Hard to believe it has been a whole year… but I have constructed a new shed/studio to put the rig in, and so took a break from development. Now it is up and working, with alloy wheels, that move very smoothly along the track. The ballscrew causes the dolly to move quite slowly, but is really slop-free. It’s not a problem when animating as there is time for it to move, but when setting up a move it takes a while to get into position. The rotation gearing works fine with the toothed gears, and the crane works OK with the belt drive. I have to be careful to tighten the motor against the belt, and to load the arm a little in the direction of travel, otherwise there is sometimes a lurch when the slack gets taken up after a few frames or in a change of direction.
Biggest problem has been blowing the Big Easy Drivers. I have gone through 8, and finally found some better drivers. These are designed for CNC work, and are optically isolated, which means they have some protection against blowing. Otherwise, apart from being physically a bit bigger, they seem much the same and capable of taking the 24V power for the steppers. As 4 of the BEDs continue to function OK, I have kept these for the time being.
The Arduino Mega isa doing its job well, and seems to have no problems getting the messages from the software. The interface on Dragonframe is not very intuitive, but once the rig is set up it drives it very well, and adds things like eases automatically.

Cost of the rig so far has been about £1000, but this includes some failed attempts. I think making another having learnt along the way the cost would probably be in the region of £600.

Because I have constructed the head (pan/tilt/focus) as a detachable unit, the next task will be to make a small dolly without the jib arm for simpler shots. And there are lots of uses for the control box using the Arcmoco interface and some more stepper motors, such as a rising sun, breathing movements, water in motion….. it doesn’t have to be restricted to the camera rig. Anything that needs a movement arc that can be motorised!