Leverage & Torque - WM2D predictive abilities - are they representative of real world ?

[WaltzCee]

Hey Art,

What on earth are you driving that mechanism with ? -

I drove it around with the motor.

There are a lot of tools in wm2d, a motor is one of them. Simulators are very powerful, however they do have limitations.

I have one more variation of the mechanism I want to try and if it's as equally disappointing as the others have been I'll start talking about it in very general terms.

[WaltzCee]

One of the axes* (where it's pinned to Circle 1) of the pendulum (5) is moving in an opposite direction as the axis of Circle 1 (edit). Where the rod of the bob is pinned to Circle 1 and the rod is pinned to the bob are moving in opposite directions. (edit)

I increased the resolution of the bob to quite a degree in this perfect world of theory and as any can see there isn't a difference between it's oscillation and zero.

I'm going somewhere with this, but torques or counter torques isn't where.



*axes is the only word in English that can be the plural of three different singular noun forms--ax, axe, and axis. Possibly the Ebonics term "to axe a question" should be included in that group.

edit

[WaltzCee]

I drove this mechanism I'm looking at around with a motor. It's CoM went around in this manner.

[WaltzCee]

If you click on the image you can see it better. This mechanism looks like a ball bouncing back into the rotation. It is as if it's being dribbled by someone standing still and putting some backspin on the ball to get it to come back to them.

I multiplied rotation by 6 so the slight difference in rotation could be seen. Right before 0.1sec and again before 0.3sec the circle is rotating into positive territory, but the CoM of the mechanism is always right of the axis and the rotation takes off c.w.

This wheel has an 8" radius with a mass of 0.2lbs. The mass of the mechanism is one pound. It spun about 15 revolutions (5285 degrees) before it turned in to a pendulum.

[WaltzCee]

I set the sim to 20,000 calculations/sec. This is the end of the sim.

I think it's strange toward the end velocity and acceleration increase and the circle looses steam. Maybe CF? I don't know.

[WaltzCee]

The first graph is the entire run of the sim. I divided position by 4 to give velocity and acceleration better vertical resolution.

The 2nd graph is a 6' radius wheel with a 10 pound weight. It only managed to spin almost 2 times. There are other differences.

[ME]

If you click on the image you can see it better. This mechanism looks like a ball bouncing back into the rotation. It is as if it's being dribbled by someone standing still and putting some backspin on the ball to get it to come back to them.

I multiplied rotation by 6 so the slight difference in rotation could be seen. Right before 0.1sec and again before 0.3sec the circle is rotating into positive territory, but the CoM of the mechanism is always right of the axis and the rotation takes off c.w.

This wheel has an 8" radius with a mass of 0.2lbs. The mass of the mechanism is one pound.

How can we recreate this thing?
Just solid disks and a pendulum with half the wheel-radius, and then spin it up for a few rotations? (I tried this, didn't work for me - it's a pendulum all the way)

It spun about 15 revolutions (5285 degrees) before it turned in to a pendulum.

So basically this double-pendulum finds some resonance and drops out again?

[WaltzCee]

First I'd like to say it's been a long week and it's getting longer.

Results of the simulation in about a week.

There have been many who have made something that works in simulation. Or it works for a while then doesn't. My point of posting it was this: It seems as it violates the idea of inertia. In its final throws instead of bouncing over the top of the wheel, it bounces back the opposite way. Why isn't the inertia of the negative rotation conserved? Leading up to the reversal there are points where average acceleration and velocity are increasing. I don't know what went wrong. I do know this is one of the most fascinating mechanical contraptions I've ever seen.

It's beauty is equal to any mechanical device you can imagine. It violates axiom III, if I can ever get it properly formalized.

Given a wheel and this work of art, for every degree you rotate it (up to 45 degrees) it imparts 90 degrees to the wheel.

Rotate it one degree, you get 90, 5? 90. 3? 90. It's one weird little bit of mechanics.

So basically this double-pendulum finds some resonance and drops out again?

Sir, it ain't quite like that.

[WaltzCee]

I usually have a large carrier wheel (of very low mass) behind any mechs to attach them to. It acts as a backboard

I did take that advice. This is one of the most significant things I think I've ever seen.

[WaltzCee]

Everything on this one is the same except I revved the rpm's to 240. Then wm2d crashed.

The prime mover isn't hindered by CF at all, rather it helps it. Strangely the wheel has the same energy requirement. I'm sure I'm not using the right measurement there.

[spinner361]

Pardon my tangent, but could someone confirm the setting for Earth's gravity in WM2D? Mine is currently set to 9806.650.

[ME]

That should be 9806.65 mm/s² (millimeters !), while you probably expected 9.80665 m/s²

[spinner361]

Thank you, ME, for the verification. I actually had no idea what it needed to be. I put a lot of trust in the software, and it does not specifically say "Earth" so I felt this was something that needed to be checked.

The only math computations I have done so far is for the part sizes and weights when constructing a build. I have learned everything about this through thought exercises and thousands of experiments (1491 wm2d files currently). I don't have a mechanical engineering background.

I appreciate your help.

[DannyBouy]

Hello Walter
The movement of Cog here does look like a double pendulum.

http://www.mathstat.dal.ca/~selinger/la ... dulum.html


Any way, how is the idea coming?


Thanks
Daniel

[WaltzCee]

Daniel,

At first glance the patterns look similar. A double pendulum is chaotic though and this mechanism is more orderly. These points about it intrigue me:

• # This mechanism seems to produce more energy than required to drive it.
  * When dropped from near TDC it rotates, 15 times in one instance.
  @ The faster you spin it, the more energy. CF isn't a noticeable factor.

I'm trying to figure out how to fine tune it and also to tap into its energy to drive its rotation. That's where I'm at now. Thanks for asking.