Half a croissant, on a plate, with a sign in front of it saying '50c'
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losslessly magnifies rotational acceleration and deceleration.
  [vote for,

Picture a small freewheeling flywheel, threaded onto a rotating shaft: a spinning nut on bolt. As long as both have the same rotational speed, the nut stays where it is, neither "tightening" nor "loosening". However, change the speed of the shaft and momentum will cause the nut to move one way or the other along the length.

Next, picture an umbrella type of mechanism, where sliding a ring along a shaft pushes or pulls on a short rib which extends or retracts a long rib. For argument's sake picture two rib assemblies. Place a weight on the end of each: it should vaguely resemble an old style centrifugal governor.

Connect the flywheel from the first paragraph to the ribs in the second, such that the flywheel is the ring, splaying or furling the ribs as it moves along the shaft. The ribs are fixed to and turn with the shaft; the connection is a plate bearing allowing the small flywheel independent rotation. We now have a large odd-looking rotating mass that acts as a flywheel.


When the shaft's rotational speed is increased, the small flywheel's momentum will pull the ribs shut, which dumps the rotational energy from the weighted ribs into the shaft... which increases the rotational speed.

When the shaft's rotational speed is decreased, the small flywheel's momentum will push the ribs open, which stores the rotational energy from the shaft into the weighted ribs... which decreases the rotational speed.

A small amount of doohickery is added, to get everything to work right.

FlyingToaster, May 11 2016

Complement to Self-geared_20flywheel
which tends toward maintaining a constant velocity, regardless of potential energy. [FlyingToaster, May 11 2016]

Jerk https://en.wikipedi.../Jerk_%28physics%29
[mitxela, May 12 2016]

Centrifugal governor https://en.wikipedi...entrifugal_governor
[Loris, Jun 21 2017]


       What if it's raining ?
8th of 7, May 11 2016

       Well that's the thing, innit: you can open and close your spinning umbrella much faster.
FlyingToaster, May 11 2016

       hmm, good point, thanks. "rotational velocity" unredundanted to "rotational speed". I'm sticking with "acceleration" for the time being. "momentum" still means "momentum".
FlyingToaster, May 12 2016

       [I T] You forgot to mention Jerk.   

       This idea sounds like it's going to be extremely unstable, with sudden changes in speed causing it to oscillate wildly. Then again, I suppose it is named anti-flywheel.
mitxela, May 12 2016

       //oscillate wildly//   

       There's a couple of factors in there: centripetal force will cause the ribs to naturally try to open up while the shaft is spinning, pulling the small-flywheel along the axis(shaft), slowly "tightening" it.   

       However, once that is compensated for, the ribs will push against the small-flywheel when it's trying to push them open and pull when it's trying to pull them closed, bringing the small-flywheel to the shaft speed, without the need for friction to do so.   

       With proper calculation of weights and thread-pitch (and friction), it won't runaway.   

       There will still be some lag effect, of course.
FlyingToaster, May 12 2016

       I just spent twenty minutes trying to figure out what the hell I had posted, last year.   

       Got a bit more insight, though...   

       The amount of energy that is dumped/retrieved into the main flywheel (the splayable weighted umbrella staves, fixed to the shaft) is equal to the stored energy difference of the small flywheel (the "nut" on the threaded driveshaft) between its original and final (when its rotation is caught up or down to the shaft) velocity.
FlyingToaster, Jun 21 2017

       I like it. The 'ol figure skater pulling-her-arms-in trick. (+)
I'm having a hard time thinking of a practical application though. Maybe to compensate for varying wind speeds in turbines?

       I was thinking vehicles, as assist/regen: apply some gas and it helps with acceleration; apply brakes and it helps with deceleration. Makes my brain hurt trying to figure out if it will actually work, or not.
FlyingToaster, Jun 21 2017

       It will work but the stress will increase on a steep curve when you try to draw in the weights. It might be easier to have the weights on cables which could be drawn inwards by pulling them down the shaft on individual pulleys. There'd be fewer moving parts and you could use a single hydraulic ram to pull the spin tighter.   

       As I understand it, it's not so much an anti-flywheel as an anti-governer.
I mean, a flywheel is a device which stores energy to use later. That's what you're doing with the flywheel here.
A governer, on the other hand, is a feed-back system to regulate the speed of a device to a particular setting. You're doing the opposite.

       My dad once delighted in describing a centrifugal governor to me as "A pair of balls which fly off at a tangent at the slightest sign of movement", and hence the name. (I'm not sure where he got that from.)   

       I put forward the name 'mutineer' for your device on this basis.
Loris, Jun 21 2017

       //A small amount of doohickery is added, to get everything to work right.//   

       I've got to get me some of that.
pertinax, Jun 22 2017

       /Pertinax/ - I think it's termed manipulation of the masses. I'm not entirely sure, though.
Zimmy, Jul 07 2017


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