Courtesy of Mr. Emil Christenson, Conrad, Montana 59425
Rte. 2, Gunnison, Colorado 81230
If your gas engine has electrical ignition but does not use a spark plug it probably uses a hammerbreak igniter. This igniter is used in conjunction with a battery and simple induction coil or with a low-voltage magneto. It has been said that the igniter system is mechanically complicated and electrically simple while the high-tension spark plug type system is mechanically simple and electrically complicated.
Because of its mechanical complications the hammerbreak igniter is limited to slower speed engines, as it begins to malfunction at speeds greater than about 750 RPM.
The hammerbreak igniter (see Fig. 1) consists of a cast iron or brass body, a, which bolts to the engine head or cylinder side so that the breaker points extend into the combustion chamber. One of the points, b, is stationary and insulated from the body with mica or porcelain and extends through the body to the outside battery or magneto connection, d. The other point, c, is movable and fastened to a shaft, e, which also passes through the body. In operation a push rod on the engine pushes against the lever, f, which transmits a twisting motion to shaft, e, through the spring, i. This holds the points, b, and c, closed so that current from the battery flows.
As the push rod continues its travel it releases, f, which strikes lever, g, which is part of shaft. This hammer-like blow causes the points to separate suddenly causing an arc which ignites the gas mixture in the engine.
Using a battery, one terminal is hooked to ground (the frame of the engine) and the other is hooked to one terminal of the induction coil. A wire connects the second terminal of the coil to the igniter insulated terminal.
The simple induction coil has several hundred turns (200-400) or about six layers of No. 14 insulated copper wire wound on a soft iron core about six inches long and one-half inch in diameter. In function, when current flows this coil becomes an electro-magnet. (The building magnetic field as the points close tends to resist current flow and prevents a dead short on the battery but this effect is of minor importance.) If the current flow is suddenly interrupted the magnetic field collapse tends to heighten the tendency of the current to continue to flow, thus it flows across the opened points momentarily, causing the arc. Four batteries (Eveready No. 6) can be used or a handy pack of these four (one Eveready No. 1461). A six volt car battery can be used but I do not recommend it because of the huge amperage output capacity. (An accidental short circuit can melt a wire almost instantly and be a fire hazard if nothing else).
Here is a picture of a 30-60 Hart Parr taken after it was loaded. This engine came from Canada and is in good shape.
Troubleshooting: Since the operation of the system requires first of all a flow of current, good batteries or magneto are required. Be sure all electrical connections are clean and free of oil. Heavy wire (No. 12) flexible or automotive type works best. Use steel wool or point file on the points but file sparingly. Be sure the movable point moves freely so the break will be rapid. Do not oil the moveable point shaft as the oil burns, forming carbon which fouls the points and gums the shaft. A few drops of high temp. lube such as heat riser valve lube (Delco Rochester X-88) will clean and lubricate quite effectively.
The hammerbreak. igniter was especially popular on marine and stationary engines used indoors because of less fire hazard. Early rubber and insulation tended to deteriorate and high tension electricity tended to short out, especially in damp weather or salt air. Development of better insulators and higher speed engines made the hammerbreak igniter obsolete.
I'll take up the low tension magneto in a later article. Mean-while, keep your questions coming and I'll keep looking for answers.
My question: Does anyone know where you can still buy the low tension coils ready made?