Why do CUT manufacturers not install larger hydraulic pumps?

[Piston]

I would love more hydraulic flow/pressure. I don't think it's as simple as putting a bigger pump on though. Look at the Kubota M59 and JD 110. They have much more flow/pressure than normal non dedicated TLB tractors like ours, but they also have a lot less PTO hp of the equivalent sized CUT. If you want more hydraulic hp, you have to give up some PTO hp. It seems they find a happy medium somewhere along the lines.

I could be wrong of course, but it seems like if it was easy to add a bigger pump, they would just add it as another available option. It's no different than having any other factory options available.

 

[Piston]

Your the one that wants more hydraulic flow. I don't. And I don't want to pay for it.

That's why having it as an option would be the best of both worlds

 

[IceStationZebra]

Most, if not all, of the CUTs have open center hydraulics. The implement gear pump is pumping say 20 gpm all the time. Shift one valve for a circuit that uses only a small flow but requires a lot of pressure and all 20 gpm output of the pump will be at that pressure and consequently sucking a lot of power. It's also why they tend to use a double section pump, one section for steering with low displacement and a larger section for implement flow. The steering is almost always in use so the low flow circuit minimizes horsepower loss.

Having a seperate section for the steering also a safety feature, it guarentees that there is always flow available. Plus steering doesn't always run at the same pressure. ISZ

 

[IceStationZebra]

I would love more hydraulic flow/pressure. I don't think it's as simple as putting a bigger pump on though. Look at the Kubota M59 and JD 110. They have much more flow/pressure than normal non dedicated TLB tractors like ours, but they also have a lot less PTO hp of the equivalent sized CUT. If you want more hydraulic hp, you have to give up some PTO hp. It seems they find a happy medium somewhere along the lines.

I could be wrong of course, but it seems like if it was easy to add a bigger pump, they would just add it as another available option. It's no different than having any other factory options available.

I don't see any reason why you can't have more hydraulic flow and a high PTO rating. If I remember correctly PTO power is simply measured at rated PTO speed so they account for the actual rivetrain losses.

What does come into play with a larger pump however is the durability of the pump drive, size of the inlet & outlet lines and hydraulic cooler size. If you want the pump to last is will need larger splines. And you need larger tubing to keep the pressure drop reasonable and not cavitate the pump in cold weather. And if you double the pump you should probably double the available cooling, especially since open-center hydraulics are about the least efficient option. (pressure-comp is much better but most costly and requires more space.) And all this leads to more difficult packaging and higher costs.

ISZ

 

[DavesTractor]

A bigger pump means the tractor has to be designed to handle that pump. Larger suction and pressure lines, larger hydraulic tank capacity, different filtering, more cooling, larger valves, etc. It is more than just installing a larger pump since it is an entire system. And a huge pump requires more HP, so how it connects to the engine becomes a consideration as it will be somehow driven off the front gears for most modern engines, those loads need to be considered as well. It gets complicated....

A power-pack off the PTO is an option.

 

[TomSeller]

What James wrote.
YOU put a $600 pump on your tractor without jacking up the prices on all tractors.

Prince PTO Tractor Pump — 23 GPM, Model# HC-PTO-3A | Hydraulic Pumps| Northern Tool + Equipment

<img src="http://www.tractorbynet.com/forums/files/hydraulics/380145-why-do-cut-manufacturers-not-pto-pump-jpg"/>

A couple if things to note about the Prince pumps. You will need a tank on whatever you are pumping if you separate say your backhoe off of the tractor hydraulics, which then leads to a filter, etc. Also, note that the max pressure on these is only 2000 psi, less than most tractor internal pumps are set up for. So you might gain speed, but lose force from the cylinders.

 

[J_J]

That 23 GPM pump at 2000 will require about 32 HP.

 

[newbury]

That 23 GPM pump at 2000 will require about 32 HP.

So with the OP's 4120 rated at 35 HP PTO would he be just making it? Or does it go by engine hp (41 hp)?

Is there a easy reference chart for GPM and PSI you could show us a link to?

thanks.

 

[J_J]

Computation for HP is just a formular.

Surplus Center

I use this. Surplus Center

Go to hydraulics on left side of page , select Pump Disp. & HP.

Just fill in the blanks.

When the engineers figure the HP, they usually leave a safety factor so there is not a constant overload of stall situation.

A lot of people do not run there engines at max rpm, so the pump flow in GPM's is lower that affect speed of operation.

When the relief valve comes on, the pump is trying to develop or maintain the pressure, which gives the cyl the work potential or the drive system potential. in travel mode.

 

[TomSeller]

When you are running a backhoe it may be okay to use up your HP with the hydraulics, but when needing to go up hills and/or pull something at the same time, you should have a fair amount of HP reserved for that.

I don't know if there is any data for what a large pump takes to simply pump through your Power Beyond ports and back to the tank compared to a small pump. But since loader lift capacity is typically more focused on than loader speed, I would bet that is why pumps in new tractors have smaller GPM capacity. Also the HP it takes to drive the big pumps would be a concern.

Your typical industrial backhoe has way more pump capacity than a farm tractor but they are not typically pulling say a hydraulic flail mower up a hill in a field. A backhoe is stationary when in use.