BigWheel Arm

Tags: design, think, innovate, and build
Personhours: 4
BigWheel Arm By Evan

Task: Design an arm for BigWheel

Bigwheel’s arm is going tied with the lifter arm as the most integral part of the robot. It wouldn’t work without it. Since our scrimmage, we have learned how to make this arm much more efficient, starting with some supports. The arm was made of two disconnected Tetrix rails scavenged from the bottom of our scrap bin, lending itself to weakness and instability, much like a country that recently won its independence. The worst part was how the two sides of the arm would be out of sync with one another, creating a twist in the arm that caused it to drive in an odd path. Since then it has been stabilized with cross beam REV rails that have significantly straightened out the robot. Why we hadn’t done it before is a mystery to me, and something we should have recognized as an issue sooner, but hindsight is 20/20 and since we can’t change the past we can only vow never to make the mistake again. Always support your attachments. The next upgrade on the arm is going to be the box to hold the minerals. Right now it’s made of cardboard off an amazon box, and it kind of sucks. I can say this because I cut it out and made it. The plan is to make it out of polycarb but we only came to this conclusion after a bit of debate. The reason polycarb was not our immediate solution is because it’s unfortunately quite heavy, and instead the first thing we came to think of was thin plywood and duct tape. Thin slices of plywood would be taped together to create a fabric like box that still had form. This idea still lent itself to breakage, and we next went to a design using a thin plastic sheet, the same kind of plastic that is used inside milk cartons. The only issue is that it’s super weak and doesn’t form well, so we would have to build a frame for it, much like the plywood and tape. Finally we came to the polycarb and decided upon that. So far it works as a nice way to hold the blocks as we transport them into the lander.

Next Steps

Right now we’re toying around with the idea of an arm that not only flips out but also extends using a gear and tooth track made from Tetrix parts of days gone by. The reason for this is to gain a little extra height that we were lacking before in the robot and a little more flexibility when we grab minerals from the crater. To do this I had to take apart the arm from our first ever FTC robot, and use the toothed track and gear plus the extra long tetrix bars to create the slides. So far the slides are surprisingly smooth and we have high hopes for the future of the arm.

Date | November 2, 2018