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Dog gears for modular attachments

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  • Dog gears for modular attachments

    I've judged a number of teams this year who are using "dog gears" to create consistent attachment points for hooking up modular motorized attachments to their robots.
    It looks like this technique is being popularized in a video from Builderdude35.
    Is this the hot trend for FLL robot building this season? I've seen variations on this technique in previous seasons, but not this widespread.
    Last edited by timdavid; 12-13-2015, 09:48 AM.

  • #2
    Re: Dog gears for modular attachments

    My son had chosen dog gears to make it easier to change attachments this year (He is the main mechanical builder for the robot as the other kids don't have as much interest). He did see the video from Builderdude35 and that was a part of decision. The big part, he says, is due to last year seeing a big problem with swapping out attachments and trying to get something easier for this year. He also used feedback from other team members to modify attachments to have minimal pin connections so that the attachments could just lay on top of the robot, except the dog gears required pin connections to keep it tight.

    He also notes that dog gears are not totally ideal as there is some play in them and sometimes they don't seat well together, especially under time constraints of the robot runs, so there were several mission failures due to that. At the very least, he has learned there are trade-offs with any of the ways of attaching equipment to the robot.

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    • #3
      Re: Dog gears for modular attachments

      I have also seen several teams using this attachment method due at least in part to Builderdudes' video on the subject. It is interesting to see how different teams adapt the idea in different ways and to different degrees to their particular needs.

      Builderdude got the idea from LEGO Vinir's videos of their Nature's Fury run and they were certainly not the pioneers of the concept either (there is a video of an Ocean Odyssey run where a similar principle is used.)

      Really the "dog gear" (LEGO Vinir called it a clutch system) concept is just one variation on the wider concept of drop on or push on geared attachments. There are several versions using tooth gear connections and I saw one team with a rather effective worm gear version (their attachments all had tooth gears which dropped onto a worm gear connected to a medium motor.)
      Team members and coaches in North Carolina, direct your rules questions to referee@nc-fll.com

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      • #4
        Re: Dog gears for modular attachments

        The team this year decided to modularize their attachments with a power take off, too. However, they've never heard of dog gears, or Builderdude35, so they went with the 4 tooth high torque gears for minimal slippage. They also designed it to be a one-axis shift in power direction (whatever the engineering term for that is) so that the motor points straight ahead, but the attachments shift the power perpendicular to that.

        One of their more complicated attachments uses two gears on the attachment, and pulls power in two directions of rotation, gaining a paired, opposite motion for it (one arm up, one down; and vice-versa.

        It's great watching them learn this stuff!

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        • #5
          Re: Dog gears for modular attachments

          Our team saw the system used by Lego Vinir and used it last year and it worked well. They built it in this year, but found they used very few motorized attachments this year--actually only one arm each for two missions, so they went back to just permanently mounting those on the medium motors. They accomplish the majority of tasks just using the push/pull of the robot. They usually strive for the least complicated ways to solve missions and pride themselves on using as few motorized attachments as possible.
          Sylvania STEM Center Coordinator
          Twisted Toys
          Trash Trek--Coach
          World Class--Coach
          Nature's Fury--Coach
          Senior Solutions--Coach
          Food Factor-Coach

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          • #6
            Re: Dog gears for modular attachments

            My older boys are also using the "wide dog gears", to power their "extra skin" (a tall robot chassis that drives over the Demo/building). Originally they tried using four point "cross" as a gear, but that was causing problems, so I suggested that there are other types of gears, they tried several different types and settled on those.
            Legolympians - 2009-2015 (retired - joined FRC team 5422 Stormgears)
            Legolicious - 5th year girls team
            Brick Force - 2nd year boys team

            2015 - Mass FLL coach of the year.

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            • #7
              Re: Dog gears for modular attachments

              My team has idolized Cassapeia, with their video of 842 punkte. They wanted the big square frame, and their attachments fit on top as a big square frame. Their solution to the whole PTO problem was standard Lego gears, the fat ones, but the gear on the actual attachment is mounted on a block that slides on an axle for adjustment.

              I'm loving their progression on this, they're starting to really explore the ideas of building instead of solving everything with overly precise movements of the drive motors.

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              • #8
                Re: Dog gears for modular attachments

                This is what "dog gears" looked like back in the RCX days.
                Attached Files

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                • #9
                  Re: Dog gears for modular attachments

                  Originally posted by Dean Hystad View Post
                  This is what "dog gears" looked like back in the RCX days.
                  That's about a century ago in "dog years"...two whole generations of Mindstorms controllers.

                  Is that from the classic "Building LEGO Robots for FIRST LEGO League"?

