I recently read through one of my old blog posts which discussed the benefits to making custom parts instead of standardized Tetrix pieces. In the post I mentioned that we were designing a steel box that would fit over the robot chassis and in theory would keep the robot structurally sound. To update the status of this project, I’m proud to say that although the box we made did not match exactly what we had on paper, the hood serves its function perfectly. Instead of the truly “box-like” design we started with (which would fit the robot like a turtle shell or diaper), we decided to make it into a hood-like design that would only go over the top and the sides of the robot.
While the turtle shell design probably would’ve been better structurally, it would’ve been a pain to get access to anything underneath it and nearly impossible for us to make ourselves. After having to remove the hood from the robot a few times to hook up motor controls, I am glad we decided to simplify the design.
In this same period of time, we have made tremendous strides in completing a functioning arm design, a block holder and sweeper, as well as a rather rudimentary flag spinner which took only about twenty minutes to design and assemble. The creation of the arm was tediously slow to get started. With very few Tetrix pieces fitting the design qualifications and structural integrity we felt was necessary, all parts had to be custom made. As mentioned in a previous post, one of the most noticeable repercussions to using custom made parts is the extra time it takes to make them. Although waiting for parts took a good deal of time, the most time-consuming task was finding certain parts. one in particular, a 12″ ball bearing drawer slide, proved to be the most difficult to source, as it seemed no such part existed (at least in our local area). Because of this, we were forced back to the drawing board to find a new solution to the issue. After a week of contemplation and refiguring, we found a new way to assemble the extendable arm which was arguably better than our initial design. Using a rack and pinion system that we CNC’d locally, we developed an arm that ran much more smoothly than our arm from last year’s competition, and that could sustain significantly more weight.
Recently we have found that the arm may be strong enough to lift the robot in the end game of a match, however more testing will be needed to confirm this.
Our bucket and flipper/spinner design has undergone many rehabs since its initial creation. The frame has remained constant; keeping its four sided cube shape, but everything that attaches to the bucket has undoubtedly moved at least once in the last three weeks, giving the whole assembly a Swiss-cheese-esque appearance.
Recently, we have attached an angled block-guider to the top of the robot which makes it easier to score the blocks accurately. The bucket is meant to carry all four of the allowed four-blocks-at-a-time to be scored in the pendulum baskets. Because of its size and shape, it can easily carry four blocks loosely, while at the same time, does not typically pick up a fifth block. If it does get a fifth block in it, the block is usually tossed back out on its own or otherwise can be spun back out by the spinner. The spinner itself, at the front of the bucket, is driven by a simple chain and sprocket system which is powered by a motor on the back of the bucket. The spinner is made of 7/32 vacuum tubing, which is stiffer and has more grip than latex surgical tubing. I believe this bucket design will be one of the most useful features in competition.
lastly, the gearing on our arm to a ratio of 9 to 1, should give us an amazing amount of torque and control when lifting the arm of the robot, up and over to the basket. Although it puts extra strain on the gears themselves, this should keep the motor from burning out and give us more control of the arm. The former is probably the most important, due to the fact that over the last two weeks, the Cougarbots and ourselves have burned out/ killed the gears of over 5 motors. I am already thinking that it may be necessary to have two motors on the arm, if we are ever going to be able to hang the robot on the bar. Danny seems to think that we will be able to make the robot hang before competition; I am less certain of this. We will just have to see how the week goes.