Subject: Re: Sears Compressors

From: [email-masked] (Kevin AstirCS "1U" KO0B)
Date: Wed, 05 Jun 1996 17:36:48 -0700 (PDT)

<[email-masked]> wrote:

>      Obviously, the unit was never designed for serious or strenuous use, though 3 HP should have been
>adequate for the limited hobby-type use I was making.

If it was _really _ 3 HP that is.

Caveat Emptor:
Air compressor manufacturers seem to be following the lead of vacuum
cleaner manufacturers and re-defining the horsepower.

For example :
I have a " rating: 4" ( granted it doesn't actually say  " 4
horsepower") Campbell Hausfeld unit which draws 15 A at 115VAC.  CH
got Emerson to lable the HP field of the motor  placard "SPL".
_nowhere_ on the unit, or in the manual that came with it is there
_any_ horsepower rating. 

Now 15A x 115V gets  1.73kVA.  If I assume  a .9 power factor
(probably generous for single phase motor, even with  a run capacitor)
thats just 1.55 k W...assuming 90% effiency (again, probably generous)
thats  1.4 kW mechanical, or just  1.87 HP!!.  Even a "perfect" 15A
motor could only make 2.3 HP at 115V!!

That being said,  It does seem to pump the rated 6.6 SCFM @ 90 psi, as
it keeps up with a 5.9 cfm rated sander just fine.   It is also the
biggest machine I could run on "common" 115VAC. I run it on 230 in my
shop, but made up some "quick change " cords (attaching cord re-wires
motor) so I can run it on 115V when a remote job demands it.

I bought this about 4 years ago, and now see even more rediculous
power ratings on machines for sale.    They  now actually have the
nerve to say "horsepower" Also, those blasted oiless designs seem to
be supplanting the beltdriven machines, which I think is a shame.

>    After that experience, I gave up on the "home-shop" type units, picked up a low-time 80-gal 5hp/ two-stage type unit
>from a small auto shop going out of business for $500.   Now I can't even begin to use all the air pressure and volume
>I get.  don't remember the brand, but it's a "major" make, about $1300 new, retail (Quincy, maybe?).

Running the electrical numbers on the "industrial" type machines lands
in the right ballpark (I still have to "guess" at effiency and power
factor).  I suppose these markets know what kind of service to expect
>from  a 5 or 7.5 HP machine, and won't tolerate the kind of nonsense
going on in the "consumer" marketplace.

> I wouldn't touch on of the new home-shop  type Sears/Craftsman units again.  Having looked them
>over since, they all seem to have the same "direct-drive",  undersized compressor-head. 

I have never been impressed with the oiless direct drive pumps.  I
inherited a  Monkey Ward (built by CH) 1 HP (honest)  unit which dad
ran for probably 15 years. I ran it for a couple more, and then traded
it for a Jet mill-drill ( straight across....best deal I ever made!).
The new owner probably runs it 2-3 times/week., and it is still going
strong. That CH 2 cyl cast iron pump with the belt drive is a pretty
solid unit.  Think they still make it...at least they look the same.

> If I couldn't 
>pop for the $500 a terrific used one like mine would cost, I'd probably build one with one of the 5 hp
>motors I have laying around and a compressor head (3-5 hp rated) from Harbor Freight.  The tank is no real trick,
>since you're only looking at 150psi in practice.  I've accumulated a couple and they're around, cheap.

I agree with this, unless you are wanting a portable unit  of around 2
HP tops.   Then go for a belt driven model with a run capacitor (two
lumps on motor) and a startup unloader. (small air line running to
pressure switch housing from tank inlet)

I think CH sells those cast iron pumps....The HF thing is an aluminum
product of china, isn't it?  Actually, the recent HSM article on using
an automotive AC compressor got may attention.

I haven't seen any lies on the electrical current ratings.  To get an
idea of "true" horsepower, multiply volts times amps, then divide by
1000 for capacitor run motor, or 1200 for  capacitor start motor.
Betcha come up with maybe 1/2 the claimed power.  Truth hurts!

Motors vary a little in effiency, and power factor, but those figures
will get you  in the infield, not just the ballpark.

Dividing by 748 would give you the power of a "perfect" (100%
effiecient & unity power factor) motor...If they are claiming more (or
even equal) then you are being lied to, plain and simple.

Check the oil, and drain the tank  regularly.

ciao, Kevin

---

From: [email-masked]
Date: Sun, 09 Jun 1996 22:37:40 GMT

<[email-masked]> wrote:

>over since, they all seem to have the same "direct-drive",  undersized compressor-head.  If I couldn't 

For anyone who hasn't noticed, we live in a world where quality seems
to be second to price in determining the viability of a manufacturer.
That is the reason that all of the low quality imports from China and
other places are successful.  At the same time, American suppliers
have often been faced with cost reduction or extinction.  This is
especially true for entry level equipment.  

