Safety inspection regarding open wheel shooters?
 

After reading through threads here on Chief Delphi, our team (1569) is concerned about our open wheel shooter. What have been the difficulties regarding open wheel shooters, and which part of the wheels need to be covered to be considered safe?

I will also upload a photo of it tomorrow, or check out the video of our robot on YouTube.

Re: Safety inspection regarding open wheel shooters?
 

We had no issues with our open-wheeled shooter at FLR... But our wheels are solid rubber 6" Colsons. I can't speak for others with different wheels.

Re: Safety inspection regarding open wheel shooters?
 

I covered this from my Hub City experience in Al's annual inspection thread; see http://www.chiefdelphi.com/forums/sh...8&postcount=30 and http://www.chiefdelphi.com/forums/sh...5&postcount=32

Bottom line -- wheels got covered on every robot.

Re: Safety inspection regarding open wheel shooters?
 

Like many things, the answer is "it depends".

I'm sure I'll get to look at lots of unshielded shooter wheels in the next few days. My feeling on the subject is that any moving parts that extend outside of the mechanism such that they could catch clothing, hair, fingers, etc in the pits, or that could make contact with another robot or the field while on the field, will need to be enclosed. Obviously, you can't cover the part of the wheel where it makes contact with the disk, which hopefully is within the mechanism and is reasonably enclosed.

Again, "it depends" on the exact implementation of the mechanism in question and the opinion of the LRI at any particular event. I fully anticipate this being the "headache issue of the year" at Championship, and my advice would be to err on the side of caution and safety.

Re: Safety inspection regarding open wheel shooters?
 

We're getting materials together to put a quick shroud around our small wheeled shooter at Lone Star. Some ABS sheet and a plastic bending heater strip. I'm assured it'll take all of half an hour to cut, bend, and mount the plastic.

Re: Safety inspection regarding open wheel shooters?
 

No open wheeled shooters had to be covered at FLR (us included), from what I observed.

Re: Safety inspection regarding open wheel shooters?
 

Thank you, and these are the exact threads an posts I was referring to. We are planning to build a shield, just to be cautious, and adjust it as needed when we get to regionals. My final question, do the front of the wheels need to be covered, or just the side and tops?

Re: Safety inspection regarding open wheel shooters?
 

It would be great if FIRST would provide some guidance on this issue so that there is a uniform standard (as much as possible) at all competitions.

I will be inspecting in Seattle and Calgary, and while the Lead Inspector is the one who gets to make the final call, I'll certainly be looking for mechanisms to ensure that fingers, hair or other unexpected objects are not likely to come into contact with the wheel. Based on my experience in previous years, I expect to be able to reach agreement with most teams on what is reasonable. No one wants an unsafe robot.

One thing that I really liked was the plan for a team to bring ABS and a strip bender... perhaps teams that have the resources will set up a "shielding shop" to help less well-resourced teams improve their robot. Even 1/16" polycarb is likely enough to keep fingers out, and it can be cut and bent relatively easily if you've got access to the material and tools.

Jason

Re: Safety inspection regarding open wheel shooters?
 

That depended on the existing design. There were some bots that only had a tiny bit of wheel uncovered in the front; we left those alone. Others had huge percentages of a wheel exposed; those were covered. Unfortunately, it's an "it depends" situation.

This wasn't just an "in case the wheel starts disintegrating" thing. One team had a wheel from a baseball pitching machine. It was factory-balanced and rated for some unearthly number of rpms. It got a cover.

One of the mentors for a team I was inspecting verbalized a great thought test for this. Ask yourself: would you be comfortable with this spinning at full speed with you and the bot in a phone booth? Both he and I are old enough to remember such structures; others may need to use Wikipedia.

Re: Safety inspection regarding open wheel shooters?
 

I am going to agree with this whole-heartedly. Last year, there were very very few guards that I saw around any shooter wheels. We ran ours at 4,000 rpm, not much different that what we're running this year.

Yet this year (per the first post), some inspectors are enforcing that they must be guarded.

I understand full well the difficulty FIRST faces in attempting to write rules. However, in this case, we have polar opposites going on at regional competitions. That's confusing, and for a robot who is right on the edge weight wise can be extremely distressing. Please FIRST, put out a rules update stating that the outside of all shooter wheels must be covered. Bite the bullet and let everyone know now so they can plan.

Re: Safety inspection regarding open wheel shooters?
 

At my regionals, my default position will be to require covers over all shooter wheels. It is up to the team to convince me that the danger of caught fingers/hair/clothing is acceptable, and that the wheel won't suffer from sudden and catastrophic failure (for example, the rubber tire on most of these pneumatic wheels could easily stretch and come off at an unexpected angle during a match).

The best route to convince me will be a datasheet from the manufacturer that specifically lists an operating range that includes the speed your running the wheel at. Good luck finding that... even AndyMark's pneumatic wheel states "The design intent is to be contacting the ground, being driven by a gearbox at a maximum speed of approximately 500 rpm".

Given that statement, running the wheel at 10 times its intended speed, with variable and sudden loading on it from shooting, I WILL require appropriate safeguards placed around the wheel.

