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Proposal for Exception to Rule G26 for Height of Lander Support Bracket

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  • Proposal for Exception to Rule G26 for Height of Lander Support Bracket

    I find the question posted by Team 13296, "Competition Lander with hook at 21.5" above mat, tolerances question," on the game play "Check the Game Manual for Answers" section extremely disturbing. Their post is laid out very well to detail the events. It is a shame that their hard work was brought to moot due to an improper field setup. Even more disturbing to me is the official response of simply referring to Rule G26.

    This is not my team and I have no idea who they are. It is the general principal involved. We ask our students to spend many hours brainstorming, designing, building, programming, testing, and practicing with the robots. Is it too much to ask that the folks hosting a competition take a simple measurement of the central point of the competition and holds such an important part of the score? Is it too much to ask that they adjust it properly, given that it is designed to be adjustable (presumably for that specific reason)?

    I find it very disappointing that any person hosting a competition would not take 5 or 10 minutes during the initial setup to ensure that this is proper. Instead, it seems that all too often, they simply fall back on rule G26 as their excuse for not putting in the necessary effort to play by the stated rules. Allowances are used in most things because perfection is not attainable. Car manufactures have allowances on critical elements that effect the safety of every one of us on our daily commutes. However, those allowances are small and very specific to the individual parts involved. The allowance on a spark plug gap is different from the allowance on a tailgate. They do not use a generic variance to apply to all pieces of the vehicle.

    In most cases with Rover Ruckus, a 1 inch variance is fine and does not affect game play. However, this measurement is critical due to the nature of when it is used. Only on autonomous does it create an issue. The robot is hanging and must lower itself to the ground and unlatch. Not being precise in the lander setup at competitions and simply relying on rule G26, it may need to lower itself from 3 to 5 inches (assuming it was designed to hang at precisely 4 inches on a correct setup). Then, it needs to unlatch. In our specific case, we are using a device that will lower the robot to the ground and then raise a hook an inch so the robot can move to the side to unlatch. Assuming it is designed for the max allowance of a 5 inch drop, the arm will be programmed to raise 6 inches (5 inches to touch the ground and 1 inch to get the hook off of the latch). No problem. However, it could also only be 3 inches off the ground. Since this is autonomous and the lander height can randomly be anywhere from 21 inches to 23 inches (according to rule G26), only one program may be used. The arm would raise the previously mentioned 6 inches. It touches the ground in 3 inches and continues to rise for 3 more inches. However, the inside distance of the lander support bracket is only 1.5 inches. Therefore, after hitting the top, the robot will still be trying to go another 1.5 inches. This will do one of several things. It will raise the lander 1.5 inches off the ground. This is not likely, since our motor for that action is probably not strong enough to raise the entire lander. It will cause undue strain on our motor. Another possible side effect is stripping out the gears used for the lifting motion. None of these are good scenarios. Of course, we can work on solutions to this problem and "plan our robot accordingly." However, I believe there is a better solution.

    I propose an exception to Rule G26 for the specific measurement of the height of the lander support bracket. It is a simple measurement and easily corrected, if it is off. It is a key element to the game. Of course, nothing is ever perfect, so some allowance would be required. However, 1 inch on this critical measurement seems to be quite excessive. I propose a specific tolerance of 1/4 inch for this specific measurement of 22 inches from the bottom of the lander support bracket to the top of the tile.

    I believe firmly that this would be more in line with the spirit of FIRST than the official response of simply referring to Rule G26. We owe it to the hard-working students to make sure that every effort is made to ensure consistency in the game play. Correcting this moving forward won't affect the outcome of Team 13296's competition. However, if this can be corrected going forward, perhaps they would find some comfort in the fact that their post sparked movement toward a change on this issue.
    Last edited by Mentor 777; 11-07-2018, 01:12 PM.

  • #2
    Totally agree with the concerns of the post author.

    Just want to throw out a tip, that if possible to use an encoder, you can time out the motor stalls so the program would move on quickly enough to try to prevent damage. But yes, field set up needs to be done with teams in mind, not rushed through and using the 1 inch tolerance rule for such a sensitive programming challenge.

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    • #3
      Mentor 777 I agree completely with your proposal. A 1 inch tolerance (i.e., 2 inch range of allowed position) for a part whose vertical opening is only 1.5 inches just seems excessive.

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      • #4
        Another post has been made on this issue.

        Lander and Field set-up
        11-09-2018, 02:57 PM

        Our robot was designed to hang and lower itself during autonomous mode. At a recent competition, our robot was deemed to be lower than the 4 inch required height before the match started. It turns out that the lander handle height was off by 1/2 inch. The handle opening is 1.5 inches. We were told that the error in the setup/measurements can be as much as 1 inch. I understand this all to be true. The concern is that the hanging apparatus must be roughly 1/2 inch in order to support your robot and that leaves ABSOLUTELY no error room if the height is off by an inch. At half an inch, you programming and mechanics are off by 33% in reference to the opening. 1 inch is a 66% difference! Not to mention all codes and mechanics would then need to be adjusted if even possible for the 18 inch requirements. My question is: can we have a game specific rule/allowance to adjust the lander (handle) to the correct specification of 22 from the floor to the bottom of the handle prior to match play?


