Randal got me thinking [as he often does] so I did a quick Google search for
"two stage compressor bore stroke" and came up with a bunch of hits. Not
wanting to make an exhaustive search I will simply use the numbers on the
first link I found that had real numbers for what appears to be an example
of the ubiquitous 5hp two stage compressor ...
http://www.grainger.com/Grainger/SPEEDAIRE-Two-Stage-5Z404?Pid=search
Bore was 4.75 and 2.5 and the stroke was 3 so the swept volume of the large
cylinder is 53.18 and the small cylinder is 14.73 cubic inches.
Arvid
-----Original Message-----
From: Randall
Sent: Monday, January 23, 2012 8:11 PM
To: shop-talk@autox.team.net
Subject: Re: [Shop-talk] Air tank fittings
> it's just all the two-stage
> compressors I'm familiar with have two cylinders, with just
> one slightly
> larger than the other.
I believe they are, in fact, sized so each cylinder does roughly equal work
for some level of output pressure. On my 2-stage, the high pressure
cylinder is quite a bit smaller in diameter (if you look between the fins).
I don't know, but I would guess that if you are seeing units where the high
pressure cylinder is almost the same, perhaps it has a shorter stroke.
> Since I assume they spin at the same speed, it
> always seemed to me you're getting small gains in pressure.)
I also have a 2-cylinder single stage unit. It works quite well below 100
psi, but above that, the output falls off rapidly. By 130 psi, it really
isn't doing anything at all. By contrast, the two-stage will easily hit 175
psi and, according to the ratings, loses less than 5% of it's output.
Here's a similar unit:
http://goo.gl/We6KG
-- Randall
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