energy producing experiments

[DrWhat]

Brilliant sim work Broli.

Now to reset the most external weights, can you add a cord to each weight which slides them in along their arms and that cord winds around a pulley fixed to the central axle.

Damian

[broli]

I have performed some simple tests with a small bicycle wheel regarding different speeds and it seems to not matter what speed you start with, the same length of wire will always stop the setup so that's one thing confirmed for me. Next up is what you mentioned is changing angular momentum but keeping linear momentum the same and still being able to stop the system with the same wire length.

[pequaide]

I combined two drill press heads to spin a 4 inch cylinder at 1.25 m/sec, when the spheres unwound I estimated a velocity of about 5.66 m/sec for the spheres. This gave a linear momentum conservation of about 91%, and a Ke increase to 407%.

I used the four inch cylinder in about 6 different mass arraignments, the higher the speeds the worse the results, so I stay away from high speeds. Obviously air resistance takes its toll at higher velocities.

Correct; the original speed does not matter the spheres will stop the cylinder if you spin it fast of slow. My data shows that with a longer tether the spheres can stop a greater cylinder mass.

[broli]

At first glance it also seems like regardless of the initial speed the time it takes to complete momentum transfer remains the same or even gets lower the faster the initial rotation is. This is based on observation as I haven't any measuring tools setup. But it means that tremendous amounts of energy can be created in a fraction of a second.

These experiments can also be quite painful to certain body parts so be careful ;).

[pequaide]

When you use the same mass arraignment (1 mass of spheres to a 4 mass cylinder for example), it appears to me that the event takes the same number of degrees rotation to stop no matter what the original rotational velocity. That would mean that it stops faster if the original motion is faster.

Yes; the velocities are high and can cause personal injury or do damage to equipment. The strings will also break which gives another opportunity for personal injury. Proceed at your own risk.

[broli]

it appears to me that the event takes the same number of degrees rotation to stop no matter what the original rotational velocity. That would mean that it stops faster if the original motion is faster.

I will specifically test that out tomorrow. In the experiments the moment I saw the wheel stop completely I grabbed it so the transfer wasn't reversed. And the point on the rim where the string was attached to seemed to stop at the same location regardless of initial speed. The small weight always swinged out in the same area, or else I would have gotten hit many times. Since I tried slow and very fast. But I will redo this to be absolutely sure.

Peq can you share some data like the moment of inertia of the setups you have been using, the mass of the small weights and the length of the string that caused them to stop. This can lead to a relation that allows us to predict the length of the wire. I'm pretty sure it will be a very simple one.

[pequaide]

In the closed position of the mentioned 91% model I had 261.8 grams between the two spheres held at 5.6 inches diameter, 734.5 grams at 4.81 inch diameter, and 302.8 grams at 4.25 inch diameter. This was all spinning at 3.25 RPS and gives us 1.45 m/sec, 1.247 m/sec, 1.10 m/sec respectively. In the open position the spheres (261.8 g) are at 13.109 inches, and are moving 5.66 m/sec.

[chap]

broli or pequaide,

Would it be possible for you to try the tape measure spring for a tether instead of a string or wire in your experiment?

Thanks,
chap

[pequaide]

A tape measure tape has quite a bit of mass, if you bend it sharply it will be bent or break, and as the mass swings out the tape would be showing its flat side to the motion. With the flat side to the motion the air resistance would be huge. I use fluorocarbon fishing line; it is very strong and highly resistant to abrasion.

[broli]

In the open position the spheres (261.8 g) are at 13.109 inches,

Is that radius length or diameter.

Edit: I assume that that is the radius. If so I don't find it a coincidence that the angular speed of both big mass and small mass are very near to each other. So I also assumed them to be equal. Using conservation of momentum then leads to a very simple equation for predicting the correct radius. See illustration. As you can see if the red m*r value remain constant then the green radius doesn't change. This is in line with one of you first experiments.

If that number is diameter the equation changes slightly by a factor of 2.

[path_finder]

Another interesting experiment on the springs:
http://www.youtube.com/watch?v=L2mdAvdPhT4

Two identical metal balls are dropped from the same height using an electromagnetic release.
One ball is dropped freely, while the other hangs from a string, acting as a simple pendulum.
Using two photogates, we see that the vertical velocity of the dropped ball is identical to the horizontal velocity of the pendulum, measured at the same height.
Potential energy has been converted to kinetic energy equally in both cases.

Read the comments also in the bottom.

[pequaide]

Lengthening the tether gives the force a longer time over which to act; which allow for the spheres to stop more mass. But data shows that there is not a one to one relationship between velocity and radius. Are you trying to conserve angular momentum?

[broli]

I think there's a misunderstanding, I haven't mentioned angular momentum. I was only talking about the fact that if m*r of the heavy initial setup remains constant the radius of the final small mass remains constant too. You proved this yourself many moons ago.

Although a constant m*r says nothing about energy gain, since you can even loose energy with constant m*r. This is the case when the big mass is located at a large radius compared to the small swinging mass. This would reverse the roles and mean that a light mass would transfer all its momentum to a heavy mass.

To gain the most energy it's best the radius from the moment of inertia is small. Now that I mention this, this pretty much solves the problem of determining how much COP a system could have.

All you do is find the radius of moment of inertia of initial setup and final setup then divide final by initial. This would be the energy COP of a specific system regardless of initial speed.

[pequaide]

Yes: I had misunderstood; sorry, thank you for the clarification.

[pequaide]

Wuggly quote: Momentum is generally not recognized as a measure of the capacity to work.

Are you going to handcuff yourself with a bunch of silly rules, or will you do your own thinking? An object moving 16 m/sec will rise 13.047 meters, is it not work because the lifting was done with momentum. I don’t care if it is or isn‘t work it is still there at 13.047 meters and that is what matters.

Wubbly answered his own spring question; “since springs store energy, “. Wubbly and Fletcher want to fail, that is why they keep bringing up springs. But not all of us are in the failure mode.

Flywheels can transfer all their motion to a small mass, and the momentum math is obvious. Energy goes through the roof.