Hydraulic Jack Reversal

[lane]

At some point in time I saw their was a way to plum a Hydraulic bottle jack so it would work up side down. I am building a Hydraulic press and would like to use a harbor freight 20 ton bottle jack turned bottom up .
Can some one explain are sketch me a diagram of what to do. John Stevenson where are you. Help.

[steverice]

Sounds like a question for an Australian.

[Andrew_D]

I've seen a couple of fixes...

Background info for those that don't know: On most of the jacks, the outer shell holds the oil. This oil flows under gravity into the base where the pump is. The pump then pressurizes it which raises the piston. The problem comes when you try to pump upside down. The oil can't gravity feed into the pump since the pump is now at the top.

Option #1: Disassemble the jack and install a pickup tube from the pump down to the bottom of the jack. (Well, it's the bottom now, but it used to be the top!) This will allow the jack to suck the oil up to it.

Option #2: Drill and tap a hole into the base of the jack (used to be the bottom...now it's the top), or in the side. Connect that to a reservoir above the pump. Don't forget to plug off the jack's original fill plug so the oil can't come out there! Now, you may find that you have to pump the jack a bit depending how far down you drilled the hole...the farther down, the more air there is from the hole up to the pump.

Good luck!

Andrew

[J. R. Williams]

Hyd Jack Inverted

The "Village Press" has an article on building a hydraulic press and mounting an oil reservoir above the jack body in an older "Projects in Metal" book. They should be able to supply a reprint for a nominal fee.
JRW

[lane]

Thanks all. I went a Googleing and found some answers . Again thanks.

[Willy]

It certainly doesn't answer your question, but is there any compelling reason that the jack has to be upside down?
Seems it would save a lot of aggravation and fabrication to leave it right side up.
Not sure of your design so I may be out of line.

[TGTool]

Thanks all. I went a Googleing and found some answers . Again thanks.

And the anwser was ... ? Some of us have been waiting with bated breath to get the story or to find out which of the propositions was right and who might have just been full of something. Please share your thoughts.

[vpt]

Most of the time the jacks aren't turned upside down. They just add a post to the bottom.

[Jaakko Fagerlund]

Neither do I understand why the jack has to be upside down, as it also makes the pump lever operate upside down.

But yeah, you can easily modify it by adding a length of pipe to the hole in the oil reservoirs bottom that leads to the pump.

I'm doing a press myself too, but I just milled the botom flat and perpendicular to the piston and added a manometer to see the pressure (which can be 55.5 MPa in a 4 ton bottle jack!).

[Carld]

The biggest reason for mounting it upside down is rigidity. I have used presses with them upright and upside down and I prefer having them upside down. So, when I saved a press frame from being scrapped out I modified a bottle jack to work upside down with a sliding head mount.

Also, you don't have the guide columns, springs and base plate to deal with and it's more compact.

It's a very rigid arrangement mounted inverted.

[vpt]

The biggest reason for mounting it upside down is rigidity. I have used presses with them upright and upside down and I prefer having them upside down. So, when I saved a press frame from being scrapped out I modified a bottle jack to work upside down with a sliding head mount.

Also, you don't have the guide columns, springs and base plate to deal with and it's more compact.

It's a very rigid arrangement mounted inverted.

Well if a guy were building the press from scratch he could use something like linear bearings for the guides and save the bushings in the jack. I had a reversed jack press years ago as well, the bushings in the press went south and then the jack started to leak. Unable to get parts for the old OTC jack the whole thing was scraped.

[Carld]

Linear bearings would be a little over kill for a press. Why scrap the whole press because of a bad jack? Why not replace the jack?

[vpt]

Linear bearings would be a little over kill for a press. Why scrap the whole press because of a bad jack? Why not replace the jack?

Well honestly the whole press was kind small and had its problems. I didn't have much room in the small shop at the time and to replace the jack would mean redoing the whole pump system again. At the time it just wasn't for me. Now with the tools I have I could have made up new bushings and fixed the OTC jack and would have definably kept the press.

There was a link posted on this forum awhile ago for a sale on linear bearings. I believe they were quite cheap (like $15 each) which I think would make it worth it on a shop built press.

[lane]

Well I am building a press out of what I have on hand as far as material goes . My up rights are 2x4 rectangle tubing and only about 5 feet long . So to gain working room i wanted to use the jack in reverse so no plate are guides needed. But have come up with better idea now. I need to find a hydraulic cylinder instead . I already have a nice hand pump I can use. And need to find material to make the table. Remember I am cheap . I don`t spend money to build stuff i beg borrow and steal.

[Jaakko Fagerlund]

How much force you need out of that press (tons)? At least here I'm able to get new hydraulic cylinders for around 50-100 EUR that can be welded, holds up to 200 bar pressure (by design, the cylinder easily holds 400-500 bar) and generates from 1-15 tons depending on the size and the travel is between 50-1500 mm.

IF you are lucky you might find a used and bigger one for cheap, but I'm suspecting that if you go too cheap your press won't hold the forces and disintegrates itself under load. This is why it is a good idea to really make some calculations regarding the strength of materials as this not only gives you the limits your press will handle but also it reduces the weight and material costs a lot.

If I would have just guessed the materials needed for my press, it would have probably had a weight of 3 times more than necessary and the cost would have jumped to around 5-7 fold. But because I spent a couple of hours learning and doing calculations I was able to have the same press - for cheap