        Last edited by brent-johnston@ksd111.org; 11-09-2018, 03:02 PM.
        Tags: None

        Apparently, the intent of the game design committee was that a robot fitting inside the 18 inch cube and hanging from the lander support bracket would inherently be 4 inches from the floor. 22 inches (intended height of the lander support bracket) minus 18 inches (maximum height of the robot) equals 4 inches (the minimum distance from the bottom of the robot to the playing field floor). I believe firmly that the use of rule G26 in this particular measurement negates the original intent of the game design committee. Therefore, either an exception to rule G26 for this specific measurement or a removal of the 4 inch rule needs to be made.

        Rule G26 - Tournament provided Playing Field and Game Elements will start each Match with tolerances that may vary by as much as +/-1.0 inch (2.5 cm). Teams must design their Robots accordingly

        1. Latched to the Lander - Robot is Completely Supported by their Alliance-specific side of the Lander with the following constraints:

        a. The Robot must be Completely Supported by the Lander Support Bracket. Incidental contact with the Lander walls or the legs is allowed.

        b. The lowest point on a Robot and Team Marker can be no closer than four (4) inches (102 mm) from the Playing Field Floor.

        c. When Completely Supported by the Lander, Robots must be within the 18 inch x 18 inch x 18 inch (45.7 cm x 45.7 cm x 45.7 cm) starting volume constraint.

        Lander Support Bracket picture - Figure B4

        Measurement from bottom of Lander Support Bracket to Top of Tile is stated as 22 inches.

        In order for a team to "design their Robots accordingly" in this situation, one of two things has to happen. In two posted cases, the teams' hard work on their autonomous program was negated because the lander was less than 22 inches from the top of the tile. So, at least twice, the field set-up crew and judges have fallen back on the G26 rule to leave a lander height at less than 22 inches. Since this is a recurring issue already in the season, teams have a couple of options.

        Move the attachment point at least 1 inch below the top of the robot. This will cause it to hang 5 inches from the ground in a proper setup or 6 inches off the ground in the case that the lander is an inch too tall. If the team is using a Tetrix rack and pinion system, these two inches make a huge difference in the design. Vertical space is limited on the robot to fit in the 18 inch cube. A balance of guides and pinions has to be considered. With that, where do you put the pinion? That is a lot of possible vertical movement and 2 inches is a HUGE difference when working on something with such limited space. Personally, we are using that system. We have two pinions to allow for this. We have a top-notch programmer that can write the code to allow for the possible variance. We are prepared for G26, but it is extremely difficult given the very limited range to work with. I am fighting this on principal. I firmly believe simply relying on rule G26 for this measurement is in direct conflict with the original intent of the design committee.

        The other option is to design the robot with a 17 inch height. Therefore, when the lander setup is using G26 and the lander support bracket is only 21 inches from the top of the tile, it will meet the 4 inch requirement. Of course, the robot still needs to be prepared to be 6 inches off the ground and this extra inch that has been taken off of the robot adds to the difficult challenge of allowing for that variance.

        So, once again, I am requesting an official exception to Rule G26 for the specific measurement of 22 inches from the top of the tile to the bottom of the lander support bracket. Since this is a simple measurement and the height of the lander is easily adjusted, this would only take a maximum of 10 minutes to correct prior to a competition. Of course, perfection is never attainable, so some variance will occur. I propose 1/4 inch maximum variance for this particular measurement. Again, it is a simple measurement and easy to correct. 10 minutes of prep time to ensure this measurement is accurate is an extremely small request compared to the hundreds of collective hours our students have committed to preparing for, driving to, and participating in the competition.

        If this exception is not granted, then please consider deleting portion b from the "Latched to the Lander" definition. Portion C of "Latched to the Lander" already says that the robot must be within the 18 inch cube. With the proper field setup, b and c are redundant. The only possible scenario where a robot meets the requirement for c and does not meet the requirement for b is improper field setup. I define "improper field setup" as "not equal to the stated 22 inches." Relying on G26 to deem 21 inches "acceptable" does not make it the proper measurement. Therefore, I propose that item b be removed from the game manual.





        Last edited by Mentor 777; Yesterday, 02:06 PM.

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        • #5

          Combined to other post. Please delete if possible.
          Last edited by Mentor 777; Yesterday, 02:09 PM.

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          • #6
            Combined to other post. Please delete if possible.
            Last edited by Mentor 777; Yesterday, 02:09 PM.

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            • #7
              Combined to other post. Please delete if possible.
              Last edited by Mentor 777; Yesterday, 02:09 PM.

