MicroTrac Baseline Calculation

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The basic design rationale for MicroTrac hydraulic pump (and engine) size requirements is the ability to power the Liberator 2 CEB press to the extent that it can produce 6-8 bricks per minute. This indicates 360-480 bricks per hour, or between 2880-3840 bricks per 8 hour work day. Wow. This involves a 2 person team, one person running the LifeTrac hybrid Soil Pulverizer, and the second person stacking bricks. This improves upon the 500 brick per 8 hour day sustained production rate that we ordealed last year with a typical 2 person team. We still got the CEB workshop addition built - under the worst possible conditions. It was a worthwhile experiment in that we now have a spacious workshop environment - and with the planned sCEB floor and other improvements, we will not complain. It's time to move on to the Solar Village. Now seeking collaborators for design assistance.

Pressing Rate Calculations

Pump horsepower requirements calculator.

based on the 12 gallon per minute hydraulic pump specified for MicroTrac - what is the possible, baseline brick production rate?

  • Start with a baseline of 12 gallons per minute (GPM) at 2500 psi (see calculations at MicroTrac
  • To calculate the number of bricks that can be pressed per minute, we start with the 5 inch diameter pressing cylinder.
  • Convert the GPM flow rate to linear cylinder motion rate.
  • 1 gallon = 231 cu in - [1]
  • The 5 inch cylinder moves 8 inches up and 8 inches down for a complete pressing cycle. This is 16 inches of travel.
  • 18 inches of height for a 5 inch cylinder is 314 cu in, or 1.36 gallons
  • A flow of 12 GPM yields 8.8 cycles for the 5 inch cylinder
  • We need to add a small amount of flow for the hopper cylinder, which moves a total distance of 14 inches to complete a full pressing cycle.
  • This 14 inch cylinder is 1.5 inches in diameter.
  • The volume of fluid required for the 14 inch motion is 24.7 cu in.
  • We are also using a hopper auger to prevent bridging. This uses a 1.93 cu in/rev, 650 rpm, hydraulic motor.
  • We will run this motor for 1 second per single pressing cycle to prevent bridging.
  • 1 second of motor run is about 11 revolutions takes about 21 cu in of fluid flow.
  • We add the required 5 inch cylinder, 1.5 inch cylinder, and auger motor fluid requirements per pressing cycle to obtain 314+25+21 = 360 cu in = 1.56 gal
  • Fluid flow of 12 GPM with 1.56 gal required per cycle - gives us 7.7 bricks per minute theoretical maximum pressing rate.

The above assumes that 12 GPM will be available. HP requirements for driving a pump are PSI*GPM/(1714*pump efficiency). Pump efficiency is typically 85%. This means that we can press at 2125 PSI with 12 gpm, or 10.2 GPM with 2500 PSI.

The latter is more realistic, given PSI requirements for pressing, so the theoretical maximum is really 6.4 bricks per minute if we have 10.2 GPM available - or 3072 bricks per 8 hour day.

The above will be attainable with solenoid valve controls, while a slightly lower number will result from manual control, where operator dexterity is the deciding factor.