This is exactly how my team is addressing this concern.
Ether,
If I listed all my concerns, too many electrons would have to die and I’d be getting hate mail from PETE, the ASPCE and a lot of angry scientists at CERN would have nothing to annihilate their positrons with…
You, as a mentor, must assume the first line of defense when it comes to safety. If you feel out of place doing this, I very, very strongly suggest that you seek out a veteran team in your area and ask for help.
Mike
Hi Mike,
I appreciate the humor :-), and I apologize for not being clear.
I wasn’t asking you to list all your concerns. Just to clarify your comment about “burden of proof for a safe design”, since what I mentioned IS what many “veteran” teams are doing.
~
Thanks for replying, Mike.
I guess the reason I posted is that the Bimba 20 in/sec recommendation has been floating around CD for over a week and I’m still seeing very experienced CD contributors pointing new teams toward designs that that seem to violate it. And as far as I know, it took my posting to get robot inspectors to weigh in with opinion.
If a ball is going 20 ft in the air then the likely speed is on the order of over 20 feet per second- (I have a Excel projectile spreadsheet that I found on the internet and modified. If I can get the permission from the original author, I will post it here.) The foot is traveling faster than the ball in the videos I’ve seen. I can approximate the travel distance ratio I’ve seen as maybe 6:1 at best.
I do want to do things safely and not get in arms race. The pneumatic piston for our kicker that my team was using was only traveling 16in/sec (measured with a 240 fps camera), but other team members saw video of low-profile robots that showing very long distance pneumatic kickers with elastic assist and wanted greater distance for our robot.
I would imagine that some teams will not have the initiative to contemplate computation of their piston speed based on their ball speed and their leverage, or to actually measure their piston speed. Both of those approaches to understanding piston speed are challenging to accomplish.
I’m not sure robot inspectors will be consistently equipped to make such an evaluation.
FIRST encourages novice teams to use pneumatics and did not choose to highlight this 20 in/second rule and its safety impact on kicker designs.
FIRST seemingly encourages use of surgical tubing for elastic energy storage.
As to your questions of could I look myself in the mirror if a child gets hurt…Yes, I could. If I let the concept of me having no relation to a child ever with any potential of getting hurt, I certainly wouldn’t ever drive a child anywhere. In fact, I would have never had children of my own or associate with children.
Question for you: have you ever exceeded the posted speed limit (by even one mile per hour) with a child in the car?
Life is not about risk avoidance, it’s supposed to be about competent risk management. We are teaching these kids that training wheels are important, but that sometimes removing the training wheels has a time and a place. It’s important that children are taught not only to follow rules but to know the relative danger of things. It’s important that they understand the difference between misusing a mechanism that will cause it to wear out too soon and misusing a mechanism in a manner that would substantially increase danger: personally, I do not know which category that exceeding the 20in/second falls under.
My intent is not that the pneumatic rules get bent…the intent of my posting was to encourage that they be enforced consistently so the arms race does not get out of hand. And I really do not understand how a leaky piston gasket could cause a significant safety concern. I would be much more concerned about kicker designs that are improperly using the end of the cylinder as the stop. (Even though there is not an explicit “rule” against such a thing).
I guess I would also suggest that elastics and springs and gravity need their own section of the robot rules. Something like: if it stores more than 50? lb-ft of energy, the design needs qualified parts that are rated for the stress.
I like robot inspectors- I think they are REALLY wonderful people that are put under totally unfair stress at the competitions and are not appreciated anywhere near enough. FIRST needs good inspectors- I thank you for your service.
For most teams, following the rules will insure a safe design. <R94> is a catch all rule when teams do anything that is questionable. It is their responsibility to prove that they are, indeed, safe. It should be self explanatory…
Think of it as a “design review” that any engineering design must pass before a product goes to manufacturing.
Please use common sense.
If you use a pneumatic cylinder part number 123 made by XYZ, you should have the design or test documentation to prove that it meets the rules.
If the inspector watches it operate and he is concerned that something might fail and, in so doing, cause drivers, referees, spectators, et al to be in jeopardy, he will ask you to prove your design is safe.
If you can not, he or she may require modification or removal of that device before you will be allowed to compete.
Mike
Amen to that.
~