Re: Safety inspection regarding open wheel shooters?
 

This will probably tick off several people but I have two words concerning guarding: Common Sense
You have a wheel turning at 5000+ rpm in the pit and it self destructs or someone accidentally drops a tool in it or someone gets too close. Would you want to call someone's parents and explain how their child was injured because you didn't guard the wheel?
If this made someone angry, I apologize.
* puts on flame suit *

Re: Safety inspection regarding open wheel shooters?
 

Agree - this falls into two basic life rules -
1. "Consider the headline" if something goes wrong.
2. Don't stand in the plane of destruction.

Re: Safety inspection regarding open wheel shooters?
 

Trouble is wheel guarding is anything apparently anything but "common sense" True guarding would prevent any chance of being able to touch a wheel while it is moving. Sort of like an OSHA approved coupling guard. The guarding you need for protecting the wheel is a lot different than what you will need for when the wheel shatters.

Common sense would tell you to keep the pit area clear of any non essential people especially visitors. Guarding in the pits should include any mechanism capable of sudden movement, pinch points, etc. I think this would impact the overall goal of First if we went fully down this road.

I am not really arguing the need to properly guard rotating components. I do think there needs to be more published guidance from First & not left up the event's lead inspectors discretion.

PS I think this needs intelligent discussion without the need for flame suits. :)

Re: Safety inspection regarding open wheel shooters?
 

Here is a photo from Frank's blog of some "great robots" at BAE tournament practice day. Presumably they passed inspection.

Re: Safety inspection regarding open wheel shooters?
 

you are correct Gregor. We never had to put a shirld on ours. In fact we use to have a shield over it but took it off because there were more pinch points with the shield. If you just have a wheel then you are less likely to get hurt, if you have a shield over it you have 10X more pinch points. If you were to put your finger (please don't do this!) into the shooter wheel at full speed your finger is likely to just bounce away, maybe get scraped. you may get your finger turned around the wheel a few times (as long as you don't have something across the wheel stopping your finger). If you were to have a cover that has holes in it then if you were to put your finger in it your finger would get pinched and broken off (likely). If you were to put it in between the tread and outside of the guard you will get your finger pulling in and ripped off. I don't see how putting a guard on your shooter wheel will protect you at all. 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.

I don't see how putting a guard on can possibly make the shooter wheel safer... 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.

Re: Safety inspection regarding open wheel shooters?
 

Nobody even mentioned it to us as a possible concern at FLR. Then again, with solid rubber 6" Colson wheels on our shooter, the probability of their experiencing some kind of structural failure approaches zero.

Re: Safety inspection regarding open wheel shooters?
 

I don't know of any Hatboro Horsham robots that had to put on guards. We certainly did not.

I've Q&A'd a request for more guidance. (Not that I have overly high hopes) We're squeezing ounces, but we certainly want to be safe (and legal). A "finger guard" is doable if useful, but if LRIs feel that shatter guards are necessary, that could be some serious practice night rework (and weight). What is the guard intended to actually do, and how can it best do so while avoiding pinch points?

Re: Safety inspection regarding open wheel shooters?
 

We were never told it either, and we were running the new Nylon VEXPro Traction Wheels

Re: Safety inspection regarding open wheel shooters?
 

I would like to see an official response/Q&A from FIRST on this.

Re: Safety inspection regarding open wheel shooters?
 

The field isn't enclosed; that net would only stop a very big piece or something smaller by blind luck. There are plenty of people standing close enough to the field that they're in danger if something big kicks off the field.

No guard will make these wheels 100% safe; that's not the point. But if we prevent damage in even one case it's worth it, imo.

It would be best if the GDC had actually codified this from the beginning. They didn't, as we all know. It'd be good if they answer the Q&A, or if the LRIs come to a common agreement & publicize it. Hopefully that happens.

Re: Safety inspection regarding open wheel shooters?
 

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

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 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.

Re: Safety inspection regarding open wheel shooters?
 

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).

Re: Safety inspection regarding open wheel shooters?
 

@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...

Re: Safety inspection regarding open wheel shooters?
 

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

Re: Safety inspection regarding open wheel shooters?
 

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.

Re: Safety inspection regarding open wheel shooters?
 

Re: Safety inspection regarding open wheel shooters?
 

Re: Safety inspection regarding open wheel shooters?
 

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.

Re: Safety inspection regarding open wheel shooters?
 

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.

Re: Safety inspection regarding open wheel shooters?
 

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::

Re: Safety inspection regarding open wheel shooters?
 

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.

Re: Safety inspection regarding open wheel shooters?
 

Here is what Q&A has to say.

Re: Safety inspection regarding open wheel shooters?
 

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.

Re: Safety inspection regarding open wheel shooters?
 

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.

Re: Safety inspection regarding open wheel shooters?
 

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...

Re: Safety inspection regarding open wheel shooters?
 

GTR East is not requiring shooter covers.

Re: Safety inspection regarding open wheel shooters?
 

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

Re: Safety inspection regarding open wheel shooters?
 

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

Re: Safety inspection regarding open wheel shooters?
 

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.

Re: Safety inspection regarding open wheel shooters?
 

Yup.