Determining motor/pump size

[dodge85rc]

I have a 72" toro mower deck that I want to drive hydraulically. I have been told by my brother, who is a mechanic for toro, that this specific deck was used on models of their groundsmaster mowers that had anywhere from a 22hp engine on them up to 40 hp. If I recall(and i am in the process of verifying this), the PTO speed for the deck is 1800 rpm. I am trying to size a pump and a motor to use for this application. I had tried collecting junk yard parts to "mix and match" to accomplish this but am quickly realizing I need to size this right or I am going to end up set myself up for failure. Not sure where to begin. This is for a home build custom tractor I am building. As of last week, I am in the works of aquiring a 100 hp subaru engine for this tractor , so powering the pump is not an issue. I currently have sitting in my shop a 5.4 gpm vane pump, 10 gpm gear pump/motor and a big hydraulic clutch pump, with currently unknown specs.

 

[J_J]

If you have 31 HP, you can run a pump pumping 15 GPM's. That means you can transfer about 26 HP to a hyd motor. That deck will probably run on 10 to 15 HP. It will depend on where you are putting the hyd motor as to the size. Are you wanting to turn the drive shaft with a hyd motor, or mount a hyd motor directly to the deck?

Do you have any pictures of the deck showing the pulleys.

This is how the Power-Trac decks look with a hyd motor. It is probably something around 3 to 5 cu in cu in. This valve will let you control the speed of the motor.

https://www.surpluscenter.com/item.asp?UID=2009120107180253&item=9-4169-10&catname=hydraulic

I would select a hyd motor that will develop about 15 HP, and work on the pulley ratios to get the speed the deck requires.

 

[dodge85rc]

If you have 31 HP, you can run a pump pumping 15 GPM's. That means you can transfer about 26 HP to a hyd motor. That deck will probably run on 10 to 15 HP. It will depend on where you are putting the hyd motor as to the size. Are you wanting to turn the drive shaft with a hyd motor, or mount a hyd motor directly to the deck?

Do you have any pictures of the deck showing the pulleys.

This is how the Power-Trac decks look with a hyd motor. It is probably something around 3 to 5 cu in cu in. This valve will let you control the speed of the motor.

https://www.surpluscenter.com/item.asp?UID=2009120107180253&item=9-4169-10&catname=hydraulic

I would select a hyd motor that will develop about 15 HP, and work on the pulley ratios to get the speed the deck requires.

The current set up I mounted, has the motor mounted via lovejoy coupler, directly to a right angle, 1:1, gearbox on the deck. The other side of the gearbox has the drive pulley. I can maybe get some pictures tonight with some pulley measurements.
Just curious where you are getting the 31 HP from though?

 

[J_J]

You said that engines from 22 to 40 HP was used on the Toro, so I just picked one for reference. If you are going to use that 100 HP engine, then we should be able to figure out which pump will work best. Of course you can drive a very big pump with that engine, we can figure the HP required on the deck. You could put a hyd motor on the deck as big as the hyd pump will support, but that is going way beyond the norm. A big enough hyd motor to develop about 20 HP should be sufficient. That clutch type hyd pump might work just fine, if you can determine the particulars.

 

[dodge85rc]

I took a couple of pics tonight. The pulleys are 6 1/2" pulleys, on the gearbox end and then to another 6 1/2" pulley that has an individual belt going to both sides of the deck. The pulley on the gearbox is splined and takes what appears to be a B or a C type belt. My bro said max RPM at the gearbox is 2700 rpm. So I would guess that the 1800 rpm I thought I remembered from before is probably a good base to start with.

 

[J_J]

I did not realize that you already has a hyd motor mounted. Do you know what the pressure and displacement of the hyd motor?

I am converting a bush hog mower into a hyd drive unit, and knew the rpm was 540 from the tractor, so looked on Surplus Hydraulics for a motor that matched up to the shaft rated at certain HP. One like this.

https://www.surpluscenter.com/item.asp?UID=2009120118352695&item=983-1034&catname=hydraulic

 

[dodge85rc]

I did not realize that you already has a hyd motor mounted. Do you know what the pressure and displacement of the hyd motor?

