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M09 - Strength Exercise - too stiff?

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  • M09 - Strength Exercise - too stiff?

    Does the bar feel very stiff to lift? When trying to lift it by hand, the mat lifts off the table (along with M10) and seems to almost stretch before the bar raises. We've quadruple checked the instructions - there is the one grey pin that provides friction, and the other 3 yellow pins on the gears. When swapping out the grey pin with a yellow, the bar moves freely, so the rest of the mechanism is constructed correctly.

    YouTube videos show behemoth robots lifting the bar with an elevator mechanism. I'm guessing the weight of the robot holds the mat down, and the elevator gearing multiplies torque to push the bar.

    Maybe it's supposed to be this stiff, but it seemed a little odd.


  • #2
    Ours is very stiff also. We've not tried it with the robot yet (may do that today), but I'm guessing it won't be able to do it. We have two practice tables and the same applies to both.

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    • #3
      The Exercise machine has a grey base. Maybe your team could make use of that.

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      • #4
        Originally posted by nedcook View Post
        Ours is very stiff also. We've not tried it with the robot yet (may do that today), but I'm guessing it won't be able to do it. We have two practice tables and the same applies to both.
        Ours is very stiff too. My son triple checked how he built it, and it is exactly as the directions have it.

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        • #5
          Thank you for bringing up the topic. It looks like we made a mistake in this step. It uses one tan and one blue axle pin. We used two tan axle pin and it was easy to move. One we replaced one of the tan one with one of the blue one it has become much more stiff. So this will require some torque to move.

          24458AA5-2389-4424-822A-54A596EBEF44.png

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          • #6
            We checked our model several times also due to the movement of the mat. We even knocked the lander out one time.
            It looks like this year, the challenge in many missions is the correct application of force and the ability to create a robot that can apply more torque or speed than the motors are able to create on their own without gears or weight. On M09, the position of the robot on the mat close to the M09 base or on the base will be important.
            The force necessary to lift the bar is over five to seven ounces. Try yours with a letter balance or similar balance scale. The large and medium motors only have working torque of 20 Ncm and 8 Ncm. So, if my math is correct, the arm of the medium motor must be about 1.5 inches or shorter and the arm of the large motor must be about 3.5 inches or shorter in order to lift the weight. There is also a problem using an arm in that the distance to the bar increases as the robot lifts it up. I think that is why there are large fork lifts and similar solutions showing up.
            FLL coach Trash Trek on, State 5x, World 3x, ref, judge advisor.

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            • #7
              Unless I planned to use a forklift device for several other missions I wouldn't waste one on this. Very little motion is required to satisfy the scoring criteria and there are lots of ways to apply a significant amount of force over a short distance. I hope to see several creative solutions.

              Lifting is usually a bad idea for solving FLL missions. In power puzzle there was a house that you needed to raise up on stilts with additional points for opening a window and door. My girl's solution did all three (and a couple of other missions) at the same time by driving into the house and lifting it up. This worked great at home, but was less successful at the tournament where the dual lock was slightly worn, During their second or third attempt the robot picked up the house, ripped it from the mat and brought the house back to base. This resulted in a lot of laughs, and they were even awarded points for the mission (incorrectly I think). The solution was redesigned to hold the base of the model down while lifting and there was no more unintentional house moving. It was a tiny bit slower than the original solution, but didn't depend on chance to score. The only thing you can count on less than the durability of field models is the largess of referees when you are in the wrong.
              Last edited by Dean Hystad; 09-05-2018, 11:39 AM.

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              • #8
                Originally posted by DJR View Post
                It looks like this year . . . the ability to create a robot that can apply more torque or speed than the motors are able to create on their own without gears or weight . . . I think that is why there are large fork lifts and similar solutions showing up.
                Originally posted by Dean Hystad View Post
                Unless I planned to use a forklift device for several other missions I wouldn't waste one on this . . .
                We're rebuilding our motor arrays for this very reason.

                It's a lot harder than one would think.

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                • #9
                  This is our large, forklift attachment (laying on its side). It's light and has over a foot of travel. Note, as-is this would be too tall to fit in base (R13) but you can easily reduce the size by removing some of the treads.
                  You do not have permission to view this gallery.
                  This gallery has 1 photos.

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                  • #10
                    We've tried both an arm, and a forklift attachment with medium motor. Neither worked and we do not have any extra large motors. That said, all of these attachments were created by the kids, and I didn't interfere very much or even suggest longer or shorter arms. Not sure if we will even attempt this one during the tournament it. We certainly aren't working on it right now and the kids have moved on to other, easier missions.

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