Size of hydraulic pump/reservoir for GN graintrailer ??

Got a bargain on a old grain trailer last year and am using it to haul manure/gravel with it (only reason I bought it). It was an old truck bed with single duals. Previous owner added another 3 ft or so and another axle with duals (all are 9.00x18). Not pretty but was done pretty well. Currently pintle hook, will convert it to GN when I got some time and $.
Hydraulic system: dual cylinders (each a "triple piston" or"cylinder in cylinder in cylinder", depending who I talk to), connected together with tractor hydraulic line at a T and single connector for power up, hold and gravity down. "Big" Cylinder total length 29", diameter 5". Been using my JD 5010 (pushing it) to power it, but wanting to get/make a portable hydraulic over electric (12V)system to unload it. Portable because I want to use it to lift up hydraulic headers on combines that I am collecting (done with jacks, lifts, holding chains etc. in the middle of nowhere....LOL).
Questions are:min/max operating pressure capability for both applications of the pump (power up, hold, gravity down) and size of reservoir? Is 5 gal enough? If a cyl. were empty, no piston, it would be roughly 570 inch2, about 2.45 gal. Just don't know how to account for the piston/cylinder itself on the 2nd and 3rd stage. Have also option of 4 gal tank if it fits, would be lighter to move around.... How about a small primary tank (1-2 gal) with an axillary tank connected to it for the trailer???
Any thoughts appreciated. Thanks in advance,
Ralph in OK.

I"m going to guess that there is about 300 cubic inches of oil in that second stage lift.

So your going to need about 4 gallons for each cylinder, 8 gallons total. So you need about a 10 gallon tank to allow for a little head room in the tank.

An extra tank could be mounted and left on the trailer frame when you remove the pump. But your hose connections will be an oilly mess every time you disconnect from the extra tank. Unless you use some large quick couplers of some kind. I"m afraid your normal pioneer couplers will not allow enough flow by gravity to keep from straving the pump for oil.

Just my thoughts. Gary

Forgot the 3rd stage. Add another gallon for each cylinder.

Gary

I am not sure what you are asking. If you want to power other things with the power unit you add to the trailer, then it depends on the hydraulic needs of the secondary need. If you have a larger cylinder on the header lifting unit you have to size it according to the largest requirement. Reservoir 2x the size of pump capacity for a minimal system, add coolers and more oil if you use it frequently.

Sorry I couldn't help more.

You can buy the pumps and reservoirs as needed from any place that sells truck hoists or go to Bailey sales they can fix you up with what you need. It will be cheaper and safer to go that route. Hoists can cause a lot of damage if they fall. Most hoists operate on about 1500-3500psi. The older ones had less psi.
You could run this off from a pto or off a hydraulic motor. We did that with one to turn the pump shaft then used the valve to lift hold and lower.

Per IaGary"s answer...Aeroquip makes special
high flow quick couplers for situations such as
this! (since Eaton purchased Vickers, Who owned
Aeroquip, this may be an Eaton product now.They
were a screw togather coupler, with big wing nuts)