Here’s another wildly creative idea from the early years of hot rodding: The Schaller Quarter-Speed Double-Lobe camshaft. How does it work? Read on.
Harold G. “Bus” Schaller was a well-regarded motorcycle racer and camshaft grinder from Turlock, California who ran at Bonneville and elsewhere all through the 1950s. Constantly struggling to squeeze more power from his 45 cubic-inch Harley flathead V-twins, he hit upon the idea of slowing down the camshaft from one-half crankshaft speed to one-quarter speed in a quest to reduce friction.
After developing and racing the setup with success, Schaller filed for and was awarded U.S. patent no. 2,877,752 on March, 17, 1959. From there he branched out into the automotive performance community, where his quarter-speed camshaft kit for the small-block Chevrolet V8 received a friendly writeup in the March 1961 issue of Hot Rod magazine.
As shown just above: With the camshaft rotating at one-quarter crank rpm, each intake and exhaust valve required two lobes on the shaft exactly 180 degrees apart, rather than one as with a conventional cam. The stock timing chain and sprockets were replaced with a pair of gears, one tiny and one huge to obtain a .25:1 ratio, which required a special timing cover to provide sufficient clearance. Also, the distributor required a step-up gearset to supply spark at the proper speed (see second photo above).
As we know, the idea didn’t catch on. Whatever the advantage in rotating the camshaft past the lifter at a reduced rate, nothing else changes. The entire valvetrain, from the lifter to the valve, must still travel the same distance at the same velocity each four-stroke cycle to obtain the same intake and exhaust events, same as before. Also, now the camshaft has only 180 degrees of rotation to open and close the valve instead of 360, so inverse-profile lobes are required—which among other things, are more difficult to manufacture and require roller valve lifters of special design. Claims for the quarter-speed cam included reduced valve spring pressures and quieter operation, for what it’s worth.
All that said, the novel cam was tried by one leading racer, and at the biggest racing venue in the world. For the 1963 Indy 500, Mickey Thompson equipped his radical roller-skate racers, powered by Chevy V8s, with the quarter-speed cams. (Masten Gregory shown below; note Schaller decal on cowl.) Two M/T cars qualified, and while Duane Carter’s entry threw a connecting rod at the halfway point, Al Miller’s Thompson-Chevy completed the entire 500 miles, finishing 9th. While Thompson continued racing for many years, there doesn’t seem to be any mention that he ever used the double-lobe cam again.
Sometimes just because it’s possible to create new products, unless it’s making things simpler and/or cheaper, then it’s probably not really a good idea.
Detroit diesel produced, for decades, diesel engines that were 2 stroke rather than four, what if you changed the cam sprocket and the grind, add a blower, ciuld you build a 2 stroke gas. Would it be more powerful?
GM Diesels got their air charge (and purge) via ports in the cylinder wall which became uncovered when the piston traveled below them. Not sure how a camshaft change alone could reconfigure a conventional design 4-stroke to 2-stroke?
Detroit diesels had intake and exhaust valves. They aren’t like 2 stroke dirt bike engines.
No .the older Detroits have only exhaust vales in the cylinder head.intake was achieved by positive pressure from a blower and ports in the liners that were uncovered at the bottom of the piston stroke.
https://achatespower.com/not-all-two-stroke-engines-are-created-equal/
This may answer some of your questions about 2 strokes with poppet valves..
The link seems to refer strictly to opposed-piston engines. I’m guessing that a workable “conventional” (V, I, etc.) design was never developed?
Pointless. But I respect the initiative.