Kitbot on Steroids – “The Yardstick”

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If you’ve ever been on Chief Delphi outside of competition season, the most common post in CD-Media is inevitably a CAD render of a drivetrain. I think it’s pretty great that students, college students, and mentors alike think about how to improve in the offseason, including the buildup of a bit of a “design library”, but often teams get carried away with dreams of custom drivetrains. They do this to the point where they ignore the very good drivetrain right under their noses, or write it off as weak or unstable. I’m referring to the Kitbot on Steroids

In some respects, the Kitbot is a bit incomplete. It comes geared pretty fast and a bit short on rigidity. Team 1114 has stepped in and provided, in painstaking detail, ways to upgrade the Kitbot to what they call the “Kitbot on Steroids“. The main upgrades include a more reasonable free speed, six powered high traction wheels, and a wooden baseplate for added rigidity. All of these together make for a very competitive drivetrain that is fully capable of performing in the upper 25% of FIRST.

But you don’t see many CAD designs that copy the Kitbot on CD. You see a lot of teams that borrow from the elegant and innovative “West Coast Drives” of 254 fame. I’m not going to pretend that my team doesn’t look up to these teams and look for inspiration, and there is a lot of 254 in 2791’s driveline. But I think that helps qualify my point here a little. These teams are copying the best as a starting point, but oftentimes ignore their own resources and limitations in doing so. So I think instead of using the Poofs as a yardstick and a starting point, people should use the Kitbot on Steroids.

Not to say one should start CADing something that looks just like the Kitbot on Steroids and fabricating that! I’m saying that the Kitbot on Steroids should be “the yardstick” – the drivetrain all other designs have to be “better than” to get built.

To make a comparison, you have to start with some design criteria. Here’s a few for the sake of this point:

  • Weight
  • Design Time
  • Fabrication Time
  • “Performance”

The Kitbot on Steroids is a pretty good drivetrain weight wise. According to my calculations (I don’t have one sitting in front of me), with CIMs and without electronics the thing should weigh somewhere around 45 pounds. In terms of design time – none! Fabrication time? One meeting. In terms of performance, the drivetrain is comparable to any high traction six wheel drive.

Compare that to the “Poofs drive”. I have to make some assumptions here to make this point, so forgive the pretense of inside information I don’t have. The Poofs drive weighs a lot less, and performs exceptionally well in terms of sheer efficiency. Their design time, while not “none”, is pretty low due to their experience. Their fabrication time, while not a single meeting, is effectively lowered as much as possible and tuned to their entire team’s resources. The thing to take away from this is that the Poofs take a dramatic weight improvement and helpful performance gains by minimizing the expensive tradeoffs of design and fabrication time.

So how does one apply this lesson to themselves, assuming that one is not a team with the resources to rival teams like the Poofs? Look at the Kitbot on Steroids when evaluating a design. If one can’t beat 45 pounds with a custom skid steer drivetrain, it is all but a waste of time, energy, money, and effort to build something that ISN’T the Kitbot on Steroids. I’d really look at the actual performance advantages a custom drive would give, and honestly evaluate if they are worth the dramatic effort they take.

It’s not THAT hard to design a solid drivetrain that shaves a few pounds off the Kitbot. But to do it in such a way that it gives a competitive advantage in the big picture – that’s a challenge. As I play around in CAD the next few months, you better believe I’ll be using the KoS as my yardstick.

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Sabbatical

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So I’ve been pretty hardcore neglecting this blog! I figure I should probably start posting to it again. I’ve been on a bit of a forced leave of absence from 2791 this year. I’ve been in Wisconsin since mid-January for health reasons and have been cheering from home for them, but not really involved in their success. Though, I wasn’t really THAT helpful to begin with…

So here’s where I’ll be posting my various musings about FIRST robotic design once again. I want to keep my “head in the game” so to speak with regards to mechanical design… so content should start appearing here soon. In theory.