Movimentum - Animating Mechanical Explanations

I think I'm going to write a program. A program for creating small movies—"animations for machines."

Why?

Well, I'm writing a blog on Austrian signalling equipment. And like the few web sites that I know with that topic, I use pictures and text to explain the various machinery used in that field. However, even people who know much about railways have a hard time to understand this sort of things. So, in these modern times, it seems obvious to show the actual movement of such apparatus in an explanation: Animate the explanation!

Now, I must obviously be more concrete about the scope of these explaining movements.
For example, couldn't I simply show an actual film clip of the workings of some machine? First of all, I do not have those clips. But more important, if you know descriptions in technical books, you know that this is not the way to go: Actual machinery is rusty and painted and obscured by housings—all great ways of hiding the important parts. So we need abstract drawings which we assemble into a "moving model."
Next question: Shouldn't one allow user interaction with the model—i.e., provide a simulation? No, for two reasons: When I explain something, I am the director who defines what is going to happen. The user may come in at a later stage, e.g. in an "exercise"—but not during the initial explanation. And, moreover, and honestly, simulation (i.e., providing "n" ways of what can happen) is much more work than animation (i.e., providing one way of what happens).

To be very concrete, here is a website that has exactly the sort of animations I'd like to provide: www.animatedengines.com. My only wish is that creating such an animation should be at most two hours of work—one hour for drawing the parts, another one for animating them. That's why I need a program.

I asked and looked around (a little) whether there is some software that can do this. Obviously, there are real simulation packages that can do all that and much (much much) more; but they are expensive, and—I suppose—hard to learn. Then, there are animation packages (Blender comes to mind, [Update:] Synfig has been suggested)—but they have huge disadvantages from my point of view:
(a) They are integrated systems—whereas I want to create my drawings in a CAD program (everything else is useless with technical systems);
(b) They have, as far as I know, only limited trajectories (linear, constant, maybe spline).

In principle, modern CAD programs can do animation—but not my somewhat cheap CAD program (derived from the German CAD program Caddy++).

So I'll try to outline (in the next posting), and then develop, a new animation process for my purposes.