I'm posting here rather than at the Rockcliff group because I can attach a picture in this forum.
Have any notes or drawings been posted on the belt drive system? There have been several references to notes, but nothing on the site I can find.
In any case, I am confused as to how the motors and belts would mount to the system. The one picture mounted to a table doesn't really explain it. The first problem I see is that if the belt is fixed and the motor rides with the gantry, won't you end up with a very heavy and unwieldy gantry carrying the weight of four motors and the router?
The second problem is that, unlike screws, the orientation of the motor has to be 90deg from the direction of travel. Will you have to add platforms of some kind?
I've attached a quick sketch of what I mean. You can see that the gantry has four motors on it. Not counting the z-axis (which I assume will just have a screw) the other motors have to be mounted on some kind of flange. Is that stable?