For those who are skeptical about propellers - Team 2526

[MrForbes]

There's a rule about the wheels being perpendicular to the floor...I don't know about any rule saying they can't steer.

[DarkFlame145]

I know they will work, I'm just a little frightened by them on a robot =P

[zrop]

Originally Posted by EricH

The inspectors will be looking for both. One piece of prop shrapnel gets through, and <S01> is probably going to be called. Then you have to remove both.

Let's say those are 9" blades going at 7000 RPM. That's C=pi*d=pi*9=28.26" per revolution. That's about a 2' circumference (rounded down to emphasize the need for protection here). So, the tips of that prop are traveling at 7000RPM=116.7RPS over a 2' circle. That's a tangential speed of 233.3 feet per second--or about 4 FRC fields in one second. If a tip breaks off at that speed, you WILL get a safety violation if it leaves the robot! And, if I were the head ref, I'd make you either remove the props or add protection to the cage. Play it safe and add material now.

Edit: I just saw this: http://www.chiefdelphi.com/forums/sh...049#post812049
I would consider this, or something similar, much safer than your current setup.

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)

[Akash Rastogi]

I'm taking Eric's word on this one.

I highly doubt that the inspectors will give a crap ( or too much) about the safety of the precious orbit balls.

I say that if a finger or even a hand can pass through the cage, then it is not safe.

+$0.02

[zrop]

Originally Posted by Akash Rastogi

I'm taking Eric's word on this one.

I highly doubt that the inspectors will give a crap ( or too much) about the safety of the precious orbit balls.

I say that if a finger or even a hand can pass through the cage, then it is not safe.

+$0.02

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.

PLUS who's running around the field trying to catch a robot by sticking their fingers into the cage with spinning blades???

[synth3tk]

Originally Posted by zrop

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.

PLUS who's running around the field trying to catch a robot by sticking their fingers into the cage with spinning blades???

Pit area? Although safety should always be first, sometimes mistakes are made.

[zrop]

Originally Posted by synth3tk

Pit area? Although safety should always be first, sometimes mistakes are made.

How about we put safety whistles behind the props so everyone can hear when they're on and uh.. think?

[synth3tk]

Originally Posted by zrop

How about we put safety whistles behind the props so everyone can hear when they're on and uh.. think?

Even if I wasn't safety captain for my team two years in a row, I would still like to think that safe practices are of the utmost importance in every FIRST member's mind during the season. While this isn't as deep as thousands of people dying, you still need to take some caution in the real world, and all the FRC is doing is preparing you to make safety second nature.

Afterall, we don't want this:
http://www.chiefdelphi.com/forums/sh...ad.php?t=65978

or this:
http://www.chiefdelphi.com/forums/sh...ad.php?t=59436

to sound like something that might happen as a result of your team's machine. I take safety seriously, and hope that everyone else does too. If not, you need to sit back, forget drilling another hole, and think about that.

[Akash Rastogi]

Originally Posted by zrop

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.

PLUS who's running around the field trying to catch a robot by sticking their fingers into the cage with spinning blades???

Who's dumb enough to accidentally turn on a robot when someone is working on the blades???

Who's dumb enough to move the wheels when someone is fixing a sprocket on the drive train?????


I can make lots of question marks too. You can get as defensive as you want about your robot design itself, but when it comes to the safety of others don't take suggestions lightly.

If you're not in it for the safety and well being of your members and others in the pit, that's fine by me.

[keehun]

Originally Posted by Akash Rastogi

Who's dumb enough to accidentally turn on a robot when someone is working on the blades???

Who's dumb enough to move the wheels when someone is fixing a sprocket on the drive train?????

Be aware, one of our mentors this build season was helping with the chains when the driver asked for "Is everything clear?" and a guy said out loud "CLEAR!" He was clear himself but not the mentors. Of course, guy behind the joystick was smart enough not to move the chains, but had the driver guy just looked down to check the voltage and move the chains at the same time, who knows if we'll still be in build season.

The guy who yelled our clear is mentally impaired and is in the special ed program. We can't quite "exclude" people so he's part of us, but it's hard dealing with having a safe season and excluding people who can not be safe. We have those "liability" forms for the school but they won't save anyone's fingers or hands.

[zrop]

Originally Posted by keehun

Be aware, one of our mentors this build season was helping with the chains when the driver asked for "Is everything clear?" and a guy said out loud "CLEAR!" He was clear himself but not the mentors. Of course, guy behind the joystick was smart enough not to move the chains, but had the driver guy just looked down to check the voltage and move the chains at the same time, who knows if we'll still be in build season.

The guy who yelled our clear is mentally impaired and is in the special ed program. We can't quite "exclude" people so he's part of us, but it's hard dealing with having a safe season and excluding people who can not be safe. We have those "liability" forms for the school but they won't save anyone's fingers or hands.

Oh what I love even more is how "No!" sounds very close to "Go!". We've already experienced a problem with that.

I think the formal testing terms are now "Red light", "green light". ;D

[TotalChaos]

Originally Posted by zrop

Who is dumb enough to stick their fingers in there??

I have to agree with Akash and Eric. I wouldn't just assume that common sense will prevent all accidents. Why do you think they put "HOT" warning labels on coffee cups? Or warnings on electrical things, such as hair dryers, not to submerge in water? ... Sometimes things can happen, and there's no reason not to play it safe...

Other than that, very cool propulsion system! I was one of those skeptical about using fans, but it turns out I was wrong and they work great after all!

Good luck at the competition!

- Austin

[KGood]

Originally Posted by Akash Rastogi

I'm taking Eric's word on this one.

I highly doubt that the inspectors will give a crap ( or too much) about the safety of the precious orbit balls.

I say that if a finger or even a hand can pass through the cage, then it is not safe.

+$0.02

Not just breaking and having shrapnel in the field, but if something flies into the stands it's going to be trouble.

[synth3tk]

Just a reminder of how important safety is:
http://chiefdelphi.com/forums/showth...540#post815540

[Russ Beavis]

To any teams that will be using propellers on their robot, be prepared for serious scrutiny from your robot inspectors. I'm still developing the inspector training materials for this particular design element and I'm leaning towards placing a lot of the burden of safety verification on the teams.

Be prepared to defend your design. I would strongly encourage you to bring a "standard finger" to demonstrate general protection.

I would strongly encourage you to calculate the amount of energy stored in your propeller(s) at max speed and determine whether that energy is sufficient to punch through your enclosure. For example, how much energy is required to "rip" a steel wire of diameter X? Maybe you can find such destructive limits on online materials databases.

Bring plenty of documentation to support your design.

Good Luck and BE SAFE!
Russ Beavis
Chief Inspector