Sizing of Motor/Resevoir/Etc of Hydraulic Power Unit

Unless you are going to buy all this stuff from a junk yard, go to a place that sells hydraulic systems and ask them for help.

Or, go watch someone lift a house to see what all is involved. The maze of hoses and the bank of valves can be daunting.

Lifting a house is delicate business.

A 4" inch ram seems large to me. 2500 PSI over 4 square inches does not equal 15 tons.

Also, I'm dying to know why you want to lift your house.

Yeah, everybody was closed yesterday with the 4th. I'm going to make some phone calls today. We've got some hydraulic suppliers around here (Southern Maine) and I'll try that. "A 4" inch ram seems large to me. 2500 PSI over 4 square inches does not equal 15 tons." Here's how I happened to come to that: quoted from a site .... If the cylinder diameter is 4 inches, then you would multiply 3.14 times 4 inches times 4 inches, divided by 4. Therefore, the area is 12.56 square inches. Multiply the pressure rating, in psi, by the area. In the example, if the press offered 2,500 psi, then you would multiply 2,500 by 12.56. This gives you 31,400 pounds.Divide the number of pounds by 2,000 to convert to tons. In the example, 31,400 divided by 2,000 gives you a force of 15.7 standard tons. You see, I've actually got 3 houses to lift in order to make certain repairs (I'm a contractor) and I've always done this with bottle jacks. Instead of running around from jack to jack I'd like to have cylinders set up. It's not the hoses or valves that I'm co fused by, it's the GPM, HP, and the size of the power unit itself that I haven't got any experience with.

Right. Don't know where my head was. _{(Somewhere out of sight, maybe)}

All other variables aside, a 4" diam. ram will generate 15.7 tons with 2500psi applied. If lifting the entire house is what you're planning (for moving the house or reconstructing the entire foundation) is tricky business. Aside from the hydraulics involved, there are a maze of support beams and cribbing installed under the structure to maintain squareness and level. That takes a lot of architechural engineering study beforehand to make sure your doors and windows will still open and drywall doesn't crack. There are lots of companies that do nothing but this, and I too am curious as to why you want to do it on your own.

I'm a contractor with many years experience jacking old buildings, barns, etc. - the hard way. I'm fully aware of the structural side of lifting the house. All I'm not sure about is which power unit I should choose. Or, more precisely said, why I should choose the power unit which is the power unit I should choose.

I should say, a company that does only this wants $18,000 for a one day lift. I'm all for using subcontractors to save me time and money, but I think I can beat that cost. That's why.

The reservoir volume should be about twice the total internal volume of all the jack cylinders. To get gpm, divide the total cylinder volume (in gallons) by the number of minutes allowable for the lift. Theoretically, hp = psi x gpm/1752, but because of imperfect efficiency, you could divide by 1500.

Exactly what I was looking for! Thank you.

Incidentally, those who respond to forum questions have no Idea the expertise of the one asking the question. It's always safe to rule out that we're not giving advice to a "Tim Allen, More Power". In your case, it sounds as if we're preaching to the choir on the structural side of things.

BTW: I tested Tornado's formula for HP against what my log splitter has, and came up with a divisor of about 3600 instead of 1752. 11HP engine, 2500psi, 16 gpm pump. I may be off-base here because it's a 2-stage pump, but was just curious.

So then what's a 2 stage pump? Any idea?

A Two stage pump is a pump with a high flow low pressure stage, and a high pressure low flow stage. Common application would be a log splitter. The cylinder will extend quickly during the first stage, producing small force, and once the load is detected, the pump switches to stage two, which supplies high pressure/high force, but little speed.

hope this helps.

-R

have you got a quote for renting the power pack , valve body and cylinders ?

i have often rented lifting gear and hydraulics

if the contractors want $18,000 per day you might find you can rent the gear for $ 1200 - 1800 per day and come out cheaper than the cost of building your own.

if you do build your own dont forget to include overcenter locking valves on the lift cylinders in case you burst a hose , secondly ensure you have check valves on the valve body so a heavy part of the house doesnt transfer pressure through the hoses to the cylinders with less weight and force them to pop up higher and twist the house's pants right off

honest... i see it happen to a girl once and it gets really messy

UPDATE: I have been searching all over for a rental house with some hydraulic jacks and everyone here in Maine is looking at me like I have 2 heads. So, option 1 is build a system for $?,000. Option 2, spend $400 on 8 20 ton jacks and run around cranking one, then another, and so on, and on. I guess it's time to consult the local hydraulic guru for a quote and weigh my options. I guess I'd like to build my own system and have it. Like I said, folks make big bucks doing that work around here.

with the economy being trashed everywhere there are heaps of second hand power packs , forget building one for 3000 when you can buy one from the guy who needs to eat tomorrow for maybe 400 bucks.

cylinders the same .....

browse online , auctions etc ?

$3000 would be very lite if you are after an ideal circuit, that is designed to do exactly what you need.

Good luck