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M11 Escape Velocity - How reliable is it?

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  • M11 Escape Velocity - How reliable is it?

    Is your team able to complete M11 with decent repeatability? Our robot reliably pounds the pad using 100% power to the small motor. Our attachment is pretty long and pretty heavy. We hit the pad every time and the spacecraft rises fast and high but rarely, like 1 in 10 times rarely, does it actually crest the corner and stay atop the mission model. We'll probably take a whack at it during the competition but I think our odds of success are low.

    Is the small motor sufficient for this mission? Is everyone else using the large motor instead? We can't get more power from the small motor so my only advice has been to make the hammer longer and/or heavier. Am I missing something else obvious? Maybe there is just a lot of random binding between the spacecraft and the track?

    This is our hammer attachment.
    Attached Files
    Last edited by WilliamFrantz; 10-29-2018, 08:15 PM.

  • #2
    We couldn't get enough power out of the medium motor alone to get that mission done.

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    • #3
      100% or very close. Can do it with a medium or large motor. It is all about momentum (speed x mass) and hitting the launch lever in the right spot.

      Longer is not better. Longer means more rotational inertia which means less angular acceleration and maybe less overall speed. There is a sweet spot.

      Friction is bad. Anything that adds friction should be minimized or eliminated. Wobble is also bad because you throw away energy moving in directions that don't contribute to the launch..

      What are you using for motor control? The Move and Motor blocks command speed, not power. You cannot achieve 100% speed with the rechargeable battery. The best I can get is 90% which quickly drops to 85%. I have not tried the unregulated motor block for this mission. It may be better, or worse, or not make any difference, but if I was having problems I would give it a look.

      I don't see a link or image for your hammer attachment. Anyone else having a problem seeing the attachment?
      Last edited by Dean Hystad; 10-30-2018, 12:19 AM.

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      • #4
        Ours is fairly reliable but the kids designed a way to drop a weight on it from above instead of pounding it. Let's gravity do the work

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        • #5
          Our solution is 100% or very close. Every once in a while the payload goes up and bounces just right (wrong??) and doesn't stay. I don't like giving out too many clues during the season, but I will say that we use rubber bands.
          Norfolk, Virginia, USA
          2014 World Class Learning (coach)
          2015 Trash Trek (coach, judge)
          2016 Animal Allies (coach, judge)
          2017 Hydrodynamics (coach, judge)
          2018 Into Orbit (coach, head judge)

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          • #6
            Originally posted by WilliamFrantz View Post
            Is your team able to complete M11 with decent repeatability? Our robot reliably pounds the pad using 100% power to the small motor. Our attachment is pretty long and pretty heavy. We hit the pad every time and the spacecraft rises fast and high but rarely, like 1 in 10 times rarely, does it actually crest the corner and stay atop the mission model. We'll probably take a whack at it during the competition but I think our odds of success are low.

            Is the small motor sufficient for this mission? Is everyone else using the large motor instead? We can't get more power from the small motor so my only advice has been to make the hammer longer and/or heavier. Am I missing something else obvious? Maybe there is just a lot of random binding between the spacecraft and the track?

            This is our hammer attachment.
            I suggest taking a video (slow-motion mode preferred) of every run, focusing on the wheel hitting the launchpad. you will be able to see what's going on.

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            • #7
              Originally posted by ssm View Post
              Ours is fairly reliable but the kids designed a way to drop a weight on it from above instead of pounding it. Let's gravity do the work
              I bet there is an equation for determining how much weight you need when dropped from a certain height.

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              • #8
                We are using the "hit as hard as you can" method using medium motor. When positioned correctly this works very well. The hard part is consistently getting into right position.

                However. We are struggling with enough power to get it back up again. That works well when battery is fully charged, AND we haven't recently made many repetitions. It seems like the motor needs a break now and then to be able to max out power. Anyone else noticed this?

                We may try to reduce weight a bit just to make this more consistent.

                So far we have only been recharging batteries. Will it make a difference using regular batteries?

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                • #9
                  Originally posted by dreamcatcher View Post
                  We are using the "hit as hard as you can" method using medium motor. When positioned correctly this works very well. The hard part is consistently getting into right position.

