# How to fabricate a hydraulic jack

Updated on October 27, 2008 ## How hydraulic jack works

The first step in designing and fabricating a hydraulic jack is to understand how a hydraulic jack works. If you already know how a hydraulic jack works you can skip this section.

Hydraulic jacks work on Pascal's law which states that "a change in the pressure of an enclosed incompressible fluid is conveyed undiminished to every part of the fluid and to the surfaces of its container."

Let A1 be the area of larger piston and A2 be the area of smaller piston of a hydraulic jack, while p1 and p2 are the pressures applied on the larger and smaller pistons respectively. In equation form:

In above equation you can easily see that the force F1 is the product of two terms: F2 and A1/A2. We can get force of F1 on the the piston 1by either having a large F2 and small A1/A2 or a large A1/A2 and small F2. The latter case is what is done in case of hydraulic jack.

Lets try to understand it with the help of an example.

Suppose we want to lift a weight of 300 lbs (i.e. F1 = 300) and if we use an area ratio of 3 ( A1/A2 = 3) we will need to apply a force of only 100 lbs at piston 2 ( 300/3 = 100).

## Fabrication of hydraulic jack

The following drawing shows the basic idea of things that will be needed to make a hydraulic jack. Note that this is not a drawing of a real hydraulic jack. It simply shows which parts are needed and where they are needed:

We will need the following things:

• Two cylinders

• Seals
• Oil
• Pistons
• Non-return valve
• Pipe

At the outset I would like to clarify that junkyard would be the best place to find the above-mentioned parts.

Moreover choose the maximum load that you will be lifitng with your hydraulic jack. Then choose the area ratio.

## Cylinders

They will be filled with the oil that's going to transmit force. You can either choose cylinders of an engine or heavy PVC pipe depending upon the forces involved. The selection of cylinders depends on the chosen area ratio. You will probably never get exactly your desired area ratio but you can get closer if you search the cylinders in

junkyard. Using PVC pipes as cylinders would give you much more flexibility as they are available in various standard sizes.

## Pistons

They will be used to transmit the applied force to oil and from oil to the load that needs to be lifted.

## Oil

Oil will be the fluid that's going to transmit force. Lubricating oil used for car engines can be used.

## Seals

Seals will be required to seal the gap between piston and cylinder.

## Non-return valve

When using a conventional jack you must have observed that it is used by applying force for a small amount of time and you keep doing it till the load is completely lifted. For this to happen, you will need a non-return valve.

## Pipe

A flexible pipe would connect the two cylinders

## Conclusion

Search all the above-mentioned things in junkyard. You will surely find suitable materials to complete your hydraulic jack.

Good Luck!