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Originally Posted by zrop
Haha. It just looks like I got close, but really, i grabbed it about a foot in front of the props. And as for the cage, we didn't have the mounting brackets completed at the time of testing... and we were anxious.  |
Wow, one foot! That's a safe distance. Two weeks ago in response to safety concerns you said:
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Yeah I agree with what you said. We just rushed to mount the prototype in order to disprove any skepticism our team had. So inevitably, safety was the first thing that was overlooked... Atleast everyone wore safety glasses...
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After the safety advice you received over the last two weeks ago, you're now educated enough to make the following comments
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....Alrighty.. We'll take care of it. We really posted this here for more the propulsion design rather than safety concerns.
....And for those safety nazis -- why yes we do have a safety cage for it
...safety cage we are going to use is designed to keep balls outs rather than keeping blade shrapnel in.
...The propellers are perfectly safe as long as they don't exceed their maximum rpm, the rate at which we are spinning them is no where near their maximum rpm (the maximum is about 13k rpm). Having them spontaneously exploding is not a huge concern to us, having balls getting in the way of the props is a much bigger concern. (oh and its 12.25 in in diameter btw ;D)
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...Who is dumb enough to stick their fingers in there?? Plus the props are far enough inside the cage that even if you can get your fingers in, they wouldn't touch the props.
...How about we put safety whistles behind the props so everyone can hear when they're on and uh.. think?
...PLUS who's running around the field trying to catch a robot by sticking their fingers into the cage with spinning blades???
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It's pretty obvious that you guys are a team of know-it-all invulnerable teenagers without adult supervision, never mind engineering mentors. Many people have tried to point out the safety issues and like all Darwin candidates you smugly dismiss them with flippant comments.
I don't expect that you will change your ways and since children, drunks, and idiots are often protected by providence I expect you'll survive without incident. I also expect that if you show up with anything like your present wire cage, you'll be promptly thrown out of the pits.
But you do provide a service that draws useful advice that less arrogant individuals may use to reduce the risk that their machines pose to themselves and any onlookers. By the way, here's one example of what can go wrong:
http://www.youtube.com/watch?v=hmcTyBxSL00
The R/C hobby has a pretty good safety record over the years, although it is not been free of de-capitations and other fatalities and many serious injuries. There are no perfectly safe propellers and no perfectly safe anything for that matter. It's a matter of understanding risks and reducing them to acceptable levels. Mostly, this happens by eliminating "UNNECESSARY" risk and you guys are a shining example of those.
Every decade or so, something changes (like mass, blade dia, rpm's, etc) and accidents skyrocket until best practices change.
Do the math. The risk potential comes from the velocity and energy of the parts when they fail and fly. Yes, the propeller arc and thrust line are the most dangerous in the open, but the blades can bounce off obstructions and continue in any direction. Vibrations and flutter can cause rapid failures. A foreign object sucked into the airstream can damage the prop or cause an immediate blade failure, especially if it impacts near the tips. Given this years robot collisions, failure modes not encountered in R/C flying can be expected. Anything short of full containment just isn't going to cut it.
Few of those who loose fingers or suffer other serious injuries intended to do so.
FIRST has a safety culture for very good and valid reasons. If you are unwilling to accept that culture and consider those looking out for your safety and that of the public to be Nazi's, then you are of no benefit to the FIRST program.