Decoupling RKE from GPE, for fun and profit

[daanopperman]

Hi cloud camper ,

You stated

" But it doesn't matter as we still have the issue of multiple riders on a
carousel not being able to come up with a coordinated motion that would
accelerate a wheel. "

I feel this is not correct , in the next drawing 4 riders are walking on a carousell , the red circle is the path 2 riders will take , and the same with the blue circle . Note that the inner riders both travel slower . There is nothing that they hold onto or pushing against , just walking in circles on the carousell table .

Would this be correct .

Daan

[ME]

Hi Daan,
I think that should work when they would accelerate... whatever they do, those riders still have to eat.
IOW: where does their energy come from?

Those riders would have a much easier job when hanging on a ferris wheel and just shift their weight a bit.

[cloud camper]

Sure Dan, we can get the wheel to move this way, but not accelerate.

The instant the walkers stop, the wheel stops due to conservation of angular
momentum.

The riders can apply biochemical energy to make the wheel turn just like any
motor but when the motor stops, the wheel stops.

You may as well have the riders walk around the full circumference of the wheel as the two red riders create CW angular momentum and the blue riders double it so the two CW momentums add together and the wheel will
assume the exact same combined momentums in the opposite direction.

Overall momentum remains zero so no gain.

[daanopperman]

Good day to all ,

Marchello , it is not suppose to be a runner .
cloud camper stated it woud be impossible for 4 riders on a carousell to make the carousell accelerate no matter how they move , without being connected to earth , that is to say there cannot be a ratchet on the carousell as this would earth the carousell at times .
I responded with a drawing where there is a rope hanging from the center , over the hand rail , dangling a weight on its end .
Every time a rider would walk into the rope , the weigtht would be lifted and it is this lifting that would turn the carousell .
The words between the " " is his words .
I have never seen a stationary body start to move without acceleration .
I am trying to prove to him motion from motion is possible .

[ME]

I think what CC tries to say (as what I somewhat tried to say, and guess you meant to say) is that a carousel just reacts to the motion of those riders.

I personally have absolutely no problem to provide some initial input for a device when it is able to run indefinitely and overcomes friction.

But as the velocity of the wheel has a direct reactive coupling with the action of his 'riders' there is an energy crisis. When the riders slow down, so does the wheel (even without friction).
So for a carousel to keep moving and overcome deceleration by friction those riders should accelerate (which needs to be fueled), or somehow be able to react to a slowdown of the wheel by perhaps the means of something like a centrifugal governor (spring retracted) per rider... but it eventually still lacks input energy to compensate for friction losses.

I guess that's the reason most of us try to find a gravity wheel, as gravity at least provides a motive for a weight to change its position - where the 'only trick' should be the direction of its motion. It's hard to see how a rider is 'motivated'.

(hopefully Jim Mitch can prove this wrong, or has another option)
---
Your example still uses gravity. This doesn't matter as I don't think a rider is able to row the wheel into rotation with such a setup. I think the wheel just rotates back to its original position when the weight is being lowered.


Marchello E.

[rlortie]

Me,

It is no different than a horizontal axis hamster wheel. As the rider pushes on the rope, he is turning the wheel via the traction of his feet. when the weight reaches the top, he quits walking into the rope allowing the weight to fall. The rider then rides on the wheel until it is time to once again push into the rope.

The wheel need not return to its original location, it will continue to turn while the weight drops.

[ME]

That would make sense when the rider is disconnected from the wheel, like walking on ground.
A bit confusing without a model. But if I would make such a model, my hand would simulate the rider, and the result would be as suggested; but that hand is disconnected from the wheel and the rope-tension creates a force to push against the hand to relax the tension, lower the weight, and rotate the wheel.

The way I see, the weight is still lifted when he quits walking with both feet firmly on the base of the wheel; the rope remains attached to the pole at an angle behind the rider; so he either needs to walk back -so the rope returns to the geometric normal of the pole and the wheel returns, or the rider steps over the rope (not sure how the wheel reacts in that case)...

(nice parallel with topic: F^2)

Marchello E.

[MrVibrating]

Update:

Ran some stripped-down sims of the last hypothesis, resulting in unity.

Method:

A 4 kg mass positioned atop a 1 kg mass, with gravity disabled.

A spring exerts a linear acceleration between them (scissorjack not needed as only an equal distribution of momentum is required).

