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From: (Doug White)
Newsgroups: rec.crafts.metalworking
Subject: Re: Shop Vac [Long]
Date: Sat, 01 Feb 97 22:50:20 GMT

>I'm used to sweeping the floor with a wimpy broom, but that thing isn't
>going to cut it any more.  A decent shop vac is more in order.

Get one of the new ShopVac brand QSP vacuums.  They are MUCH quieter than
any of the old ones of any brand.  Although still loud, you can
comforably use them without diving for ear protection.  I'd get the
smallest one you can that has the large diameter hose.  Home Depot tends
to have good prices on them, as does Walmart.

A while back, I did some research on vacuums in general, and posted it to
one of the woodworking groups.  Here's a copy:



I measured all of the various vacuums I have around my house for sound
level, and relative suction.  For the sound level measurements, I used a
Radio Shack Model 33-2050 Sound Level Meter, set for 'C' weighting (flat
freq. response).  The sound level readings were taken at a distance of
3', which I judged to be about as close as one was likely to get to one
of the big vacs, and roughly arms length for the 'Dust Buster' type hand
vacs.  The suction measurements are a bit less precise, but should
provide a good measure of relative performance.  These tests were done
using a Davis Instruments 'TurboMeter' hand-held wind speed meter.  It
turns out that this fits almost perfectly over the end of the 2 1/4"
diameter hoses used on all the shop vacs and my dust collector.  The
wind speed measurements were done at the end of whatever the typical
hose was for the vacuum.  The 'Dust Buster' type vacs were tested by
trying to obtain the maximum reading at the nozzle.  For the 2.2"
inside diameter of the wind meter, 1 mile-per-hour (mph) corresponds
to 2.32 cubic-feet-per-minute (cfm).


Old ShopVac:  This is a 16 gallon model bought about 8 years ago, before
the 'Horse Power' wars.  It probably qualifies as about 3 HP from the
amperage rating compared to the other vacs I've got.  I originally
tested it with the full-bag filter, which was full of dust and debris.
I then replaced the bag filter with one of the small-bag filters, to see
how much this increased the air flow.  I had fitted this vac with a
muffler (3" O.D. PVC pipe lined with foam) a while back.

   Air Flow: 42.3 mph (Dirty filter)     Sound Level: 92 dB
             50.5 mph (Clean filter)                  89 dB (Muffled)

QSP ShopVac:  This is a new 4 HP 16 Gallon model, bought at Walmart for
$85.  I first tested it with just the foam filter, then a 'disk' filter,
and finally a new full-bag filter.

   Air Flow: 58.8 mph (Foam filter)      Sound Level: 83 dB
             57.9 mph (Disk filter)
             60.6 mph (Full-bag filter)

Black & Decker DustBuster:  This is tired and old, and barely ran when I
first tried it.  I think it's about time to scrap it, particularly when
I measured the air flow.

    Air Flow: 0.6 mph                    Sound Level: 74 dB

Black & Decker DustBuster Plus 3000:  Much newer, much more powerful
than it's older brother.  The filter in this one is a bit dirty.

    Air Flow: 5.4 mph                    Sound Level: 86 dB

Sear's Sucker:  This is a standard household Kenmore canister vacuum
with a power head for carpets.  The filter bag had recently been
replaced, but wasn't completely new.

    Air Flow: 31 mph                     Sound Level: 86 dB

Sear's Shop Vacuum:  This is a 2 year old 2 1/2 HP 8 gallon model that
uses a cartridge filter.  The filter hasn't been cleaned or changed
recently, but I use this in my metal working shop, so the filter doesn't
see much dust that might clog it.

    Air Flow: 59.2 mph                   Sound Level: 92 dB

Black & Decker 'Collector':  This is like a DustBuster on steroids; it's
bigger, and plugs into the wall.  Actually a very handy gadget, which
was therefore discontinued years ago.  Tested with a clean filter.

    Air Flow: 19.8 mph                   Sound Level: 88 dB

Shop Smith Dust Collector:  Rated at 300 cfm, and grossly overpriced at
around $350 (on sale).  This comes with a fairly short filter bag, and
a larger bag is available.  This has an 8' hose, compared to around 6'
on the shop vacuums.  I first tested this with a somewhat dirty short
filter, and then retrofitted a new large filter.

    Air Flow: 52.6 mph (Short Filter)    Sound Level: 89 dB
              53.9 mph (Tall Filter)


The sound levels measured didn't seem to vary much between clean vs
dirty filters, or different filter types.  The exact sound level on most
machines was somewhat directional, and varied by a dB or so depending on
where you measured it.  The new QSP ShopVac seemed to get more powerful
every time I measured it, and may have been 'breaking in'.  The sound
level meter doesn't tell the whole story, because the screaming 89 dB
from the muffled old ShopVac is FAR more annoying than the 89 dB of low
hum of the Shop Smith Dust Collector.

I don't know how much liberty Shop Smith and other vendors take with
their CFM measurements, and how much my wind speed meter was biasing the
readings.  The highest calculated CFM was around 140, a far cry from the
300 Shop Smith claims.  Of course, they probably didn't measure it
through 6 feet of hose either.

For shop use, the hands down winner was the new QSP ShopVac.  It was
3 dB quieter than anything else I tested except my dead DustBuster, but
it had as much suction as any of my other vacuums.  I had a feeling the
Shop Smith was a bad investment the first few times I used it.  Compared
to the QSP ShopVac the Shop Smith Dust Collector costs more than 3
times as much, was 6 dB noisier, and had about 10% less suction.  It's
also twice the size of the ShopVac.

Doug White
(Who has no connection with any of these outfits, but who is looking for
someone who wants a 'really good deal' on a Shop Smith Dust Collector)

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