Before drawing the first line on his blank sheet of paper, Charles Franklin first decided that a smaller motorcycle was essential. No more stretching of arms and legs. The success of the 61ci (l,OOO-cc) and 74-ci (1,200-cc) Powerplus flatheads of 1916 through 1919 suggested that a smaller engine of the same layout would provide ample power for everyday requirements, especially since the smaller motorcycle would reap the reward of lighter weight. Although there would eventually emerge a new small engine with significantly different internal layout, this was surely a fine-tuning process that came after the new motorcycle concept had first been laid out entirely. Franklin selected an approximate wheelbase, shorter of course. The smaller flathead engine would be low slung, which saved weight by permitting a lower tank and thus a shorter front fork. The shorter distances between the ends of frame tubes gave additional strength, which permitted lighter tubing. This followed the same commonsense logic that one confirms by breaking in two a new pencil, and then breaking one of the pencil halves in two. The shorter the tubes, the stronger the tubes.
What about the frame layout of the new motorcycle? This was probably the first design question, because from the answer came all the other hallmark features of the new motorcycle. By considering the frame first, the rest of the thought process flowed as smoothly as syrup over pancakes. So what useful purpose was served by the current universal use of single-tube main frames in Indians, Harley-Davidsons, Excelsiors, and Reading-Standards? These frames had simply evolved gradually from single-tube pedal-bike frames, in a process that might be termed "design inertia." If instead of a single center-aligned tube, two lower frame tubes were used, one on each side, then the engine and transmission could be firmly anchored between the tubes and enjoy protection in spills. Goodbye bent clips and fractured brackets; hello tidiness. A double-lower-tube frame also meant that footboards could be more securely mounted by fixing them directly to the frame tubes rather than to intermediary fixtures.
Since with a double-lower-tube frame there was no need for an upturned frame tube behind the engine, this awareness must have logically extended to a new possibility: securing the transmission against the back of the engine. The engine, the transmission, and the primary drive housing could be bolted up together into one compact and strong assembly. The temptation to consider a gear-driven primary drive was suddenly upon the designer. If management wouldn't go for the expensive gear-drive layout, at least the drive mechanism could be operated in a cast-aluminum oil bath.
With the realization that the concept was for an integrated "powerplant" rather than a separate engine and transmission came consideration of three-point mounting. As photographers know, any three-legged device always stands firm on the ground. As everyone knows, a four-legged table or chair can wobble around because of unequal-length legs. By mounting the front of the engine to the left and right frame tubes, a single center rear mount can secure the back of the powerplant (the transmission) to a horizontal frame member between the two lower main tubes. Three-point powerplant mounting eliminates any twisting loads on the frame. The major features of the new motorcycle all flowed together, each as a consequence of companion features, to produce one integrated vehicle.
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