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There are two types of coils to make. Four of them are wound on soda straws and four of them are wound on 1" strips of plastic cut from the top of an ice cream container. Two of the straw coils have 1 ½ turns and the other two have 2 ½ turns. Begin their construction by preparing strips of aluminum foil to use as the winding. Use cheap thin foil for a higher Q coil. It will produce a stronger magnetic field per unit of amperage than a expensive heavy duty cooking foil would. However, you may wish to use the heavy duty foil instead because it will be easier to work with.
To cut the foil, prepare ½" strips of paper. Tape the paper to the aluminum foil using single sided scotch tape. Use a sharp pair of scissors to cut along the edge of the paper. Separate the foil from the paper when you are ready to use each piece. The length of a sheet of notebook paper is long enough. Make 6 strips ½" wide and 2 strips 1" wide. The other strips are for the flat coils.
Four coils made by winding strips of aluminum foil onto soda straws. The papers that the coils are on have ½" strip markings and the alignment page.
Next, prepare an alignment page. The page guides you while making the first contact between the foil and the tape covered straw. Each of the two pencil lines shown are 40 degrees from the horizontal blue ink lines on the paper. There is a line for each of the two directions of winding the coils. To use it, place a strip of foil along a pencil line. Lower the straw into contact while holding the straw parallel to the blue ink lines. Use your little fingers to hold the foil down. It will tend to jump up at the straw.
For each of the four straw coils prepare a coil form by placing two pieces of double sided scotch tape along a 6" length of straw. There may be a tiny gap between the two pieces of tape. Place a piece of foil on the alignment page and lower the straw into contact with the foil. Once contact has been made simply wind the foil around the straw to get the desired number of turns. When you get to the stopping point for the winding place a small piece of single sided scotch tape upon the double sided scotch tape so that the foil will not stick to the straw beyond that point. Cut the excess coil form off just beyond the foil winding. Produce matching pairs of clockwise winding and counter clockwise winding for each of the two sizes.
The point where the foil first makes to the tape is where it tears easiest during construction. Place single sided scotch tape on the outside of the foil strip at that area. The tape should cover the foil for about 1/4" on either side of the first location where the foil is stuck to the straw. These pieces of tape are not shown on the prototype.
The length of the foil strip is barely long enough for the 2 ½ turn coils. Produce them so that they each have a 1 ½" leg.
The flat coils are made by winding the strips of foil around 1" strips of plastic. Two of them are 2 ½ turn coils made from ½" wide foil. The other two are 1 turn coils made from 1" wide foil. Each pair has a coil of each winding direction. The length of the coil forms is not critical. There were made as long as possible to allow other larger coils to be used later in the same holder. The coil forms shown are 4" and 5 ½" long. That length includes the 1/4" x 1/4" tab feet that go into the wood block.
These coils do not use a tape coating on the form. Mark the longer coil forms at 5/8" intervals. When the foil is wrapped around the form there should be a 1/8" gap between the windings. The legs from these coils turn away from the forms at 90 degrees. If they were to wrap around in the usual way it would be a 3 turn coil. Place a small piece of double sided scotch tape along the edge where the winding stops. That will hold the foil to the form when the foil gets bent back at 90 degrees. The 1 ½" leg should be at the top of the coil.
For the other two coils wrap the 1" ribbon around the form for 1 complete turn. There should be a 3/8" gap in the winding. Use a piece of tape as before to hold the ends of the windings. For these coils the legs will wrap on around the form instead of turning away from it.
Two flat coil forms in their holders along with two of the capacitors.
Produce a holder for each pair of coils using two flex joint soda straws for each. A regular straw may be used if that type is not available. The holder frame should be 3 ½" wide. Prepare two slots on the bottom side of the top bar by melting holes at the endpoints of the slots. The slots should be 3/4" apart. Use scissors to cut between the two pairs of holes. The top of the coil forms will be inserted into these slots. Cut the legs of the holders of at ½" beyond the foot tabs. They will be inserted ½" into holes in the wood block.