Welcome to page 2 of my Builders Notes:
Here we'll discuss building techniques.
Let's start with the cones, as they are critical to proper operation, and seem to give everyone the hardest time, short of actually balancing and operating a 3CD / M3CD.
First let me state, for the record, we're not going to do the math involved on this page. There are plenty of terrific sites which explain this math much better than I ever could! For a sample of these sites, return to the index page and go to my links.
Cones: All the cones, as far as I'm concerned, should have a master template. Every cone in your device should be made using the same template! This keeps all cones uniform, to one another, and this is very important when you reach the stage of trying to balance your device! Templates can be easily made from cheap posterboard available in most department stores for less than $1 each. Once you have made the templates for your inner, and outer cones, you can put them together as if they were the finished product to get an idea of how they will fit together.
Once you are satisfied with your templates, mark them however you'd like to know that they are ready for use.
My personal technique, is to lay the template on a sheet of aluminum and use clear celophane tape to temporarily attach the template to the aluminum sheet. Then use a scribe or scratch awl to mark the aluminum for cutting. I have found that using heavy sissors or shears does a nicer job of cutting the aluminum flashing than actual tin snips. You should be able to find these heavy shears at most hardware stores. I prefer the ones with a small spring between nice plastic handles, simply for comfort.
If you're making an M3CD, before bending your aluminum into the desired shape of a cone, to make the tip come out better, anneal the aluminum. This is done by heating the aluminum evenly with a small torch, using a wide adjustment on your flame if possible. Heat the aluminum just to the point where a very, very slight glow can be seen, and then quickly quench the piece by putting into cool water. The aluminum, then, will be very soft feeling, and will bend very easily. The hardness will return, after bending, with time. Usually less than 3 to 4 hours.
When making an M3CD of fairly small size, 6"X6" cones or less, I prefer to solder the seam with aluminum solder, also available at most hardware stores. The solder comes with instruction, but basically, heat the aluminum with a small torch while rubbing the solder stick against it. Be sure that the heat from the aluminum is what's melting the solder, and not the flame from the torch. It's helpful to clean the edges to be soldered with a stainless steel brush before beginning, to remove any microscopic corrosion and roughen the surface slightly wherever the solder will be. The inner cone can be soldered into place, or rivited, glued etc. after attaching the mid-point magnet to the tip.
The top cone will need a cover to attach a rejection / activation magnet to the center of it. I made mine from the same aluminum as the cones.
The mid-point magnet can be attached by making an aluminum platform for it to be attached to, and soldering the platform to the cone, or some strips of aluminum could be bent around the magnet and fastened with rivits.
Be sure to use aluminum rivits if you choose to use that method.
My M3CD uses 3/4" round magnets attached directly to the cone with glue, at the same angle with the sides of the cone, and then wrapped with aluminum tape. The tape completely covers the magnets. You can choose to mount an aluminum ring to your cone, and attach the magnets to this ring, that way they won't be at a different angle than your suspension rings. Just make sure that all of the magnets attached to your cone are, A: below the top edge of the cone, and B: they are all the same distance from the tip of the cone.
You will want to make sure that your cones are concentric, before putting them to use! I used a piece of wood with a divot in it, clamped in the vice of my drill press, and a sharpened dowel in the chuck. I placed the cone tip on the block, then gently raised the bed until the dowel was firmly in contact with the inner cone's pivot point. Then, BY HAND, rotated the cone to measure any run-out. The run-out was adjusted by adjusting the placement of the inner cone, before it was attached. I glued the two cones together in several places, to temporarily hold them while removing from the set-up.
Suspension rings: These are pretty much cut and dried, once you know what gap you want between the suspension magnets and the cone magnets. I used a strip of 16 gauge sheet steel, the same width as the magnets, and bent it by hand into a circle. If you want, a disk of wood can be used to help get the right diameter. Cut a notch out of the wood disk for a place to drill a hole, then remove the metal band from the disk and rivit it from the inside. If you have access to a spot welder, use that to fasten the ring together instead. I attached the magnets to the rings with electrical tape. I then wrapped the magnet wire around the rings, 2 wraps at each magnet touching point. The wrapping was done in the opposite direction for the center ring, because I used north poles together for the top and bottom rings, but south poles together for the center ring. Leave enough wire to attach the ends to make a continuous loop from the top to the bottom. I then wrapped this up in electrical tape, for protection of the wire. I then wrapped this all up in aluminum tape. You can choose to either put some tabs on the rings, before installing the magnets, to attach the rings to the frame, or simply use nylon wire ties without the tabs. Once in place and adjusted correctly, make sure that the rings won't slip on the frame, or you'll lose a lot of work in a heart beat!
The frame: This is still up for debate, as to the best way to go. Some have used steel, or other metal pieces for the frame. I used 1/4" thick pieces of wood. Thinner is better, for the upright pieces, to keep the shell as close to the suspension rings as possible.
The Oscillator Base: This is where the movement of the cones is reflected back, mechanicaly, to the cones. This is also where the energy is focused. I used plywood, and covered it with aluminum tape. I think that solid pieces of aluminum would have been better. You'll need two pieces of identicaly sized plywood, or aluminum. Triangle shaped is better, but I used round pieces. In three places, spaced in the shape of a triangle, is where the pinion balls are to be placed. I used cups made from ping pong balls for the pinion balls to set in. Then I used antique stone marbles, the kind that kids used to play with, for the pinions themselves. Rule of thumb is that the cups should be made of something twice the diameter of the balls. Ideally the balls would be about 1/4 the size of your cones. The cups are necessary to get some slight up and down movement, as well as side to side with your oscillator base. A magnet is then attached to the top oscillator piece, north up the same way as the center magnets in your cones, in the exact center. A second magnet is mounted on the bottom piece in attraction with the one on the top half. This puts tension on the base to stay centered. The top piece needs a pivot point installed for the bottom cone to set into. I made an extra center cone, and attached it for the pivot.
The Shell: This should be made of steel, I used stove pipe from the hardware store, and cut it to size. I then welded a piece of sheet steel to the bottom, and sealed the edges with silicon. The center / bottom piece needs a hole cut into the center for air flow, my hole is cut at 2" diameter. You can cover part of this hole with tape to adjust air flow if necessary. The shell needs small vent holes in it near the suspension rings. The total area of holes placed in the shell should equal about the same as the hole in the bottom. Again, you can adjust with tape. The top piece for your shell should also be steel, and will need a magnet attached for rejection of the top cone.
I'll get into the assembly of all these components in the next section. Till then, have fun building, and take your time to do it right!
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