Dispute on “MOULD EFFECT” (Chain Fountain)

Maybe scale up this to use the metal chain? https://www.reddit.com/r/didntknowiwantedthat/comments/p396ns

sand500

Yes and it works ... You can find it in YouTube

Has anyone tried this with string or rope?

I was wondering if you can try out the software tracker to analyse the system. It can be helpful to verify your theory. Or maybe you can upload the video so we guys can get and analyse the data

What if you used a liquid, which would have tension and momentum but certainly no lever effect... perhaps a cup with appropriate hydrophobic coating would do it?

If you normalised the graph on the local gravity (9.8m/s/s parabola), you'd see a sine wave multiplied by the MCR reflected from the highest moment of tension. The MCR would describe the HMoT (ie the refelecting node) and also help calculate the approach and leaving waves. The approach would be compressed and then lengthen to the HMoT, and the leaving would be stretched by the length and mass of the ever growing column until finally compressed by the chain stopping once hitting the ground. Mehdi should be able to draw a representation of this on a white board.

Reckon this would be quite a good demonstration. If you use high-density foam so the chain 'snugs' in a bit, you'll see it alter the MCR (Mehdi Chain Rating) and lessen the amplitude of the 'chain fountain'. Ostensibly putting a brake on the chain, you'd notice the acceleration will have less affect and you would see his 'base propulsion' effect (This is actually just the wave reflecting from the highest moment of tension) only knock a couple of 'before movement' links (I'm guessing there's a better term for this) out of the foam. [EDIT Guess this is actually a node of the wave behind which there isn't enough force to move the balls out of their 'snug', the brake moving this backwards along the chain]

Also i wonder if you could simulate different drop heights by using a vacuum cleaner to suck down the falling chain, or maybe just a motor and a spindle, but perhaps that will introduce other dynamics winding the chain. I'm thinking a box with a with a hole for the vacuum and another hose to suck the chain down, you could vary the suction with a slide lid on the box

Allan Lindqvist

You could try putting the chain on a soft foam board, the if he is right the effect should be dependent on the surface the chain is falling from. zig zag it along the surface so it's all touching the foam and drop the end from the table

Allan Lindqvist

Mould even proves you correct in his weird pseudo-science 2d explanation of his 'base propulsion' theory. 'Mehdi's Constant' x 'Specific Chain rating' (some sort of rating of mass of chain and turning friction) x Acceleration (here motors could be used or you could change gravity... could do an experiment at sea level and then on top of Mt Everest ... No no, too crowded and we don't want to endorse that sort of tourism, but you know, a high place) could be used to calculate amplitude (height) and period (distance) of the 'Chain fountain'. [EDIT Mehhdi's constant here would only describe some sort ideal chain, so would be redundant and could be absorbed into the specific chain rating .. although we could call it the Mehdi Chain Rating] To be fair, Newton's polynomial interpolation was most probably a try at explaining/drawing this. A LaGrange interpolation would most probably get you quite close. Looking at it as a wave is most probably preferable as you could then calculate all those other little standing waves made.

The next step of your horizontal setup would be to use a motor to pull the chains. This would let you control the force/speed of the chain being pulled. If you make the chain a closed loop ,then you can send the chain back "up" to the reservoir. If you run the motors at constant speed, the size of the loop should be constant. If you increase the speed, the size of the loop should be increase as well.

sand500

A mass of chain moving thru a distance &; changing direction generates centrifugal force. Like all centrifugal forces - it tends to force the matter undergoing acceleration to some edge of a curved boundary. Because you also have tension on the chain as gravity pulls it downward - the forces (tension vs. centrifugal) seek equilibrium which occurs in the elevated "loop" that rises off the edge. That's my analysis.

CURTISSCOTT

I love Steve Mould, and watch all of his videos too, but in this case, you're right and he's wrong.. Sorry Steve - I predict you're going to owe some pennies on this one. It's obviously just the inertia of the balls going up!

Steve Jones

So, the most interesting thing that Steve demonstrated was the kickback on the chain in his 2D case. When I looked at your 2D case frame-by-frame, I noticed that, despite the chain being spaced out, the chain goes back a little and does make contact with the previous bend of chain. Could you do a couple of different runs where you use the same length of chain with various amounts of spacing to see how that affects it, Mehdi? Also, maybe improve your 2D test set up by creating a mechanism to pull the chain in a constant direction with a constant amount of force? Also, maybe see if a peg to represent the lip to see how the presence of a lip affects things? Also, if you're right, shouldn't this happen with just plain ol' rope? Have either of you done a plain rope test?

