[TheForge] duplex and quadplex air compressors

[Andrew Vida]

terry l. ridder wrote:
> there are the rotary screw air compressors to consider. less noise is
> the main advantage that i have been able to find so far.

	There's more than that - screw compressors will pass higher volumes at 
higher pressures than piston compressors by a large margin, size for size.
> 
> does anyone have a rotary screw air compressor? how does it compare to
> the reciprocating air compressors?

	Far and away better.  Far and away more costly, in general.

	Another compressor you may want to look for are the double-acting 
piston-types.  If you can find one for scrap it may be worth taking - 
but these are usually quite large, produce prodigious volumes of air, 
are more trouble to maintain, and are probably a nightmare to have to 
repair.  Some look like a radial aircraft engine and are driven by a 
central crankshaft.  The pistons move air on both up- and down-strokes, 
hence the term "double acting".  A rod passes through the centers of 
each piston and one end attaches to an articulating connecting rod which 
in turn connects to the crankshaft.

	I only mention these because I always thought they were ultra-cool 
industrial technological art.  I'd love to have one just to look at. :)