Friday, March 9, 2007

Parts Parts Parts!

I realize I have been bad this week about posting updates. I spent the week making parts out of PVC. Honestly much more time was spent designing, cutting pieces and then redesigning. This took longer than I expected (which puts me even farther behind schedule) but I wanted to be sure I have all of this working they way I want. Otherwise it will likely cause more delays later. My goal it to have interchangeable parts that I can easily make duplicates of. So far I have made enough parts for 2 bots. I plan on building 2 both so I have a backup and also because the expert division of the competition allows for cooperating robot swarms so I do plan on using both at the same time if all goes well.

I made the wheels out of 1/2 PVC sheet and silicone. The silicone is sold as mold making material for casting flexible molds which can be used to cast plastic parts. It comes as a liquid with a hardener. This is the first I have used it but it was easy to work with and turned out great. For those interested it is HobbyMold 150. I made a form out of larger PVC pipe which I cut into 3 sections (to allow it to be removed from the final part) and drilled shallow holes with a unibit to create the tread pattern. I am very happy with the result. So far I have only made 1 pair of wheels but most of the time was spend designing the form so making another pair won't take long. It takes about 24 hours for the silicone to cure but not much effort needed at this point.

I have all but 2 minor pieces needed to make the base of the robot. This is where most of my week was spent. Each robot is made up of 18 PVC pieces (not counting the wheels). I designed it so that it should go together like a kit. We will see tomorrow when I actually start assembling the first robot.

Once I was satisfied with the design of each piece I used xfig (a nice simple UNIX drawing program) to draw each part up and print out a template. I then stuck the template onto the PVC sheet using an elmers glue stick. This made drilling holes go fairly quickly. I bought a new drill press a while back that has a laser sight which puts an X right where the hole will go. This made life much nicer. My old drill press didn't have that and it also had a bit of a wobble making accurate holes nearly impossible.

I will put it all together tomorrow. I will take a pic an post it. I should have enough of the electronics mounted to make it move about on its own by the end of the weekend!

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