The Kickoff
Upon learning this year’s competition, team 1742
quickly assembled around ten general types of robots utilizing
several different strategies while at the kickoff on January
7. The more realistic and reasonable concepts we came
up with included; a three point shooter with hopper and
ball collector, harvester, one point shooter with a hopper
and ball collector, and a simple rolling box. Taking note
of the complexity and resources that our rookie team would
need in order to fulfill the various robot concepts, our
team eagerly ruled out the simplest designs in favor of
the most difficult upon the premise “go big or go
home.” Which is a long-winded roundabout way of
saying, we decided to build a ball collecting, hopper
loading, three point shooter.
The Beginning
With our minds reeling in anticipation we simply couldn’t
wait to get to work. There was only one little hitch.
How exactly were we going to build it? Well, to help us
in this little endeavor, we split our team up into smaller
groups to tackle the various subsystems of the robot
such as drive train, shooter, ball collection, and hopper.
From there we began narrowing down our options, figuring
out the best way to construct our bot; building it from
the ground up starting with the frame and drive train.
The Frame
After opening up the Kit of Parts (KoP) and examining
all the various goodies FIRST provided us with this year,
we decided to use the frame they provided us. To begin
with, it’s simple. We didn’t have to take
time to design our own custom frame and wait to have it
built, and then hoping we designed it well enough. The
KoP frame was lightweight and structurally rigid and so
suited our purposes.
The Drive-train
Our team identified the drive train as one of the most
important aspects of the bot. Since, without a strong
system, competition is all but impossible. We desired
a drive system that was both strong, reliable, and we
wanted to be able to shift on the fly. After doing a little
research, we found the “Nothing but DeWalts”
white paper from Team 647 the Cyber Wolves. It explained
the modifications necessary to port the CIM motors to
DeWalt XRP 3-speed transmissions. Looking at reviews from
past events and the simplicity of the design we decided
to utilize them on our bot. The transmissions themselves
give us gear reductions of 12:1, 4:1, and 3:1, giving
us a high, mid, and low gear.
We then used nine tooth sprockets on the DeWalt transmissions
with a 40 tooth sprocket on our center drive wheels and
connected the front and rear wheels to the center also
using 40 tooth sprockets giving us six wheel drive.
The Conveyor
For our ball collection system, we outlined two main
ideas and had no little trouble in settling the issue.
The first would have used a high speed roller to launch
the poof balls up a scorpion tail type track and either
into the hopper or directly into the shooter itself. There
were several doubts about the design’s feasibility
and whether or not it would serve our purposes. We deemed
not to use the idea partly due to the fact that given
the size of the poof balls, we wanted to be able to hold
balls in our conveyor/collection system in order to more
fully utilize our space. The second idea, which we used,
comes from looking at designs from several years back.
It uses two conveyor belts in order to squeeze the poof
balls and lift them up to the hopper. The design utilizes
less space than the scorpion tale would have and was much
simpler to build especially since we built it out of PVC
pipe.
The Shooter
The shooter was the last piece of the robot we worked
on. We had several ideas for shooting the balls, most
involving at least one spinning wheel to launch it. We
decided we wanted to use the wheel design, and that we
wanted the wheel(s) mounted vertically, but in the end,
the debate came down to whether or not we should have
one wheel or two. With one wheel, we could have simplified
our bots design, decreased both weight and the rate we
drained our batteries, but on the other hand, with the
two spinning wheels, we could vary the speeds of them
in order to give the exiting balls a spin that could help
us improve our distance and accuracy. We decided in favor
of the two wheel design since, gauging the progress so
far on the bot, weight wasn’t going to be a major
issue, and also since we weren’t very worried about
draining our battery within the competition period. Once
we had this settled, we didn’t have just a whole
lot of time left to create prototypes and go through trial
and error. So, we turned to Autodesk Inventor to aid in
the design process. We fully designed the shooter on Inventor
before we ever began building it, then, using drawing
sheets generated from the assembly models, we began building
the necessary components. After finishing construction
on the shooter and mounting it on the robot, we decided
it was a good time to throw everything on it and see how
we were doing on weight. To our dismay, we were over eight
pounds over weight. So, we removed much of our structure
for mounting the shooter, and dropped it down as low as
we could without interfering with our drive transmissions
in order to save weight. After much hacking, cutting,
and a very strenuous extra hardware removal program was
conducted, our bot weighed in at a trim 118lbs minus the
batter and bumpers.
The Circuitry
For our electronics board, we mounted all of our electrical
components on a single piece of quarter inch thick Plexiglas
horizontally on our robot between the shooter and the
conveyor. But, as a consequence of our weight removal
program and dropping the shooter down, we remounted the
electronics board vertically to allow more room for the
shooter.
