Re: Al's Annual Inspection Thread
 

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.

Re: Al's Annual Inspection Thread
 

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.

Re: Al's Annual Inspection Thread
 

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.

Re: Al's Annual Inspection Thread
 

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.

Re: Al's Annual Inspection Thread
 

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.

Re: Al's Annual Inspection Thread
 

If it is obvious that when your shooter self destructs that all shrapnel will be contained safely inside the robot, then it would not be necessary to dry-fire the mechanism. The safety concern is with a robot where the mechanism is not contained in such a manner and the possibility exists that it could throw parts outside the field border into an area where people are present. Or throw parts into an adjacent pit. I would consider a robot that was designed to contain all parts in the event of a failure to be consistent with the desired intent, and would commend the team on the design.

Unfortunately, however, not all robots fall into that category yet. I eagerly look forward to that day.

Re: Al's Annual Inspection Thread
 

Here's my thoughts and response, but I suspect Al will chime in as well...

There are some safety issues that can only be minimized to a point based on the game design requirements. Exposed spinning shooter wheels at output orifice (2012,2013), launched frisbees, etc. This year's game piece is harmful when launched at close range to a person also (though probably likely to cause less injury than from a frisbee.)

So the fact that live firing is unsafe has no bearing on issues associated with the safety of dry firing. The point is to maximize safety to the extent that it can be reasonably maximized. And the threshold FRC has chosen is that dry firing should not result in parts breaking off at high speed. If dry firing is shattering lexan parts, that may not be safe enough, since projectiles and parts flailing at high speed in directions they are not designed to go is the concern here.

Re: Al's Annual Inspection Thread
 

Thus, can we expect all stored energy launchers will be expected to demonstrate a dry fire as part of the initial inspection and any subsequent re-inspections?

Re: Al's Annual Inspection Thread
 

Thanks for the response. I do understand the point of the rule, as some systems may fail more catastrophically than others.

EDIT: Just to clarify, when we dry fire, the shooter arm goes > 180 degrees into the bottom of the robot where the lexan on the arms shatters. None of the lexan leaves the robot.

Re: Al's Annual Inspection Thread
 

And if that's the case, I would fully expect you could explain it to the inspector (and possibly go through a low-energy/slow motion demo to show where the stress will occur without actually breaking your arm) and get agreement that dry firing is safe without requiring full test. I'm not saying we'll require every robot to dry fire... It's a judgement call on safety when a dry fire does happen. If I think the results of a dry fire will be bad (like launching the head of a 30lb sledge hammer into the crowd), then I'm going to arrange for a safe dry fire to see how the system holds up, even if there's a sensor the team swears won't let it dry fire. If a dry fire will result in a situation that's safe for those in the stands and next to the field, then I won't have a need to ask for a dry fire test.

Re: Al's Annual Inspection Thread
 

I don't believe anyone restricted this to only software interlocks.

For instance, two limit switches in series (which require contact from the ball to close), and connected in series with one of the leads for the solenoid would be robust, and not open to software override.

-Karlis

Re: Al's Annual Inspection Thread
 

And would be illegal per R53:
Note that R64 mentions the solenoid breakout as part of the control system.

Re: Al's Annual Inspection Thread
 

Custom circuits (which your switches are considered) can't alter solenoid pathways, so your system is illegal on non safety grounds.

Re: Al's Annual Inspection Thread
 

It would probably be an effective system, but it would violate the robot rules. Custom circuits may not affect the power pathways to robot actuators. The only "hardware interlocks" permitted on an FRC robot are limit switches connected to the Jaguar switch inputs.

Re: Al's Annual Inspection Thread
 

No. You can expect any stored energy launcher that, upon review by the LRI, appears to present a risk of catastrophic failure resulting in parts leaving the robot, to probably be dry fired in a safe area. If the robot design is such so that risk does not appear to be present (mechanism is contained, mechanism is significantly robust) then it is reasonable to expect that a dry fire will not be necessary. If a shooter is modified and the modifications appear to possibly affect the structural integrity of the mechanism, then a possible demonstration during a re-inspection is possible. If you worked on some other part of the robot we are not going to re-inspect the shooter each time.

Rule R8 requires that robots not "be unsafe" or "cause an unsafe condition". The burden is on teams to be able to show compliance with the rule. I would welcome teams to provide written analysis that shows that the energy present in the mechanism is not sufficient to cause the materials used to exceed their yield strength, with sufficient margin, in lieu of physical demonstration of the mechanism.

Please keep in mind that if something goes wrong with a robot that we did not verify was safe, and parts go flying into the crowd, that in today's litigious environment, the lawyer's are going to sue everyone they can, including the robot inspectors that said it was safe.

The inspectors are not "out to break your robot". We want everyone to play with a fully functioning robot. But we are also responsible for making sure everyone goes home in the same condition they came in.