hydrostat vs gear hp loss

[Keith_B]

For those intermittant times when I need every hp the engine can muster directly on the ground, I'll accept the fact my equipment will require me to work 10% slower than a geared one would...for that moment. I think the time will be more than recovered when the load lightens. If my work included a significant amount of ground tillage, then that's a whole different story.

It wouldn't be a matter of working slower, it would be a matter of having to adjust the size of ground engaging impliment being used. For the tractor owner who doesn't worry about the power at your disposal to pull the differences are negligible.

 

[BillyP]

OK, I gotcha now but there's still not a 20% difference. Below is a link to some interesting reading. Although it doesn't go into HP loses, it's interesting. Look on page 4

http://www.eurageng.net/files/nl.pdf

 

[dieselsmoke1]

That's an equally valid method of saying it. I rarely use ground engaging implements any more, but if I were shopping, the HST characteristics would make me rethink the size.

I used this terminology for a purpose. A novice may not understand that the drawbar horsepower difference does not equal "how much I can pull" , more like "how fast I can pull it".

 

[dieselsmoke1]

Look on page 4

That is interesting. I'd love to see the full test parameters and results.

 

[JerryG]

That's an equally valid method of saying it. I rarely use ground engaging implements any more, but if I were shopping, the HST characteristics would make me rethink the size.

I used this terminology for a purpose. A novice may not understand that the drawbar horsepower difference does not equal "how much I can pull" , more like "how fast I can pull it".

I may not be understanding what your are saying. But, drawbar horsepower does effect more than ground engaging equipment. It effects anything that the tractor pushes or pulls. If a tractor has less drawbar hp, it will pull less as well as have less power to push. (push as pushing a loader into a pile)

 

[radman1]

Billyp:

The article your posted, eurageng.net is really a flawed comparison for the question I posted concerning drawbar hp. That article really addresses productivity. The hydrostat was more productive probably due to its manuverbility rather than hp. For drawbar hp, the test should use the same tractors and engine and compared on a dyno at the same RPM. Hydros are less efficient and the inefficeincy is released as heat. Granted, most of us don't notice the inefficency in our daily usage. If the majority of the work was pulling tillage equipment such as subsoiler, disc, blade and possibly hard digging loader work, the difference would probably be noticeable.
The article used tasks such as moving bales, tilling and mower work which require relatively little draw bar hp.
I have recently driven a Jd 3520 hydro and at road speeds and hills, it is noticably less powerful than my Kubota 3710 GST. Both are nearly identical in hp and weight. I must add however, the torque of the 3710 engine is 120 N-m and the 3520 about 96. This maybe part of the noticeable difference. Not trashing Jd. I am considering getting a 3520 hydro cab (37hp) but I ask the question, should I get a 3720 (43hp, 114.3 N-m) instead.

 

[BillyP]

radman1,

You're right, the article had nothing to do with you question and I did say that in my post. Sorry if you read it for nothing.

I think everyone hear will agree with you that hst isn't as efficient as a gear. The thing I don't agree with is the 20% difference.

Now to you last question. Get the 3720, if that's what you want

 

[dieselsmoke1]

I may not be understanding what your are saying.

And I may not be saying it very well. My point is that as long as there is adequate power delivered to the ground to spin the tires, no matter the tranny type, then the ultimate limitation of what can be accomplished with a CUT will be traction. The geared equivilant to the HST model I have is practically the same weight. The HST model should be able to pull (or push) anything the geared one would, however when at full ground delivered engine load, the HST would have to work slower due to lost efficiency in the drivetrain. The number often tossed out in approx. 10%.

No facts to back this up other than logic. Am I missing something?

 

[JerryG]

That is where ideal ballast come in. If they have the correct ballast the gear will get more work to the ground. If the tires are spinning excessive then the ballast is off. If the ballast is off then efficiency is lost.

 

[dieselsmoke1]

That is where ideal ballast come in. If they have the correct ballast the gear will get more work to the ground. If the tires are spinning excessive then the ballast is off. If the ballast is off then efficiency is lost.

Not trying to be obstinate here, but I just can't get my arms around what you're saying. How can a gear drive develop more traction than an identical HST? More work to the ground, yes I can see that, in terms of speed. Is that what you mean?