How does an HST compare in pulling power with the same tractor and a gear trans?

[Mat4644]

But if both tractors are traction limited, and both are equipped with tires and weight the same, then it is not quite as clear cut on "pulling power" what ever that is. No one has defined " pulling power" to me. Now a better question would be. In plowing an acre of ground with two identical tractors one hst and one gear, which one will use more fuel per acre? That is an easy to question to answer. The hydro tractor is not as effecient as the gear tractor and therefor will use more fuel.

I contend that hooking up two equal in every way tractors drawbar to drawbar, equal heights equal tires, and equal weights (we would need to put some distributed weight on the gear tractor to be equal), I contend that they would be equal with a slight edge to the hydro tractor. Because the hydro tractor can start and apply power smoothly without breaking traction. But a lot of this would be the man operating each tractor and clutch and hydro pedal technique. Both tractors in their lowest gears are going to be traction limited. Not engine power limited NOT engine power delivered to the tires limited. NOT transmission efficiency limited. They are going to be traction limited. Someone is goin to break traction first and is going to be pulled backwards. I am betting on the gear tractor will break traction first. But it would make for an interesting spectacle. Efficiency wise, NO question gear is more efficient with less losses from prime mover to the tires. Which as far as I know has nothing to do with "pulling power". Morons that test hydro tractors in MED or HI range excluded.

No need. There have already been Nebraska drawbar HP tests of identical tractors with HST and gear. Gear always higher HP to the wheels. Tested on dry pavement pulling test rig.

 

[RickB]

No need. There have already been Nebraska drawbar HP tests of identical tractors with HST and gear. Gear always higher HP to the wheels. Tested on dry pavement pulling test rig.

Exactly. But this is surely an entertaining diversion from oil and filter discussions.

 

[k0ua]

Exactly. But this is surely an entertaining diversion from oil and filter discussions.

Don't forget R1 and R4..

 

[Industrial Toys]

My wheel loader has a hydrostat yet has a conventional gas pedal. It's kind of the best of all worlds, in that you have hydro but not an engine that is always screaming away. I guess it's part of what Kubota calls LS or Load Sensing. All non electronic. I know for PTO work, you need the Revs, but it would be nice to have the option to run both ways. It's what I mostly don't like about hydro tractors.

 

[Sawyer Rob]

Rob.

Funny. It was one of the misleading sales tactics Deere was using marketing the 110TLB. Comparing the transmission to their hydrostat Dozer!

Back in the day, I was looking to buy a NEW dozer... I already had a hystat dozer and just wanted something a bit bigger/newer.

My trip to the deere dealer, I learned that hystat dozers were pretty much junk! He explained to me how in many ways the power shift dozer was MUCH better and more efficient, he talked Case dozers down because they had hystats!!

Funny thing is, a couple years later pretty much all the deere dozers had hystats!!

SR

 

[RickB]

Yeah, Deere did nothing but run down rotary combines until they invented the technology decades after IH, Gleaner and New Holland adopted it.

 

[Industrial Toys]

Guy I know bought a used 755, I think. NICE looking machine Wide tracks. Brought it here for a job. Blew about six hoses, before it did any real work. Then a hydraulic final drive motor. I don't think it ever ran again, on account of the high price of those motors. It was cheaper for him to find another used 755.

 

[Sawyer Rob]

Yeah, Deere did nothing but run down rotary combines until they invented the technology decades after IH, Gleaner and New Holland adopted it.

How about that "quad track" they invented!! LOL LOL

SR

 

[CobyRupert]

......They are going to be traction limited. Someone is goin to break traction first and is going to be pulled backwards. I am betting on the gear tractor will break traction first. But it would make for an interesting spectacle.

Doesn’t one, or both, tractors immediately break traction, unless one is getting its wheels turned backwards? I submit that in this scenario the winner will be the one that can put the most spinning tire power on the ground.

Now.... going back to the loaded hill climb test: perhaps there’s an argument for hydro winning in very specific conditions. Consider there’s a best possible (theoretical) climb rate based on the engine horsepower, load weight and slope of hill. (i.e. theoretical tractor has a 100% efficient transmission)
Perhaps a scenario exists where the geared tractor’s engine rpms are on a lower spot of the power curve at this speed and engine output is reduced (say 15%), eliminating the 10% transmission advantage, but also it has to stay in a lower gear at max engine rpms, and thus lower speed, and losses the pulling contest.
Possible? Maybe. I think the conditions (weight, slope, etc..) would have to be rigged just right with a tractor whose gears don’t have very much overlap and a tractor whose engine has a steep torque curve (non-diesel perhaps?) to get this result.

 

[Slowpoke Slim]

Hm.. I always thought the deciding factor that determined how much drawbar pull a tractor had was the type of tires and whether they were correct for the pulling job at hand to "hook up" to the surface they were suitable for AND the weight on those tires.

With the more weight on those tires determining if the tires would lose traction with the surface and spin or would deliver all available torque the engine would provide. Of course factoring into this is the tractor in the proper gear for the attempted pull, and hopefully some moron did not put a hydrostatic transmission in too high of a gear range so that the hydro relief valve did not open and thus prevent the maximum power to be delivered to the hydraulic motor. Of course the same could be said if the moron put the gear tractor in too high of a gear and stalled the engine. But again the biggest determining factor is tractor weight, with heavier tractors "outpulling" lighter tractors each and every time as long as their gearing is such to not stall the engines or open the relieve valve and as long as their tires "hook up"

These types of questions have only one answer: "it depends" It is kinda like asking which pickup pulls harder, Chevy, Ford, or Dodge. Well it depends. And it depends on dozens of factors.

Let me ask you a question: What difference in "pulling power" (and first we would have to define what that means to you) would the fact that a hydrostatic transmission loses about 15 percent of the energy going into the hydraulic pump from the engine and between the output shaft of the hydraulic motor IF the hydrostat equipped tractor can and does spin its tires when pulling against an immovable object. So if the gear transmission tractor spins it tires too, what does that tell you? It tells me that more drawbar pull could have been achieved if both tractors had the correct tires fitted for the job and both tractors had sufficient weight added so that the tires would not spin up to the point that the engines stopped or the relief valve opened. But when someone comes along and makes a misleading video to "stir the pot" and stir up FUD what can we say?

Now I suppose It might be possible to cause a hydro transmission tractor to open the relief valve in Low range, I have never seen it and I have owned 3 hydro tractors. Mine have always spun the tires even with loaded tires and a heavy ballast on the 3pth. Of course I have usually had R4 tires too. Perhaps If the test was in soil and I had R1 tires, perhaps the tires would not have spun and perhaps the relief valve would have opened.

How dare you use a very reasonable, rational response when dealing with The Religious Cult of Gears!

You will be burned at the stake for this heresy.