Pendulum calculation

[Fletcher]

I agree that you don't need a 100% momentum transfer to prove the theory of energy gain from momentum transfer - the Newton's Cradle approach was first discussed as a method in relation to ballistic pendulums which were ruled out by peq, presumably because of energy/momentum losses due to one object being buried into the other [i.e. not 100% thereabouts momentum transfer] - the problem was addressed again but the next time by using a perfect elastic collision [if possible] example or as near to it as practical N.B. steel has an elasticity of 95% thereabouts - the rationale was that even if 5% of the energy were lost by collision & deformation etc that if the theory were correct then there should be an abundance of surplus energy to observe - that too was unacceptable & the cylinder & sphere's was quoted again.

[then came the addition of an Atwoods to slow the drive weight fall down & create vast momentum reserves & finally that statement that calculating Moment of Inertia was not understood by scientists & if it were calculated correctly then vast amounts of energy gain would be observed by experimentation as per the combination cylinder & spheres & Atwoods devices].

No sim shows a surplus of energy, even with theoretical 100% elasticity, & the only real world 100% elastic examples are behaviour of ideal gases & gravitational slingshot where all energy in conserved.

The asymmetric pendulum masses & shaft lengths attempt to convey 100% momentum transfer, as per the theory, rather than something way less with shafts of the same length & different masses which don't come close in proportion to the mass differences.

I would like to sim a controlled practical real world experiment & compare it to that experiment, to find out why they might have different results, or not.

[Tarsier79]

If you know the elasticity of a material, than you should still be able to calculate a theoretical PE at the end of the collision by the measurements of the imperfect material used.


Back to Clays pendulum, If you know the distances of his pendulum arm and movement amounts of the two weights, in the start position(both weights together) and the end position (both weights completely separated), you can adjust the weight ratios so that the inertia isn't changed in these two positions only. There will be a change as the weights are in transit along the arm, and I'm not sure you will ever be able to get CF to pull the weights into position, but due to the difference in weight, gravity will (but will probably do so opposite to the way you want it to happen.)

So if you can change weight position without affecting inertia, you can also change inertia without changing the arms leverage. An increase in inertia always slows the rotation down, can changing the weight position without affecting inertia assist in achieving a reset?

[Richard]

Isn't a gain of energy seen in the transfer of motion...in cooperative fluid dynamics?

..when two race cars draft...the speed of both vehicles increase..

this must be a transfer of momentum...friction aside...M x A and or F x D are increased.

in bump drafting..the increase of both vehicles is significantly higher ( up to 15 Mph)..

These principles can apply to transfer of energy in pendulums can't it?

[Fletcher]

No, it's a decrease in Drag Coefficient or Resistance due to elasticity & vortices of fluids, IINM.

N.B. the same fuel energy is used to achieve the velocity as separate entities except the Drag is less when one drafts the other - IOW's, a new equilibrium velocity is achieved because there is less opposing Drag force.

Think of it this way perhaps - two identical sailing boats except one has a longer water line length - the longer water line length one will go faster.

Fluid dynamics is a big subject.

[Richard]

thanx Fletcher...

will think on this...and move other questions to new post later on.

richard

[rlortie]

Fletcher,

While speaking of boats, I have a little input regarding a 'decrease in Drag Coefficient or Resistance due to elasticity & vortices of fluids'.

If a boat is in calm water and there is current flowing on one side, one would think that when that side of the boat hits the edge of the current it would push the boat back into the calm.

It will not, It sucks the boat into the current not unlike the air foil of an airplane wing.

Ralph

[Fletcher]

Whilst I'm not particularly familiar with boats Ralph I & Mr Bernoulli would tend to believe it ;7)

[pequaide]

Quote “Nick, Wubbly & ovyyus built real world versions� No they did not; they moved the vertical wheels to slow so that gravity ate up their results. My slow wheels were horizontal wheels. Some of you would rather fail than succeed: success is not an option for you.

Repeating an experiment is not doing something similar it is doing it right. No bouncy balls, no springs, no slow verticals, etc. Don’t do it wrong and then claim to have repeated the experiments.

I gave you numbers.

