This is a LONG post, sorry. But someone asked how the Greyt elevator kit worked out for us.
TL;DR - We purchased and used the Greyt Elevator Kit this year, and we had a fantastic, and very inspiring, experience with it. Our team had plenty of challenges, our students learned a tremendous amount, it was not “too easy” and did not mean we could sit back and twiddle our thumbs, or that we could walk away with a basket of blue banners without really doing anything. An elevator kit (or a shooter kit, or a grabber kit, or even, to be honest, a robot kit) is not going to destroy FRC; not having one might have meant the end of at least one team this year. (OK, I’m probably being melodramatic. But it was a godsend to a team in a tough situation.)
Now for the details, if you want them…
I would say our team is a mid-level team, but because we are on one of the outer Hawaiian islands, shipping time and cost is always a challenge for us. We have one sponsor who waterjets parts for us, but our robot is often sort of a “Home Depot” robot (that being almost the only place around where we can buy parts, supplies, stock, etc.). This year, we had some additional challenges, as we had a fairly small group of students (about 14, a few of whom were not very invested/motivated and left mid-season, we ended up with 10 at competition) and our main mechanical mentor and fearless leader for the past 11 years had just “retired” from robotics to deal with other personal and family issues. Also, we had less money this year, having spent quite a bit over the fall to start an FTC program here on Kauai. So, we knew that unlike the past three seasons, when a trip to a mainland regional before our local one gave us much-needed ‘out of bag’ time to “shake down” and spiff up our competition robot, and practice driving and competing on the real field, we would only be able to attend one regional this year, our local one in Honolulu, week 5. Hence, it was more important that (a) our competition robot be in pretty good shape when we unbagged it, so we could get in some practice time, and (b) our practice bot be finished early enough to get in a decent amount of drive practice and auto-coding/testing time before week 5.
We had a new leader (me) with no engineering training and minimal mechanical/electrical knowledge/experience (I didn’t know what a “flange bearing” was, how motors and gearboxes worked together, or how to rivet something), a brand-new mentor with great general mechanical knowledge and skill, lots of time, but no teaching (or robotics) experience, and two other experienced mentors with design experience, but limited availability. Plus a couple of excellent software mentors. And a student team with exactly two seniors (one of whom was brand new to all of robotics, and had to take a bus for over an hour each way to our shop), a couple of juniors, and a few sophomores, plus two eighth graders. No student who had ever driven an FRC robot in a competition; a few had taken some CAD classes and had some familiarity with SolidWorks, but not a lot of actual design experience.
We first decided on our basic chassis design, which would be a 6- or 8- wheel, chain-driven WCD with traction wheels. We have always done mecanum drive (since 2010, at least - that is when I joined the team), and the team was hesitant to stray from that (we DO have the software and control systems down for 4-wheel mecanum), but when one of our mentors found the WCD chassis kits at WCP, and offered to buy them for the team, the kids loved the idea, thought it would work well in the game, and decided to try it. Those kits were ordered first and the kids designed a C-shaped chassis (first year we did that, too) to accommodate a partially-recessed cube grabber. (We did not use a COTS grabber. Because we had the elevator solution partly in hand, we used the extra time to develop our first “active” grabbing mechanism, which also gave us a lot of experience with the design process, prototyping and iteration, experimenting with different wheel configurations, etc. It ended up working acceptably, but could use improvement. But back to the elevator…)
We decided fairly soon after kickoff that we wanted an elevator (after doing a lot of geometry and drawings, and figuring out that we could not get the height we needed out of a single-jointed arm, without making our chassis too big to fit in checked baggage or exceeding the 16" limit), so we went looking for existing solutions (the engineers on the team having pointed out that this is usually what engineers do, first - whether to use those solutions, or just get inspiration or information from others’ successes and failures). Someone found the Greybots Cascade Elevator videos on YouTube, and when we inquired of them (I PM’d their mentor, on here) about getting their CAD drawings (so we could see if the elevator would fit into our chassis, which one of the students was CADing), we were told a kit would soon be offered. The kids agreed that this was fantastic, and would allow us to focus on designing a grabber, integrating everything, and building it all.
Unfortunately, I did not order the kits very first second I could, and we were down a bit on the list, so ours weren’t in the first shipment out. We waited. And waited. And were eventually told that they were out of the pre-drilled 0.100" 1x2, so would we accept 1/8" or 1/16", undrilled, instead? We decided that since the undrilled was less expensive, we could get more total stock (which would give us extra for boo-boos and other things), and we took half 1/8" and half 1/16". When we finally got the elevator kits, the kids decided to build the outer frame out of 1/8" and the inner frame out of 1/16". Also they initially built the carriage from 1/16", IIRC, but later switched to 1/8". We built about 3 different revisions of the carriage (innermost part of the elevator that holds the grabber), as we discovered that it had to be shorter than the Greyt design in order to start low enough and end up high enough for the game. (From this, important lessons were learned about unintended/unexpected consequences of changing things, see below.)
