Tremper’s second igniter patent, granted just four months after his first, dispensed with the spring-loaded contact in the piston crown and instead incorporated a “flexible sparking strip,” which could be designed any number of ways, giving far more flexibility to design.
Last issue, we looked at San Francisco, California, engine pioneer Frank E. Tremper’s 1893 patent for a “make-and-break” ignition system. A key feature of Tremper’s patent no. 495,281 was a spring-loaded contact set into the crown of the piston.
Patent no. 503,016, granted just four months later on Aug. 8, 1893, was a further development of Tremper’s igniter scheme, but it dispensed with the spring-loaded rod in the piston. Instead, a bolt was firmly set protruding from the crown of the piston, and a “flexible sparking strip” was attached to the bolt. The strip, which could be configured in any number of ways, made contact with fixed electrodes protruding into the combustion chamber at whatever position in the cylinder deemed desirable.
This design appears inherently simpler than Tremper’s first patent, and is similar to other early piston-tripped igniter designs. It’s not clear which design was actually more effective, but the existence of the later design suggests there may have been problems with Tremper’s original scheme.
Rotary Valve
Incorporated in Tremper’s original patent and not discussed last issue was Tremper’s design for a rotary valve, the most visually intriguing feature of the early Safety Vapor engines.
Tremper’s design for a rotary valve was integrated into his original patent. “Fig. 3” shows the ports in the cylinder, with “P” and “P4” representing the disc valve and valve port, respectively. “Fig. 4” shows the ports in the valve body. The valve could also be head-mounted, chain driven through bevel gears, as shown in “Fig. 5.”
Essentially a rotating plate that opened and closed off intake and exhaust ports on cue, Tremper’s rotary valve is noteworthy. By design, the rotary valve was set either in the cylinder wall itself or in its own compact housing bolted directly to the cylinder. With no valve chest carrying a poppet valve, and no corresponding chamber between the valve chest and the combustion chamber, combustion was confined to the cylinder proper. Further, Tremper’s design meant he could dial in overlap between the intake and exhaust cycles. An endless chain running from the crankshaft connected to the rotary valve’s shaft, and timing was a simple issue of gearing and porting.
Other companies experimented with rotary-type valves, but the familiar poppet valve, still with us today, eventually became the industry standard for internal combustion engines.
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