> I'm sure this has come up repeatedly here and apologize for possibly
> thrashing a dead horse, but seeing as I've been unable to find archives to
> search through here it goes.
Archives are at http://www.team.net/archive/shop-talk
> We just bought an old house and while we're redoing everything else I
> thought we might as well get the steam radiators blasted and
> primed. Seems
> it will cost $500 to have them done or $300 to rent the equipment
> and do it
> myself. Seeing that $300 will cover the cost of buying a (supposedly) 5hp
> compressor down at Lowes or Homer's, why rent?
What you can buy for $300 will be woefully inadequate for any real
sandblasting.
> So what's good and what's to be avoided? I think I have the wife talked
> into the idea and need to act fast to before she changes her mind.
The main thing to avoid (IMO) is using 'hp' as a rating to compare air
compressors by. You have to compare air delivery, as the 'hp' figures are
flat lies at the DIY level. My favorite litmus test is to check the
nameplate on the motor, and calculate how much power it draws. If it
doesn't take roughly 1000 volt-amps per horsepower, someone's lying. Note
that this means a 5hp compressor running at 110 volts has to draw something
like 45 amps !
Also keep in mind that air tools (sandblast guns, etc.) are commonly rated
in cfm, while compressors are rated in scfm. That 's' (which is frequently
forgotten by the same people who lie about horsepower) is roughly a factor
of 7 at 90psi. So, that "4 cfm @ 90 psi" sandblast gun needs a "28 scfm @
90 psi" compressor to keep it in air. (Yes, I'm ignoring all sorts of minor
factors for the sake of simplicity here.) Also, watch out for compressors
rated only in "air displacement", it's a useless number too.
Randall
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