HST Power Consumption

[crazyal]

This thread has gotten way off track. It's not even worth reading anymore. For me I'll head back to the real world where HST is a viable option for a tractor and leave the theoretical world behind.

 

[SPYDERLK]

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

You said earlier "could or can be designed". So that opens the situation to where both are designed to do the same thing with the same steady state limit. With that, the higher overtorque limit allowed when the operator has real feedback foretelling the approaching limit lets him know where he begins to go into the overdesign safety factor, and know breakage is a multiple of the experienced lugdown torque. Theres lots to play with above the lugdown point and where the clutch will slip by design. This indication is not there with a HST and demands an automatic safety device. This causes an INHERENT deficiency in force capability of the HST. You want to turn up the relief? Fine, but realize the presence of the automated limit is part of the design. Since it is a highly repeatable "instant acting" limit the designers have set it much closer to the ultimate system strength. >>Suitable design demands high overtorque support with a hard linked system because that engine is going to experience a hard stall in a pull, perhaps many times. This torsions the geartrain and buckles the tire sidewalls and maybe induces a few revolutions of clutch slip. The gear was not designed to do this. It was designed to be able to survive it. You will never see such forces in proportion to its design goal in a system with an automated protective device. Turn your HST up 50%, and at load requiring that pressure you are operating beyond its safety limit with no indication. Turn it up 100% to make it able to deliver anywhere near the force induced in a gear stall and it might do it once ... Engine singing happily at lo pedal. But it made a new sound and now it doesnt seem the same...:confused3:

This thread has gotten way off track. It's not even worth reading anymore. For me I'll head back to the real world where HST is a viable option for a tractor and leave the theoretical world behind.

Fine.
larry

 

[xtn]

Awwww... I wanted to keep going. At least Spiderlk and I kept our debate civil and related to the subject at hand, unlike the results of some threads.

 

[CJONE]

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.

I agree 100% that would be way better in a evaluation of the tractor. CJ

 

[dennis52]

This thread has gotten way off track. It's not even worth reading anymore. For me I'll head back to the real world where HST is a viable option for a tractor and leave the theoretical world behind.

For me, it's been very informative, even with the side tracks.

 

[crazyal]

For me, it's been very informative, even with the side tracks.

In a theoretical way yes. In a practical sense all one would do is shift to a lower gear.

Here's a simple question for HST tractor owners. In low gear can you spin your tires? Yes or no. I can, actually pretty easily.

Question #2. Is there any difference between a gear tractor spinning it's tires and a hst tractor spinning it's tires?

 

[jenkinsph]

In a theoretical way yes. In a practical sense all one would do is shift to a lower gear.

Here's a simple question for HST tractor owners. In low gear can you spin your tires? Yes or no. I can, actually pretty easily.

Question #2. Is there any difference between a gear tractor spinning it's tires and a hst tractor spinning it's tires?

#1 yes

#2 no
With the HST I can rapidly reduce the power enough to stop spinning without digging a hole in most cases.

 

[Alan L.]

If you have ever owned a hydro you would know instantly. I had a TC45DA with a hydro. Dig the buccket in the ground or get in soft earth. The hydro will get to a point of stop and whine. My gear drive 55 will grind those big tires til there is no more clearance and do it with little effort. On the hydro I wore ear muffs because of the tranny noise, not the diesel engine. My 4110 Deere sub compact with mower / loader has a hydro and it is convenient. ( Same stopage with the loader ) Same old story... you pay for convenience, one way or another.

I guess it depends on which hydro. On my kubota B2710 I dig the bucket in the ground or get in soft earth. The hydro will grind those big tires there is no more clearance and do it with little effort. Sometimes it kills the tractor if you don't let off. No ear muffs necessary.

 

[xtn]

In a theoretical way yes. In a practical sense all one would do is shift to a lower gear.

Here's a simple question for HST tractor owners. In low gear can you spin your tires? Yes or no. I can, actually pretty easily.

Question #2. Is there any difference between a gear tractor spinning it's tires and a hst tractor spinning it's tires?

Just so I am understanding correctly...

Spiderlk and I both graciously gave up our debate at your request, and you keep discussing it? The only difference is you're limiting yourself to real world conditions wherein your power exceeds your traction. Our discussion was assuming we've added enough weight to solve that problem, which is no less a real world situation than yours.

Have I understood correctly?

xtn

 

[SPYDERLK]

Just so I am understanding correctly...

Spiderlk and I both graciously gave up our debate at your request, and you keep discussing it? The only difference is you're limiting yourself to real world conditions wherein your power exceeds your traction. Our discussion was assuming we've added enough weight to solve that problem, which is no less a real world situation than yours.

Have I understood correctly?

xtn

Good statement. Hopefully understood. ... Actually, I did not give up. I just dont want to reply to anyone who is changing the subject by assertion without exhibited understanding. The points have been made. Real questions, not rhetorical, would be productive.
larry