I am trying to build a vacuum pump by myself and move rocks from one place to another. After some online search, I came across this video on Youtube. I am trying to build something like this. Can anyone explain the science behind it and tell me how I can make this by myself?

  • $\begingroup$ blow compressed air down the pipe $\endgroup$
    – jsotola
    Jul 11 at 4:00
  • 1
    $\begingroup$ How big are these rocks? $\endgroup$
    – Solar Mike
    Jul 11 at 7:13
  • $\begingroup$ It is quite big actually, 6 inches in diameter on average $\endgroup$ Jul 11 at 16:25
  • $\begingroup$ You can rent a small front-end loader for less than the rental cost of the air compressor necessary to generate the venturi suction. $\endgroup$ Jul 11 at 20:18

What you are seeing in the video is a vacuum generator/vacuum ejector/aspirator.

enter image description here

Figure 1: Venturi effect (source: wikipedia)

It uses the principle of the Venturi effect. I.e. that for steady, incompressible, inviscid when there is an increase of speed there is a drop in static pressure. This is mathematically expressed as:

$$p_1-p_2 =\frac{\rho}{2} (v_2^2- v_1^2) $$

Application in vacuum generators.

This is used in vacuum generators, in the following way:

enter image description here

Figure 2: Application on Vacuum generators (source: COVAL)

Initially, Compressed air is driven through a nozzle. This increases the velocity (and the kinetic pressure) and drops the static pressure. At the exit of the orifice there is pressure drop which creates a negative pressure which sucks in air (and other small materials).

  • $\begingroup$ To the OP: If you can make a good seal between the vacuum cup and object then a vacuum generator with low flow but high vacuum will do the job with efficient use of compressed air. If the object is leaky or there is a poor cup-object seal then you need a high flow vacuum generator. With 100% vacuum you can lift 1 kg/cm² of vacuum cup internal area. $\endgroup$
    – Transistor
    Jul 11 at 12:53
  • $\begingroup$ Can you tell me how much will be the cost of building such a system? $\endgroup$ Jul 11 at 13:07
  • $\begingroup$ You can buy it of a shelf for a few dollars.building it from scratch would not be cost effective. $\endgroup$
    – NMech
    Jul 11 at 13:32
  • $\begingroup$ What will the total setup cost? $\endgroup$ Jul 11 at 16:22
  • $\begingroup$ That will depend on the local market. I'm guessing that the highest cost will be the supply of compressed air. $\endgroup$
    – NMech
    Jul 11 at 16:32

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