Final Team Documentation!

Final Strategy

For MS10, our machine followed our strategy previously described in the blog post "Revised Strategy and Design". The machine moved from the starting box and then drove to the front of the arena. Our machine used the ball collection  mechanism on the front to collect the black squash balls and yellow ping pong balls by driving along the front edge of the arena. It then dropped the balls into the other team's goal. Finally, the machine either prevented the other team from scoring in their goal or collected ping pong balls from the tower and dropped them into our goal.

Final Machine

Our final machine has three modules. I will go through each module from least important to most important.

Tower Pushing Module

 This module consists of a pushing bar (1/2" square stock aluminum and 1/4" plate aluminum) centered on the backside of the machine and two guides (1/16" plate aluminum) on either side of the machine. These were attached to the chassis with bolts and screws. Our original re-design did not have the pushing bar, but our team soon realized that we needed an extension to reach over the tower's bottom platform and make contact with the tower's side. The guides on either side a bent out slightly to make it easier to position the machine around the tower. During the competition we ended up not using this module because using the ball collecting mechanism was much faster.

Ball Collecting Module

This module consists of the 1/16" plate aluminum which has been bent into the shape shown in the image below. This was attached to the chassis with bolts and screws. Our team selected the shape because it was simple and the box-like shape on the left side of the module would be able to hold the balls and prevent them from rolling out as more balls were collected. The bottom edge of the module is angled downward to keep the black squash balls from getting stuck under the module and keep the balls rolling smoothly. Our team used this module to collect balls when we executed our strategy. During the competition, it was pretty effective in keeping all of the balls as long as the driver did not suddenly stop.

Chassis

Our most critical module was the chassis. The frame of the chassis consisted of the 1/4" plate aluminum.  Each of the four side pieces plus the bottom piece was fastened together with square brackets (made from angle bracket) and screws. The motor (double gear box motor at a gear ratio of 344:1) and two pillow blocks (made from the angle bracket and bearings) were mounted on PVC spacers to align the wheels with the motor correctly. These are fastened onto the bottom plate with screws and washers. We decided to use the double gearbox motor since it was the best choice in terms of making it easier to align the wheels and in getting the right amount of speed and torque. We also added two extra points of contact to the ground at the front and back of the machine to make the chassis more stable and less prone to tipping. These were lathed on the mill from the 3/8" diameter aluminum stock and then fastened with screws and washers. The coupler that connected the motor to the wheels was lathed and milled from the 1/4" diameter steel shaft. Steel was used since steel is very strong and was less likely to bend and cause alignment problems. Finally, we used the laser cutter and the 1/4" acrylic plate to create a top piece for the entire chassis. This acrylic plate is held in place with four dowel pins.

Initially when we were testing the finished machine we had no problems with the chassis. The day before the competition we had a problem with the set screws and the motor axles. We found that the set screw was cutting into the axle. As a result of this, the wheel and the motor axle were not rotating in unison. We replaced the axles with allen wrenches that we cut to the length of the original axles. The allen wrenches were made of a stronger material than the original axles, which prevented any problems with the set screw. After this, our chassis as well as the entire machine, were ready to go for the competition.

Here is a final picture of our machine at the competition: