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Reference: This question from Worldbuilding.

I'm writing a time travel story set in 1962 and I'm in need of an analogue to Doc Brown's plutonium (or bolt of lightning!). What I settled on for my inventor's 'contraption' was flywheel energy storage. To be precise, two counterrotating 830 lbm 60" rim diameter flywheels constructed (mainly) of martensitic steel operating at a maximum speed of 5000 rpm.

My specific questions are: Would this be feasible and reasonably safe with late 1950s technology, and could the RPM be increased without shaving the factor of safety too greatly? The device, for fictional purposes, is being installed in a DC-3; while it's not practical to increase the radius/diameter an increase in RPM would permit less flywheel mass and thus more useful load.

Please note that I'm postulating that the "activation energy" which opens the time continuum is not frequency-sensitive and so it is possible to place windings directly around the flywheel to generate the pulse. The "sustaining energy" which keeps the object stable in the time continuum, though, is very frequency-sensitive and is supplied by a separate, governed alternator. However, its power requirement is much less and can be continuously supplied by a gas turbine APU (available from 1956 onward).

ehbowen
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  • feasible? Sure. Safe? Probably not even now. 5000 rpm anything is tough to make within vibration specs. – Tiger Guy Sep 11 '22 at 19:28
  • Poor choice of words on my part. My merge onto the freeway every morning isn't 'safe'. And I'm sure taking off in a DC-3 with an experimental time machine in the back doesn't fall into that category either. But if it's feasible and not the most risky part of the endeavor, I think I'll keep it as it is. – ehbowen Sep 11 '22 at 19:31
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    1962 Ferrari 250 GTO max engine speed 7400rpm. So yes possible. – Solar Mike Sep 11 '22 at 19:53
  • ... but flying with giant flywheels makes it *really* hard to maneuver. – Phil Sweet Sep 11 '22 at 20:39
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    "In Tesla's final attempt to commercialize his invention, he persuaded the Allis-Chalmers Manufacturing Company in Milwaukee to build three turbines. . The third had 15 disks 60 inches (1.5 meters) in diameter and was designed to operate at 3,600 rpm, generating 675 horsepower. During the tests, engineers from Allis-Chalmers grew concerned about both the mechanical efficiency of the turbines, as well as their ability to endure prolonged use. They found that the disks had distorted to a great extent and concluded that the turbine would have eventually failed." – Phil Sweet Sep 11 '22 at 20:41
  • @PhilSweet, I thought the same thing but the OP may have covered that with the "counterrotating" specification. I'd still be concerned that there will be an inertial moment due to the difference in centre of gravity of each. – Transistor Sep 11 '22 at 20:41
  • the above from https://auto.howstuffworks.com/tesla-turbine.htm – Phil Sweet Sep 11 '22 at 20:43
  • @PhilSweet, turbine technology advanced between 1910 and 1962. A LOT. My own ship had turbine rotors five feet in diameter which spun at 6000 rpm at full throttle...and it was designed in 1942! Never had an issue with it as long as we kept oil to the bearings and moisture out of the steam. My biggest concern was with stresses in the rim of a steel flywheel at 5000 rpm; afraid I haven't got the chops to compute that. And sixty inches is 'just a little' bigger than the flywheel of a Ferrari GTO... – ehbowen Sep 11 '22 at 22:16

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