Hola amigos, it's been a long time since I rapped at ya. The I video below is a quick update, and this post will provide detail.
So, the main news of the past months is the arrival, assembly and tweaking of the Makerbot. Assembling it is fun, but the tweaking takes awhile. And, it tends to break a lot so you have to fix it all the time. But, the MK5 plastruder, which arrived in September has greatly stabilized it and now it is a prototyping tool rather than a troubleshooting time sink. There is a great on-line community and I give the product, company and community a big thumbs up. They also just came out with a new product, essentially the Cupcake v2, which is called the Thing-O-Matic. The leap they are attempting with the thing-o-matic is automation -- the fabrication of many parts, unattended. Using the Cupcake made me re-think the design. The initial intent was to make something that others could assemble themselves with off the shelf parts. It's clear now that automated custom part fabrication will soon be commonplace and there is not a reason to exclude custom parts from a public domain/open source design. If custom plastic pieces can make the heliostat work better, assemble easier, facilitate upgrades, and simplify repairs and maintenance, they should be included.
So once the gears were done (pleasingly easy) the next element I focused on was the motor, mount, and threaded-rod component. The new motor is the GM17 from Solarbotics, mentioned earlier. It's got good torque and takes about 1/3 less power (253mA stall current at 3V vs 400mA) than the GM2 used previously. I wanted a mount that would fix the motor in place using simple connections to the angle iron. Another bracket holds the threaded rod in place relative to the motor.
First pic shows the mount and the motor. You can see an embedded notch which receives a nut that holds the motor mount to the angle iron. Easy to do on a Cupcake and it makes for a simple installation.
The motor fits into the mount like this...
Then the whole thing mounts to the angle iron like this. You also see the top bracket, which holds the spur gear down (so it doesn't float up the rod) and provides the pathway for the threaded rod.
It's not perfect but I like the direction. Motor is kept securely in place without having to drill into the metal of the angle iron, it's fixed with simple screws. The motor also keeps it's place relative to the spur gear and the threaded rod. Installation takes a couple minutes.
This was the piece that convinced me that plastic pieces are a net positive even though you can't easily buy them at the store. I'll upload the files. Once they're mature enough, anyone with a makerbot could make them, or, there are many on-line production shops that could fabricate them. It should be noted that in some cases the parts are made to accomodate constraints in the build capabilities of the Cupcake. C'est la vie. Ultimately all the parts (except the heavy stuff like cinderblock, concrete and a mirror) could be bought on-line as a kit. There is nothing proprietary so costs will be low.
Next, a parts list and posting of source files. It's not there yet. This is first assembly, it needs many adjustments, and many improvements are tempting. But, it shows some promise and there is now (or will soon be) enough detail that others can take the design and run with it if they wish.