[cptopher]

The side balancing was our plan from the start. We realized that the bridge area supported 3 wide bots, but not three longs. We assumed that 3 wide bots would fit but could be potentially unstable and tip over (correct assumption). We never envisioned the stingers or pogo sticks used by the wide bots to balance. We were very impressed with that solution as well. However, as a small team with limited skills to build an accurate shooter, we were looking for a niche to enable us to join an alliance in elimination rounds. We thought the niche was to allow stable long bots to get the 3 bot balance points. We recognized that two long bots filled the length, but left width unused. A super narrow bot seemed unsuable. The inspiration came from when skateboarders slide or "grind" down a rail and balance on the edge.

Our chassis was designed from the start for a heavily biased center of gravity. A sliding battery tray was designed to give reasonable driving on the field, and maximum weight shift when needed. In the photos you can see that we positioned the KoP CIM motors and gearboxes all on the right side of the bot. We ran chains down to a jack shaft to drive the right side wheels, and a long drive shaft for the left side wheels. We built very light to allow us to use steel bars on the right rail for center of gravity ballast. Our first attempt used a simple U channel on the bottom of the chassis for aligning to the rail. It turned out that the sliding friction was too much to overcome with the limited right wheel traction.

We created a belt driven track using the KoP Gates pulleys and belts that would give us very good traction on the bridge edge. The pulleys act like bogey wheels on a tank for the belt to run around. We attached a sprocket to the rear pulley side for drive power and a tensioner in the front the make the belt tight on the bottom. We then attached a sprocket to the existing drive shaft to power it. We calculated the sprocket ratios so that the linear speed of the belt is exactly the same as the linear speed of the wheels on the floor so that the bot would drive straight up the bridge. Its 6wd + belt all the time. The camera is used to align to the bridge edge between to sighting posts. Two curved guides helped guide us to the center of the belt. The belt height from the floor was also critical to maintaining a level bot side to side. Another outcome was a super low center of gravity that made our bot an excellent balancer at any time.

The team won the creativity award at the Livonia districts with a two bot side balance, but our goal was the 3 long bots. We are so happy to have accomplished this goal with our alliance partners at the Kickoff. It has been very rewarding to take on a unique solution and see it thru to completion.

Thanks to everyone for the positive comments!

Team 3534 House of Cards
Chris - ME Mentor