Brick Pressing Rate Calculations

Introduction

Under the assumption of incompressible flow and fixed hydrauilic cylinder volume, the brick pressing rate of The Liberator can be calculated for a given hydraulic flow rate.

Let's take 25 gallons per minute for the design flow rate of The Liberator II Beta v2.0.

The Liberator

The Liberator uses a 5x8x2 inch cylinder (diameter x length x rod diameter) for pressing, and a 2.5x14x1.125" cylinder for the soil loading drawer.

The effective volumes for both cylinders differ. This is because the cylinder rod takes up some volume - thereby reducing effective volume and force for the contraction part of the stroke. The expansion part of the stroke uses the full cylinder volume.

Main Cylinder Volume, D= 5 inches, D_rod=2 inches

• Cylinder volume (expansion volume) = 157 cu in
• Rod volume = 25 cu in
• Cylinder volume-rod volume (contraction volume) = 132 cu in
• Volume filled for a complete cycle of the cylinder (expansion volume + contraction volume) = 289 cu in

Secondary Cylinder Volume, d=2.5 inches, d_rod=1.125 inches

• Cylinder volume (expansion volume) = 69 cu in
• Rod volume = 14 cu in
• Cylinder volume-rod volume (contraction volume) = 55 cu in
• Volume filled for a complete cycle of the cylinder (expansion volume + contraction volume) = 124 cu in

One complete cycle volume

One cycle volume = 413 cu in

1 gallon = 231 cu in

1 cycle = 1.8 gallons of fluid

Pressing Rate Results

The results above yield 14 brick per minute results.

We need to consider 10% inefficiency in the CEB hydraulic system (-1.4), intermittent operation of the soil grate shaker (-.5), and reduction of the main cylinder speed towards the end of the compression stroke (-1).

With these considerations, we obtain 11 bricks per minute for 4" thick bricks.

Similar calculations and reasoning for 2.5" thick bricks yield an overall results of 13 bricks per minute.