Comments by "" (@EbenBransome) on "This Tiny Engine Part Changed Everything - Flathead vs OHV vs OHC!" video.

Before WW2, the British motorcycle industry tended to use bevel drive OHC for the sports models. After the war they went back to pushrods. Development of pushrod designs had improved a lot whereas bevel gears were expensive. Engines like the Velocette used pushrod tubes that resembled the prewar bevel drive covers, though some makers like BSA and Norton used holes through the block. Vincent used a design that looked like a WW2 radial engine with 2 pushrod tubes per cylinder. But the most produced 4 stroke engine in the world has never been flathead. The Honda 50 (to 110) cc engine started as pushrod and changed to Morse chain OHC - where it stayed.
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The German engines, BMW, Jumo and DB, all had very well engineered roller cam followers. They also experimented with disc valves to try and get the cross-section down. RR used crappy non-rotating flat cam followers in the Merlin. They wore out but were cheap to replace, and minimised the cross section. The engineering that wins wars is the good enough, not the expensive best.
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@erikkeever3504 Back in the 1980s I was involved for a bit in MBT R&D. Several people commented that the NATO doctrine of going nuclear the moment Soviet tranks crossed the German border ws ridiculous: just wait till they'd got far enough to break down and then deal with them conventionally. In the 1990s we discovered that the USSR was expecting to be invaded by the US from Germany, so their tanks were designed for a defensive role, on the assumption that when they broke down they would be static artillery, if they survived that long. By the time the USSR was invading Germany the T34 engine and transmission was a lot more reliable because even if the tank was destroyed the engines might be salvageable, as when you are taking territory you can recover them. All about logistics.
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@Mcfreddo Not for V engines, but twin cam pushrod engines have been constructed and one example - the Triumph twins - was rather successful. In theory you could have fitted them with VVT.
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@tubaman66 Also Ricardo invented the squish head which isn't actually as flat as the old US ones were.
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@Southghost5997 We really need to drop the "degree" in Celsius too, since 1 degree C is exactly one kelvin.
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At one time around the late 1990s I had the idea, for amusement, of seeing how much power you could get out of a B&S engine (with a lot of mods including forced lubrication, reworked valves and cams etc.) I couldn't find a B&S engine in decent condition, they were all Honda OHC or Husqvarna 2-strokes. So someone saying "20 years" is I think exaggerting.
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