Turing Eret

The lever theory is slightly ridiculous, since it requires a ton of "extra" logic to explain all the 2D demos Mehdi performed. Mould's refutation of the 2D "rise" is that the chain follows the "mysterious" curve, "like any chain would." But the more likely reason the rise doesn't increase in the 2D demo is that the chain isn't accelerating uniformly as it would under gravity, and no mystery curve-conformity is needed. Finally, to my eye, all the chains exhibited some fountaining, and the Mehdi explanation is essentially one of simple momentum -- the chain is jerked out of (or off of) its container, which lifts it, and the momentum is then smoothly overcome by gravity. The loop us the transition of momentum from up to down, and should occur (as it apparently does) in any analogous type of chain. It probably would occur in a very subtle, relatively unobservable, way even with a cord.

Allen Cobb

Great video! That motion reminds me of a whip traveling through the air. I am sure the forces are related.

Matt Larson

I think Mehdi is correct but he did not comment on the fact that the chain (at least in some instances) goes higher out of the glass as it falls. Simple momentum will not cause this unless you allow for the chain speeding up. Assume the falling part of the chain is on the right, there is a curved section over the top that has a horizontal link at the apex. As you start the fall, the right side of this has a downward force equal to the weight of the falling chain and an upward force equal force from the weight of the chin being lifted so it has a net moment (spin) in a clockwise direction (assuming you pulled out enough chain to start the fall). As the downward side increases in length, it now adds a greater downward force from the falling chain on the apex but is resisted by the same initial counter balancing force as the short initial chain distance it wants to spin faster. This spin (torque) will lift the left side of the chain and drag more chain behind it. The lift force will increase until the system reaches steady state where the drag on the system makes up for the increased weight of the falling chain. This may be assisted by the falling chain hitting the ground but is not necessary. BUT WAIT - you say "have resolved the spin of the apex but it is not just one link at the top and all others are vertical" . This is true but the sum of all the smaller vertical forces as you sum all the links as it goes around the curve give the same effect. "OK - you have shown how a link spinning in place will spin faster but now why it doesn't just fall'. The answer here is that it IS falling. It is following a parabola up and then down due to gravity just like any object thrown upward. As each link follows this parabola, it has further forces added to it by the adjacent links that allow it to transfer it upward momentum to the link behind it as it travels. This is why the arc at the top starts to fall at the beginning, then as the downward chain increases in length the arc rises to a steady state. The fixed time for different speeds is an interesting observation but I have not come up with an equation to verify this. Still Team Mehdi all the way on this (although I think a $100 lunch seems a lot even in Canadian dollars).

I’d kind of assumed the effect was just the chain’s momentum slowing down the direction transition, the Cambridge ’levers’ just sounds wrong. I’m definitely on Team ElectroBOOM

Adam Pepper

My first instinct when watching the original chain move out of the glass was that the energy of the falling chain was pulling the chain upwards and since it has tension and mass it pulls the chain upward, loses momentum and then is pulled downward. There is inertia, tension, and a constant force. It seems like you are explaining this correctly. I don't think that torsion explanation works for all the other things you showed.

Rabon Kyle Ragan

After watching the introduction about the problem, i instinctively thought along the same lines as you. After watching your presentation of the mould-explanation, same as you, i dont think thats the explanation. My money is on this explanation. But hey, either way i will be happy to be mistaken and learn something new

Are we going to have some good old fashioned YouTube beef?

Allan Lindqvist

Oh this looks interesting... Maybe a case for extreme rectification? (Glowing eyes)

Matthew Shooshtari

I never bought the "lever" explanation in that paper, it just didn't seem to make sense. Nice to see a possible explanation that is a bit easier to accept, and also those 2D floor tests were brilliant! I noticed that the test with the sparse "chain" of weights in a jar was done a bit weirdly both by you and in the video you showed - in both cases, the chain was pulled *downwards* over the edge, which slowed it down significantly. When you did the test from the balcony, you pulled it upwards first and then down, so it had a chance to rise over the edge and form the overshoot arc.

With ball and solid rods, the back force you drew on the diagram continues due to (semi) compressibility of the chain. In your run experiment with O-loop chain, yours worked because the chain was constantly under extension so an equal force to your pulling force could travel all the way back and create the effect. Any situation in the video where you cannot enforce a tensile resistance is doomed to fail. I think you may be right.

Bahram Dahi

"As an electrical engineer, I'm over-qualified!" Love-it!

Mark Roberts

First!