R21-G Clarification (Bumper Mounting Question)

[EV4300]

In section R21-G of the manual, it's stated that a 'robust' connection is necessary between the robot and the bumpers. While a few examples of what is not secure are given, our team wasn't sure whether a standing idea can remain sensible. The question is: is it possible for 3-D printed 'brackets', which secure 'plates' of acrylic with bolts and nuts, which then secure the bumpers (again) with bolt and nuts, to pass through that check? It's essentially:

' ' '
=====
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Where ' represent brackets mounted to the frame supporting our tread, = represents the acrylic plate mounted upon the brackets, and / represents the bumper then mounted upon the plate.

[rsisk]

Really hard to determine from your description but here are some things you can do to determine robustness for yourself.

1. Pick the robot up by the bumpers. Does the connection hold? Then it's probably robust.

2. Kick the bumper as hard as you can several times in several places. Does the connection hold? Then it's probably robust.

3. Drive the robot into a wall at full speed. Did the connection hold? Then it is probably robust.

Okay, well maybe #3 is not practical, but those are the kind of forces you will experience on the field and wouldn't you rather have your bumpers fail in your controlled situation than have them fall off on the field and have your robot disabled?

[orangemoore]

I would suggest using polycarbonate instead of acrylic as a first step. I would bet most inspectors would have a problem with that material.

I'm not sure about the rest of your plan. But I sounds like it could end up being very robust.

[Daniel_LaFleur]

Originally Posted by EV4300

In section R21-G of the manual, it's stated that a 'robust' connection is necessary between the robot and the bumpers. While a few examples of what is not secure are given, our team wasn't sure whether a standing idea can remain sensible. The question is: is it possible for 3-D printed 'brackets', which secure 'plates' of acrylic with bolts and nuts, which then secure the bumpers (again) with bolt and nuts, to pass through that check? It's essentially:

' ' '
=====
/////

Where ' represent brackets mounted to the frame supporting our tread, = represents the acrylic plate mounted upon the brackets, and / represents the bumper then mounted upon the plate.

1> Without seeing the design (and material) of the 3-d printed brackets, we cannot answer if that is robust or not.
2> Acrylic typically is brittle. I would consider ABS or Delrin.

The true test will be on the field. Do you believe that the bumpers will not fall off during the match? Do you have enough faith in that design to risk taking the penalty/disablement should it fail? Those 2 questions should answer your question.

[Richard Wallace]

I recommend posting a clearer sketch that shows more details of your robot's FRAME PERIMETER and how the BUMPER attachment system you have in mind will connect those two.*

To pass inspection, your system will need to satisfy all the rules given in section 4.7 of the Manual. You should review all the rules in that section. Pay close attention to R21 subsection G, and to R26.
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* Note the Glossary definitions of terms shown in all capital letters.

[dmorewood]

Basically what the safety inspectors do to inspect your bumps is they grab one end and try to shake them and they're looking for vertical or horizontal movement. If you can prove your plates don't shift and wiggle to much then your fine.

[EV4300]

Thank you all for the advice.
I'm gathering a clear sketch right now (I'd rather hand-draw something and scan it), but thanks to your advice our team is now considering a sturdier-yet-simpler metal mounting frame.

[GeeTwo]

Originally Posted by dmorewood

Basically what the safety inspectors do to inspect your bumps is they grab one end and try to shake them and they're looking for vertical or horizontal movement. If you can prove your plates don't shift and wiggle to much then your fine.

Sounds just like checking that a load is properly secured to a roof rack. If you pull back and forth on the load and the load moves relative to the car, start over. If the car moves on its springs, drive it a couple of miles and check again.

With FRC bumpers, I would recommend ramming a brick wall a couple of times, both head on and at an angle. Better to break it at home when you have a few days or at least hours to fix it than at competition when you have minutes.