "effective" gear ratio that is 1/3 of the highest available. (The available range can be played with by specifying different displacements for the pump/motor.) So effectively by moving your foot you are choosing an input/output ratio.

The "safe" limit in a hydraulic system is mostly determined by how much you want to spend on the robustness of parts. If you want to go all out and use super strong hoses, fittings, coolers, valves, pumps, etc., then you can use a relief that is much higher.

Combine those two facts and the result is that an hst system can be designed to put down as much torque as you want and effectively geared as low as you want. You want enough torque on the ground to slowly spin the treads of the biggest track hoes... it can be done. Maybe your BX can't do deliver as much torque as its geared twin. But please stop suggesting that there is some quality inherent in hst systems that automatically prevent them from ever transmitting as much torque as a geared system can. After all, a gear box must be engineered to handle some design goal amount of torque too, and as it can be, so too can an hst system.

xtn

+1 CJ1

No. Designed for any given maximum sustained force application and with customary safety factors for each, the gear will always be able to work beyond the point where the HST will not. -At the point where the HST cannot make its wheels turn to get you out of the hole [traction assumed], the identical gear platform having 10% less HP will get you out. - The issue is that direct gearing makes one for one use of all energy stored and produced by the spinning engine whereas at limit the HST flushes it thru a valve to sump. The HST must have this automated safety because of the variable pump. It camouflages how much pressure is being produced by allowing the engine to seemingly spin freely. This is inherent. With direct gearing you are quickly aware when the trans is working hard because the engine tells you. Safety factor there is just component strength built in as some multiple of full engine torque input to the gear train. Probably about 3X.
...-2.
larry

 

[CJONE]

No. Designed for any given maximum sustained force application and with customary safety factors for each, the gear will always be able to work beyond the point where the HST will not. -At the point where the HST cannot make its wheels turn to get you out of the hole [traction assumed], the identical gear platform having 10% less HP will get you out. - The issue is that direct gearing makes one for one use of all energy stored and produced by the spinning engine whereas at limit the HST flushes it thru a valve to sump. The HST must have this automated safety because of the variable pump. It camouflages how much pressure is being produced by allowing the engine to seemingly spin freely. This is inherent. With direct gearing you are quickly aware when the trans is working hard because the engine tells you. Safety factor there is just component strength built in as some multiple of full engine torque input to the gear train. Probably about 3X.
...-2.
larry

I have never been there yet, the HST at very low speeds, lower than a gear tractor will go. [unless it has a very deep reduction] Will bury itself. When the relief opens you still are building pressure at the relief setting so the engine tells you as you said by listening to it. As far as direct gearing being 100% efficient, no not hardly. It still generates heat and that is from HP being wasted to friction. Is a gear trans more efficient, you bet. Easier to run, no. More durable, depends on the operator. So it all comes down to operator preferance. CJ

 

[xtn]

No. Designed for any given maximum sustained force application...

I rest my case.

Yes, due to inefficiencies you will need a more powerful engine with hst, but as a drive line system including the engine, either system type can be designed to produce X maximum power to the ground.

So please specify exactly which part of my previous post you are saying "no" to.

xtn

 

[SPYDERLK]

I rest my case.

Yes, due to inefficiencies you will need a more powerful engine with hst, but as a drive line system including the engine, either system type can be designed to produce X maximum power to the ground.

So please specify exactly which part of my previous post you are saying "no" to.

xtn

Where you said inherent. Design for design to a force spec the gear will stop after the HST. Also, I said nothing about 100% efficiency. At this level of discussion I regard std mechanical inefficiency as assumed. Only where special situations exist need they be drawn apart.
larry

 

[crazyal]

OK so I finally get enough money together to buy the 45HP tractor that is recommended for the range of jobs on my size acreage.

Then I find out that 9 to 13.5 HP will be consumed by a HST transmission.

That's OK ; just spend even more cash to size up to a 55 to 60 hp to accommodate that loss of power.

But wait there, that size of machine ( HST or Gear) is, for me, just too large to work in those tight places: the narrow creek crossings and tree plantings that separate large open fields.

Firstly, I want the HP I need but I also want a size machine that can be operated efficiently and conveniently in a fair range of conditions.

There's a real difference between real world and theoretical differences. In the real world there are very few times where you notice a difference between the two power wise. Most times I've seen a tractor that had so much traction that it couldn't spin the tires yet enough power not to stall, guess what happens? The front end lifts off the ground, lots of YouTube videos. When it can't it spins the wheels or stalls the engine.