[clay973]

Heres a vid of my pendulum experiment which pretty much shows what Fletcher is describing would happen http://www.youtube.com/watch?v=l3OSYFUEJD8

[Richard]

clay973...

thanx for vid....

It occurred to me while viewing the vid...that we are not limited by "straight" arm Pendulum(s)...have you experimented with moving weights on curved swing arms?

[ovyyus]

Some of you would rather fail than succeed: success is not an option for you.

Twaddle.

[clay973]

clay973...

thanx for vid....

It occurred to me while viewing the vid...that we are not limited by "straight" arm Pendulum(s)...have you experimented with moving weights on curved swing arms?

No, hadnt thought of that. Curved which way?

[Fletcher]

Ok, as promised.

These sims were constructed using a 2 meter pendulum shaft to easily see the effects of Cf's on the sliding mass(es).

All components are virtually massless with the exception of the sliding masses - for the single mass sims 2 kg [yellow] & the dual pulley connected masses sims 1 kg each [other colours] - they have the same CoM in each case.

The sims are built with One-Way Clutches or One-Way Ratchets & Pawls etc analogues - they release the mass etc when a predetermined angle of rotation is achieved & locked again by the same method - the angle is CCW from west i.e. 9 o'cl - the T bar section radius of the pull mech controls the distance each mass can move - the T bar section is made that way so that the pendulums pull mech CoM doesn't change in deployment.

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A couple of worthy points to note that I didn't necessarily expect.

1. the control pendulum [locked mass] swings from 9 o'cl to 3 o'cl [no friction losses].

2. in the single mass Cf pendulum with pull mech disabled the mass changes radius & the Pe is no where restored, not achieving close to starting height - this was expected.

3. with pull mech enabled [addition of gears to sim] the pendulum almost restores Pe - expected.

N.B.1. when the pull mech is disabled the CF's are generated & the release mech lets the mass move - the direction of the force is inline with the pendulums axle/pivot & there is no means to use that force to accelerate the pendulum forward in rotation - it falls well short.

N.B.2. when the pull mech is enabled the Work Done capability of harnessing the Cf's can provide a thrust vector in the direction of rotation & it achives close to restoration.

N.B.3. the shortfall in Pe restoration in all cases is because the the Work Done Joules [thru the pull mech] must be considered in relation to CoE - if the pendulum could achieve close to Pe height & the Work Done thru the pull mech could swing it higher than start height then CoE would be violated - it isn't in sim world [at least with my skills].

4. in the dual pulley connected 1 kg masses Cf pendulum, with pull mech disabled the masses change individual radius [CoM remains constant] & the Pe is close to being restored, achieving close to starting height - this was unexpected - I thought it'd be far worse than the sim showed.

5. in the dual pulley connected 1 kg masses Cf pendulum, with pull mech enabled the masses change individual radius [CoM remains constant] & the Pe is close to being restored, achieving close to starting height - this was expected - the pull mech allows the Work Done form the F x D relationship to add velocity, Ke & momentum to the pendulum.

N.B.1. but .. it doesn't break CoE & achieve a final height greater than it started with because of extra velocity & momentum given to it.

Conclusion in sim world:

CoE is conserved when Cf's are allowed to do useful Work [F x D] via a mechanical linkage to pull the pendulum forward.

P.S. analyze graphs for best understanding & run the sims if able to see clearly what happens though it can be inferred from the graphs of shaft velocity [blue] & position [red] i.e. not reaching the zero line.

[Fletcher]

Sims showing Pendulum Tests.

When a mechanical linkage is added to the pendulum shaft to convert Cf's into a pendulum thrust force the Cf's generated are insufficient into terms of Work Done capability [F x D] to accelerate the pendulum sufficiently to violate CoE - it simply makes up the shortfall in Pe loss from a mass moving to a greater radius & affecting Angular Momentum & speed etc.

It cannot be leveraged to greater effect.

Ratchet & Pawls, One-Way Clutches etc are reasonably complicated to build in real world - an alternate is a stator at the pivot & a meshed rotor on the pendulum shaft [with a one-way bearing] that is pulled on release of the latching devices - the analogue I have built shows the generic method to accomplish this.

[clay973]

Nice sim's Fletcher!