Hydraulic Pump Sizing

[MReeb]

I'm planning on installing a FEL on my tractor. The OEM pump designed for the tractor is rated at 12.8gpm at 2000rpm. I found some Cessna pumps that will pump up to 18-20gpm at the same rpm. I was thinking about upsizing the pump to allow for future expansion (adding a grapple or maybe a log splitter). Is sizing the pump roughly 50% larger going to cause issues with oil heating, etc...? The system will be open center.

 

[SPYDERLK]

Are you replacing your existing pump or adding one at the PTO? If replacing, is the drive mechanism able to apply the added torque required? Heating may be an issue with losses incurred by the higher flow in the original sized tubing. All that can be dealt with but it will take some knowhow. The simplest is if you can add reservoir capacity conveniently. This lets you get rid of the wasted power without running the oil too hot. The harder but better way would be to limit the waste by making the system freer flowing - larger hose and valving.
larry

 

[Farmerford]

Mreeb:

12.8 gpm @2,000rpm, even at only 2,000 psi, is 15-18 horsepower (depending on pump efficiency, line size, etc.) Unless you load a log splitter much faster than I do, that should be more than adequate for a 4" or even 5" diameter cylinder. It is certainly more than enough flow for a FEL. For example, the FEL on my Kubota Grand L4330 lifts 2500#+ faster than I usually want it to on 9gpm. My John Deere 455D crawler loader lifts 10,000# faster than I want it to on about 20gpm.

Unless the new pump is very cheap and easy to install, I would try the old pump first. You may discover something else to spend the money for.

But if you do get the larger pump it will increase the heat generated when the fluid is just circulating (by 50% unless the lines are so small that the flow becomes turbulent when it increases), but that heat is usually insignificant. You will also increase by 50% the heat when the system is working hard, and that might be a problem, if the system heat dissipation capacity is matched to the present flow. But you can easliy measure that with a hand held thermometer on the fitting nearest the pump output.

 

[MReeb]

Sorry guys, I guess I wasn't too clear about what I'm doing. Here's a bit of an explaination of what I'm looking at doing. I have a Massey 165 and the tractor can have a front mounted pump fixed to it. I checked the specs for the pump and it is 12.8 gpm at 2000 rpm. That pump will cost me around $400.00 - $450.00. I did some searching and found that it is a SAE-B flange mount pump with a splined shaft. I checked over on Surplus Center and they have a bunch of different Cessna pumps anywhere from 9 to 23 gpm with the same flange, etc... The cost of these pumps are around $100.00 less than the OEM unit. Rather than getting the one that is rated at 12.5 gpm at Surplus Center, would it be worthwhile to upsize it some (say another 2 to 6 gpm extra).
The FEL I'm looking at specs a 12 gpm flow requirement. With a higher flow pump I wouldn't need the tractor throttled up full to get it moving. I know I will need some throttle to get the hp out of the tractor when getting a bucket full of rock, etc... but I'd hate to have the tractor close to full open just to raise the bucket out of the barn.
I'm hoping to buy just one pump so it would be a pain to buy the lower gpm pump to find out it would be nice to have a bit more umpff out of it (and yes umpff is a scientific term )
Is my thinking right or just stick with the flow rate recommended for the FEL?

 

[SPYDERLK]

Sorry guys, I guess I wasn't too clear about what I'm doing. Here's a bit of an explaination of what I'm looking at doing. I have a Massey 165 and the tractor can have a front mounted pump fixed to it. I checked the specs for the pump and it is 12.8 gpm at 2000 rpm. That pump will cost me around $400.00 - $450.00. I did some searching and found that it is a SAE-B flange mount pump with a splined shaft. I checked over on Surplus Center and they have a bunch of different Cessna pumps anywhere from 9 to 23 gpm with the same flange, etc... The cost of these pumps are around $100.00 less than the OEM unit. Rather than getting the one that is rated at 12.5 gpm at Surplus Center, would it be worthwhile to upsize it some (say another 2 to 6 gpm extra).

MF seems to think the system is sized for 13gpm. A couple more shouldnt hurt and extra speed is nice when you want it. If you go much more you will start noting more significant engine loads when using the hydraulics. That could be quite bothersome under heavy pushing while lifting conditions for instance.
larry
larry

 

[Wayne County Hose]

I would be careful as valves also have a max gpm rating. When you increase the flow within the same system, you do increase pressure. It could give you a new set of issues. I would stay close to the 12.8 gpm rating. You would be shocked at how much flow 2 gpm is in a hydraulic system.

 

[MReeb]

Well I ended up ordering the 14.4gpm @ 2000 psi unit. I checked into the hydraulics on the FEL and it has an adjustable relief valve built into the joystick control. As well, the joystick valve is rated at 24gpm so I think I'm ok there.

Farmerford, I did the math to figure out how much time and force I will have with the cylinder I want to use for the logsplitter. You were right about the speeds. Increasing my pump size drops the cut time from 30 to 20 seconds. Not really much of a time saver to be using that much more hp from the tractor. I think I can make up more time by using a hand control that has the detent return so I don't have to hold the handle on the return stroke. The cylinder is off of an old TD20 dozer and I should be generating somewhere around 50 tons of force.

Thanks for all the input guys! Much appreciated.

 

[Farmerford]

50 Tons of force! You don't even need to sharpen the wedge.

Send us pictures.

 

[B2400]

Wow, 50 tons!! I know how bad it hurts when a piece of wood pops off at around 20T, but that should ensure broken legs!!! What type of beam are you using? I've twisted 6" I beam and 3/8 flanges with the 20T set up, so I hope your using something big-n-stout!!

 

[SPYDERLK]

Wow, 50 tons!! I know how bad it hurts when a piece of wood pops off at around 20T, but that should ensure broken legs!!! What type of beam are you using? I've twisted 6" I beam and 3/8 flanges with the 20T set up, so I hope your using something big-n-stout!!

The trick to prevent twist of an I beam in splitter use is to split a 3" or so pipe and weld the halves back together around the web. - Theres a Greek letter that looks like that, I think. Mines a 6 X 4" beam w 3/8 flanges. No problems for 20 yrs. You can see the beam bow on high push, but no twist. Nowhere near 50 tons. Cant see any need - ever - for over 30. Big cylinders just slow you down.
larry