December 26, 2013 at 5:32 pm #21619
I’m glad to hear about the (partial) success– and we’d love to help you get the rest of the way there. :)
We have generally found that when a WaterColorBot is correctly tensioned for the first time, it will need to have some additional slack removed after about an hour of use. But after that initial stretch, it will stay tensioned correctly for months on end. So, after running for a bit, check that the rods are square to the chassis, and take out the excess slack in the cord, and that should be *most* of the fine tuning that you need.
If the cord is correctly tensioned and the rods are square, you should be able to turn the winches like knobs (with the power off), as though it were an Etch-a-sketch, or perhaps a bit more easily. The cords should be tensioned enough that they can be plucked like a string from a stringed instrument– such that they vibrate in place, rather than fall down listlessly. If it is too loose, the cord may fall out of the grooves in the bearings. On the other hand, it shouldn’t be so tight that it sounds like a guitar or violin string– if it’s too tight, that could increase friction and prevent motion.
If it’s “stuttering” — I imagine the same thing that we call cogging (jumping steps on the motors) — after checking that the cord is tensioned correctly, then please read through our troubleshooting section about other possible causes: http://wiki.evilmadscientist.com/WaterColorBot_Troubleshooting
You should definitely not lubricate the rods unless you are finding corrosion to be a significant issue. The bushings are self-lubricating.
In the picture, it looks like the effective brush width is increasing as you go along, suggesting that the paints are getting wetter and wetter as you go. I’d suggest pre-wetting the paint dishes with a drop of water each, and perhaps raising the brush up slightly, so that it isn’t pushing down quite as much.