Message text written by INTERNET:DRSkruffy@aol.com
>Also, and now we are getting to spending some real money, look for one
that
turns at lower RPM. Most of the 500 dollar compressors turn at 3450RPM but
the "good" ones run at about 1450 as I recall.
<
Not to split hairs (well, OK I'm splitting hairs here) but a two pole AC
motor runing on 60 Hz AC has a syncronous speed of 3600 RPM and will run
about 3400 to 3500 RPM under load. Many oilless compressors are direct
drive meaning the motor shaft is connected directly to the pump shaft which
turns at the same speed. This high speed operation accounts for the
obnoxious noise emminating from these compressors. But high speed meand
the pumps are smaller and thus cheaper to build.
The oil type compressors which are more traditional run at much slower
speeds and hence are bigger pumps. Most of these are belt drive and run
under 1000 RPM. But the lower speed means the noise is less and at a
lower pitch. The bigger pump also means better heat disipation and these
pumps tolerate continous running better and last longer. Of course one can
manufacture even this style of compressor in a cheap manner that will fail
in record time.
Dave
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