At last, with the help from some friends I have built the long awaited third prototype of my project. The following details some of the design changes:
I decided to go with laser cut plastic gears like last time because the only decent range of timing belts and pulleys comes from McMaster-Carr and they don’t really offer a range of metric sized parts, which is a pain, there seems to be a real lack of mechanical power transmission parts. I am going to try contacting the 3D printer community about this as the gears are always super loose.
That aside the plastic gears work okay for now, and were designed using Matthias Wendel‘s Gear Template Generator software I still want to use pulleys but I need to find a better supplier that has the range I need. Why can’t I be an expert electronics engineer, mechanical engineer, computer programmer and designer all in one?
The housing was constructed of a thinner 2mm clear Perspex, last time I used 3mm, one disadvantage is that 2mm seems to shatter easily when dropped, also coloured Perspex isn’t readily available in 2mm thickness. It is also scary to cut in the laser cutter as you can see small pockets of fire under your work which are usually hidden by the opacity of the coloured material. I bought it from Hamar Acrylic, London and used a fantastic and cheap product they recommended for gluing called Plastic Weld, it’s basically a solvent that melts the edges, bonds them and evaporates leaving the two surfaces welded but no residue.o2
The idea for the catch came from a friend who suggested inserting a sheet of rubber rather than plastic that hangs down from the top giving it a ridged flexibility that allow the flaps to push against the catch until it flaps by without putting pressure on the sprockets.
The new design is dramatically bigger, by volume probably 100-150% larger! Next up I need to work on screen printing the flaps and the electronics I was working on before, having some trouble with inverted UART to RS485 signals, anyway here it is: