On Mon, 28 Feb 1994, Scott Fisher wrote:
> Well, Chris and I picked up my new Sears air compressor (4 horse,
>If you were replacing your complete installation today, what changes
>would you make in tool selection, hookups, or any other decisions that
>affect how you use (not to mention how you spend money on) your compressor
> and the tools you use?
Sorry, everybody, for the verbosity today. I've been in sunny Utica, NY
for a week, and returned to 358 messages, which I have been chewing
through today.
Dear Scott 1,
Well, I guess in honesty I would have to say the first thing I'd do is to
get at least a 5 horse compressor. Wait, wait, don't kill me. The issue
is the cubic feet per minute at the output you want. Some 4hp compressors
are better than 5hp, etc., and yours may be fine. But generally, the
bigger the better. For sandblasting and painting, a high output 5 hp is
very desirable. If your new compressor puts out as many cf/m as the
biggest tool you want to run, you are ok. But then you want to install a
glass bead cabinet, and it isn't big enough, and it is a major bummer.
I started ca. 1957 with a 0.5 horse Sears. I painted a couple dozen cars
and a house or two with it. But I had to paint cars in three sections.
Then four sections, as the compressor wore out. 30 years later, I was
getting seriously vexed by the output of the compressor, but my wife (now
ex wife) would not hear of my buying a new one. Then my daughter, while
learning to drive (with my wife teaching) tried to put the car in
the garage for the first time. She lost focus, and hit the accelerator
instead of the brake.
The Audi effect followed, and she booted that 0.5 horse compressor half
way through the back wall of the garage, crushing it flatter than a
flitter. Of course, she bruised the car, which could not be painted
without a compressor. She could not understand why dad was so
philosophical about the loss. Next was Sear's best 2 hp. It puts out as
much air as their cheaper 3hp models. It is way marginal for sandblasting
and barely suffices for spray painting with bleeder type guns. An honest
4 or 5 hp would be better.
Anyway, installation:
Don't install at the front of the garage, where your teenage daughter (or
son, Teri-Ann) can crush it, until you are ready for a replacement.
Remove the wheels, and mount it permanently, preferably on a rubber
mounting, for (relative) quiet and stability. Mount it in the least dusty
part of the garage, or rig a fresh air intake, or rig some kind of
automotive air filter. Typically, the Sears compressors have small felt
filters that clog, severely reducing output.
The compressor should be 220 V, on a dedicated line. I don't recommend
running on an extension. If you must, go buy some serious #10 braided
wire and HD plugs, make your own, and keep it short. You must choose
between electrical resistance causing a voltage drop to the motor (which
can fry the motor) and flow resistance causing a pressure drop to your
tool, which can be fixed by larger tubing and turning the pressure
guage up. Obviously, the latter is easier to deal with.
I would use copper 3/4 water pipe with soldered connections, and make a
distribution system to supply each end of the garage. General pattern:
horizontal line should slope upward
(e.g. 1/2 inch/ft) as it goes from the
compressor to the outlets
_____________________________________
| | |
| | |
| | * | *
Compressor <--flexible hose-->| |_| |_|
| | |
X drain valve X (dv) X (dv)
At the points marked *, you should put outlets supplying different areas
of the garage. You attach the rubber hoses to these with quick
disconnects. These outlets must include water/oil filters to trap
whatever moisture or oil gets past other precautions. You may want to
have at least one outlet that includes an oiler for tools; the hose for
tools must then be separate from that used for clean air uses such as
painting.
Do not use any rubber lines less than 5/8, 1/2 gives too much resistance
(resistance to air flow is proportional to the inverse of the 4th power of
the radius). I have no idea what pressure would burst 3/4 inch copper
water pipe, but up to 120 psi or so you should be fine.
The point of this setup is that the air compressor, not to mince words,
compresses air. As the hot compressed air cools off, water condenses out
in the tank and lines. It will ruin paint, and do damn little for
sandblasters. During continuous running, the copper tubes act as
condensors, and you want as much of the water as possible to end up in
traps. So you slope the lines to run water back into the trap below the
compressor inlet, and provide traps to catch water that makes it to the
outlets, and use commercial filter/traps to catch what gets by all this,
and if you are smart, put a final filter on your spray gun when you paint.
Before or after each use, drain the tank and all traps with about 10
lb/in2 pressure in the lines.
Ray Gibbons
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