How to make a simple hydraulic arm

Hydropneumatics and hydraulic systems have been some of the main industrial automation systems in existence for many years. Today, most industrial robots use the principles of hydraulics to move high-precision mechanical arms combined with advanced programming systems. In this article, we will look at how to make a simple hydraulic arm that with a little imagination can be converted into an interesting robot arm for any project we have. If you don't want to complicate things, you can always buy one in pieces and make it easier.


- A 10cc injector.

- A 5cc injector.

- A rubber or acrylic tube, as used for serum, should fit snugly into the nozzle of the injector.

- Water.

- Wooden slats.

- Hinges or joints allowing movement.

How to make the hydraulic arm

The first thing we are going to do is the hydraulic system that will move our arm. To do this, we must fill the 5cc injector completely without leaving any air inside. To avoid air, it is advisable to fill it under water. This same procedure is done with the 10cc injector, but we only fill it about 3cc.

Now, we fill the acrylic hose with water without leaving any air inside (it is advisable to do this in a large container with water) and connect the nozzles of the two injectors with the hose. Once fixed, we take out our hydraulic device, dry it carefully and fix completely the hose to the nozzles of the syringes with an instant glue (cyanoacrylate), covering well the joints and avoiding future air inlets.

Once our hydraulic device has been completed, it is time to make a simple arm. To do this, we place two wooden strips in the shape of a 7, joining them with hinges that allow it to move up and down. Next, we place the injectors on the arm with the help of instant glue or adhesive tape. The 10cc injector is placed on the slat to be moved by resting the slat on the plunger of the injector, while the 5cc injector is fixed to the lower part of the arm.

When pushing the plunger of the 5cc injector, we will see how the arm rises thanks to the force that makes the plunger of the 10cc injector move.

How it works

The force exerted on one side is transmitted by communicating vessels to the other injector, exerting a greater force to move the plunger a shorter distance, i.e. applying a force of 1 kg on the 5cc injector will transmit a force of 2 kg to the plunger of the second injector, which moves a shorter distance, but can lift a greater weight.

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