Homemade Vacuum Pump

[tonyfoale]

I think it's possible to use more pumps for a better vacuum, when you have a large chamber.

More pumps in parallel will not create a better vacumn but they will create the same vacumn quicker and so will have an advantage when sucking down a large container.
If you have good good compressed air supply you can buy or make a venturi vacumn pump which can provide a surprisingly good suck.