Inverting an hydraulic jack for a workshop press.

[tonyfoale]

Perhaps I should post a series of pictures of my setup. My pipe connections are a copy of the high pressure couplings used on older models of Citroen cars. A very simple and effective system that easily withstands over 2000 psi.

Don't bother with the picyures for me but they may be useful to others.
I tend to use motorcycle brake fittings and hoses for hydraulics. That's because I have them, Citroen know a thing or two about hydraulics.

[steelspray38]

Thank you so much Tony for sharing. I have wanted to attempt this for ages, now I am sure I can succeed.
Best Regards
Steelspray38

[katy]

I'm not an hydraulics guy, so I don't understand the need for the external reservoir and air bleed. Can you please explain that to this hydraulics dummy.

[tonyfoale]

I'm not an hydraulics guy, so I don't understand the need for the external reservoir and air bleed. Can you please explain that to this hydraulics dummy.

The internal volume changes as the ram moves in and out so provision must be made for the changing volume. A standard jack does this by having an air space above the oil and pump, the air expands and compresses as needed. My jack had the pump at the top where any internal air would be so I had to fill the jack with oil, no air, and have an external oil tank for oil to flow in and out of as the ram moved.
See this later post which has more detailed explanations of how this stuff works.
More on improvements to bottle jack shop press.

[Hans Pearson]

If the jack is inverted and a pipe is run from the pump intake to the 'top' of the jack an external reservoir is not needed as long as the jack bottle is kept filled to the level of the fill point. I found that the standard vicosity oil used in jacks is a bit too thick and the pump may not draw it up. The purpose of the air bleed is to allow any build up of pressure to escape, otherwise the bottle 'top' seal may blow out. This was my Ver. 1.1. I now use an external pump and reservoir but still have a bleed point.

[tonyfoale]

If the jack is inverted and a pipe is run from the pump intake to the 'top' of the jack an external reservoir is not needed as long as the jack bottle is kept filled to the level of the fill point. I found that the standard vicosity oil used in jacks is a bit too thick and the pump may not draw it up. The purpose of the air bleed is to allow any build up of pressure to escape, otherwise the bottle 'top' seal may blow out. This was my Ver. 1.1. I now use an external pump and reservoir but still have a bleed point.

"an external reservoir is not needed as long as the jack bottle is kept filled to the level of the fill point."

That is true, but an external reservoir is not a major addition and I prefer to use a full cylinder. The air bleed was to allow full filling and once the cylinder was full it actually transformed itself into an oil return. My second version dispensed with the outer oil containment cylinder and that did need the external reservoir.
A couple of weeks ago I needed to increase the force capability and I got (actually a Xmas present) a dedicated cylinder and separate pump/reservoir to replace the jack based one.

Click for full size.
The photo was taken during the fitting and shows the pump/reservoir upsidedown, like a normal jack the pump needs to be below the oil reservoir.

[DIYer]

Thanks tonyfoale! We've added your Hydraulic Press Modification to our Brakes and Presses category,
as well as to your builder page: tonyfoale's Homemade Tools. Your receipt:

Hydraulic Press Modification by tonyfoale

tags: hydraulic, modification