Hydro or Shuttle for the long haul?

[TMGT]

So what I'm wondering is how the two horsepower difference in the above example is "calculated". Is it based on an amount of drawbar pull in a given gear range, at a given ground speed, given RPM or is it just a SWAG.
For example, running a PTO driven chipper/shredder (at zero MPH hopefully) what happens to the two horsepower difference?

It is measured/calculated from a dynamometer, the difference in HP between the gear and hydro is the parasitic loss from just turning the pump assembly.
Some hydro's are more efficient so you'll see less difference between the gear and hydro pto HP.

 

[npalen]

But wouldn't the loss be much greater at full RPM and/or draft load? Of course it would since much more heat is being generated. It takes power to generate heat. I'm saying that the two horsepower can't be the same under all conditions.

 

[TMGT]

It most likely isn't, would depend on efficiency of the hydro and gearing, load, etc.
That's why I said I would really like to see what the pto difference is under operating conditions.
You also lose efficiency through every gearset so it might not be as much difference as we think.

But wouldn't the loss be much greater at full RPM and/or draft load? Of course it would since much more heat is being generated. It takes power to generate heat. I'm saying that the two horsepower can't be the same under all conditions.

 

[jaydee325]

These gear/hydro discussions just leave me scratching my head.

If you need X horsepower at the PTO, then buy a tractor with that HP PTO, gear or hydro.

I hear you guys saying well, there is a loss to the drive wheels. True, but that is highly dependent on soil conditions and tire (traction). Most cases on SCUTs and CUTs, the power transferred to move the tractor forward is limited by traction. So, most won't see or feel more overall power between the two drive lines.

 

[jaydee325]

These gear/hydro discussions just leave me scratching my head.

If you need X horsepower at the PTO, then buy a tractor with that HP PTO, gear or hydro.

I hear you guys saying well, there is a loss to the drive wheels. True, but that is highly dependent on soil conditions and tire (traction). Most cases on SCUTs and CUTs, the power transferred to move the tractor forward is limited by traction. So, most won't see or feel more overall power between the two drive lines.

 

[the old grind]

It is measured/calculated from a dynamometer, the difference in HP between the gear and hydro is the parasitic loss from just turning the HST pump assembly. Some hydro's are more efficient so you'll see less difference between the gear and hydro pto HP.

And there are are three things that can cause PTO hp to be however much less than rated hp. Two are parasitic, one is not.

I'll start with what isn't. PTO hp is at a fixed speed by gearing, not necessarily at max hp rpm. Engine efficiency at PTO rpm can reduce available hp to be further reduced by the parasitic losses. Also, rated hp may be taken at the crankshaft as the old SAE ('gross') method sans fan, alternator, steering pump vs the now common DIN ('net') with basic accessories considered or 'taxed'. Automotive stds don't apply to tractors.

So now either way we have the engine turning gears, shafts, and hydraulic/steering pump. These parasitic losses reduce PTO output, but the HST is turning another pump for the HST, what a geared machine doesn't have. Plenty more moving parts/friction whether moving or not & the cost here seems to be 2hp for that at PTO rpm. I doubt if the tractor would be moving when on a PTO dyno.
`
I kinda don't get the HST power loss confusion & I never seem to lack PTO power for flail or tiller. (53" flail jacked to cut to 1", 5' KK tiller to go 5"+ deep ) I've hung a 7' 2-row disc on my (same size/hp) CUTs for rear ballast, filled tires or not, and never lacked a range to spin all four tires. The WM 25 HST is most like my past '98 NH/1520 1.3L, 23hp in weight & size but with the '98's much less hydro gpm and loader capacity. (both ~1/3 or so less)

Another thing, my 3 have treadle and brakes on the same side. Brake-steer won't be easy if I can do it at all. IMO WM does much better with no clutch the and brakes & go pedals on each side. I'm coming around to dual-pedal vs treadle go-go and independent PTO. As much as I like the Kioti & Bobcat IMO this is a serous competitor. Sheet metal hood, check. Easy service access, check. Front/rear PTO and easy activation, check.

btw, IMO loaded 15 x 19.5 rear and 27-8.50x15" vs 25-8.50x14" front R-4s are best all year & for FEL work, and easy on the lawn with this size & wt tractor. :2cents:

 

[TMGT]

And there are are three things that can cause PTO hp to be however much less than rated hp. Two are parasitic, one is not.

I'll start with what isn't. PTO hp is at a fixed speed by gearing, not necessarily at max hp rpm. Engine efficiency at PTO rpm can reduce available hp to be further reduced by the parasitic losses. Also, rated hp may be taken at the crankshaft as the old SAE ('gross') method sans fan, alternator, steering pump vs the now common DIN ('net') with basic accessories considered or 'taxed'. Automotive stds don't apply to tractors.

So now either way we have the engine turning gears, shafts, and hydraulic/steering pump. These parasitic losses reduce PTO output, but the HST is turning another pump for the HST, what a geared machine doesn't have. Plenty more moving parts/friction whether moving or not & the cost here seems to be 2hp for that at PTO rpm. I doubt if the tractor would be moving when on a PTO dyno.
`
I kinda don't get the HST power loss confusion & I never seem to lack PTO power for flail or tiller. (53" flail jacked to cut to 1", 5' KK tiller to go 5"+ deep ) I've hung a 7' 2-row disc on my (same size/hp) CUTs for rear ballast, filled tires or not, and never lacked a range to spin all four tires. The WM 25 HST is most like my past '98 NH/1520 1.3L, 23hp in weight & size but with the '98's much less hydro gpm and loader capacity. (both ~1/3 or so less)

Another thing, my 3 have treadle and brakes on the same side. Brake-steer won't be easy if I can do it at all. IMO WM does much better with no clutch the and brakes & go pedals on each side. I'm coming around to dual-pedal vs treadle go-go and independent PTO. As much as I like the Kioti & Bobcat IMO this is a serous competitor. Sheet metal hood, check. Easy service access, check. Front/rear PTO and easy activation, check.

btw, IMO loaded 15 x 19.5 rear and 27-8.50x15" vs 25-8.50x14" front R-4s are best all year & for FEL work, and easy on the lawn with this size & wt tractor. :2cents:

There are quite a few things that can cause the variations, probably too much to get into here lol, I've been fortunate to be able spent a bit of time on inertia chassis and water brake engine dyno's. Always interesting to see the effects of fluids/friction/parasitic loss etc. on output.

There are standards for equipment engine testing and most will list 4 outputs: gross intermittent, gross continuous, net intermittent, net continuous. Not all manufacturers have listed the same output type over the years so it can be confusing when trying to compare.

I remember seeing a test being done where they were measuring pto output while pulling a set load, not sure if it was Nebraska or not, don't remember ever seeing results listed from those test though. This was from old literature.

 

[5030]

When I spec a tractor there are 2 constants I apply. Displacement and the amount of boost. Me, I'm into torque rise so turbocharging and charge air cooled is necessary.

 

[buck12]

I have no idea of the exact HP HST cost me. Whatever that cost is it is worth it. After having a gear tractor for 12 years, I love HST for my uses. For others a geared tractor likely works best.

 

[Blue Mule]

Brought home my new Workmaster 25 yesterday. With the loader, bucket, and fluid in the tires she's a heavy pig. Made the ramp on my enclosed car hauler crack and pop like it was going to snap. So far I like the tractor a lot, just not a fan of the non-removable side panels on the hood. But hopefully it'll be a good tractor. The hydro controls are so nice. If it's got enough power to drag a 5' box blade full of #57 crushed stone up a 10% grade, it'll be all the tractor I need.