Last year's iteration of my filtering/transfer setup used a 16gpm @ 3600rpm pump driven by a 1/2hp 1750rpm motor by a belt drive. The belt drive let me change pump speeds to some extent. I normally ran the pump at about 900rpm, or close to the 4gpm mark. The pump uses a 4f17 mount & the motor's on a slide base to adjust belt tension. The motor has a thermal cutout built in, in case it overheats. If I'd known, I'd have spent the extra $30 for a face-mount motor. Doh!
With cold (40deg F) oil, the 4gpm rate got the motor hot to the touch, but didn't trip the cutout or cause any other issues. Hot oil barely causes any warming of the motor. Hot/cold times were within a 30 seconds of being the same from a full barrel on level ground.
I recent pumped several barrels of oil at about 60deg with the pulley ratio changed to drive the pump at 1750rpm. The motor handled it well, if rather warm. I had rather more belt slippage than I really wanted- a pair of 3.5" pulleys rather than the 2" ones I had would fix some of that.
One of my cohorts uses a 11gpm pump directly-driven with a lovejoy coupler & motor/pump mount. The 1hp 1750rpm motor doesn't have any issues at all, no matter what we throw at it. I suspect my 16gpm pump would work well on a 1hp 1750rpm motor.
My new centrifuge pump has a 1hp 3450rpm motor direct-driving a 4gpm pump. I'm really tempted to see if that warp speed motor will handle running the 16gpm pump at full speed, or just pop the breaker. If it works, I may buy a second 1hp motor just to use as a transfer pump- if not, a 1750 should work. I chose a 1hp motor for my centrifuge pump just because the 1/2hp was getting warmer than I'd like.
Note: log splitter pumps come with a hose barb to connect to the tank- some can be unscrewed & replaced with a 3/4" NPT fitting, others use a weird ultra-fine thread. Check the spec sheet closely before buying!
Much as I liked the adjustable nature of the belt system, the tension needs adjusting & it's a LOT more dangerous to use as a transfer pump. The direct-drive has a little access cover that keeps all the moving bits away from fingers, clothing, cords & hoses. A 1/2-3/4" NPT 90degree fitting will accept a 3' stick of iron pipe for an intake, leaving a few inches behind in the drum. Adding a short extension will fix that, if you want to suck one dry. The motor noise drops off when the pump starts sucking air- if it does that while running, grab the pliers & tighten the draw pipe a little more. I usually don't even need to bother using thread sealant.
Here's most of my parts list. I've gotten a lot of stuff from these guys, but they're not the only places to get these things. My new motor's a pretty stainless washdown-rated model from eBay. For a transfer pump, a small gas engine can be used with a matching mount. Ignore the HP ratings the pump calls for- unless you plug a line you won't need anything over 3-5hp, even for a monster 28gpm pump.
Uh, one down side to hydraulic pumps- if you forget to open the outlet valve, the motor will likely run long enough to pop any non-hydraulic hose before the breaker goes. NOT pretty.
Foot mount for belt-driving smaller log-splitter pumps
https://www.surpluscenter.com/item.asp?item=1-3242&catname=hydraulic
4F17 PUMP FOOT MOUNT
Direct-drive motor/pump mount
https://www.surpluscenter.com/item.asp?item=1-3246&catname=hydraulic
56C/145TC TO 4F17 PUMP MOUNT
C-face 1750rpm motor to direct-drive the pump, 1/2hp for 4gpm works great.
https://www.surpluscenter.com/item.asp?item=10-2377&catname=electric
https://www.surpluscenter.com/item.asp?item=10-2379&catname=electric
Disconnects for the outlet hoses: self-seals on both sides & acts like a swivel to prevent kinking. Chose 3/4" for better flow rate. A few drops to wipe up & never leaks.
https://www.surpluscenter.com/item.asp?item=928-C&catname=hydraulic