Now I am as big a capitalist as anyone.   I am glad that we have the
variety of machines available today.  I think that there is a market
for low end machinery, and it is just the ticket for some people.  

I can sympathize with the poster of this original article.  But, not
all Sears compressors should be indicted.  I have had a Sears
Commercial 2 HP 220 V Belt drive compressor for years.  Any real 2 HP
motor should be run on 220 V or more.  The compressor has run
faithfully for years.  I bought it used for $150 about ten years ago.
The original owner used it to make a racing boat, so it has seen
plenty of usage before I got it.    

 I run air tools all of the time in my shop.  There are times that I
have to wait for the compressor to catch up with the consumption from
a sand blaster or die grinder, but if fits the bill for better than
95% of my usage.  For that other five percent, I can wait a little
longer.  Now, I have been tempted to replace the unit with a bigger
compressor from time to time, but I would have to justify it based on
that five percent need.  Consequently, the old reliable 2 HP Sears
unit gets worked pretty hard on occasion.  

There are a few rules that I use when buying equipment.  

--Buy the machine that meets at least ninety percent of your needs.  

--Avoid wasting money on machinery that exceeds 100% of your needs.  

--Learn what makes a good tool or machine.  Apply that knowledge when
you selecting used or new equipment.  

--Buy the best tooling and machines that you can afford.  If you
cannot afford what you need, then wait, or implement a temporary
solution to your needs and save your money for the final solution. 

--And finally, as with many situations, if the price seems too good to
be true, it probably is.  

I do not claim that any or all of these ideas are mine alone, but
these processes have worked for me for many years.  

J. M. Stuart

Engineer / Inventor / Patentee

---

From: [email-masked] (Nick Irias)
Date: Mon, 10 Jun 1996 20:38:03 GMT

>motor could only make 2.3 HP at 115V!!

The fine print usually says "peak horsepower".  I think by peak, they
mean the power produced during the 10 seconds between the time the
motor is overloaded and the circuit breaker trips.  During that time,
the motor is drawing somewhere around 30 amps and may even be
producing the 3 HP.

Technically, they arent lying, since the motor can put out a 3HP burst
of power for a few seconds.  Of course you can't use a 9 second burst
of power with an air compressor - the compressor motor has a longer on
cycle.  But the tool manufacturers only said you had a motor capable
of 3HP peak.  They never said you could actually use the horsepower.

Too bad you cant buy these tools with confederate dollars.  Its real
money, you just cant spend it.

---

From: [email-masked] (Andrew B. Forte)
Date: Mon, 10 Jun 1996 17:14:02 GMT

I have a 5 year old Sears compressor that is doing beautifully.  It is
5hp, 30 gal.  It has sand-blasted and painted two station wagons.  It
regularly gets used for an air pump and sheet metal shears.

I have only had one complaint, it needs "more power".  (grunt, grunt,
grunt)  I can not get the necessary psi and cfm out of it to run a
1/2" drive Ingersol Rand air gun.  It can't get enough air to take
lugnuts off a car.

I would only trade it for a bigger Craftsman compressor.

					Andrew
disclaimer:
	These views are mine and not my employers.

<[email-masked]> wrote:

>     I had a 3 h.p. 20 (or was it 30) gal. Sears Compressor.  Cost: $300 or so on sale.  It committed suicide
>aafter only a few sessions of reasonably hard work followd by an afternoon or two of sand-
>blasting.  (This was not _abuse_ -- the sand wasn't allowed to get into the compressor, all filters were good, etc.;
>it was just a rather wimpy compressor-head, typical of a 2 hp or so unit, with a somewhat larger
>motor.)

>   Hope this helps.

---

From: [email-masked] (Blake Malkamaki)
Date: Wed, 12 Jun 1996 23:53:43 -0400

In article <[email-masked]>,
[email-masked] (Andrew B. Forte) wrote:

}I have a 5 year old Sears compressor that is doing beautifully.  It is
}5hp, 30 gal.  It has sand-blasted and painted two station wagons.  It
}regularly gets used for an air pump and sheet metal shears.
}
}I have only had one complaint, it needs "more power".  (grunt, grunt,
}grunt)  I can not get the necessary psi and cfm out of it to run a
}1/2" drive Ingersol Rand air gun.  It can't get enough air to take
}lugnuts off a car.
}
}I would only trade it for a bigger Craftsman compressor.
}

Why would you only trade for a bigger Craftsman?  These compressors are
"home-owner" quality and are not built as good as more industrial,
American-made machines.  I know a Craftsman will probably do what the
better machines will do- but for a much less amount of time.  And probably
with less dry and less oil free air, because they work too hard and get
too hot.
Blake Malkamaki, Little Mountain Ironworks, Concord, Ohio <[email-masked]>
>>Steam engines - Cletrac Crawler Tractors - Maple Syrup - Metal Signs<<
http://www.ncweb.com/users/blake