Dangers of High Speed Pneumatic Gun

[boomergeek]

Originally Posted by Mike Betts

Dick,

The UL safety inspectors only hand out an award. The robot inspectors are the enforcement arm for this situation.

Most of us read CD regularly...

I'm going to refer you to this post I made.

Put yourself in our shoes. What would you do? Could you look yourself in the mirror if a student gets hurt?

What do you think?

Mike

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.