Nathan,
It's been a couple of days and I haven't started a new thread. I've looked at some details of wm2d and it uses ....non-uniform rational b-splines (NURBS) geometry, and it may be approximating but the method it uses is definitely Kutta-Merson. I know there's a concept of single and double precision but from what I understand you need a cray to have double precision. It might be that all cad models approximate. It seems to me that I read there are times when wm2d can do calculations rather quickly based on the idea that the motion is easily defined. I just rotated a beam 10 to the minus 22 radians. I couldn't see it move. The other day I made two beams 100 meters long and pined them together and to the background then rotated one beam 1/1000 of a degree. I could see the movement at the end of 100 meters.
I just made two beams 1000 meters long and moved one 10 to the minus 23 radians and couldn't see the movement at the other end so it could be that amount of precision isn't factored into the calculations. I'll try 2000 meters.... no difference there either. That amount of rotation is minuscule and the tangent seems to me to be 5.55 repeating to the minus 26th. I might have to make the beam end in bfe before I could see any movement.
I've been trying to make a wheel turn by gravity for the last 3 years or so; I'd have to look at some notes to pinpoint it. I know self proclaimed mechanical geniuses that are in their 70's that have been looking for the same idea most of their lives. So far I've done as well as any genius I've ever met.
A point I'd like to make is that I don't think the idea of approximation vs. real representation of reality is a factor in trying to model with a simulation. I had thought some time ago that if you could increase the rate of acceleration (moving a mass faster than gravity would move the mass) to reposition mass on the wheel that it might work. By increasing that acceleration the product of it and the mass would give you an increased force or torque. The major problem with that idea is that if you could manage that acceleration of the force of gravity you'd put the mass further from the center of rotation and would be faced with the task of accelerating it closer to that center. I think that task is insurmountable.
Another idea that I've had is the idea of movement that is opposite and equal. The flaw in that reasoning is that no matter how many weights you have moving relative to one another your center of gravity remains unchanged or you end up gaining some torque more quickly by giving up lesser moments of torque. Basically you eliminate the top part of the wheel or rotations from 0°-30°. A real problem with that is that you're giving up time. One particular self proclaimed mechanical genius I read has the idea of 'center of gyration'. He's looking at the idea of causing equal and opposite movements that increase or decrease the density of portions of the wheel thereby changing the rate they spin. By pulsing the wheel in that manner he's hoping to cause rotation but I think that idea is a waste of effort. He needs to supply some power to cause those equal and opposite movements to obtain a difference in the centers of gyration and I doubt seriously any power that idea could generate wouldn't be sufficient to cause it.
I've shared some of the ideas I've had for a couple of reasons. If it is possible to cause gravity to rotate mass continously, before anyone could hope to find a solution they need to have some very specific ideas. The method of trying this or that configuration without an ability to verbalize what you're attempting is pretty futile. Attempting to model what would be a description of an out of balanced wheel is equally fuitle in my opinion (ie causing the cog to be mostly on one side of the center of rotation).
I am currently looking at several ideas that I'm going to attempt to model. I've tried to simulate them with wm2d but they're too complex for it. I have a method that I look at curves that I call clay-alculus. When I'm looking at 2 dimensions I use clay of equal height to fill a curve so I can compare different curves. If I'm looking at 3 dimensions I put the appropriate relief in the curves (like little hills); when I'm looking at 4 dimensions I take the hills and throw them at the wall.
Gene