Al's Annual Inspection Thread

OK,
Another year and another list. As we wind down to stop build in a few days, teams should be thinking about inspections coming up and should be performing a pre-bag inspection of their own.

  1. The inspection checklist and the BOM template are both located here…
    http://frc-manual.usfirst.org/
  2. As Q&A or Team Updates modify robot rules, the Checklist may also change to reflect the rules change.
  3. Stored Energy. Just about every robot will have some form of stored energy this year. To keep safety in mind at all times, springs will get an extra look by your inspectors. You may be asked to “dry fire” a shooting mechanism to check for the possibility of “destructive disassembly”. If you are using COTS springs, please think about adding some type of cable (aircraft cable preferred) to keep the parts together should the spring crack or fracture. If you are using surgical tubing or some other form of latex or rubber, please be sure to have the ends secure. Inspectors may ask Safety Advisers for assistance in determining the safety of these mechanisms.
  4. Bumpers. These are an issue every year and I am only mentioning them here so you can think about them. Bumpers do not need to be included in your bag with the robot. You do need them at competition and they will be required for practice rounds on the field. There has been a recent Team Update that allows you to use tape or other fasteners to affix the pool noodles to the “robust wood” to aid you in making pretty bumpers while you secure the fabric covering. Whatever method you choose, the intent is not to change the overall cross section of the pool noodle or compress it nor to add hard parts beyond the 1" dimension from the frame. Please refer to Fig. 4-8 for guidance.
  5. Pneumatics. As last year, you are allowed to use any 12 volt DC compressor that does not exceed 1.05 cfm. If your compressor is not a common type, please be ready to provide documentation to show it meets spec. A new compressor that has become available requires a stainless steel, woven hose ( provided and as stated in the manufacturer’s spec sheet) for operation. That has been ruled by the Q&A as part of the compressor and must be included. Reminder that pneumatics parts must be unmodified COTS devices rated for 125 psi working pressure.
    More to follow, good luck everyone.

Does this affect pneumatic-based catapults? If so, will we be required to run it through the Driver Station/program or would the manual overrides provided on the Solenoids be acceptable for showing a test fire?

Yes and we will ask you to dry fire using an powered and enabled robot in a protected area of the venue or a corner of the practice area if safe for others.

How does that work for all electric shooters? We have several shooter presets and a slow manual mode. Will/ could inspectors ask for us to dry fire all of them? Its powered by 6 cims so dry firing it could cause a problem.

Also if we instal a sensor to prevent dry firing (right now it just takes a button sequence) then will we be asked to bypass that sensor or will that exempt us from that test?

I’ll chime in here with my biggest concern: R8, specifically the “cause unsafe conditions” part. This year many, many teams will utilize springs or tubing to create a mechanism that can fire with a lot of power. The last thing we want to see is a team picking up their robot and the thing firing without warning, injuring a student when it hits them on top of the head or under the jaw (given the speed and power of these shooters, I wouldn’t be surprised if this caused a serious concussion or broke a jaw). Please, Please, Please design in some safety interlocks to make sure this doesn’t happen! A locking pin, or a carabiner that can keep the shooter from hitting someone carrying the robot is really all that’s needed.

Max,
Should an inspector request a dry fire, it is because the mechanism looks unusual or appears to impart a large energy transfer. We are concerned about that “destructive dis-assembly” mentioned above. Many of our inspectors have seen these types of mechanisms over the years, and our concern is first and foremost the safety of all participants and audience. The last thing we want is a mechanism coming apart and launching it’s kicker into the stands and injuring a grandmother or young child. We certainly feel a need to protect the field personnel. You don’t want to hurt a ref or judge do you?

Spontaneous Deconstruction can plague any type of shooter. Elastic or electric or pneumatic

Al:

This is our situation as well. Pneumatic shooter, ball sensing interlock (eg shooter doesn’t fire if the ball isn’t present.) If we need to disable the interlock, we would rather do this in a way that is consistent with the interlock being as fail-safe as possible.

We’ll certainly comply, but the ball (between it’s weight, as well as it’s air resistance) has a significant impact on the loads and speeds that the shooter sees when fired.

-Karlis

So true. There are now two clips that I will forever look at differently. (The other is the image of the Poofs singing “Call Me Maybe” to Karthik - always brings a smile whenever I hear that song being played.)

Karlis,
Your RI will figure it out when you are inspected.

I’m sorry, that’s unacceptable.

If there is a system in place to prevent dry firing is an inspector asking a team to bypass it a reasonable request? Should we anticipate it? Could you provide guidance under what circumstances this request may be made? (Being more specific than ‘at the discretion of your RI’ would be greatly appreciated) I am merely trying to understand the circumstances under which an inspector should ask a team to disable a safety mechanism which the team has deemed necessary given the behavior of their system.

