hydrostat vs gear hp loss

[BillyP]

I assue you meant as a signature.. Yes it does!

Dang it! Yes, as

Thanks

 

[dieselsmoke1]

The reality is more drawbar HP allows the tractor to run a lot more efficiently with heavier loads.

Yes, I agree.

Just comes down to opinion if the hydro can gain back the lost efficiency with what some would consider an agility advantage. I expect it depends on the job and the operator.

Next time I get into a debate, I hope I'm on the fact side. The supposition side is a lot of work

Have a good night.

 

[_RaT_]

Yes, I agree.

Just comes down to opinion if the hydro can gain back the lost efficiency with what some would consider an agility advantage. I expect it depends on the job and the operator.

Next time I get into a debate, I hope I'm on the fact side. The supposition side is a lot of work

Have a good night.

Just think of what a Bobcat track or skidsteer or a ZTR would be like without a hydrostatic drive? Being a user of both, I know the answer...

 

[neverenough]

I am considering moving up to a hydrostat cab tractor. Does anyone know the amount of drawbar/rear wheel HP loss for a hydrostat compared to gear drive. I have a Kubota 3710 GST and dealer said expect to lose about 20% in pulling power with hydro. He recommended an increase from 37hp to 46hp (ie. 4630) to have the same pulling ability with hydro. This would suggest considerable power loss. Most bigger tractors talk about drawbar hp in specs but don't see this in the compacts. Is this because of so many hydro's in the compact class that companies don't want to show specs with lower drawbar hp for hydro tractors with the same engines?

The reason they don't do ratings for compacts, is becouse they are not considered farm equipment. Nebraska has a law that requires ALL FARM tractors to be tested by an independent testing facility for belt, PTO, and draw bar HP. The tests are almost alway's done by the University of Nebraska. Becouse the tests cost $$$, they don't do them for compact tractors as they are not required by any local, state, or federal government.

Hydro drive is more efficient than most people give it credit for ( depending on maker). Deere, for example, used to sell their hydro lawn tractors at a deep discount in order to get people to try them. People came back for more. Over the years, they have improved them to the point they are quite efficient. Fluid power, working properly, can produce a lot of torque (rotational "work"). This can then be easily transfered in to horse power (linear "work"). You can also "amplify" torque through the flow of fluid, just as you can with gears. Therefore, it comes down to the system in operation and how well it works. If you are losing 20% by going to a hydro tranny tractor, it's best you find a brand with a better system. I think they were just trying to feed into your "manlyness" and trying to get you into something bigger.

 

[john_bud]

So, if a hydrostat loses 20% in the drivetrain -- where does the heat go? 6+ Hp of heat is a LOT of heat.

Just wondering...

jb

 

[SPYDERLK]

So, if a hydrostat loses 20% in the drivetrain -- where does the heat go? 6+ Hp of heat is a LOT of heat.

Just wondering...

jb

Ive read this thread with great interest. Many times Ive wanted to reply, but the next 2 or 3 posts said what I was thinking. I have a perspective that I believe is borne out by the thread however, and a theory regarding that 20% quoted by the dealer. - - The ball park numbers from the 1980s were loss of 10% in a gear trans and 20% in a hydro. These #s hold close to references quoted here. I think the dealer has misused this comparison to get his 20%. In actuality tho depending on how you make your comparison you can say a lot of correct things that mislead. Like; the H is half as efficient as the G, the G is twice as efficient as the H, the G is 100% more efficient than the H. The opportunities to confuse boggles the mind. I try to keep it straight by comparing what the H transmits vs the G. Out of 100HP input this would be 80H vs 90G or 80/90 or 89%. You get 11% less power out of the Hydro. But it is true that the H is throwing away twice as much power as the G. Notice the large reservoir, finning, and auxiliary fans on Hydros to take care of this waste heat. Theres really no way around the extra losses because there is inefficiency in converting energy from one form to another. In the engine youre losing about 1/3 of your energy out the exhaust pipe, 1/3 thru the radiator, and getting the last third as mechanical HP. When you take that mechanical and convert it to fluid flow and then back to mechanical you have more losses. For this you get convenience and ease of finesse.
Larry

 

[normde2001]

Too many long-winded posts here to read them all; however, unless you have someway achieved perfect traction you are going to run out of traction long before you run out of horse power in either case, making it a non-issue.

 

[SPYDERLK]

Too many long-winded posts here to read them all; however, unless you have someway achieved perfect traction you are going to run out of traction long before you run out of horse power in either case, making it a non-issue.

No. Not if you have a strong FEL and can push and lift at the same time.
Larry

 

[_RaT_]

No. Not if you have a strong FEL and can push and lift at the same time.
Larry

I suppose it depends on soil conditions but I can almost always run out of HP before traction. This applies to my hydrostatic drive and my gear drive. As you said, going forward into a pile of dirt, lifting and loading the front tires and my RPM's drop. The good news is that it is really easy to remedy. On the HST let off on the pedal pressure and on my gear, push in the clutch. Problem solved...

 

[SPYDERLK]

I suppose it depends on soil conditions but I can almost always run out of HP before traction. This applies to my hydrostatic drive and my gear drive. As you said, going forward into a pile of dirt, lifting and loading the front tires and my RPM's drop. The good news is that it is really easy to remedy. On the HST let off on the pedal pressure and on my gear, push in the clutch. Problem solved...

Yeah, I run out of traction before HP usually too. In 1st gear the 7520 4wd with FEL and loaded rears will spin its wheels with the throttle set at 1200rpm -- unless weight is augmented by lifting. Then I can use as much power as I have, and more. With a dirt pile its not too big a deal. The bucket is full, or you can always take a smaller bite. However, when pushing and lifting a large tree that I can not lift off the ground I sometimes need a little more than the engine can give. With the gear tractor pushes like this can be made a little at a time, letting the engine recover each time it boggs down. With a hydrostatic drive you cant do this because you hit its limit suddenly. The pressure relief operates and your horsepower diverts to that wasted flow. If you push the pedal down more you get more wasted flow and very little more push. On the gear drive that HP goes to the ground even as the engine slows.
Larry