Our team has discussed using fishing line to restrain part of the robot until we need to climb at the end of the game, so when our climber drops down it would snap the line in order to keep the particular part from smashing into the ground, but also remove that constraint.
So my question: is intentionally ‘breaking’ a part of your robot legal? If we intend to just replace the fishing line after every match with pre-made sets, is there any issue with that?
As far as I know as long as it is not left on the field it is ok. If the part were to fall off the game manual says it is a red card.
They may require you to add a safety feature so if the line breaks during transport to the field there would not be possibility of deployment and injuring a team member. the safety feature (Pin or Latch) would then be removed when the bot is in place for the match. then (arming) your device.
There are probably other solutions to the same problem that don’t require you to fix your robot every match. This sounds really risky and I don’t think that risk is necessary but It would make an interesting robot.
If you’re using potential energy (by, say, putting something heavy way up high, then letting it fall to raise the rest of your robot), then Rule R45 has something to say in that.
OP, could you use Velcro instead? I’m a lot more confident in the legality of detaching Velcro, and you don’t have to replace it every time.
Would a falling weight not be considered a change of altitude in the ROBOT center of gravity, which is specifically allowed in part B?
Legal, but there’s going to be the possibility of the string getting caught in something during the match. Depending on how much breaking force you want/need, you may want to consider using dual-lock or Velcro and breaking that grip instead.
To clear things up, the point is to let the string reach it’s full length, causing a ‘jerk’ on the mechanism which deploys/allows time for other features on the lift to fully deploy.
The line will not bear any load until the mechanism drops near end-of-match, at which point we’re hoping that it will cause a temporary stop at a certain elevation while dropping.
Hopefully that clears things up, but I think overall we’re set on the legality side of things.
Whether or not there’s a more finessed way to accomplish the same result, well…
We’ve had masking tape restraining parts intentionally break on our 2015 can grabbers and also our 2016 climber. It’s totally legit.
Personally I don’t think this is a very good idea. My team i making sure to add extra precautions to make sure our climbing/ramping mechanism does not extend until the end of that game. Lets say worst case scenario you would extend at the beginning of the match. Not only do you receive a red card, you also become another obstacle your alliance has to either avoid, or breach through (potentially damaging your robot). In addition, having to replace parts on your robot is easier said than done, and will cause unneeded stress for your pit crew.
As for legality, from my understanding this is perfectly legal, as long as you do not extend until the very end of the match.
Paulius Pace
Team 3161
Yeah, I saw that and I can make a case either way. It would certainly CAUSE a change of altitude in the center of gravity, but that rule seems to be focused on things like the robot changing in orientation.
Our team has had a lot of success with methods like these, not because they are necessary, but because they work well with low effort. To the OP, I would advise that as soon as your team begins to experience issues, such as accidental or failure to deploy, long repair times, or even just not remembering to repair it, design an alternative mechanism, but a simple fishing line (or dental floss:) ) mechanism can be a powerful tool in simplifying mechanical design.
This implies that there is likely to be a loop of string flopping around during the match. That loop catching on some part of your robot, some part of another robot, a game piece or some part of the field can cause an unintended operation of your mechanism. Hence, Gus’ warning. It may be possible to constrain the loop of string with some masking tape.
I have seen this used in the past. Can a non-breaking thing work? Say, thin wire cable and velcro? The velcro provides the jerk and release.
If I’m understanding your purpose here well enough, a servo attached by a spring/string to one side of a lever/latch blocking the mechanism from moving will let the mechanism fall when the servo is spun. This is a relatively simple and re-settable solution that might work for you.
Consider using a magnet and a piece of steel (1/4" nut for example).
Install the magnet and nut at the break point.
Besides being quickly returned to a ready state, you can fine tune the separation (or loosely consider it the breaking strength), buy adding a non-metallic spacer around the steel part.
If the string doesn’t work you could always use a servo motor with a half circle.
Have a light spring help the release or to keep the mechanism pressed against the servo motor attached half circle. When its time to release, spin the servo and let the mechanism pass.
If you need still more holding force, pull a pin with a pneumatic cylinder or something like an Andymark integrated motor/transmission/sensor.
Dave
Should be totally fine. Our climber last year had two spring loaded jaws that closed around the rope which were held back by zip ties which were broken at the end of the match. We just held the zip ties down which tape so they wouldn’t fall into the field. That climber won us a 5 seed at SVR and a creativity award.
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In 2004, team 971 had a similar problem to solve.
Our solution is now very much against the rules, #trendsetting I guess.
The solution was to hot-short NiChrome wire that was wrapped around a bit of string retaining our climbing arm. While it was not in violation of any existing rule, a rule was made on the spot to prevent anyone else from doing this. We were allowed to compete, under close watch.
It only failed once!
Sorry for the nostalgia, just a cautionary tale of rule-bending with a frangible link.