I thought the easiest thing to make the top drum from was a piece of 150mm (6") PVC that I used for the big Cyclone's main ducts. The cone is made of some left over sheet steel from the big one but I did not have a piece quite big enough so I pop-riveted two pieces together. I used two small 50mm PVC pipes for the inlet and outlet pipes. Other materials required were a few pieces of Ply, some Pop Rivets, Screws and Gutter Flashing Tape.
For measurements, I used Bill Pentz's Cyclone Design Spreadsheet and just entered in the smaller Drum size and inlet/outlet sizes and it calculated everything just fine.
I followed Bill's spreadsheet and marked up the cone on the sheet steel with a marking pen then cut it out with a pair of Aviation Snips.
The top drum was cut to length and then had an oval hole cut in the side to accommodate the inlet pipe. This hole is angled down slightly so that the Inlet pipe will direct the air down the sides of the Mini-Cyclone. I then cut a piece of Ply in a circle for the top of the drum. A 50mm hole was then cut in the centre of this piece to accept the Outlet pipe.
I placed a piece of 50mm PCV held in my Bench's Wood Vice as a former and then slowly hand curved/formed the cone around it (hint were thick gloves as the metal is sharp - wish I did - duh). I used three clamps just to help with the first bit of the curve and I removed them to curve the majority of the cone. I found that doing such a tight curve (compared to my big cyclone) caused the metal to bend (facet??) a bit but it seemed unavoidable.
The Cone was pop riveted together with most of the pop rivets put in "back the front" i.e. the flat head is on the inside of the cyclone. This is to make it smoother on the inside so as to minimise any air flow disturbance. I could not do all of them this way due to the reducing size of the inside of the cone and could not get the Pop Riveter in.
The Cone was fitted to the top drum using four pop rivets and the joint was then taped over with Flashing Tape for full strength. I fitted the Inlet and Outlet pipes using one bolt for the Inlet and a couple of screws for the outlet as I had the Ply to attach it to. Again, a liberal covering of Flashing Tape was applied over these joints.
Checking the Cone fit.
I mounted the Unit on a backing board made from some pieces of Ply with a piece of metal strap to hold it in place. This board was then screwed to the collection drum lid from below. I then cut a 70mm hole in the collection drum and shoved the Mini-Cyclone's Cone into it. I again sealed up the lot with Flashing Tape to ensure no air leaks. Hoses to the Vac and one to the Inlet, for hooking up to tools, were then added and Duct Taped in place.
The collection drum I used is actually the same size as the one on the Big Cyclone (I
bought them together). I did not use it for the big one as it is a Heavy Cardboard one
with steel top/bottom (the other is all Steel) and I was worried about fires in the bin
caused by spontaneous combustion of the dust pile if left for long periods. I am
sure the Heavy Cardboard bin will work fine for the little one and I will make sure I
empty it at the end of each days woodwork.
(Note: Both drums are ex chemical drums. Apparently Pool Shops get them for bulk chemicals. These had been long out of use and I picked them up from the Weekend Paper.)
$3 for sheet metal .6mm (24 gauge I think)
$2 for Pop riveter and rivets
$5 for flashing tape
$5 for Plywood/MDF
$5 for other bits (screws, tape, etc)
$0 for plans from http://cnets.net/~eclectic/woodworking/cyclone/CyclonePlan.html
$5 for second hand Vacuum Cleaner from a Garage Sale
$?? for 4 hours of time
I would like to upgrade to a better Vac sometime as the old one does not have much suction to start with. Probably get a proper Shop Vac one day or try and acquire the Minister of Finances VAX (not likely).
BTW Total construction time was only about 4 hours!