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?