So I have been seeing a lot of people posting pics of robots with unshielded chains and sprockets, and getting comments back about those robots having possible issues during inspection. This has cause me to question our design. The image attached is our only close up of the arm before it shipped. Basically there are 3 sections each have pulleys on either end. The steel cable seen in the picture is fastened at a fixed position on the pulleys. This allows the upper sections to move as the bottom section moves. My question is does anyone see any reason this won’t pass inspection. I have read through the rules and havent seen anything that says that guards must be put on cables and chains but then I have seen a lot of discussion around this.
Any comments would help a lot. Especially from inspectors! (if you are an inspection please put that in your post)
Shielding is not necessarily required by the rules, but when there’s a risk that, say, a finger gets stuck, the safety rules do require shielding or other mitigation(<R04>, if you look in the blue box).
However, for the design in question, I don’t think that sort of shielding will be necessary. It’s steel cable, it’s close in to the arm, I don’t think there will be too much of a problem unless something breaks.
The other factor, and the prime reason for shielding when the rules don’t require it, is that other robots will get tangled in a device’s chain and cable run. If done intentionally by either team involved, it’s illegal–but accidentally, the rules are a little more lenient, and accidents do happen.
As an inspector (well, not this year–I won’t be attending any events this year), I don’t see any reason that you wouldn’t pass inspection. However, depending on exact geometry of both your robot and the tube-grabbers on the ends of arms of the other robots at your event, I might suggest putting some light shielding on–what and how is up to you.
I doubt that this would be a problem. I’ve built a forklift mechanism which was driven by a steel cable and a large spool pulley and it was never questioned while going through inspection. Additionally, my team last year, used a winch and steel cable to hang from the bar and it was not an issue. I’ve only seen problems with pinch points if they pose a direct risk to persons who are servicing the machine. Consider the kit drivetrain, it includes many exposed sprockets and the chain running between them, but it is something that FIRST, in the fashion of supplying you with it and assembly instructions, deems safe. It is relatively contained inside of the robot and standard procedure dictates that the robot should be powered off before any work is done on it.
As far as having other sprockets, belts, pulleys, or chains running about the robot, be smart. If the sprocket poses an obvious risk to other machines and the field, you’ll need to put shielding on it. I’ve been surprised by some of the machines that have been allowed through inspection in past years, but I suppose there was a good reason for allowing the mechanism to pass.
For your machine, I wouldn’t worry about it. Its minimal exposed cable and everything else safely contained. The chance of something being caught and pinched in the mechanism are very slim.
It looks like you’ve got plenty of shielding there already; we have a somewhat similar design at our arm’s first point of articulation, and we don’t even have the cable channels that you guys have got.
I am inspecting at the SBPLI Regional this year and have been for the past few years. If I were inspecting you at a Regional I would have no issues with that area of your robot.
Of course, I cannot comment on what the inspectors at the event you’re attending will want. As they say “Your mileage may vary…”