I am converting a bush hog mower into a hyd drive unit, and knew the rpm was 540 from the tractor, so looked on Surplus Hydraulics for a motor that matched up to the shaft rated at certain HP. One like this.

https://www.surpluscenter.com/item.asp?UID=2009120118352695&item=983-1034&catname=hydraulic

I am in the process of finding more of that out. It is a hydreco model 1510c3c1 . I was told by my dad, who bought it new, that it could be either a motor or pump. I did contact Hydreco directly to inquire about specs and was able to get specs from them on their superceded part as this model is no longer in production. However their superceded model is not recommended for use as a motor, so I am waiting to hear back from them on if that applies just to the superceded model or the one I have as well. Like I said, I had mounted the motor before when I was trying to use the mix and match what I can find for free method and it can come off real easy if determined that I need something else. I do have a huge motor from a hydrostatic drive unit, but I would imagine that that would never be able to spin fast enough to be usefull. I also may have access to what I am told is a 1800 rpm motor off of an old dirt stacker/conveyor from a screen machine.

 

[J_J]

One thought on the gearbox. Is it a 1 : 1, or 1: 2, or 1 : 3 ?

 

[dodge85rc]

According to the manual 1.26-1

 

[dodge85rc]

Found out some info on the motor currently mounted on the deck. The 1510M series pumps/motors. Specs as pump. 10 gpm at 2000 rpm. Max rpm 3000, max psi 2000 . At 2000 psi it requires 20 hp input at 3k rpm.

As a motor. Max psi 2000, max rpm 3600. At 2000 psi at 3000 rpm it requires19 gpm to create 14 hp. However at 2000 rpm it requires 14 gpm to create 10 hp.

At least that is how I am reading the manual the manufacturer sent me.

 

[J_J]

Have you decided whether to drive the deck directly, or drive it through the gearbox?

 

[J_J]

According to the formula at Surplus Hydraulics, a 10 GPM pump at 2000 psi, will take 14 HP to run it.

Did the manual state the cu in of the pump/motor?

 

[dodge85rc]

Have you decided whether to drive the deck directly, or drive it through the gearbox?

I would like to go through the gearbox. Then I don't have to worry about trying to match the splines on the pulley to the splines on the motor.

The manual does not state that specification. I will email the company again and see ifthey can provide that.

 

[dodge85rc]

1.180 cu.in

 

[dodge85rc]

bump.

 

[J_J]

1.180 cu.in

Using a pump of 1.2 cu in, GPM at 1000 rpm = 5.2 GPM, HP required 11
-------------------------------- 2000 rpm = 10 -GPM-------------21
-------------------------------- 3000 rpm = 14 -GPM ------------29

A hyd motor, 1.2 cu in, with a hyd input of 14 GPM will turn 2695 rpm and develop 573 in lbs
-------------"""""""""""---------------------10 GPM ---------1925
-------------"""""""""""---------------------5.2 GPM---------1001

 

[dodge85rc]

So will that motor work do you think?

 

[J_J]

So will that motor work do you think?

If in fact it is a hyd motor, with a 1.2 cu in displacement, it will work if you use an engine with about 22 HP. It will work to some degree if you use a smaller engine.

We still don't know if the pump/motor was driven directly off the engine or had the rpm reduced down to a certain rpm just for the pump. Whoever has the manual on that unit would know the answer.

 

[dodge85rc]

That motor is able to be used as a motor. I did confirm it with the manufacturer. I had originally looked at the wrong section of the manual. So ideally, I would want to find a pump that will put out 10-12 gpm?

 

[jenkinsph]

What is wrong with the existing hydraulic motor? Any reason you cant use it as is?

now if it is worn out I would consider crossing over to a Commercial Shearing motor with the similar specs. These are good quality and also available with the end fed hoses.