Bottle jack conversion

[jmc]

Hello,

How difficult would it be to convert a bottle jack to a jack run off an external pump?

Thanks,

John

 

[KennyV]

Remove the plunger and piston, then block the inlet from the jack oil reservoir, tap threads to attach a hydraulic line in the cylinder bore, and it should work.

 

[Scotty370]

Wouldn't you just be turning your jack into a single-acting cylinder? What's your application? ~S

 

[jmc]

Scotty,

I bought two nice 20 ton bottle jacks at an auction for $13 each. Made in Canada, not Asia. Couldn't find single acting cylinders for that, especially with a flat base. I'm going to make a special purpose hydraulic press and want to incorporate a pressure gauge.



Kenny,

Thanks. Nice to find that out without having hydraulic fluid dripping from my elbows. Would that inlet from the reservoir normally be threaded?

John

 

[KennyV]

John...
The jack oil supply will be port into the hand pump cylinder. It could be external or internal. It has a check valve that may prevent your supplied hydraulic pressure from getting into the jack oil reservoir. You can try to remove the check valve and plug the port but it sounds as if it could be a quality jack you are working with so the supply check valve may be more than adequate to prevent pressure being applied to the reservoir. You can make a great press this way, sounds as if you have it mostly under control. KennyV.

 

[jmc]

John...
The jack oil supply will be port into the hand pump cylinder. It could be external or internal. It has a check valve that may prevent your supplied hydraulic pressure from getting into the jack oil reservoir. You can try to remove the check valve and plug the port but it sounds as if it could be a quality jack you are working with so the supply check valve may be more than adequate to prevent pressure being applied to the reservoir. You can make a great press this way, sounds as if you have it mostly under control. KennyV.

Kenny,

That makes sense. Thanks.

BTW, do you know if these bottle jacks are designed to operate at 2200 psi or so?

John

 

[KennyV]

do you know if these bottle jacks are designed to operate at 2200 psi or so?

John

Yes it should easily take 2200psi, if you know how large the piston, in square inches, (ram base) is you can multiply that times your applied pressure, that will give you the lift force. KennyV

 

[RonMar]

How big around is the main part of the bottle jack body? If you know the body diameter, you can subtract a little for the wall thickness and probably get pretty close to the approximate hydraulic piston diameter. Once you know the piston diameter, it is pretty easy to figure the pressure required to deliver the rated 20TON force. As an example, a 4" cylinder has 12.57 SQ/IN of surface area. If you divide that surface area into the jack output force of 20Ton/40,000 LB, you get a hydraulic pressure of around 3182 PSI to provide that much force. A 6" piston has a surface area of 28.27 SQ/IN and would only require 1414 PSI of hydraulic pressure to deliver the same 20TON force.

Once you dig into the valve, you may also find a safety pressure relief valve associated with the valve mechanism that prevents the maximum pressure/jack force from being exceeded while pumping. It would probably be a good idea to duplicate this relief circuit in some fashion to keep the bottle jack or press frame structure from being damaged if your hydraulic source inadvertently delivers too much pressure to the system.

 

[Bill Barrett]

I did it by cross drilling in to the center of the jack.
I then hooked up a air over hydraulic pump.
I can use the jack as made, or use the pump, just have to make sure the small jack piston is off when using the pump.