Safety inspection regarding open wheel shooters?

FIRST General Forum
#22

You’re joking, right? A guard with holes you can put a finger through is not a guard.

Another reason we took it off was because while testing our tread ripped off from the guard and jammed up the shooter wheel, which if I left the shooter turned on the motor could have possibly burned, and possibly started a fire.

Again, I hope you’re joking. If the guard hadn’t been there, that tread would have gone flying in an indeterminate direction. Wouldn’t you agree that a fried motor is preferable to an injured student?

The only thing it would help with is stopping tread from flying out, which while on the field won’t hit anyone because the field is enclosed.

The field netting is sized to stop frisbees, not nuts and bolts and chunks of wheel tread. Note that the robot is only running on the field for a few minutes at a time, while it’s likely to see hours of use in the pit where no such netting exists anyway.

#23

We have been very worried about this recently, especially since our shooter has many reasons for possibly needing one. Our shooter wheel is one of the KOP wheels from last year with some tread bolted to the outside. It’s a 90 degree angle shooter with no top and a rather large belt above it that powers the wheel from the CIM. Our wheel has spokes and sticks out about 1.5-2 inches out from the front of our shooter plate. Unfortunately, the shooter is in the bag with the robot and there are virtually no mounting points for a guard. Even if we could mount a guard, much of the shooter wheel would still have to be exposed. Would you not pass us through inspection because of this? (I ask this as we are currently working hard on a shooter guard, but I need to know if we should start going into to overtime).

#24

@Inspectors

What would your ruling be on this mechanism?

https://dl.dropbox.com/u/27736599/IMG_1263.JPG
https://dl.dropbox.com/u/27736599/IMG_1264.JPG

I get the feeling that I already know the answer, unfortunately…

#25

It’s hard to tell, exactly, from the photos what the rest of the mechanism looks like, but it does appear that you have high speed rotating equipment exposed. It also looks like it should be relatively easy to put a thin layer of polycarbonate around the exposed part of the wheels.

I’d also like to recast your final sentence… “fortunately it looks like it will be relatively easy to improve our shooter’s safety”. I know you don’t really consider it unfortunate that your robot should be as safe as reasonably possible.

And I think that’s what I’d be looking for… FRC robots are large, powerful machines. There is an inherent danger in working on and around devices such as these. It would be impossible to remove all risk from a shooter… I think what we all want to do is reduce the risk as much as possible. Having a needlessly dangerous machine is not particularly good engineering practice.

Jason

#26

So if a team has ran their wheel and shot roughly over 500 frisbees with mentors and students by a semi covered wheel (meaning that it can not fly off its motor shaft) then will it require sheilding. I understand the need for safety, but if it has been proven safe during testing then why would their be a need for a fully covered wheel? I understand the reason behind it, but I personally believe my robot to be safe even though it has an expossed opening. I wish first would set a rule update to R08 to set a standard on the issue.

#27

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#28

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#29

I’m sorry, but there’s no possible way for anyone to prove shooters are 100% safe. Any of these could occur when your shooter happens to be pointing towards the crowd or a volunteer next to the field:

  1. A bolt comes off another robot & falls into your shooter.
  2. The wheel decides to come apart due to the forces imparted on it by a frisbee.
  3. A student is feeding a frisbee into the shooter on the practice field at your event. Another robot is mis-aimed & fires a frisbee into the back of your student’s head, startling him or her. He or she flinches and puts fingers where they shouldn’t have been put.

You can come up with other scenarios, I’m sure. Although we can’t shield to prevent ALL possible problems, it behooves us to add shielding to limit the issues.

I agree with you; it’d be best if the rules gave us more specificity. Hopefully an update is coming.

#30

Unprotected/unshielded shooters, team balanced wheels, flying parts and injury to participants are a concern for everyone. This is currently in discussion as to how to proceed in the future. The LRI will make the decision based on direction from FRC HQ and your actual implementation of parts.

#31

My only other issue with this is that uncovered wheels last year did not come under as much scrutiny as this year even though the same rule is in place. Also many freak accidents can occur at a regional and I would like to caution teams to focus on proper safety measures when they are testing their robots. Teams should make sure that they have total control of their robots when they are on the practice field whether the robot is shooting, using pneumatics, or climbing. I would like to add to this that the new 888’s fans can draw blood quite easily. ::safety::

#32

In light of the current discussion, we took off the wheel & are using our tee shirt cannon. Not sure what the rules say about sticking the barrel up the feeder.

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#33

Here is what Q&A has to say.

Q. Would FIRST be willing to publish further guidance on the guard/protection requirements for open-wheeled shooters, in order to help teams operate safely and prepare for smooth and consistent inspection processes?
FRC1640 on 2013-03-05 | 4 Followers
A. Due to the large number of design parameters which affect the safety of a particular ROBOT MECHANISM it is not possible to provide absolute guidelines regarding compliance with [R08]. When considering MECHANISM safety, teams are advised to consider factors such as velocity, exposure, and material ratings. The Lead Robot Inspector at each event has final authority on any ROBOT’S compliance with [R08].

#34

We just completed the Central Valley Regional in Medara, CA. Upon arrival there was a lot of concern from Inspection. But as we talked further, the biggest concern was regarding those Robots with riveted on threads that could have a rivet or rivets fail and fly off the Robot. They were also looking for Robots that had balanced their Shooter Wheels. This was a plus with Inspectors. We did balance our wheels. Our Team did not bring material to make a cover. So, we were at the mercy of Inspection. But after further review they passed our Robot. I suspect this issue is not dead and when we go to the Silicon Valley Regional, in San Jose, Ca we will “face the music” again. Our Shooter is a two Wheel Linear Shooter with two Pneumatic Wheels.

#35

I’d be surprised if anyone questioned 1551’s shooter wheels. We chose 6" x 2" solid rubber Colson wheels for two reasons, and one of them was that the chances of their causing harm to a person (who didn’t try to, like, lick them at speed or something) was vanishingly small.

#36

Do they have a recommended maximum RPM? When I looked at Colsons all I saw was generally cart or caster applications usually implying walking speeds. If I had no choice other than to be hit by a wheel coming apart, I would much prefer a hollow pneumatic wheel to a chunk off of a solid rubber wheel…

#37

GTR East is not requiring shooter covers.

#38

Not that I could find. In-house testing shows basically zero deformation at shooter speeds, though.

#39

In-house testing shows basically zero deformation at shooter speeds, though.

How are you measuring them while they’re spinning at probably several thousand RPM?

#40

Measuring the deformation at speed is relatively easy in qualitative terms. Place a fixed reference point close to the wheel, but where it will not touch when the wheel is at speed, an visually observe the deformation. Like truing a bicycle wheel. If the wheel always returns to the same size when stopped, you are in the elastic region of deformation. The pneumatic wheel’s change of shape is not a good indicator of it being safer or less safe than other wheels. It is really just telling you it is not as stiff as other choices.

#41

Yup.