Wayne Grenning offers a technical history of the Fairbanks-Morse Z series gas engine.
3 HP engines
This is written to help Fairbanks-Morse collectors. Original manuals, catalogs, documents and reprinted sales literature were used. For this article only 1, 3 and 6 HP engines will be discussed.
The Fairbanks-Morse Company was founded in the late 1880s with headquarters in Chicago, Illinois. Fairbanks-Morse manufactured many kinds of engines including the 'Eclipse Pumper,' 'Jack of all Trades' and many industrial engines. In September of 1916 the 'Z' series was introduced. In the following paragraphs and figures the development of this style will be outlined. Development of the 'Z' engines will be described chronologically through the years 1916 to 1944.
In September of 1916 (Number 200,000) Fairbanks introduced a new engine line, the 'Z' series. The 1, 3 and 6 HP engines were 'headless,' with valves and igniters on the governor side. 'Headless' describes a type of casting in which the cylinder and head were cast with the crank-case body as one unit. Rotary, Sumter magnetos were used on these early 'Z' engines and were driven by the crankshaft gear. 'Headless' construction for all models was short lived because of the difficulty of overhauling and 'take down' of the engine. 'Headless' engines were characterized by a governor located on the upper left side of the cam gear.
An 'improved' model of the 'Z' series was complete in January 1917, (Number 260,000) just four months after the first 'Z' series. New 3 and 6 HP engines were made with removable heads. Location of the magneto and governor remained the same as the first version. On this model as well as all future models, the gas tank was located within the base. An exception to this practice, were those engines with a partial base. The carburetor and exhaust outlets were changed to the head. The carburetor was on the side, while the exhaust was on the bottom of the head. At first this type 'Z' engine used a water injector to cool it while operating. Later, it was taken off because of too many poor starting engines and fouled igniters.
(Poor starting was caused by water leaking by way of the needle valve into the carburetor from the hopper.) A fuel starting reservoir and pump were incorporated in the carburetor of the 3 and 6 HP engines. In this series, engines had an igniter and magneto installed as two separate units. A change later became necessary because of the difficulty in timing the magneto with the igniter. The 1 HP engine remained a 'headless' hit and miss, while the 3 and 6 HP were throttling governors in design.
Next, a change was made in June of 1917. (Number 295,000). The difference between the January and June versions can be seen in figures 1 and 2. On the 3 and 6 HP engines the magneto and igniter were mounted on a cast iron unit. Magnetos used remained Sumters. Instead of having the magneto driven by the crankshaft gear, the design was changed to an oscillating magneto with a trip and springs. (When the magneto was tripped a lever on the end of the armature hit a movable contact arm and separated the contact points.) This method was useful because it was 'self timing.' (See figures 1 and2.) The 1 HP engine still remained a 'hit and miss.'
Another change in the development of the Fairbanks-Morse 'Z' series took place in the latter part of 1918. (Number 340,000). (See figures 2 and 3.) On 3 and 6 HP engines ignition was changed from igniter to sparkplug. Sparkplugs eliminated problems of cleaning igniters and retiming when removed. Fairbanks-Morse at this time introduced the American Bosch oscillating high tension magneto which was triggered by a peg on the cam gear. (See figures 7a and 8.)
Location of the magneto was above the cam gear while the plug was mounted on top of the head.
The exhaust was switched from the bottom to the side opposite the governor. The carburetor on this engine had a starting reservoir which was filled with gasoline or alcohol. While running off of this fuel source it warmed up, then it was 'switched' over to the working fuel, most likely kerosene. A flutter valve was introduced on this model. It provided a vacuum in the carburetor and drew fuel without the use of a pump. In the early versions of this model, Fairbanks-Morse again tried the use of the water injector to cool the engine, but as before water leaked into the carburetor when the water valve remained open. (See figures 4 and 5.) Location of the governor was changed to the lower left of the cam gear. The hopper was cast separately from the cylinder. Two reasons for this were: to allow for cleaning of the water jacket and for ease of manufacturing. The 1 HP model was finally changed from 'hit and miss' to throttling governor. (See figures 6 and 7.) Hoppers on the 1 HP model were not removable. All Fairbanks-Morse 'Z's' from this date on were of the throttling governor type.
Further developments on the Fairbanks-Morse 'Z' series were made in 1926. (Number 672,000). The 1, 3 and 6 HP engines were equipped with the Fairbanks-Morse high tension rotary, type 'R' magneto which replaced the American Bosch models. (See figures 8 and 9.) The governor bracket which mounts the magneto was changed from cast iron to white metal. White metal lowered costs, as it was the goal of Fairbanks to make engines more competitive in price. Location of the carburetor and exhaust port remained the same as before. Solid disc flywheels now appeared on the 1 HP models.
In 1929 (Number 727,000) 3 and 6 HP engines were changed very little. A small change occurred in the location of the drain plug which was changed from the front of the cylinder to the rear. Also the gap in the water jacket was widened for increased cooling. 1 HP engines were designed with a crank handle in the flywheel face. Oilers were changed from brass and glass to steel without a sight.
In 1932 (Number 777,000) the magneto was changed from a high tension Fairbanks-Morse type 'R' to a Fairbanks Morse type 'J.' The 'R' and a copper wound armature which rotated inside a magnet. The 'J' had an armature which rotated inside a copper wound coil. On all of the 'Z' engines (1, 3 and 6 HP) the lubrication was changed from grease to oil. An oil reservoir in the bottom of the crankcase in conjunction with a splasher, oiled all the internal parts. Horsepower ratings were changed to higher rpm's. For example, the 3 HP was raised from 475 rpm's to 650 rpm's. Also on this model the diameter of the flywheel was decreased from 22' to 19'. Improvements made in the carburetor allowed less fuel to be used, and it was smaller. The flywheels on the 3 and 6 HP remained spoked. In 1932 the 1 HP engine was reduced in size with fewer exposed parts and looked more like a box with two flywheels. (See figure 10.)
Final developments in the 'Z' series saw larger diameter flywheels. The last 'Z's' were manufactured at the close of World War II. (See figure 11.) Almost all of the Fairbanks-Morse 'Z' engines were painted 'grass green' with machined flywheel surfaces, however, a few were painted red.
Gasoline, kerosene, alcohol, coal oil, oil tops and other low grade fuels were commonly used. 'Z's' were originally sold with air compressors, vacuum pumps, water pumps, corn shellers, light plants, feed grinders, food cutters, power heads, washing machines and saw mills. Often they were purchased by a farmer for multiple uses around the farm. Over 550,000 'Z' engines were manufactured.
Questions and comments about this article or the Fairbanks-Morse 'Z' engines will be graciously received by the author.