For the very few times where the gear tractor could keep moving without spinning the wheels. All one would need to do is slow down a little with an hst and hp will not be an issue. That's why people always say that gear tractors work best for things like pulling a bottom plow. However most people are willing to trade off that advantage for all the hst advantages.

 

[dusty3030]

HST is the work of the devil. The whine of the HST is actaully the banshee scream of beezlebub. Clutches make you tired and humble so you will stay out of mischief I tell you.

 

[BeeferMan]

There's a lot of interesting information in this thread - some of it is probably even true, lol...

But as for which is better or more desirable, HST or geared, that question is impossible to answer unless you specify the job to be done. Comments such as "give me a HST over gear any day" just don't make sense. If, for instance, the job is pulling plows all day long at constant speed where maximum fuel efficiency is important a geared machine is probably the better choice. If you're loading all day long, or working back and forth in tight quarters then an HST is more likely the way to go.

Lots of things "steal" HP from a tractor - power steering, a loader, 4wd, A/C - deciding which of these "power drains" makes the job at hand more efficient is going to be different for different tasks. Choosing the right tool for the job is the sign of someone who knows what they're doing!

 

[CJONE]

HST is the work of the devil. The whine of the HST is actaully the banshee scream of beezlebub. Clutches make you tired and humble so you will stay out of mischief I tell you.

:thumbsup::laughing::laughing: I love it!!!

 

[xtn]

Where you said inherent. Design for design to a force spec the gear will stop after the HST. Also, I said nothing about 100% efficiency. At this level of discussion I regard std mechanical inefficiency as assumed. Only where special situations exist need they be drawn apart.
larry

Okay maybe I'm reading you wrong. When you say "to a force spec" I'm imagining two engine/drive systems designed to deliver some predetermined amount of force. Some project coordinator tells two engineers that he wants a geared system an an hst system that will both deliver X pounds-feet of torque to the driven axle before giving up. In that case, both systems will deliver that amount of force. Both will pull the same weight up the same hill.

Unless you're trying to suggest that all hst implementations fall short of their design goals. But I don't think you're trying to say that, right? What am I missing here?

xtn

 

[SPYDERLK]

There's a real difference between real world and theoretical differences. In the real world there are very few times where you notice a difference between the two power wise. Most times I've seen a tractor that had so much traction that it couldn't spin the tires yet enough power not to stall, guess what happens? The front end lifts off the ground, lots of YouTube videos. When it can't it spins the wheels or stalls the engine.

For the very few times where the gear tractor could keep moving without spinning the wheels. All one would need to do is slow down a little with an hst and hp will not be an issue. That's why people always say that gear tractors work best for things like pulling a bottom plow. However most people are willing to trade off that advantage for all the hst advantages.

Im talking force not power. Speed is not the issue. There must be enuf torque [~force] to make the wheels turn. The force capability is directly related to pressure and gearing. As long as pressure can be made to rise there will be more wheel torque available. As you let off the pedal you reduce displacement of the pump making it possible for the engine to keep turning it as pressure rises. With large resistance to moving, pressures, particularly with cool fluid, could easily go too high for the system to withstand and with so little engine load that you wouldnt notice. That is why the HST must have a relief valve. The setting of that valve gives you a sudden force limitation that occurs w/o warning, wastes all your power to sump while maintaining that force[pressure] set by the valve. Motion stops almost instantly. >> A gear designed to supply the same force would lug down when it encountered the same force limitation. Since there is a direct link from engine to ground, the wheels would continue to turn as it lugged down. If it was only a few % overload the gear tractor would move several feet while augmenting combustion power with energy stored by the spinning engine mass, before you had to clutch. ... Let the engine rebound and then go a few more feet. When you get beyond the area unload a few pounds and go tow the HST out. - Actually you could just pull/grunt it on up the hill with you in the 1st place if you could somehow preserve its ability to help by keeping it from burning its fluid. :confused3:
larry

 

[Redneck in training]

As I see it there no a manufacturer in the sane state of mind that would design a tractor that will not meet user expectation. Similar tractors, one HST and the other gear, will deliver similar performance but HST might use marginally more fuel to achieve it. Experience with my tractor shows that traction is the limiting factor to what the tractor can pull. I could probably hang way more weight on it to achieve more traction but something will break. With the number of hours most of us put on the tractor the higher fuel consumption is not too significant factor. In my opinion HST is the best tractor for first time users. They lack the "macho" factor though. They are too easy to operate.

