pump/motor/reservoir size help for two 36" stroke cylinders-first timer

[vince12]

I have a pair of 2500psi cylinders going on a dump trailer that will carry no more than 2,000 lbs. The cylinders are 48" long, 5" diameter with a 2" rod, 36" stroke, power up/power down . They are overkill but I got them cheap! I need help deciding what size of motor/pump/ and reservoir to get to power these cylinders. Thanks

[J_J]

This unit will power and down, pumping 1.3 GPM, @2500 psi

Surplus Center - 12 VDC 1.3 GPM 2500 PSI SPX DA POWER PACK

That 36 in stroke, and 5 in cyl bore, will push 49,000 lbs at .3 in per sec. = 120 sec or 2 min.

With that kind of power, you could rip the bed off the trailer. There will be less power at smaller angles.

At 45 degrees, you are still pushing at 37,000 lbs/16 ton.

Extended, each cyl will hold about 3.12 gal x 2 = 6.24 gal

Retracted, the cyl will hold about 2.63 gal. Difference of .489 gal x 2 = .978 gal

Larger tank.

http://www.surpluscenter.com/item.as...name=hydraulic

[davedj1]

Seeing how it won't be used like a log splitter I would get a pump and reservoir just big enough to fill them. Your not going to heat the oil up in that short period.
That being said, you will have to do some math to figure gallons required including all hoses.
I know my 30" stroke 4" with 1.75" rod will hold over a gallon, closer to two.
I'm not the best at the math but I think this is how to do it,
piRsquared times length of stroke minus piR squared times length of shaft
R for cyl would be 2.5" and R for shaft would be 1". Then convert that to gallons. About 231 cubic inches to the gallon.

[Farmerford]

Each 36" x 4" x2" cylinder requires almost exactly 1 1/2 gallons for a full stroke. So two cylinders is 3 gallons. If you use the full stroke your pump will have to discharge 3 gallons into the cylinders, plus a bit for the pump body, lines, etc. Seems to me you need a 3 1/2 or 4 gallon reservoir. I am sure there are some 12V DC pump/reservoir sets that hold that much, but I don't think they are very common. One that size may be expensive.

[J_J]

Cylinder volume capacity (Gal.) = Pi x radius2 (inches) x stroke (inches) / 231

I would say those 5 in , 2 in shaft cyl are a waste of potential power.

Save them for another project.

[davedj1]

Monarch hydraulic DC pumps

You may have to buy one with a smaller reservoir and modify it.

[Farmerford]

OOOPS! I made a math error. Each cylinder requires nearly two gallons for a full stroke.

[vince12]

Seeing how it won't be used like a log splitter I would get a pump and reservoir just big enough to fill them. Your not going to heat the oil up in that short period.
That being said, you will have to do some math to figure gallons required including all hoses.
I know my 30" stroke 4" with 1.75" rod will hold over a gallon, closer to two.
I'm not the best at the math but I think this is how to do it,
piRsquared times length of stroke minus piR squared times length of shaft
R for cyl would be 2.5" and R for shaft would be 1". Then convert that to gallons. About 231 cubic inches to the gallon.

Thanks for the input guys. I appreciate the link JJ I will look into that powerpack. Davej the reason I want to leave them power up/down is due to the fluid volume, it will take around 3 gallons per cylinder im guessing to fill each cylinder, which means id need around a 7 gallon tank...

[Leejohn]

You might not need any bigger tank then what comes with that pump. Just pull the cyls all the way out and leave the hoses off the base end. Fill the tank and start pumping into the rod end, don't let the tank run out of oil. After they are full just run the pump in the other direction long enough to fill the lines. now hook up the base end lines and it should be full of oil and has no air in the system. Then pump well use the returning oil to keep oil in the tank. If you pump into the base end first the tank well overflow a little, but after 1 or 2 times going all the way in and out it well level off.

[vince12]

You might not need any bigger tank then what comes with that pump. Just pull the cyls all the way out and leave the hoses off the base end. Fill the tank and start pumping into the rod end, don't let the tank run out of oil. After they are full just run the pump in the other direction long enough to fill the lines. now hook up the base end lines and it should be full of oil and has no air in the system. Then pump well use the returning oil to keep oil in the tank. If you pump into the base end first the tank well overflow a little, but after 1 or 2 times going all the way in and out it well level off.

Useful info thanks leejohn. Another question, how do I split the power up/down lines to go to each cylinder? (2 up lines and 2I down lines, one for each cylinder) just a coupler the splits off?