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              • #8
                I just thought of another implication of applying G26 to this issue. The scores for deploying and re-latching accurately reflect the difficulty of the task, even if the lander is setup properly. Until now, I have thought there were only 2 possible reasons the height of the lander support bracket would not be 22 inchers. The set-up crew is either inept or doesn't care. I don't believe the first one applies. I don't believe there is a single person that would be setting up a field that is incapable of using a tape measure to determine the height of the lander support bracket and using a wrench to turn the adjustment mechanisms to make sure it is 22 inches. So, the latter would apply. If the height of the lander support bracket is not 22 inches, it is simply because the person setting it up and the people inspecting the field simply do not care. There are a lot of measurements on the field. I don't believe any of the people setting up the field are uncaring in general. They are volunteering to help in this and, therefore, are most likely generally concerned about providing a good experience for the teams. So, the only logical explanation is that they do not realize the importance of this measurement. Therefore, an exception to rule G26 for this particular measurement would highlight the importance of this measurement and they would react accordingly by ensuring that it is accurate.

                The other possible scenario that just occurred to me is intentional cheating. Certainly, that would not be the norm and I would like to think that it is not even a possibility. However, if a team hosting an event does not have an autonomous program that can deploy the robot, they can not score the 80 points for deploying and re-latching. Knowing the extreme difficulty of this task and rule G26, the hosting team has the potential to deliberately set the height at 21 inches, rendering the 80 points non-scorable for teams that developed their robots according to the specifications intended since the robot would be less than 4 inches from the ground. That would level the playing the field for the hosting team. Again, I seriously doubt this would ever happen intentionally, but the combination of Rule G26 and part b of the Latched to the Lander requirements do allow for that possibility.

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                • #9
                  From Mentor 777 "using a wrench to turn the adjustment mechanisms to make sure it is 22 inches"

                  As the Field Setup guide is currently written there is no adjustment mechanism. The Lander foot sits on the tile and a nut goes over the foot.
                  (Lost rest of post, edit typed in again.)
                  See section 3.2 of the Field Setup guide

                  It would be easy to add one nut under the foot to make an adjustable system.

                  I agree with the above posts that the standard tolerance is inappropriate for this part of the game.
                  Last edited by 3805Mentor; Yesterday, 02:05 PM. Reason: I really really hate the way this forum is set up.??I just lost a lot of my post yet again, and had to edit to type it in again. Frustrated!!!

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                  • #10
                    Originally posted by 3805Mentor View Post
                    From Mentor 777 "using a wrench to turn the adjustment mechanisms to make sure it is 22 inches"

                    As the Field Setup guide is currently written there is no adjustment mechanism. The Lander foot sits on the tile and a nut goes over the foot.
                    (Lost rest of post, edit typed in again.)
                    See section 3.2 of the Field Setup guide

                    It would be easy to add one nut under the foot to make an adjustable system.

                    I agree with the above posts that the standard tolerance is inappropriate for this part of the game.
                    I also agree on your reason for editing. It is frustrating. It took me several attempts to get my post added today.

                    As for your response, WOW! I looked at the field setup guide that you directed me to. I had not looked at our lander until recently. I thought it was fully assembled, but we were not at the point of testing. Now that we are approaching that point, I went to measure the lander. It was too short, even sitting on the floor. I discovered that the feet had not been installed. I was going to install them, but found that one of the angle pieces that screw into the bottom of the leg was missing. We've searched for it, but have been unable to find it. We will need to either order a replacement or possibly 3-d print a replacement. So, I haven't been able to check on that. I did see a nut on a threaded bolt and assumed that was for adjusting the height. Yes, I know assumptions are generally a bad idea. I'm pretty sure, though, that I read somewhere about the adjustment in the height of the lander being an easy task. I thought it was the original post that I mentioned at the start of this thread. I went back and checked, though, and there was no mention of the ease of adjustment. Now, I am wondering if I just made that up in my mind!

                    Well, if the lander is not easily adjustable to be precisely 22 inches from the bottom of the lander support bracket to the top of the tile, I believe that is a serious design flaw. Since the teams that have posted the issue were both on the low end of the variance (less than 22 inches), perhaps the design failed to include the fact that the feet sit on the floor and the measurement goes from the top of the tile. If that is the case, most lander support brackets will be approximately 21.5 inches high (as in the two posted issues).

                    This new revelation (to me) that the feet may not be easily adjustable does negate a large part of my argument for reducing the variance on the measurement. However, it seems to me that a design flaw where the intended measurement of 22 inches appears to have become 21.5 inches on a large scale only strengthens the theory that part b of "Latched to the Lander" should be eliminated. With a lander designed to the intended specifications, b and c are redundant. A robot matching c will automatically match b. Therefore, the only time b comes into play is an improper field setup. If the lander design produces an improper field setup on a regular basis (which would be the case if the height is not readily adjustable and regularly comes in at 21.5 inches), then b should either be eliminated or changed to the norm (21.5 inches height minus 18 inches max robot height equals 3.5 inches minimum clearance.


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