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                  • #10
                    Re: Dog gears for modular attachments

                    Originally posted by Dean Hystad View Post
                    This is what "dog gears" looked like back in the RCX days.
                    Some teams still use that connection. It worked well for the Droids for World Class.
                    Team members and coaches in North Carolina, direct your rules questions to referee@nc-fll.com

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                    • #11
                      Re: Dog gears for modular attachments

                      None of these ideas is new. They keep getting discovered over and over and over, which is a good thing. What would be very bad is if somebody created a repository of all these ideas where you could search for "best practices" on how to solve different problems.

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                      • #12
                        Re: Dog gears for modular attachments

                        Originally posted by Dean Hystad View Post
                        None of these ideas is new. They keep getting discovered over and over and over, which is a good thing. What would be very bad is if somebody created a repository of all these ideas where you could search for "best practices" on how to solve different problems.
                        While there's something to be said for kids "re-inventing the wheel" in the context of FLL, I do think there's value for the kids at least being aware of different approaches. That said, showing a kid a hammer may inspire them to come up with a sledgehammer by opening their eyes to the possibility of a whole class of tools. To mix metaphors, if all you've ever known were hammers and nails, being presented a screwdriver and screws would likely stimulate a lot of creativity without having to overcome the obstacle of independently inventing the screwdriver.

                        From what I've seen of the FLL game over the past 2 years is that there are several common tasks - push an item, retrieve a loop, pull a widget. I don't think it is at all a bad thing if someone were to create documentation discussing different ways to interact with models (active / passive attachments) complete with generic examples. I've found a channel on YouTube that is quite helpful in demonstrating tools without solving specific FLL field problems.

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                        • #13
                          Re: Dog gears for modular attachments

                          Honestly I ask "Why is that a good thing?"

                          I agree that all teams should have access to generic information, such as "A color sensor can report the color of an object or the intensity of reflected light. Here is an example program that reports the color of object placed in front of the sensor. Here is an example program that drives forward when the room lights are turned on and stops when they are turned off." Or a building example could show how you can make a really strong and light structure by connecting pieces in different orientations. As far as I am concerned this is the toolbox and it contains a hammer and a screwdriver and maybe some additional tools.

                          How to push an item or retrieve a loop or pull a widget is not a basic tool. That is the challenge the team is supposed to solve. Supplying that information, even in a supposedly generic form, is giving the team a circular saw or a hammer drill. Yes, that will let them build a solution faster, and build a better solution, but are either of those a good thing? Isn't figuring out how to build faster and better the really important part of FLL, and the actual results of little to no importance. Why do you want to short circuit the learning experience.

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                          • #14
                            Re: Dog gears for modular attachments

                            Originally posted by Rbbbbb View Post
                            My team has idolized Cassapeia, with their video of 842 punkte. They wanted the big square frame, and their attachments fit on top as a big square frame.
                            Wait until you see their robot this year. It is even bigger and squarer.. And they routinely score 953 points.

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                            • #15
                              Re: Dog gears for modular attachments

                              Originally posted by Dean Hystad View Post
                              Honestly I ask "Why is that a good thing?"

                              I agree that all teams should have access to generic information, such as "A color sensor can report the color of an object or the intensity of reflected light. Here is an example program that reports the color of object placed in front of the sensor. Here is an example program that drives forward when the room lights are turned on and stops when they are turned off." Or a building example could show how you can make a really strong and light structure by connecting pieces in different orientations. As far as I am concerned this is the toolbox and it contains a hammer and a screwdriver and maybe some additional tools.

                              How to push an item or retrieve a loop or pull a widget is not a basic tool. That is the challenge the team is supposed to solve. Supplying that information, even in a supposedly generic form, is giving the team a circular saw or a hammer drill. Yes, that will let them build a solution faster, and build a better solution, but are either of those a good thing? Isn't figuring out how to build faster and better the really important part of FLL, and the actual results of little to no importance. Why do you want to short circuit the learning experience.
                              Why is your example of demonstrating a really strong and light structure built by connecting pieces in different orientations OK but example of a dog gear or a passive one-way box or a modular attachment system not OK? I don't understand where you're drawing the line.

                              Why do you think learning how to build faster and better from external resources is worse than learning how to build faster and better in isolation? I view the point of FLL as a way for the kids to learn problem solving skills. Independent self-discovery is one way; standing on the shoulders of those who came before is another.

                              I know I would be way less productive in my day job without resources like Stack Overflow and Google. Learning how to learn is a valuable skill. There's no way I would have come up with functional programming on my own. Having learned about it, though, opened my eyes to solving problems in an entirely new way.
                              Last edited by dcieslak; 12-17-2015, 08:17 AM.

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