Comments by "Vikki McDonough" (@vikkimcdonough6153) on "Naval Engines - Rotate that shaft!" video.

  1. 32:47 - The terrible efficiency of turbines at lower speeds was also a major part of why steam-turbine power never caught on for locomotives, since these spend lots of time at low speed for various reasons and steam locos were almost-universally direct-drive (no gearboxes or generators).
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  2. "1 person per 200 tons of cargo" still works out to over a hundred crew for a reasonably-sized cargo ship, though...
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  3. 38:00 - Also, given the extremely high speeds and tight clearances needed by turbines, a shock of that magnitude would likely cause the blades of even a direct-drive or geared turbine to contact the turbine case, with potentially-spectacular results, or cause the gears of a geared turbine to jump (likely shearing off the gear teeth when they came back into contact).
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  4. 29:53 - Why weren't opposed-piston triple-expansion engines (where the large mass of moving metal is balanced out by an equally-large mass of metal moving in the opposite direction at the same speed) used to give a smoother ride (especially since opposed-piston engines also have a considerably-higher thrust-to-mass ratio than non-opposed-piston ones, due to not needing cylinder heads)?
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  5. 39:54 - On the other hand, on a geared-turbine ship, the turbine's speed still varies in direct proportion to the propeller speed, meaning that going faster or slower necessitates speeding up or slowing down the turbine itself, which can easily take it outside its power band and cause efficiency to drop off (unless you equip the ship with a mechanism for shifting the turbine-to-propeller gear ratio to compensate, like in an automobile, which would add considerable additional weight and moving parts), potentially to a degree sufficient to exceed the conversion losses of a turboelectric ship. And, indeed, turboelectric drives came back with a vengeance in warships during the Cold War...
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