 

[MHarryE]

If you go by a Kubota dealer who has Grand Ls in stock, different transmissions, look at the difference in size of the oil cooler between the HST and both the GST or manual transmission. What, you couldn't find the cooler on the manual or GST? Rule number one in hydro transmission design - provide an oil cooler equivalent to at least 30% of max engine horsepower because that is the heat rejection due to inefficiency. On these tractors the hydrostatic have oil coolers but the others get adequate oil cooling from surface heat rejection from the transmission case. That doesn't make a hydro bad. It is fantastic when you need to vary speeds a lot or shuttle back and forth. I have a hydro for work around my home, but on our 2 farms we have 18 other manual or power shift equipped tractors. I can load large round bales faster with my hydro than anyone on the farms can with the shuttle shift tractors, but I can barely pull our largest implements down the road with the wings raised let alone drop the wings and sink 30 foot of implement into the dirt, but that's not it's job.

 

[milkman636]

I specifically said PTO not DRAW BAR. So yes once you put the HP through a tractors powertrain either trans gears or HST they will be close but you WILL loose more through a HST at full HP. That is the key how hard you are running the HST. They are very efficient at low flow levels. The higher the flow/pressure the less efficient they are depending on their design. CJ

The published pto numbers provide a relevant reference for the turning force that can be applied to the pto shaft a 540 rpm, that's it.

The drawbar testing is valuable because it provides real measurments of ground speeds, fuel consumptions, and actual sustained forces being applied to the drawbar. If a specific model of tractor in both geared and HST were both subjected to the same test, the differences in the measurements could only be attributed to the transmissions that were applying the power to the ground. That would settle the discussion in less than 20 pages.

 

[beppington]

The published pto numbers provide a relevant reference for the turning force that can be applied to the pto shaft a 540 rpm, that's it.

The drawbar testing is valuable because it provides real measurments of ground speeds, fuel consumptions, and actual sustained forces being applied to the drawbar. If a specific model of tractor in both geared and HST were both subjected to the same test, the differences in the measurements could only be attributed to the transmissions that were applying the power to the ground. That would settle the discussion in less than 20 pages.

You can adjust TBN so this is "only" the 4th page ... but 156 posts?? :confused2:

 

[rsewill]

You can adjust TBN so this is "only" the 4th page ... but 156 posts?? :confused2:

Yes! I use my iPad and this topic is on its fourth page. There is a 'Settings' option along the bottom of my tablet that allows me to choose the number of posts to be shown.

 

[SPYDERLK]

Yes! I use my iPad and this topic is on its fourth page. There is a 'Settings' option along the bottom of my tablet that allows me to choose the number of posts to be shown.

Up to 40 as I recall. Thats where mine is set.
larry

 

[xtn]

Im talking force not power. Speed is not the issue. There must be enuf torque [~force] to make the wheels turn. The force capability is directly related to pressure and gearing. As long as pressure can be made to rise there will be more wheel torque available. As you let off the pedal you reduce displacement of the pump making it possible for the engine to keep turning it as pressure rises. With large resistance to moving, pressures, particularly with cool fluid, could easily go too high for the system to withstand and with so little engine load that you wouldnt notice. That is why the HST must have a relief valve. The setting of that valve gives you a sudden force limitation that occurs w/o warning, wastes all your power to sump while maintaining that force[pressure] set by the valve. Motion stops almost instantly. >> A gear designed to supply the same force would lug down when it encountered the same force limitation. Since there is a direct link from engine to ground, the wheels would continue to turn as it lugged down. If it was only a few % overload the gear tractor would move several feet while augmenting combustion power with energy stored by the spinning engine mass, before you had to clutch. ... Let the engine rebound and then go a few more feet. When you get beyond the area unload a few pounds and go tow the HST out. - Actually you could just pull/grunt it on up the hill with you in the 1st place if you could somehow preserve its ability to help by keeping it from burning its fluid. :confused3:
larry

Okay I agree with all of that. But you could just run more robust components and a higher relief pressure. It is NOT AN INHERENT QUALITY that an hst drive must give up before the engine does.

If you have a clutch (or gear set even) that isn't robust enough to transmit the engine's full torque, you will have the same result you describe; no drive when you need it most. You spec the parts right and either drive system will keep doing the job above and beyond the engine's output capability. If you don't, they won't. It's that simple.

xtn