Crank-driven hydraulic pump sizing

[Brutus]

Another one for the collective wisdom:

I have a 1960 Case 400B, which is about 35 hp gas. It has live hydraulics that put out about 9 GPM at 1300 PSI with one set of remotes.

I recently bought a pile of parts including a complete loader and front end from a Case 530 backhoe (with power steering!!!), which is a close relative of the 400B. The backhoe had a crank-driven hydraulic pump that put out 20 gpm at 2000 PSI. I have everything except the pump (crank drive, mounting plate, etc), and the loader frame is the hydraulic reservoir for the loader/backhoe. I also have the original spool valve with power beyond valve that could be useful for an additional remote, or to run a 3pt backhoe in the future.

I could run the loader off of the torque tube hydraulics, but since I have 90% of the parts I need and the loader is such a monster, I was thinking that it might be worth it to install the crank-driven pump. Pump sizing has me a little concerned. I would like to run a large GPM pump so the loader moves quickly and to have lots of flow available for future usage as a backhoe, but I am thinking that too big is equally bad. Princess has a pump for 180$ that is rated to 3000 RPM max, with a 25 GPM max flow, and 3300 PSI max pressure. It has the correct physical size and mounting characteristics. I ran the figures through an online calculator, and at 2000 PSI and 25GPM I am looking at roughly a 30 hp draw. This is pretty much brake horsepower of the engine, but it would only be working at that load if the loader was stalled, which is pretty unlikely given that it's an absolute monster of a loader, with really big cylinders, and it will be used for moving dirt, bales and snow instead of gravel and rocks (which is presumably what it was designed for).

Is there a rough guideline for percentage of brake horse power for pump sizing? the 530CK backhoe had a Case gas engine that wasn't much more powerful than the one I have now, but it was only 20 GPM. 

Opinions?

[a109]

Get the PA  pump, set the relief valve at around 1500 psi to leave a good safety margin and you'll have lots of flow and won't stall the engine when the loader can't lift.
John

[Brutus]

Thanks John that is a very good idea. My logic was that I could always add in a flow divider/controller and lower the flow to the loader spools if it was too quick acting, but I doubt it would be necessary. The PA pump is an aluminium body, probably not exactly the best quality out there, but it's made in Italy, and this machine will see mostly hobby use and has a very large reservoir (clean, cool oil), so I think I should get good life out of it.  Can't argue with the price!

[Brutus]

Duplicate post

[BenP]

Will it give you the flow you need at a not-too-high crank speed?

[a109]

He should get plenty of flow at mid engine speed for the loader. All in all I'd say its a good choice
John

[Brutus]

UPDATE:

I finally got this done. I used an MP Filtri pump from Princess Auto that is rated for 25 GPM at 3000 rpms. It is direct driven off the nose of the crankshaft wit the factory coupler shaft, but I had to make the mounting plate.  I am really impressed by the quality of the pump for the price, it was on sale for $150 and it was described in he catalog as having aluminum end caps with an aluminum body, but in fact it has iron end caps and steel gears with an aluminum body. I did some digging and it's a very common pump, which Princess must get a screaming deal on to sell at that price.

Anyways, the loader is fantastic, it moves fast, it's very strong, and the best part is that even at a 2000 PSI relief valve setting the engine will still drive the pump without stalling at anything above idle. It's really nice to have a big, strong loader with down pressure and high lift. As we're moving again this fall I'm not sure if I will hang onto it or sell it, tractors (especially with loaders) are the handiest thing!

[a109]

You know you won't be able to sell it...once you have had a tractor and loader you just can't do without one!!
John

[Brutus]

The part that really hurts is outfitting them with the requisite fashion accessories such as a blower, loader buckets, forks, blades, etc 

[bens101fc]

You know you won't be able to sell it...once you have had a tractor and loader you just can't do without one!!
John

Yes,  I'll never let go of my backhoe.

Ben