(NB: Linear springs are slightly dodgy - as explained earlier, the ability to apply a linear force indefinitely implies an effective N3 violation, and such a spring would have infinite PE. However it is perfectly feasable to apply a linear force over some finite displacement.)

Accelerating the 4 kg mass upwards at 9.81 m/s, against the inertia of the 1 kg mass, requires accelerating the latter downwards at 39.240 m/s.

The spring constant (K) is thus 39.240 Newtons.

This is applied for 515 milliseconds.

At this point both masses have a momentum of 20 kg-m/s

The 4 kg mass has 51 Joules of KE, the 1 kg mass has 204 J, so the total on-board work performed and thus the PE of the spring over the 515 ms period is 255 J.



Now this config is re-run with gravity enabled:

Over the same 515 ms period, the 1 kg mass descends by 8 meters.

The 4 kg mass remains motionless, its downwards acceleration under gravity cancelled by its upwards acceleration against the spring and the descending mass's inertia, so it has zero momentum and KE relative to the static frame.

A 1 kg mass falling 8 meters has 64 Joules.

Ours has 319 J - precisely that 64 J of GPE plus the 255 J of on-board work performed.


------------------------


Conclusions:

In the prior scenario the ambient displacement of a flying scissorjack was added to the displacements performed on-board, resulting in a gain in energy of the leading mass as measured from the stationary frame.

That energy gained by the leading mass was equal to the energy lost by the trailing mass, plus the PE stored and released by the spring.

So the speculation for the current test was that the lower mass might still gain the KE "lost" by the upper mass, despite it remaining motionless as measured from the stationary frame.

It evidently doesn't.

Which in retrospect makes sense - if one mass is to gain the KE lost by another, as measured from another frame, then both KE's have to be real (ie. non-zero) relative to that frame.

If gravity's inertial equivalence is to have any utility in these investigations, this clearly isn't a means to exploit it.

That hunch persists however - the concept of "virtual displacement" implicit to gravity's inertial equivalence would seem a canny alternative FoR, and the ideal wildcard 'd' for a variable F*d integral.. if only there was a way to apply it.

Will have to see what ideas this leads to next.. the core objective remains the same; accessing the PE gradient afforded by a real N3 break, using only a virtual one, and so allowing a linear rise in input PE for an exponential rise in output KE.

I remain convinced this is the only possible chink in the armour of mechanical CoE...

[Kirk]

If the upward mass is stationary the spring pushing down should have the additional traverse that used to be used behind the large mass. Force /time should get extended in other words.

[MrVibrating]

LOL it's a funny one - having worked through the solution above, it makes perfect sense - and it was the null result i expected; the final KE of the lower weight is equal to the distance it's fallen against gravity plus the spring's PE. Obviously.

But then on the other hand, i could see various possibilities why the result might be positive - as mentioned, perhaps the small weight would still gain the KE not manifested in the large weight, as in the no-gravity scenario. That would mean OU. Similarly, perhaps the net weight of the upper large mass would still be bearing down upon the lower mass, adding its effective mass to the lower weight's fall... that too would've meant OU. And even if the KE of the leading mass did break unity, we'd still have the problem of dealing with the counter-displacement of the trailing mass the moment we harvested the KE of the leading one - the resulting recoil would still decelerate the source frame, so its momentum would need replenishing by gravity somehow... so balancing its upwards and downwards accelerations so that it never moved in the first place would've neatly solved that little problem too - no motion, no recoil.

So it would've been ingenious if it worked... Which is a dumb statement you could say about any dumb idea. But at least i'm still learning new stuff..


There's a slight twist on that last experiment that i think would bring it into closer alignment with the previous no-gravity scenario, and that's to allow the trailing mass to fall a little way, before its upwards acceleration from the spring brings it back to stationary in the static frame. Then, logically, the leading mass should gain the KE that the trailing mass has lost, as in the no-grav run, while still avoiding the counter-displacement recoil when the KE of the lower mass is tapped off.

Maybe.

I'll give it a try and report back.


Another potential exploit might lie in the fact that the equal and opposite momentums caused by firing the jack don't affect its motion (at least until the KE is harvested), so any work advantage gained from firing it while falling shouldn't affect the net GPE of the jack + weights during its descent.. So maybe that could be useful...

Not through with this yet..

[primemignonite]

So . . . WHAT might you have found, MrVibrating?

- James -