We took a stab in the dark on the motor (bag motor) and gearbox (VP 63:1), and ended up switching to a different motor (Redline? some kind of 775, anyway) for more speed. We had to turn the motor mount 180 degrees to fit the motor between our two drive gearboxes (3-CIM ball-shifters, with only 2 CIMs each and we didn’t use the shifting capability), but they did it first in CAD and figured out how to make everything fit.
The challenge of putting the CAD elevator drawings (provided by Greybots) together with the CAD chassis drawings (done by our student), making modifications in CAD, etc., then adding the grabber, was perfect for our students. The challenges of assembling the gearboxes (learning about speed and torque and figuring out that we didn’t really need to have the gear ratio shift), chassis and drive system (figuring out the hard way that certain parts needed to be bolted, not riveted, for strength); building the elevator from the drawings and kit parts; making the necessary modifications to the carriage and motor to get the cube up high enough, fast enough; figuring out how to attach our grabber, and wire and ‘plumb’ it (for the motors and pneumatic cylinder) using a ‘snake’; troubleshooting all the problems (brackets that kept bending and had to be made thicker, from steel, then thicker still, then bigger, sturdier, etc.; chains breaking when the elevator was brought down too fast (fixed in software by a “soft landing” - auto-slowdown at x" above the bottom, which I say was our programmer’s way of keeping me from having a heart attack every time the elevator came down); figuring out the sensors (what to use, how to mount), control systems (how to know where the elevator was using sensors and an encoder, control its speed, and hold it at a point), and programming; etc. - were plenty of an engineering challenge for our team. Not to mention designing, mounting, wiring and troubleshooting the electronics and pneumatics.
One example. As a result (probably) of using the 1/16" stock for the inner frame of the elevator, it could bend more than originally intended. Because the carriage was smaller (top to bottom), it could pivot around a z-axis in the frame, and the frame would bend outward allowing the carriage to get out of vertical (really hard to describe in words), and bind/stick when the grabber was going up and down. The kids solved those problems by adjusting some of the spacers on the elevator bearings. They figured out the problem, brainstormed, and found a solution. They did this OVER AND OVER all season long. The problems were significant, but not catastrophic. It was a perfect level of challenge for our team.
We kept our grabber out of the bag as our “withholding allowance” and continued to work on it. Since we’d built a practice bot with the same elevator and carriage, we knew we could just remove the grabber from it and attach it to the carriage on the competition bot. That worked very well, as it took us several weeks to finish the grabber, and we were still experimenting with different wheel arrangements right up to competition.
The Greyt Elevator helped us to have a decently competitive robot at our one and only regional. We did not win, though we had a chance. (In some past years, we have not even had a chance, and that is pretty demoralizing - to work for 6-12 long, hard weeks and realize that you don’t even have a chance to win, or rank in the top half. I don’t think that helps kids to get inspired about engineering, at least not most kids.) We ended up ranked 12th and were the captain of the 7th alliance. (We almost beat #2 - long story - isn’t it always?) Our robot carried and lifted cubes onto the scale and switch. It did not break down (very much). We were able to perform at our first and only regional at a level that was on a par with - or maybe a little better than - our performance at our second regional in the past. Since we’ll never have districts and it costs us over $15,000 to go to another regional, that’s a great thing.
We had fun and exciting auto routines (our programmer got enough time with the practice bot to get routines working that could put a cube in the switch or the scale, on either side depending on the field data). The first time our bot successfully got a cube in the scale in auto, you could just feel the pride and happiness flow through every single team member - suddenly the long, long hours and all the work and frustration were worth it, you could see it in their grins and high fives. EVERYONE had contributed to that moment - the builders, the CADers, the electricians, the programmers, even the strategists.
Our strategy team actually got to develop and test strategies; MUCH more interesting when you can actually consider and choose what to do in a match, rather than simply hope your robot works and can maybe play some defense. Were mistakes made? Maybe. Were things learned? DEFINITELY. Did the kids have fun competing? Oh yeah.
Our kids learned MUCH more, and were WAY more inspired, than they would have been if they had had to design and build everything from scratch this year. I can say from experience that this team would not have had the chance to do half of what they did, in terms of experiencing and solving engineering problems that arose in the course of assembling, testing, and competing with the robot, if we had not had the COTS kits (chassis and elevator) that we had this year. We might not have had a robot at all, or at least not one that could do anything fun. I’m sure our auto programmer wouldn’t have had a chance to do or learn as much as he did with a working, solidly-built robot.
Now, in past years (last year for example) we had different kids, with different levels of experience. Last year, we had 4 seniors who were able to design, build, wire and program the robot, from scratch, basically themselves. Would they have wanted/used a kit elevator? Probably not, they might have preferred to come up with their own. Could this year’s team have done that? No way.
Different strokes for different teams. We found the kit elevator was a ‘Greyt’ option for us this year! Our kids are ready to take their robot around to the elementary and middle schools and do demos, help the FTC teams this fall, bring some of their friends next year and dive into a new challenge in January. And now we can actually choose between a WCD and a mecanum drive next year, depending on the game, rather than have to go with one thing because it’s all we know how to do. (Though there are rumors that we might be experimenting with swerve this summer… )
Thanks, Greybots and WCP.