Mowing Mower deck hydraulic motor.

[J_J]

Thanks Duane. That motor is much smaller that I was anticipating.

I did a search, but I didnt find anything. I'll give it another shot and see what comes up.

How much HP can you dedicate to a hydraulic pump, that's going to be your limiting factor. If say you have 30 HP total, the drive line will use some, Any HP left over with a reasonable speed, can be used to power a hydraulic motor. Plus every thing Bob said. Do you know what kind of blades do you want, a bush hog blade, single shaft, two blade, or a finish mower with three shafts and three blades?

 

[Mith]

Bob, at the moment I'm really just looking to gain a bit of information rather than copy the PTs system specification.
I might be wrong, but I believe that the PTs only have one PTO circuit that is used for all the attachments, so I would suspect that the flow from that PTO is a compromise to fit as many attachments as possible. I'll be doing the sums as you suggest, probably even working back from the HP requirements for different sized mowers, but knowing the specs of the motors used on the PT attachments gives me a good grounding to work from.

JJ, the machine has 31HP, and it is set up so that the drive is capable of using nearly all of that (I believe about 25HP at full flow and pressure).
However, while using a mower I wont be going at full speed (~10mph) and it wont be running at full pressure so I'll have more HP available for attachments.
I'm thinking about the possibility of getting a larger motor that runs at 540rpm and attahcing that to the back of the tractor and using standard 3ph attachments with a PTO shaft, I can always add a diverter if I want to use that flow for a boom mower or something.
There is alot of possibilities and I havent really decided what I want to do yet.
There is an argument to adding a high flow pump that is capable of using the full 31HP, and sizing the attachments so that there is enough HP left over for drive. If the attachments need more HP I can just slow down on the drive.
That would also allow me to use the full engine HP through the PTO when the machine is stationary.

Thanks guys, its interesting to hear your thoughts on this. I dont have much experience with hydraulic driven mowers so its good to hear from those that have.

 

[SnowRidge]

Not sure how the 48" finish mower is designed...

The 48 inch finish mower for the PT-425 is also a three spindle design, with the motor driving the center spindle directly. The outer spindles are belt driven off of the center spindle. There is also an adjustable idler pulley.

I think it would be helpful if folks responding to Mith's request would mention the size of their deck along with the motor data.

 

[J_J]

Mith

I have acquired the hydraulic PTO motor that runs at or near 540., and the bush hog. It was sized for 18 GPM, and 3000 psi. The intent is to power 3pt attachments on the front of a skidsteer. I have every thing necessary to put it all together.

 

[KentT]

Bob, at the moment I'm really just looking to gain a bit of information rather than copy the PTs system specification.
I might be wrong, but I believe that the PTs only have one PTO circuit that is used for all the attachments, so I would suspect that the flow from that PTO is a compromise to fit as many attachments as possible. I'll be doing the sums as you suggest, probably even working back from the HP requirements for different sized mowers, but knowing the specs of the motors used on the PT attachments gives me a good grounding to work from.

JJ, the machine has 31HP, and it is set up so that the drive is capable of using nearly all of that (I believe about 25HP at full flow and pressure).
However, while using a mower I wont be going at full speed (~10mph) and it wont be running at full pressure so I'll have more HP available for attachments.
I'm thinking about the possibility of getting a larger motor that runs at 540rpm and attahcing that to the back of the tractor and using standard 3ph attachments with a PTO shaft, I can always add a diverter if I want to use that flow for a boom mower or something.
There is alot of possibilities and I havent really decided what I want to do yet.
There is an argument to adding a high flow pump that is capable of using the full 31HP, and sizing the attachments so that there is enough HP left over for drive. If the attachments need more HP I can just slow down on the drive.
That would also allow me to use the full engine HP through the PTO when the machine is stationary.

Thanks guys, its interesting to hear your thoughts on this. I dont have much experience with hydraulic driven mowers so its good to hear from those that have.

Mith,

FYI, the PT-425 (25HP gas) has an 8gpm at 2500 PSI (max) dedicated PTO pump, an 8 GPM at 2500 PSI (max) pump that powers the steering, lift, curl, and Aux PTO/QA circuits (with priority given to those multiple demands in that sequence), and a 16gpm at 1500 PSI variable displacement pump -- so the sum total output of those 3 pumps can potentially exceed the power available from the engine. All three are direct-connected to the crankshaft -- i.e. spinning at 3600 RPM max.

