While the commercial vacuum pump serves well in research and
industry, they have severe
limitations when used in educational presentations.
(1) Because the machine is opaque, the mechanism shown
in the previous page is not visible.
It is not immediately apparent for the newcomer how the vacuum is produced.
(2) The machine is electrically driven so the student
is denied the direct physical experience
of the work that it takes to evacuate the chamber.
(3) The machine looks tough, but is quite delicate. Commonly
such pumps are used to boil water
at reduced pressures. The water that is removed ends up in the pump.
This causes the oil in the pump to assume the character of
salad dressing and can cause the iron pump interior to rust. There have been cases of abuse like
vacuuming up water or other liquid chemicals.
(4) The machine is expensive, Teachers tend to hover
around in fear that students might
want to touch or operate the pump and possibly cause damage.
The pump is hard for the average student to obtain. There are no common
inexpensive consumer devices that contain vacuum pumps.
(5) The machine is made from very specialized precision
parts so that it is impossible to
reproduce without access to an extensive industrial support infrastructure such as a
highly experienced and equipped machinist.
Because of its great precision, students cannot disassemble, study the function of the parts
and reassemble the machine with the knowledge of its theory and operation.
Often neither teachers nor students are qualified to maintain the machine.
A need for a simple and obvious
(1) Such a pump should be completely open and all of its principal
parts should be visible to the
Its operation must be obvious to those who see it for the first time.
(2) The student should have an opportunity to operate
the pump in order to get a real feel
for the amount and nature of the work that is necessary to evacuate the chamber.
From this, the student will have a far richer life experience of science.
(3) The operation of the machine is durable, robust and
Few acts can cause permanent damage to the pump. Since the pump is inexpensive,
is easy to replace should it be completely damaged or stolen. It can be even be given away.
The pump can be easily cleaned. It is made from water resistant materials
so it cannot rust. There are no hidden places for contamination to accumulate.
(4) The teacher should be able to easily obtain all the
construction materials for building the pump.
These materials and components can be found in most towns.
(5) The student should be able to assemble the pump with
tools found in a typical home or K-12
school classroom. No special skills above normal aptitude are required.
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