| January/February 1990

25/1/44 Magneto Information Q. Some models of the Fairbanks-Morse 'Z' engines use the Bosch AB-33 oscillator, and others use the Fairbanks-Morse Type R rotary magneto. Can you provide some understanding on the differences?

R. N. Holden, 2844 E. 12th Ave., Apache Jct, AZ 85219.

A. The AB-33 Bosch was used on FBM 'Z' engines from late 1919 to mid-1924. Effective with Engine No. 592989 the change was made to the gear-driven FBM Type R magneto. The AB-33 was simply a high-tension magneto with a long arm on its armature. A roller on the cam gear contacts this arm, moving it forward, and simultaneously pulling against a pair of heavy springs. When the roller goes past the tip of the lever, the armature suddenly returns to its resting position, and in so doing the points open and a spark is delivered to the plug. The gear-driven Type R on the other hand, is a conventional rotary style with an impulse built into the armature gear. This provides a hot spark that could not usually be obtained by the slow speed of hand cranking.

Later on, FBM introduced their Type J magneto, and it was used on the ZC models, as well as some of the later 'Z' engines. This magneto could however be retrofitted to earlier 'Z' models, using the J1A2 style. The old impulse and drive gear was used on the new magneto, and other changeover parts were furnished by FBM.

25/1/45 Graham-Bradley Tractor

See photos 45 A, B, and C showing a 1936 Model 503-93 Graham Bradley tractor I recently restored. It was purchased four years ago in Central Indiana. I have the original parts and owners manuals plus the service manuals. In 1939 this tractor, complete with cultivator and wheel weights sold for $1195.50. My brother and I farmed with four Graham Bradley tractors at one time. My nephews still have one of these and it is now restored.


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