more power

[jinman]

The available HST gear ratio is infinite, except that limited by the pressure.

And the pressure limit on ours is 5000 psi. With the pedal only slightly depressed, you are producing a tiny flow at super pressure. Just a tiny lifting of the relief valve and you are done.

Push the pedal all the way down and you produce a huge flow, but now the gear ratio stalls the engine. Should the engine have enough power to not stall, then the 5000 psi rule applies. You lift the relief valve and now have a torrent of fluid instead of the trickle you had before.

Same result for either scenario. My tractor stops and I cuss.

 

[SPYDERLK]

The available HST gear ratio is infinite, except that limited by the pressure. I can travel 0.1 mph(or less) with the tractor at full power. The lowest speed on a gear tractor is typically 1 mph. [[[I could pull a train with a chain with the my small HST.]]] Most gear drives can't provide the torque to get the train started. In essence, the appliable torque(to the ground) is significantly higher for and HST than most gear systems.

Impulse loads are a different subject, and I agree that the HST is much better at handling them(that is why I ignored the simplicity=reliability argument when choosing my tractor). However, the clutch system provides impulse protection as well, and clutches are designed with that in mind.

As other have said, it would be interesting to get the chain, and have a pulling contest.

Chris

[[[Its easy to fall into that trap.]]] Actually, regardless of how slow it will go, you get no force multiplication beyond the actual gear ratio the HST is delivering torque to. And regardless of the small amt of fluid the HST is pumping at low pedal, the torque output is limited by the relief pressure and the displacement of the hyd motor that the pressure limited fluid is being fed to.
As to a pulling contest: If equal engine HP HST and Gear had low gears with 2mph top speed and both could link max net transmission output torque to the ground, the Gear would win. No matter that there would be a little clutch abuse on the gear while engaging and preventing stall. Gear is close to 90% efficient. Hyd is only about 80% and net output is less. After several hundred such pulling contests the Gear would need a new clutch and the HST wouldnt even need an oil change. But it shouldnt take that many tries to be assured that the Gear will pull harder.
larry

 

[RickB]

[[[Its easy to fall into that trap.]]] Actually, regardless of how slow it will go, you get no force multiplication beyond the actual gear ratio the HST is delivering torque to.
larry

Are you trying to tell us that a hydro transmission will deliver the same output torque at a low pump swash plate angle as a high pump swashplate angle? And in the case of the NH Class III tractors, HST output torque is not affected by the HST motor swashplate angle being low or high?
I am either completely misunderstanding you or I am in absolute and total disagreement, not sure which.

 

[SPYDERLK]

Are you trying to tell us that a hydro transmission will deliver the same output torque at a low pump swash plate angle as a high pump swashplate angle? And in the case of the NH Class III tractors, HST output torque is not affected by the HST motor swashplate angle being low or high?
I am either completely misunderstanding you or I am in absolute and total disagreement, not sure which.

You are right. We are in disagreement. What I said is correct and Im not sure why what I said in the post does not convey the pertinent info clearly. Sorry.
larry

 

[RickB]

You are right. We are in disagreement. What I said is correct and Im not sure why what I said in the post does not convey the pertinent info clearly. Sorry.
larry

Yeah, I'm sorry, too. Sorry I added to this pitiful thread which has been a waste of bandwidth since the middle of page one.

 

[Dodds]

Bottom line here is what simple engine ajustments can be made to the NH 35-45DA to deliver a little more power to replace the HP loss at the PTO? I'm willing to try it.

 

[SPYDERLK]

Yeah, I'm sorry, too. Sorry I added to this pitiful thread which has been a waste of bandwidth since the middle of page one.

That would be the point where the actual Physics of the issue was brought to the fore. It worries me that accurate assessment of a situation turns out to be a waste. There is plenty of other good info in the thread. Its just that a great deal of it must stand in abeyance until the physics overriding the
situation regarding application of force thru a HST is dealt with.
larry

 

[Dodds]

So will someone step up to the plate and tell us what adjustments we need to make to get 2 or possibly more HP on a DA to match or exceed the A PTO HP? My service manual doesn't divulge how to adjust the fuel pump. I have even considered removing the muffler assembly at the manifold and building an identically located open exhaust of larger diameter.

 

[RickB]

I could, but I won't. I will not violate EPA regs for the supposed benefit of a total stranger. That's my bottom line.

 

[RobJ]

So will someone step up to the plate and tell us what adjustments we need to make to get 2 or possibly more HP on a DA to match or exceed the A PTO HP? My service manual doesn't divulge how to adjust the fuel pump. I have even considered removing the muffler assembly at the manifold and building an identically located open exhaust of larger diameter.

Didn't we cover that?? Buy a bigger tractor!