I have to squeeze in one more update before I have to drive to Boston. The video below shows the fully functional Clear Walk system, with mirrors installed, capable of redirecting sunlight anywhere it is needed under remote control. It could be an icy walkway or driveway that needs to be cleared, or it could be an indoor plant (redirecting sunlight through a window), or it could be some laundry hanging on a line.
Here is a close-up of the electronics module showing the Bluetooth module, the arduino, the Dc-DC converter, and the H-bridge motor drivers all crammed into a neat little box:
It may not be too obvious from the videos but there are over twenty 3-D printed parts in the system, not including the parts that did not work out.
I haven't had time to reflect on this project yet but perseverance and adaptability are necessary when you run into a project like this. Although I have to leave town right now, for the critical last few days of the project, and consequently cannot do a grand finale, I will continue improving the system when I get back - until I can finally try it out on some snow. After all this work, I really want to see how well it performs.