It's likely that the manufacturer offered different models with the same
pump on them, but with different HP motors (and outputs).
A pump that's used on a 5HP model may be the same one used on a 7.5HP model,
with the 7.5HP model having a slighly larger motor pulley diameter.
A pump used on a 10HP model probably isn't the same one used on a 5HP model.
I will probably be more difficult to find a larger pump pulley, than to find
a smaller motor pulley.
A motor pulley that's too small could have a tendancy to slip at startup if
the belt contact area with the pulley is too small.
The pump manufacturer may provide minimum and maximum pump speed
recommendations. Proper lubrication is probably the only vital issue with
reducing the pump speed.
Reducing the upper pressure limit cut-out is another option, in conjunction
with a slower pump speed. The upper end of the cut-out limit is where the
highest power demand is involved.
Reducing an original upper limit of 175psi to 150psi, for example.
--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html
"Ecnerwal" wrote in message
...
I _may_ have an opportunity to pick up a compressor a bit "too large"
for my needs at reasonable cost (depends on the bidding).
GRANTED (wanna bet some people ignore this part) that doing so will
provide less air than the compressor is rated for, and GRANTED that I
don't mind that, what actual problems would be encountered by running a
5 or 10 hp compressor on a 2 or 3 hp motor AT REDUCED COMPRESSOR SPEED
(larger pulley on the compressor, or a jackshaft) such that the 2 or 3
hp motor is not being overloaded.
In engine service, lower speed is a good thing, so 3600 rpm motors wear
out much faster than 1800 rpm motors.
What, other than reduced air output that I'm willing to accept, are the
actual downsides, if any, of running a compressor slower than it's
"supposed" or rated to run?
Lack of fan action from the pulley is easily compensated by putting a
fan on it, and heat production will be lower at a lower speed anyway.
Not enough "splashing" for splash lubrication? Something less obvious I
can't think of?
While I could always harvest the large tank and try to flip the big
motor and compressor for a smaller one, the less stuff I'm trying to
swap, the better, generally.
--
Cats, coffee, chocolate...vices to live by