For example, if you're trying to simultaneously drive, steer, lift, and curl, with the PTO engaged -- everything potentially slows down (most noticeably the steering and lift/curl response) -- it can't produce the max pressures (only the gpm flow) on all three pumps at the same time. I can't tell by the sound if the mower on the dedicated PTO pump slows down, because there's no significant working load (you're not mowing with the deck up in the air only spinning the blades and chopping air)...

Theoretically, both the dedicated PTO pump and the steering/lift/curl/QA pump can produce about 8 HP each at the point of work, given the hydraulic calculators I've seen that factor in efficiency. I haven't done the calculations on the variable displacement drive pump...

Bottom line is that the 25HP machine spins a 60" finish mower (or 48" brush cutter) with about 8 hydraulic HP (max) available at the attachment... that may sound like low HP to those used to ag/CUT/SCUT tractors, but I'd remind them that my 12 HP Simplicity drives a 48" belly mower, giving arguably the best cut in the business (for a tractor), while hauling my butt around...

The design of the deck itself is also important -- the PT finish mower deck would handle tall thick (or wet) grass much better if it were a deeper deck with more room for the clippings to churn around underneath the deck, without having to chop them over and over...

 

[Bob999]

Bob, at the moment I'm really just looking to gain a bit of information rather than copy the PTs system specification.
I might be wrong, but I believe that the PTs only have one PTO circuit that is used for all the attachments, so I would suspect that the flow from that PTO is a compromise to fit as many attachments as possible.

Mith,

PTs have one PTO and you may well be correct about compromise but I think that mowing is likely the design point for the following reasons:
1. The 1845 is primarily a mower. While it is true that other attachments can be used the design appears to be optimized for mowing steep slopes.
2. For the other units, if you look at the hydraulic attachments available none of them require much power for movement when being used, with the possible exception of the powered rake. Conversily mowing, particularly on slopes which is a forte of the PT design, requires substantial power to move the tractor/mower/operator around and the selection of the amount of power to allocate to the PTO must take that into account to get a machine with satisfactory performance.

 

[woodlandfarms]

Belt design identical to my 90" mower...

 

[J_J]

At 18 GPM PTO, a 540 rpm hydraulic motor with a torque of 3,678 in lbs to drive 3pt implement, would need to be 7.7 cu in displacement , and pumping 18 GPM at 3000, would take 37 HP. The efficiency of hydraulic pump to motor is 85 %. This is assuming that hoses are short and sized correctly and QD's if used are sized one sized larger. If you want to know exactly what you have when finished, put a pressure gage and a flow meter in the line and you will know.

 

[MossRoad]

Mith,

PTs have one PTO and you may well be correct about compromise but I think that mowing is likely the design point for the following reasons:
1. The 1845 is primarily a mower. While it is true that other attachments can be used the design appears to be optimized for mowing steep slopes.
2. For the other units, if you look at the hydraulic attachments available none of them require much power for movement when being used, with the possible exception of the powered rake. Conversily mowing, particularly on slopes which is a forte of the PT design, requires substantial power to move the tractor/mower/operator around and the selection of the amount of power to allocate to the PTO must take that into account to get a machine with satisfactory performance.

The PT425 has one MAIN pto with 8GPM@2500PSI and one AUX pto. The aux is what powers the cylinder for the quick attach, steering and lift arms, as well as the angle on the plow, the grapple, etc...

 

[SnowRidge]

Mith, the deck mounted hydraulic motor that came on my 48" brush cutter was a re-branded M+S Hydraulic MLHR 50 wheel motor. M+S Hydraulic is a Bulgarian company. The motor seized, and I replaced it with a Parker TJ0050US080AAAA wheel motor, which has roughly the same specs. The Parker was built to order for me. Nobody had them in stock.

I strongly suggest you do not directly deck mount the motor, as Power Trac is now doing with the 48" brush cutter. In my opinion, the shock loading is what caused my motor to fail very early in life. The older models have a different motor mounted on a bracket. The motor is coupled to a blade hub by a Lovejoy coupler. It provides at least some isolation from shock loads. The variant I have has none.

It is easy to find straight shaft motors of the right size for the old style brush cutters. It is very difficult to find tapered shaft wheel motors for the current models, other than the M+S model that failed, which is quite expensive. The Parker was much cheaper, but must be built to order, and most US suppliers don't catalog it.

I did not want to go with a larger displacement wheel motor, which are much more readily available, as it would have produced unacceptably slow blade speeds.