Most collectors know Abenaque engines for their unique water-cooling setup. Designed by John Ostenberg (who went on to found the Ostenberg Manufacturing Co. in San Jose, California) for Abenaque Machine Works, Westminster Station, Vermont, Abenaques featured a pair of thin cooling tanks situated just above the engine, one on either side and running the length of the engine, and typically tall enough to double the engine’s height. The twin tanks’ massive surface area allowed quick heat dissipation, and their construction kept both water volume and evaporation rates low. The tanks were a feature of the majority of Abenaque horizontal engines, but the Abenaque’s novel characteristics extend beyond the cooling design to its intriguing means of ignition, fuel and valve actuation.
Ostenberg eschewed the then common atmospheric intake in favor of mechanical actuation. The intake and exhaust valves, set at roughly 4 and 8 o’clock, respectively, were opened by rocker arms set on a common pivot below the front of the cylinder head. A leaf spring mounted just above the rocker arm pivot provided closing pressure for the valves.
The igniter ignition featured a star-wheeled rotary contact open to the combustion chamber. A ratchet wheel was fixed to the opposite end of the star wheel’s horizontal shaft, outboard of the shaft’s brass mounting fixture. A hooked pawl driven by the sideshaft pulled the ratchet wheel on its downward stroke. As it was rotated, the six-lobed star wheel contacted a vertically mounted, battery-charged wire held under mild spring tension. The star wheel brushed the wire, spark being generated when contact was broken as the star wheel rotated past the wire. Gross adjustment was provided for initial contact of the wire to the star wheel, along with fine adjustment to adjust contact time with the star wheel to affect ignition timing.
A horizontal “dog-bone” governor on the sideshaft worked a pawl that engaged a lever arm, the arm pulling on linkage to lock the exhaust valve open. When the exhaust valve was in the locked position, an angled swipe ahead of the intake lobe contacted the moveable intake roller, which ran in a horizontal shaft fixed to the intake rocker arm. The swipe pushed the roller out of the path of the cam lobe, thus keeping the intake valve shut. When the exhaust unlocked, the exhaust rocker arm lifted and an angled bar mounted to the rocker arm pushed the intake roller into the path of the intake lobe.
The governed linkage also affected fuel admission. When the exhaust rocker was held open, the fuel pump was locked out of operation. Upon release of the rocker arm, the fuel pump was brought back into function. By design, the fuel pump was synchronized to deliver fuel after the intake valve had closed. In operation, fuel was pumped to a pre-chamber just ahead of the intake valve, where engine heat caused it to vaporize. Upon the next intake stroke, the vaporized fuel was drawn into the combustion chamber, primed for effective combustion. When the governor latched out the exhaust rocker arm, it latched out the fuel pump plunger in its downward stroke. The plunger lifted only when the intake was allowed to open, so if the exhaust was latched out, the plunger remained in its bottom position. When the governor released the exhaust rocker arm, intake linkage pulled the plunger up, ready for its next downward stroke to prime the intake chamber.
The governing linkage that locked out the fuel pump also interrupted the ratchet pawl driving the igniter, knocking out ignition. The ratchet pawl actuated simultaneously and only with the downward stroke of the fuel pump plunger. This occurred after the intake valve had closed, previously mentioned while also igniting the waiting compressed fuel/air charger.
Ostenberg’s design apparently proved durable and reliable, but it wasn’t enough to keep Abenaque competitive. Engine production ended about 1916, after Abenaque declared bankruptcy following a disastrous foray into tractor manufacturing. The company continued producing other products, including, it is presumed, engine parts, until a second bankruptcy in 1921 put it firmly out of business.
You can see one in action at 1909 5HP Abenaque Video.
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