We are planning on using a bungee-like material such as surgical tubing to tension a catapult to shoot the ball. Is there a rule about needing a way to safely and slowly release the energy in the bungee once the robot is disconnected and off? I was unable to find one in the manual, but I may have missed it or was not looking in the right place. Any help would be appreciated. Thanks.
Short of a specific rule, the only ones that would come to mind would be the usual R8, stating:
If the catapult would be fully enclosed by the robot and you’re fairly certain that no one could get an extremity pinched or hit by said catapult then I think you would be fine.
This will largely be a determination by the event inspectors. Personally, I’d want to take a long hard look at how the team plans to safely move a robot on or off the field with tensioned springs.
Aside from safe release of stored energy, consider the safe retention of stored energy. For a variety of reasons you may find it necessary to charge the mechanism while people are near the robot or for extend periods of testing. Consider how you can prevent the device from accidentally actuating and what the ramifications would be if it did.
This might be, for instance, a pin that can be placed on the robot that would lock the shooter in place.
With bungee and springs consider failure modes. Make sure the connection points have no opportunity to slip off or may be easily bumped off accidentally. Ensure springs have zip cords or something running through to contain it should failure occur. Goal is to keep bits of springs or bungees from turning into a projectiles on or off the field.
In the past we have used “remove before flight pins” to hold any mechanism that involved stored energy in place. This allowed the drive team to safely place the robot on the field. You just have to train them to pull the pins (and the brightly colored streamers attached to them) after setting up the robot on the field.
Edit: We also have used tethers to constrain an element to the robot incase it failed, much like auto racing does with suspension components. Even if it fails catastrophically the part is unlikely to fly across the field.
Maybe you could have a tie point, from the actuator to the frame, that slowly (using friction) allows the mechanism to return to neutral. When you want to release some energy, you just place that apparatus (similar to a tape measure with the brakes on). That could slowly take the energy away. Otherwise, just place a pneumatic piston on, temporarily with the exit partially blocked, and that will resist the force!
For robot safety, I suggest some solenoid with a pull-pin, so the pull pin will be pulled with the robot enabled, and put back in upon disable!