I do not recall any such behavior in 2008 when more energy was stored.

Have you ever seen a fool-proof mechanism or sensor on a FIRST robot? I know I haven’t… It would take quite a bit for a team to convince me that whatever system they have in place to prevent a dry fire isn’t going to break at some point during the competition and allow the system to dry fire anyways. We’ve all seen some crazy stuff happen to a robot that no one expected…

If you don’t the ability to do stuff manually in your code, then you are setting yourself up for failure. What happens if a sensor goes out during a match…you still want to be able to function without the sensor.

So honestly, just figure it out and stop crying about it…

So what I think Al and Jon are saying is that you should (and RI’s will) assume the worst case that your robot will dry fire at some point unexpectedly regardless of your mechanisms designed to prevent that, because mechanism fail, especially when interactive with other bots.

If it only fires ‘safely’ with a ball loaded, then that is not good enough, and the robot is considered to be too unsafe for FRC standards, and it probably shouldn’t be good enough for your team’s standards due to the risk of serious injury.

Make sense?

That is not always the case. There are many times I’d prefer to not do something if a sensor goes out during a match than have manual control over it. I don’t want a motor over driving through a hard stop because an encoder went out and the motor was manually over driven. Better to lose one match than break something on the robot.

Also, no need to be rude about it.

I agree, there are no robots out there that are perfect.
You’re saying that inspectors need to make sure that when the robot malfunctions, it’s safe.

So, let’s look at another malfunction. If my robot were to try to fire a ball as the intake was stowed, I’d break my intake. Does the inspector need to watch me break my robot that way too?

However, dry firing my shooter will break it, but pose no safety hazard.

This whole test is a bit stupid. It’s kind of like asking teams to drop their robots from the top of the pyramid to make sure that when it falls, it isn’t dangerous.

Next thing you’ll be asking me to demonstrate that my gearbox properly constrains parts if I break my gears…

We’ll have a system in place to bypass any safety systems we end up with.

I’d hoped to clarify under what circumstances dry firing will be needed. I just don’t like being told “oh, it depends on how your inspector feels” because I’d like to think that all robots are inspected equally and fairly and an inspector can’t cause undue wear and tear on a mechanism/stress on a team merely because they feel like it.

The difference is that a robot on the pyramid has a large amount of potential energy that could end up directed as kinetic energy towards the ground (or maybe onto another robot), where a spring or winch on the robot stores a lot of potential energy that is many times directed upwards and at an angle, which could potentially go towards any number of volunteers, human players, or audience members.

No, not really. When my shooter dry fires, the lexan arms shatter in an enclosed area at the bottom of the robot. When we break the shooter, it’s safer than if it took an actual shot. Standing near an arm smashing itself into the bottom of our robot is way safer than having a 2 lb ball be thrown at you from a foot in front of the robot, and getting the shooter arm to hit you on your head.

I personally do not trust any sort of “software interlock” to prevent a dry fire of a robot mechanism. We all know that programmers are allowed to tinker with the code after inspection, and there is no sort of control in place to prevent the removal of a software interlock, either intentionally or accidentally.

I realize that the ball being present changes the physics of many shooters. However, it is my opinion that stored energy mechanisms should be designed to withstand the additional stresses of potentially being fired without the ball being present.

These are my opinions. You may not agree with them. However, be aware that I am the individual that presented this section of the rules during LRI training, and these are the opinions regarding this subject that were given during that presentation. There was discussion, but no disagreement on the subject. And I know all the Championship division LRI’s are in agreement on the subject.

If a sensor goes out and my default is to not allow firing how is that failure? If we determine that the potential risks of not being in a known good state are not worth the cost of losing a match I would say that is both OUR call to make and the proper call.

This isn’t my first rodeo, when designing a system that has potentially dangerous states I prefer to know exactly where things are and be sure that the system protects itself from damage and keeps itself from getting into states that could be dangerous. Dry firing the system is potentially dangerous due to the fact that it bypasses the regular firing procedure meaning any of a handful of other systems could be in the wrong configuration and could be damaged, destroyed, or cause other problems. There is a firing procedure for a reason. If the forks were to hit the intake neither system would likely be destroyed but it would present an unsafe condition for the humans that have to sort that crap out.

Asking for clarification isn’t “crying about it” it’s making sure we are adequately prepared for any known contingencies. It’s something engineers try to do. I will comply with any and all procedures that the LRI’s deem necessary to ensure safe operation of robots, I just want to know what they are and what the expectations on my team are.

I would assume you wouldn’t talk to one of your mentors as you have just done to me, I will ask you nicely once to change your tone. After that I will be contacting your team leaders to have a discussion about how your team is representing itself online.