On 8 Oct 2008 00:20:25 GMT, "DoN. Nichols"
wrote:
On 2008-10-06, Vernon wrote:
On Oct 6, 12:54*pm, Bruce L. Bergman
wrote:

* It can't be a single cylinder and a two stage at the same time...

* Two stage normally implies a multiple of two (four, six, eight)
cylinders - and the second stage will be physically smaller. *Of
course, they could do something really odd like having three feed
two...

[ ... ]
Bruce, that was incredibly helpful. Thanks. Since "it can't be
single cylinder and two stage at the same time" then I stand corrected
about it being one or the other. The data plate mentions so many cfm
at 175psi. The cylinder does have a secondary "protrusion". Maybe
this is the second stage piston. I was confused because it is so much
smaller.

If you are seeing a 175 PSI output, it HAS to be two stage.

As a practical matter, 125 PSI is about all you can get in a single
stage shop air compressor without building it solely for high pressure
and getting very poor CFM volume output.

Really high pressures like filling scuba tanks are 4 or more stages,
they keep boosting the pressure in increments till they reach the
target.

Yes -- that makes it two stage. That smaller cylinder allows
compressing air which has already been compressed once without having a
great deal of force on that connecting rod. As it is, I suspect that
the two cylinders need about the same force, so the crank is balanced.

That, and the two crank throws (and therefore the pistons) are
usually out of phase with each other on purpose, so the first stage is
on the exhaust stroke into the intercooler at the same time as the
second stage is on it's intake stroke. Just enough time for the air
to dump some heat on the way through.

-- Bruce --