So after all this effort I finally built the present one which seems to just work: Hurley Dolly 9.1.
By this time I have done a lot of design and building, tested and scrapped a lot of ideas, and done a lot of web research. I knew about the guys at Dynamic Perception, with their OpenMoco based dolly system (www.dynamicperception.com) and (www.openmoco.org).
Pete bought a Dynamic Perception setup, and I bought their Arduino shield to build one myself. It works really well, and is very clever. The quality of their board and the detail in their engineering is superb. If you want really good stuff, go to them. Best I’ve seen without costing very large dollars.
However, a couple of things didn’t quite suit us with the Dynamic Perception gear. The track is only 6ft, and is made of specialised aluminium section which you can’t get in Australia (or if you can it’s probably very expensive). This track isn’t long enough for distant shots, though they are selling a 6ft extension now. However, I’m looking for something which is adaptable so we can use onsite meaterial if necessary (like a ladder). And, oddly enough, it’s too clever. The problem is the wide range of settings in their menu-driven interface, and the large number of things it will do. As I said before, people get tired, hungry and cold and make mistakes. The simpler and more rugged this gear is the better – what I’m after is knobs and switches.
But if we are doing dolly-timelapse in controlled environments, Dynamic Perception’s gear is the way to go – and I reckon we will use it too. But we want to sling this stuff in a backpack and take off into the bush with the camera – and still get superb footage. So I continued the original design route concentrating on a simpler approach.
What I really liked about the Dynamic Perception setup was their drive mechanism. It’s a heavily geared 12v DC motor with a toothed pulley and guide wheels. They have also started selling 12ft belts. So when I was recently in USA I bought the motor and belt and made some electronics to drive the motor and trigger the camera. Put an internal battery in the box, rigged a tensioning system for the belt, strapped on the old skateboard wheels, and here we go. A big plus is that this will also work with nylon cord – wrap some around the pulley wheel and tension it right, and it works just as well (not so good uphill though).