A Brief Word

| June/July 1991

26/6/16 Fairbanks-Morse Q. I have a 1923 FBM 11/2 HPZ engine, s/n 536505, with a drive gear on the shaft inside of the right hand flywheel to run a pump jack that is bolted to the engine and pump head as one unit. The right hand flywheel had additional casting numbers B-3R1V-ZA13. Ail other 11/2 HP flywheels I have seen only have ZA13. Both flywheels look the same. The problem I have is trying to find a gear to fit the magneto. I want to set it up as original. It has a Fairbanks-Morse conversion kit to replace the old AB-33 magneto with the newer FBM rotary magneto. It consists of a plate and a gear. Casting No. ZAA2561A2 is attached to the old AB-33 magneto bracket and cam support. The special gear 33 TEETH Casting No. ZAA2993A is attached to the plate and is driven by the crank gear with 24 teeth. The magneto runs off this spiral idler gear and not the cam gear, as later engines do.

Does anyone have an engine with this conversion? I would like to find out the size and number of teeth on the special magneto gear or loan of the parts to make the replacements.

Also, in the February GEM you note that the 11/2 HP Z engines used an 'R' magneto, but in your book it says the AB-35 was used up till 1924 . Which is right?

A. Regarding the body of your question, we cannot give you the answer, since we do not have enough FBM parts books for a cross-reference. However, regarding the various magnetos used on the 11/2 HP engine, it appears that the Model Z Plugoscillator was discontinued in late 1919, being replaced with the American Bosch AB-33 oscillator. It was used on the 11/2 HP size until early 1924, when it was replaced with the AB-34 for a short time. It was then replaced with the FBM Type R magneto, effective with s/n 592989 of mid-1924. This one stayed in use until being replaced with the FBM RV-1 magneto in 1933, and followed in 1938 with the FBM Type J magneto.

26/6/17 Thermos? Q. I have a question, not about engines, but about the simple thermos bottle. It says, 'Hot stays Hot, and Cold stays Cold.' How does this happen? Willy Toucher, Box 488, Wilmington, DE 19830.

A. The thermos is technically called a vacuum bottle, and as such it tends to keep whatever is poured in at the same temperature as it was when it entered the top. There is nothing in the thermos except the replaceable liner.