J. Motts posted:That is simply AWESOME, I loved the video. Your work is superb, the action of the turntable is so smooth, and it lines up really well. Does it slow down when you put a heavy steam engine on it? I just love the whole ball of wax, you have really put a ton of thought into this and it really shows. Any thoughts on producing them for sale? I'd love to have one for my future layout and I think it will turn my SP AC-9 and my N&W Class A locomotives. They are shorter than the Big Boys. If you plan on building and selling them or if you might build a few, I'd most definitely be interested. Thanks for sharing, terrific work.
The motion of the turntable is exactly the same empty as with my massive C&O Greenbrier on it.
Stepper motors operate by basically taking a fast series of very small steps. The cool thing about steppers is, as long as they are operated within their design limits, when the controller sends a step command, the motor takes one step - no more, no less. This allows you to control the motion exactly as you want. So to make it move, you send it a series of steps. To make it move faster or slower, you adjust the step rate from the controller. And to make it move a given distance, you send a particular number of steps.
So for the turntable, for example, the siding change shown in the video takes 16,416 steps. That's what the controller sends, and that's what the stepper does. The speed is set in code, and never changes, regardless of the load. Similarly, the acceleration and deceleration rates are programmed in code, and don't change. The positioning, travel times, and smooth starts and stops are the same every time.
As for selling it - while it would be really cool to contribute to the hobby in that way, that would be a whole 'nother project.... 