                  However. We are struggling with enough power to get it back up again. That works well when battery is fully charged, AND we haven't recently made many repetitions. It seems like the motor needs a break now and then to be able to max out power. Anyone else noticed this?

                  We may try to reduce weight a bit just to make this more consistent.

                  So far we have only been recharging batteries. Will it make a difference using regular batteries?
                  The motor doesn't need a break, the battery does. When you draw a lot of power out of a battery quickly it becomes less efficient at delivering power. This is partially due to temperature and partially due to chemistry. This goes away after a period of rest and stabilization. I wouldn't expect this to be noticeable, but you may have better eyes than me.

                  Using regular batteries will make a BIG difference. Motors can go 10% to 20% faster with fresh alkaline batteries compared to the LEGO rechargeable. You can use alkalines if you want a lot of power, but you have to weigh that against the stability, simplicity and cost savings of using the rechargeable battery.
                  Last edited by Dean Hystad; 10-30-2018, 06:46 PM.

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                  • #10
                    My team is getting 100% on that mission with the medium motor. The 'hammer' is too heavy to lift again so they decided to use it to do the observatory mission and then head back to base (for a total of 3 missions on that run). During their testing I think the biggest factor between success and failure they found was getting the correct placement of where the hammer hit the pad on the launcher.

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                    • #11
                      My team also has gone the hammer route. I'm not a big fan of how they are doing it and the amount of weight they are using but, it's their choice. The part I do like is that they figured out that the wall never moves and the base of the mission model never moves. With those, they have an x/y axis they can use to hit the target in the same location every time. They are hammering it to pieces and I keep watching to see if it breaks but, at least they are hitting it in the same location each time. The team uses disposable jigs on several missions where the robot pushes the jig for alignment and then leaves it on the mat and backs away from it. This makes alignment a bit easier with the launch target.
                      FLL coach Trash Trek on, State 4x, World 2x, state ref, state judge.

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                      • #12
                        The qualifier tournament was yesterday and the kids successfully completed M11. I was shocked. It only worked occasionally in practice but it worked when it counted.

                        They simply added a lot of extra weight to the head of the hammer. Once the hammer dropped, the bot couldn't pick it up again, but it didn't matter. The bot simply drove back to base with the hammer down. It's pretty easy to drag because the head of the hammer is just a large wheel. Also, the bot hit the paddle from the side (rather than from the front) so the robot was already pointing at base when it was time to return.

                        For the extra weight, they used one steel caster ball (#99948) and 3 metal flywheels from Chima Speedorz (#11125c01). Those were the only metal parts we had on hand. At the competition, I saw other teams using weight bricks (#73090b). I might try to buy a couple of those before our next tournament. I think they should also try dropping the weight straight down on the paddle instead of using a hammer.

                        I say, "next tournament" because the team actually advanced to the next round. They had the highest score on the tables with 118 points. I think there were about 15 other teams and none of them broke 100 points.

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                        • #13
                          My current thing I want to see in competition: A chima speedorz flying across crater crossing.
                          Coach, FLL Team 3146 Peace By Piece 2013 - 2016; Team 29410 The Dragon Bots 2016-2018
                          Judge, FTC 2014-2015; Field Technical Advisor, FTC 2016-2018; Robot Inspector, FRC 2018

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                          • #14
                            Originally posted by shelbydavis View Post
                            My current thing I want to see in competition: A chima speedorz flying across crater crossing.
                            This is another thing I've wondered for a long time. Can the kids manually load up some energy in base before launching the robot? Is that allowed? For example, if the kids pull a ripcord on a speedor in base, can the robot then transport the speedor over to the craters and drop it? Certainly, the flywheel would still be spinning and would probably have enough energy to cross the barrier but I'm not sure if this type of thing would be legal.

                            I assume it would have to be legal since lots of teams manually load up energy in base. I've seen kids manually pump up pneumatic tanks or manually wind up rubber bands. Technically, even perching a weight on top of a robot or raising a heavy hammer wouldn't be any different than pulling a ripcord. Almost everybody puts some energy into something for the robot.
                            Last edited by WilliamFrantz; 11-07-2018, 02:42 PM.

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                            • #15
                              As long as you're using lego parts and not touching the robot during the run, I don't see why not. We've definitely seen people use lego rubber bands this way.

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