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

 

[MReeb]

Well I was planning on using the cylinder because I have it. It is not worth anything to anyone so...
I came across a 8' long 12" high piece of I beam with 8" width on the top and bottom a few years back. That's the piece I planned to use for the frame of the splitter.
I've had a few logs come popping out at me too if the blade was vertical to the beam. I've used one that had a slight angle on it and didn't have the same problem with the logs. I was also thinking of having the stationary edge on a slight angle.
Think 50t will chop the logs? It would save wear and tear on the chainsaw

 

[Wayne County Hose]

I think I'm missing something here. What is the bore of the cylinder?

 

[Leejohn]

I'm with you Wayne something sure went over my head. And one that took my hat off (full rpm to raise a loader to back up.)

 

[MReeb]

I think I'm missing something here. What is the bore of the cylinder?

The cylinders on the loader are 2 1/2" (times 2 cylinders for the lift and times 2 for the bucket). The cylinder for the logsplitter is 8" with a 2" shaft. Doing the math for the logsplitter (force = 3.1415 X r^2 X psi) I get just over 100,000 pounds or 50 tons.

I'm with you Wayne something sure went over my head. And one that took my hat off (full rpm to raise a loader to back up.)

Growing up on a farm, we had quite a few tractors with FEL on them. It always seemed like an issue to get any decent movement out of the loader without the throttle at 75% to 100%. So my thought was that if I increase the pump flow rate I would be increasing the cylinder speed.
If I want to run something like a logsplitter then having that extra flow would keep the cycle time the same without having to keep the tractor throttled up. (theoretically if I still have enough hp at the lower rpms to keep the pump from bogging down the tractor)
The cycle time for the logsplitter will be increased from roughly 75 seconds down to 60 seconds by going from 12 to 14 gpm.

 

[SPYDERLK]

The cylinders on the loader are 2 1/2" (times 2 cylinders for the lift and times 2 for the bucket). The cylinder for the logsplitter is 8" with a 2" shaft. Doing the math for the logsplitter (force = 3.1415 X r^2 X psi) I get just over 100,000 pounds or 50 tons.

That must be a low pressure cyl. That rod is the smallest Ive ever heard of on an 8" cyl. Only other thing I can think of is its a single acting 'pull' cylinder.
larry

 

[Wayne County Hose]

Larry is correct. I too wonder what function that cylinder was for.

 

[john_bud]

To answer your original question - there will (95% sure) no problems going to a larger pump. Fords of the same era and size usually had 14 gpm pumps at 1800 rpm. Going up to 16 gpm at 1600 rpm should still be ok.

jb

 

[Wayne County Hose]

The cylinders on the loader are 2 1/2" (times 2 cylinders for the lift and times 2 for the bucket). The cylinder for the logsplitter is 8" with a 2" shaft. Doing the math for the logsplitter (force = 3.1415 X r^2 X psi) I get just over 100,000 pounds or 50 tons.

I'm willing to bet that this is a pneumatic cylinder. Tan in color maybe?