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.