# Passive Hydraulic System to Transmit Mechanical Power

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1. Jan 28, 2016

### ElectricJosh

Hi All,

I am trying to displace mechanical power using a hydraulic system with the fluid as the energy conduit.
I will be using two cylinders with a connecting pipe, so when I push one down the other rises.
This video illustrates well what I am going for in terms of hydraulic topology.

My requirements for the system are to move 200N with a speed of 0.4 m/s and I am thinking of a cylinder length of 0.2m.

The two cylinders on either side of the system should be identical, but I have no idea where to begin designing the system to meet my requirements (I'm an electronic engineer... go figure).

I need to find the dimensions that will allow me to transfer this power from one side to the other without significant pipe losses due to friction etc.

Are there any hydraulic engineers/fluid dynamics engineers out there who can tell me where to start/what equations I should be using for cylinder dimensions and minimum pipe dimensions?

This question might be a bit vague but I would be very grateful for a push in the right direction?

Thank you very much. :)

2. Jan 28, 2016

### Nidum

Last edited: Jan 28, 2016
3. Jan 28, 2016

### Nidum

4. Jan 28, 2016

### ElectricJosh

My intention is not to build a robot, I used that video to illustrate the cylinder arrangement that I want. Sorry I did not make that clear.

OK, I've done some calculations and with 200N on a cylinder with a inner diameter of 0.05m and length of 0.1m will give a pressure of 10bars (1MPa) acting outwards on the whole cylinder.
(I've seen some cylinders rated at 10 bars hence this number).

So if I wanted to push it down with a speed of 0.4 m/s the volumetric flow rate out of the cylinder and into the pipe will be 784 E-6 cubic meters per second.

So how do I work out the diameter of a pipe that will accommodate that flow with a workable level of friction?

Thanks again. :)

5. Jan 28, 2016

### Nidum

Last edited by a moderator: May 7, 2017
6. Jan 29, 2016

### ElectricJosh

Ah, that's a nice reference manual that might save me some tedious calculations. Thanks :)