ROLL YOUR OWN

(SPARK COIL)

by John Roy Doggett 411 Cherry Street Manassas, Virginia 22110

The following is in regards to Howard Wagenblast, Page 29, January-February, 1970 Issue. It never occurred to me that my experimentation with Hit-Miss engine coils would be of interest to my fellow Spark-Plugs. Make your own spark coil in one hour or less. Please don't waste your time and question my values or measurements, just rely on my experience, WA4DVV, Amateur Radio License, and get right to work.

Buy or use your own methods, HI! to secure a common carriage bolt that is seven-eighths or one inch in diameter and four and three-quarter inch in length. Cut off the head of the bolt, leave on the squared part of the bolt; so that you have the full four and three-quarter inches in length. Threads on other end of bolt do not harm; so forget them and continue to work.

Secure from your local TV Repair shop one roll of 18 Sgl. Beldsol wire, number 8049, one-half pound; approximate cost one dollar. This should be your total cost to make the coil. Wrap the bolt with two layers of plastic electrical tape from end to end. Measure three-quarters of inch in from each end and on top of the electrical tape make a mark at the measured points with Band-Aid tape. Put one end of bolt in a vise with the mark even with the vise-jaws. Now take the coil of Beldsol wire and roll off some. Measure six inches from the end of the wire and put this measured point against the bolt tight against the vise-jaws. Now proceed to roll the rest of the wire by hand tightly around the bolt working toward the mark at the other end of the bolt. Now start winding a second layer on top of the first layer and work your windings back to the vise-jaws. Keep your winding tightly spaced, but if some of the windings keep slipping down into the layer below the layer you are winding, don't worry, but keep winding as the coil is not that critical. Now continue your windings from end mark to mark until you have used up the whole coil of wire. You should end up with a second six inch pig-tall of wire at the vise-jaws, which is your point of beginning, but many layers deeper. If you can not make the last layer and leave a six inch pig- tail; then unwind this layer hack to the vise-jaws and measure out six inches from the jaws and cut off the excess, as one layer is not that critical.

Secure enough hard wood or plywood of three-quarter inch thickness to cut two blocks, three inches square. Bore a hole to fit the diameter of your bolt in the center of each block. Cut a third piece of wood three inches wide and six inches long. This will be the base.

Bore two holes one-quarter inch in diameter in one of the three-inch square blocks. Bore the holes one-quarter inch from the edge of the block and one inch apart. Secure two bolts of one-quarter inch diameter and one and one-half inches in length with two nuts each bolt.

Now assemble the two blocks, one on each end of the bolt to the marks which is now the ends of the coil. Then compress the end blocks to the coil ends and hold tightly by hand and nail on the bottom piece of wood to the end blocks. You now have the coil sandwiched between two blocks of wood which are nailed to a wood base. Now insert the quarter inch bolts through their holes in the one end block with the bolt heads facing the coil. Take the wire pig-tails, one to each bolt head and make a turn or two under the head of the bolt and cut off the excess wire. Now put on one nut to the other end of each bolt and tighten securely as this is a permanent operation. Now take the second nut, one to each bolt and you have a sandwich between the nuts for a cheap, but efficient terminal for your engine hook-up wires. You may now make one wrapping of the plastic electrical tape around the coil for protection against scarring the shellacked finish on the wire, but even this is not critical. You may now paint the whole coil and wood, for looks, as even liquid is not a critical factor to the coil.

Note on high tension coils. At this writing it is exceedingly less expensive to order a new reproduction Model "T" coil from Whitney in Chicago at approximate five dollars than roll your own. I am still experimenting with high tension coils and if I have any practical results I shall share my results with you through the Gas-Engine Magazine. Roll your own "Big John" and may a BLUE ARC be yours.

This article originally published in GEM Vol. 3 No. 5

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