I have no experience
with soldering, welding, or metalwork. So, reading Bill's site and the
various links, I determined that I was not going to solder this beast.
They spoke of enormous torches and irons that I did not want to get
involved with. A friend of mine who works with metal and was familiar
with the cyclone style dust collector that I was trying to create suggested
that I use pop rivets and epoxy. Luckily, I had a plethora of pop rivets
from a suspended ceiling installation, and am fortunate to have a stock
pile of West System epoxy and thickening additives.
I used a 4' x 10'
sheet of 26 gauge galvanized sheet metal, which I got for $25. Unfortunately,
I am dealing with a 7' ceiling height, and even with the motor sticking
into the rafters, Bill's ideal cyclone size would not fit. Bill wants
a cyclone to have an 18" diameter and a 1.64 cone/length ratio. My cyclone
is 17" in diameter with a cone/length ratio of 1.3. The result of this,
I think, is that some of the chips that are sucked into the system rotate
around the lower part of the cyclone for a while, sometimes until it
is turned off, rather than falling right down into the bin. This is
not a problem: I have seen no particles in the filter housing, so it
hasn't affected the cyclone's ability to separate. But (I think), because
of the physics of the air circulating and then going up and out the
top, my cyclone seems to suspend some of the chips as they go around
the bottom of the cyclone.
seams overlap to create a smooth surface for rotating air and dust
The cyclone went
together very well with the aid of a 17" diameter plywood circle. This
circle eventually became the top of the cyclone that was fastened to
the blower housing. I was also careful to make sure that the overlap
of the sheet metal in both the upper cylinder and the cone was oriented
in such a way that the air/dust didn't hit a ridge as it rotated around,
but rather saw a "ski jump", as Dale
Critchlow called it.
Tabs were formed
on the cone, and it was pushed over the outside of the bottom end of
the upper cylinder. I put the 17" diameter piece of wood at the very
bottom of the cylinder during this process which gave the proper shape
to the cone and cylinder. Pop rivets were installed from the inside
out whenever possible, and I took special care to make sure they were
inserted flat and as tight to the surface of the sheet metal as possible.
Those rivets that had to be installed from the outside during assembly
were eventually drilled out and re-installed from the inside out. I
took great pains to make sure that the inside was as perfectly circular
and as smooth as possible. All seams, every pop rivet, and every tab
was sealed with epoxy from the outside.
first attempt at an air ramp. Note: air ramp is upside down
The air ramp proved
a little more complicated. The picture at the side is my first one.
Everything is fine with it, except it spirals the wrong way, and these
are not reversible. The way I wanted my ducting to enter the cyclone
meant I had to have the directing of rotation within the unit be the
opposite of what most cyclones have, and so I had to re-do my air ramp.
This one is identical to the one that's actually in my cyclone in every
other way: the rivets go from the inside of the 8" outlet pipe to the
outside, the tabs on the ramp all are oriented up so they are out of
the air flow in the cyclone, and the seam where the ramp meets the outlet
pipe was sealed and smoothed with epoxy.
up the cyclone from the bottom. Note: all rivets are installed
as flat as possible
The picture at the
side shows what the air ramp and outlet pipe look like from the very
bottom of the cyclone when they're installed. I was able to reach all
the way down with a caulk gun and run a bead of duct sealant around
the joint where the air ramp meets the outside edge of the cylinder,
which you can see in the picture. I was originally concerned about using
26ga rather than 24ga sheet metal for this cyclone project, which some
recommended. Until I had installed the air ramp, I felt that the upper
cylinder might be a little fragile and flexible. The air ramp made the
entire cyclone much stronger and much less likely to crush (I have run
this thing for a long time with all gates closed and neither the ductwork
nor the cyclone seem to have been crushed as some said might happen.)
In this sense, the air ramp has additional benefit. Not only does it
get the air flowing in the right downward direction within the cyclone
and reduce turbulence, it also adds strength to the entire cyclone assembly.
inlet and transition from round ductwork to rectangular inlet
The air inlet is
rectangular, so I understand, because it reduces turbulence in the cyclone
by feeding in the air and chips in a laminar fashion. The air inlet
transition transfers the round network of ducts to the rectangle of
this air inlet. Rather than forming my own transition piece, I was able
to find a good HVAC fitting that was almost the perfect size. A little
hammering with a ball peen hammer to smooth all the inside ridges, and
this piece was riveted and sealed in place. At the bottom of the cyclone
I began with a 7" to 6" HVAC reducer, cut off the 7" portion of it,
cut tabs, and fit it over the outside of the bottom of the cone. I was
able to install the rivets from the inside to the outside, and took
special care before I put this piece on to hammer out any ridges on
the inside of it that would catch dust or affect the downward circular
rotation out of the bottom of the cyclone. This piece was epoxied from
the outside as well. I spent a good deal of time making sure the entire
cyclone was air tight from the moment of entry to the bottom of the
Finally, the entire
cyclone was spray-painted with two coats of machinery grey paint.