Subject:
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Perfect geometry for large pump compressor
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Newsgroups:
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lugnet.technic, lugnet.robotics
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Date:
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Mon, 9 Jun 2003 12:58:29 GMT
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Viewed:
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277 times
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Conventional wisdom says that compressors made with small pumps are best (ever
noticed the price differential between large pumps and small pumps on
bricklink?) Primarily this is true because the large pump provides much more
resitance than the small pump, and that the small pump is easily driven by a
single motor.
In a quest to try to make the best compressor I could I tried an experiment with
1 to 7 small pumps driven by one or two motors at different gear ratios. One
small pump driven at a 1:1 ratio with two motors was the fastest, and it came up
equal to my two motor four large pump compressor geared down. Running a single
pump fast reduced the total friction and clatter associated with multiple pumps.
I decided to try a single large pump driven 1:1 by four motors. Along the way,
I realized that I could achieve perfect compression geometry for the large pump.
In the geomtery used, the pump handle reaches the limits of the pumps expansion
and contraction. This makes the large pump operate at maximum efficiency.
http://www.brickshelf.com/gallery/kclague/compressors/p6060070.jpg
There are two things that make help achieve perfect geometry:
1. Offseting the pump base by 1/2 a stud. By combining a 1x2 with two holes
(or a 1x1 with hole), the holes are offset from the holes in the neigboring beam
by 1/2 stud.
2. Using one of the outer holes of a 40T gear, instead of the holes in a large
pulley. The distance between the center of a large pulley to the center of the
holes at the perimiter is 1 1/2 studs. The distance between the center of a 40T
gear and one of the outer holes is slightly greater. It has to be calculate
using pathegorian theorem, because the line from the center of the gear to an
outermost hole is the hypotenuse of a triangle.
One side of the triangle is 1 1/2 studs. The second side of the triangle is 1/2
a stud. This means that the distance from center of the gear to one of the
outer holes is 1.58 (versus the 1.50 of the large pulley). This little
difference allows the pump to be expanded and contracted further, driving it to
its limits.
Kevin
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