Mowing PT mowing with hydraulics

MuncyBob · May 9, 2004

If I'm understanding everything I've read(that may be a stretch)...the PT uses hydraulics for the mower deck? Was discussing this over a few beers last night with a friend and he was not crazy about any mower that uses hyro's vs. a PTO.....but I don't recall seeing any posts stating anybody was having any problems with power while cutting unless on a very steep grade and then only with a machine smaller than the 425??? Any thoughts here /forums/images/graemlins/confused.gif

Bob999 · May 9, 2004

The PTO on PT is hydraulic. That means that the PT mower has an hydraulic motor. Most, if not all CuT's us a mechanical PTO. Most have rear mowers because that is where the PTO is. Some also offer a belly mower and have a PTO take off for a belly mower.

Hydraulic PTO makes it easy to have a front mower--just route the hoses forward.

Hydraulic is also easier to hook up than mechanical PTO--one of the things you see in this forum is praise for the ease of changing attachments on a PT.

The only downsides to hydraulic PTO that I am aware of are cost (you need a separate motor for each powered attachment) and efficiency (there is greater power loss than with good mechanical arrangements).

smartguyz · May 9, 2004

Good question -

I purchased the PT in part *because* of the hydro PTO. Take some time and study hydraulics - it is a little-understood topic on the part of the general public. I happened to study some hydraulics in High School (fluid power), and during Engineering classes in college.

Hydraulics have many fascinating capabilities and advantages. For example, as Bob said, you have a motor for each attachment that needs it. The motor can be exactly the right one for the job. It can be used as a force-multiplier - that's why the lift arms on a PT425 can do 800 lbs of lift on such a dinky machine. It is self-lubricating to the motor, and self-cooling. The motor can be positioned in unusual locations, so that you can build all sorts of attachments that would be difficult with a mechanical PTO.

Check out the attachments on the PT website - I think that the sump pump and the winch would be much more complicated, and assume that the winch has some kind of way of mutiplying force, and of being variable speed (I am making assumptions here - I don't have one). Using hydraulics, you can vary the flow using valves, and you can multiply the force, especially if you trade off speed. Note the winch has a 5 ton pull, which is 10,000 lbs - probably the limit of the PT traction.

In summary - there are some advantages to the hydraulic method compared to other methods. Force multiplication, flexibility, simplicity, lubrication, compactness. I would certainly not discount this aspect of the PT - in fact, I would consider the advantages.

Sincerely,

-Rob /forums/images/graemlins/grin.gif

tracdoc · May 9, 2004

Hi folks,

I originally posted this on another thread in the PT forum, but I think it may have gotten lost there, since the subject of hydraulics was a fringe of the original thread subject. I was interested is seeing if anyone had seen/read the hydraulics manuals which are published by J Deere Publishing.

For machinery under 40 HP, the series is called Fundamentals of Compact Equipment. It includes a number of books covering electrical, power train, etc. There is a book on hydraulics, and there are also Instructor and Student Guides, priced individually.
Compact Equip Hydraulics Cat # FCP-82102B $32.95
JD: Fundamentals of Compact Equipment Series

For machinery over 40 HP, the series is called Fundamentals of Service. In that series, there are 2 books dealing with hydraulics:
Hydraulics (Cat # FOS-1006NC) $38.95 [Companion I/S Guides, also]
Hydraulic Sys Diagnostics (Cat # FOS-6401NC) $18.95

JD: Fundamental of Service Series
The Deere website (at least in terms of their publications) is somewhat arcane, and I ran into several URLs citing the books, others citing the prices, and finally the ones which had Catalog numbers/prices together, as given above.

I don't know whether they can be returned to Deere Publishing if they don’t measure up. Have any TBNers used or studied these book or any others in the two series?

Thanks for your help.

Schultz · May 10, 2004

I wouldn't be afraid of the hydraulics powering a mower or other attachments. It is a very versatile and reliable method of power transfer.
There are other commercial mower examples such as Toro, Jacobson that use hydraulic pto to power the real mowers on the golf courses. Also Case/Ingersol garden tractors use hydraulics to power their tractors and any PTO attachment is power by hydraulics too.
The biggest disadvantage of hydraulics is the power loss. Typically motors and pumps are only 70-95% efficient depending on the type. Gear & piston types are very efferent 85-95%, vane less, and variable volume even less. Combine a pump and hydraulic motor and you have more loss.

MossRoad · May 10, 2004

One note about the power loss issue.

Many folks seem to think that means the machine is less powerful, or not powerful, etc...

If you size the machine correctly to do a job, it will do it. You may need more engine HP/Torque to do the same job as something with gears, but so what. The plusses outweigh the minusses in our applications. /forums/images/graemlins/laugh.gif

MuncyBob · May 10, 2004

All very good points...and I'm learning as I go...somewhat familiar with hydraulics from snow plowing and the Farmall...just no experience with a hydro PTO. Thanks to a generous offer from a fellow member that is fairly close to us I'll be getting my first in person look at a PT this Saturday...my suspision is I'll be ready to order soon...now if my wife wants to kiss it (like the frog post in other forum) then I know I'll have it real soon! /forums/images/graemlins/grin.gif

SnowRidge · May 11, 2004

( You may need more engine HP/Torque to do the same job as something with gears, but so what. )

Well, the price of gas, for one thing. /forums/images/graemlins/frown.gif

The biggest downside I see to hydraulic everything is increased cost of operations--mainly in fuel costs. As you say, its the price you pay for the plusses.

SnowRidge

Bob_Skurka · May 11, 2004

Snowridge, I think the cost of gas is a minimal issue. So let me try to put some dollars to it.

I switched from an 18hp Cub Cadet to a 21hp Ventrac. The Ventrac uses a bit more fuel than the Cub. The Ventrac uses hydraulics. By a bit more, I could quantify it by saying in 3 weeks worth of mowing, it probably used 1 more gallon of gas. I only burn premium grade gas, so that means I have spent an extra $2.00. Assume that every 3 weeks I need 1 extra gallon. Assume I mow my property for about 36 weeks a year. At that rate, I would use about 12 extra gallons or $24.00 worth of fuel.

Now what do I get for that extra $24 per year?

I get 4 wheel drive and articulated steering which amount to zero wheel slippage and super tight turning radius which cuts my mowing time down 1.5 hours per week. So I spend $24 per year, but I save 54 hours in labor (36 mowings x 1.5 hours saved per mowing).

To give me the combined articulation & 4wd in a mechanical unit the tractor would be much larger and that would eliminate the ability to turn tight around trees, which would wipe out the time savings that I get from added manuverability, which would then lead to burning more fuel because I'd be running the engine longer.

I think the concept of efficiency must be measured in many ways. I also think that SOMETIMES mechanical is better than hydraulic and SOMETIMES hydraulic is better than mechanical. But I think that the right tool for the right job is what we all need to look for, and there will be trade-offs with any system we buy.

SnowRidge · May 11, 2004

( I think the concept of efficiency must be measured in many ways. I also think that SOMETIMES mechanical is better than hydraulic and SOMETIMES hydraulic is better than mechanical. But I think that the right tool for the right job is what we all need to look for, and there will be trade-offs with any system we buy. )

No argument there. In fact, we bought the PT-425 because we couldn't find any other machine better suited to our application. Nevertheless, it still seems to drink an amazing amount of fuel, especially compared to the rate I use diesel in my bigger Branson CUT.

The point I was making is the old "there's no such thing as a free lunch." All-hydraulic doesn't just require a bigger engine, as Moss pointed out, it also means increased operating costs. It's just one more factor that a potential buyer needs to take into account when making a purchasing decision.

SnowRidge