The Cougarbots did a decent job at the qualifier this Saturday in Mount Vernon. We finished 4th in the preliminary matches and became a choosing alliance captain for the semi-finals. Despite the fact that we got the alliance partners that I wanted, we had two bad runs in a row which kept us from advancing. This first qualifier was eye opening for me, and has led us to discover new ideas of what we could (and should) expect from our robot.
To start out this analysis, I feel I need to make a statement I do not often say. I was wrong. I was wrong in that, throughout many of these blog posts, I have been writing under the influence of the harmful substance that is close-mindedness. My thinking was incredibly contradictory to what my message actually was; though the message was mostly sound. In the process, I feel I may have alienated a metal that is the most abundant in the world, and the third most abundant element on earth. And so, I must apologize to you, aluminum; I was wrong. I have changed my mind about this soft, non-ferrous metal, and I now believe that aluminum may actually be the saving grace to our robot.
As for you, 16 gauge steel; you are dismissed.
At the competition, I saw only two or three robots that were anywhere near our weight and relative size. Although it is probably necessary to mention that these robots ended up winning the competition, it is equally as important to mention that they, as well as almost every other robot there, were constructed largely of aluminum! This left me to consider how our robot is constructed. Although, yes, having a shell made of thick steel makes the robot very sturdy in its frame, I feel that the degree we have taken this to is a bit over the top. Frankly, the cage is very heavy, doesn’t utilize space well at all, and is a bitch to drill through. Aluminum, on the other hand, can be easily drilled (like a hot knife through butter), and is much lighter weight. Although it does not possess the ability to be bent like ferrous metals, aluminum is a much easier product to work with than steel, and although it is nowhere the strength of my beloved Titanium (don’t worry Ti, you’re still my favorite) it has enough strength to support the robot in this year’s competition.
So where did the hatred for aluminum come from? Ah, that’s right – Tetrix. Indeed, my hatred for Tetrix is still alive and well (although I will admit the predrilled holes do come in handy sometimes). The distain I have for Tetrix lies in the fact that all of the parts they make are too thin and small to be durable, and when a large portion of these parts are aluminum, this creates a bad situation for all involved. I have recently lost all respect I had for this brand’s integrity after making the discovery that they have altered the gears they use in their DC motors; replacing them with what I think is some sort of graphite composite. Whatever it is, they snap under pressure a lot more easily than the previous iteration. So how can aluminum and I mend this bond? The answer lies in a product that I have seen team 4150 Dark Matter use frequently in their robot design.
T slot aluminum channels appear to be the answer to the structural issues I sense within the robot. These channels are much thinner in area and denser structurally than those made by Tetrix. An even larger improvement to this would be V-slotted aluminum channels, made by OpenBuilds.
Unfortunately, the channel size we would need is out of stock, so let’s go back to the t-slotted channel idea for now. Even without the V-slot adaptation, T-slot channels are still an improvement on both Tetrix channels, and the steel frame we had before. Not to mention that I’m guessing that T-slotted rails can be turned into V-slotted rails just by beveling the T-slot opening. This is just a guess, but the concept seems straight forward enough. To add an additional factor to this concept of robot frame reconstruction, it’s important to remember that our next competition is less than a month away, with thanksgiving in between. I would love to have a large block of time for our drive team to practice, but in reality, this seems like a farfetched idea. A compromise I have considered is to create an aluminum channel frame with square tubing. This will give us the strength and lightweight design we need, without having to order supplies online. The down side is the lack of a modular design with easy-to-assemble brackets and connectors, as well as the lack of being able to create a linear slide design with the channels. Despite all the downsides, it is a possibility, and is probably the cheapest too.
The next structural change I feel is necessary goes against a big portion of what I have been saying in this post. I believe that we need to replace the aluminum Tetrix gears we have been using, and mill new gears out of steel. Although aluminum and I are now friends, and heavy steel and I are mostly through, we ran into a problem at competition that can really only be solved by strong metals.
Just before our first match at Mount Vernon, Danny and Tyler noticed that one of the large gears that we use in our arm design was (for lack of a better word) de-toothed, and therefore would not run at all. After running the gear for only a week, the teeth of the gear had stripped away enough that the arm clicked in an awful way, and dropped unexpectedly when tested. To apply a quick fix to the problem, we replaced the gear using a borrowed gear from team 5466 Combustible Lemons, and ran the rest of the day on that gear. My hope is that by replacing the gear with a steel gear we will not run into these same issues because the force exerted on the gears should cause much less damage on the teeth in comparison to the aluminum Tetrix counterpart. In addition to this modification, the arm is also being repurposed to lift the robot in the end-game (a plan we have agreed on before the competition). To put less stress on the motor running the arm, I feel that we need to reallocate the motor we are currently using in the flag spinner to support the arm on the opposite side. This will of course mean that we will need more gears, bringing the total to four 40 toothed, and four 120 toothed gears. Just in case we need extra, six of each should do fine. Personally, I feel we should do the same for the rack and pinion system, but given that the rack is aluminum, the gear would shred it quickly if we didn’t re-fabricated that in steel too; we’ll see how the steel gears pan out before trying that.
These are only some of the changes we could easily attempt to do within the next month, but the clock is ticking and there is little time to accomplish such a daring rehab. Therefore it’s time to ask “What can we really change before competition?”.