Improving hydraulic bottle jack

[nhengineer]

This is basically what I tried, but I got to the stage where I got concerned about breaking something. I had to google what a MF wrench was, it was what I tried but I am used to them being called Stillsons. Trans-Atlantic language differences..

I'm curious what GOOGLE thinks a "big MF pipe wrench" is. Around here (central NH, USA) the "F" part is an expletive and the "M" part stands for mother. It looks like this only the handle is 48" long.

Here's the WEB page. https://www.whitecap.com/shop/wc/p/r...iABEgICk_D_BwE

In the case of my jack a calculation showed around 8,500 psi for max load.

There seem to be much better seals available than those fitted, it looks like most would require a different piston but that is almost a trivial thing to make. With your experience do you have any recommendations for a better seal type? I am thinking of a U seal with O-ring backup.

Back 30 or so years ago I purchased my parts kits from The Jack Pack & Tool Company on N Marianna Ave, Los Angeles, CA. They are out of business - couldn't compete with $25 Chinese throwaways. Now, if it won't hold the weight, I put in a new ball check (from McMaster-Carr). The ram cup is usually not available but ram cups seldom are the problem anyway. The only other "seal" is the shaft wiper (and now-a-days that usually just a standard O-ring), the release needle valve housing and the pump ram (and they're usually just O-rings too). I've seen some jack rams with double or triple O-rings instead of a cup. That kind may NEVER give satisfactory results under max load after a bit of use and maybe not even when brand new.

Basically, if it won't hold the weight, it's the ball check and that's just a commercial steel ball bearing. If the ram cup is worn out, I trash the jack because, if it's worn out by spending its life in nice slippery hydraulic oil, it's seen a great deal of use and time to be retired. Same deal for the pump ram. The pressure is generated by the pump ram with a ball check usually on the far end of the chamber.

The gauge on my 20-ton press is maxed out at 40K psi. That's when the relief opens. Working pressure is red lined at 30K but I've occasionally loaded it up to 40K on special occasions. 8.5Kpsi should not be much of a challenge even for Chinese jack power units.

Does the ram creep back under load? That would most likely be the check valve. I'm glad to share what I know with you.

I hope I've helped somewhat. Get back to me if you need more information.