My team is planning on doing west cost drive this year. Does the wheel and shaft behind the bumper count as robot frame? It is my understanding that R410 is not explicitly saying the bumpers are mounted to the robot every 8 inches but has something behind them every 8 inches.
2 Likes
A very small fiberglass rod can also work instead of a full tube, or even a tensioned string.
You’ll probably have to run it up to the event LRI, but “structure/frame” can mean a lot of things depending on your design philosophy 
4 Likes
Please don’t. You’ll have issues with your LRI is you try to layer this and not put something structural to support your bumpers.
3 Likes
Structural bumpers and brackets seem to do fine 
To boot, they’re incentivised by how the robot and bumper weight rules work.
If the GDC wants a piece of metal of a certain size, or a specified deflection limit, they can ask for it. As written, a small rod or related is acceptable and has been implemented several time since the creation of the rule.
2 Likes
Perhaps, but I’ve also see teams get upset at champs when @Al_Skierkiewicz told them their supports weren’t structural and they needed to make a change. Why take the risk?
3 Likes
Flexible components are specifically disallowed as structure. Don’t make your inspection a pain over a few ounces. We have used both the constructions nuclearnerd suggested and they both work.
Here is a picture of the side of our 2022 bot. We used the gearbox as a bumper “support”. It didn’t touch but was closer than a 1/4 inch. Didn’t have any problems with inspection but if your bumpers don’t look or feel well attached/supported they will look closer and tell you to fix it. You want inspection to go as smooth as possible.
2 Likes
Please be sure to also read the blue box associated with R410 for clarification on the intent of structure/frame.
Also, R101 specifies that the FRAME PERIMETER must be fixed and not articulated. Wheels and axles would not be considered “fixed” but would be articulated.
Not to be that guy, but…
Aluminum box tubing is flexible in the same way as “thin plastic” or a fiberglass rod or etc. It will deflect less for the same force applied, but that limit isn’t specified anywhere. How thin is thin plastic? one person may say a plastic bag, another will say 3/16" polycarbonate sheet.
I’m not necessarily advocating going out of one’s way to push the rule here, but it can and has been “bent” when necessary to cut weight.
Robot weights too much? Make giant aluminum corner brackets that “minimize the likelihood of breakage on impact” while staying within the bumper weight allowance, then replace those box tubing side rails with a lightweight rod. Stated intent is satisfied, but somehow that’s incorrect?
This has been an issue since like 2014 (2013?) and seemingly no effort has been made to clarify or supplement other than “you should know what our actual intent is”. Possibly because the intent is apparently “bumpers should deflect a little but not too much when I push on them”.
8 Likes
I think the intent is something like:
“3/4 inch thick plywood will crack if deflected more than 1/4 inch over a greater than 8” unsupported span".
How stiff/strong should the supports be every 8 inches? We don’t need to go all the way to structural calculations. If I were a ref I’d want the supports to be stronger than the plywood which it’s trying to stop from bending.
This is one of my pet peeves of the WCD. Vendors show you plenty of photos of cool-looking drives, all of which are illegal because of this rule. See, for example:
5 Likes
This right here has to be one of the more elegant solutions to that rule. Leaves absolutely no question, and gives plenty of mounting surface for lots of things.
3 Likes
I get upset when “Refs” infer what they think the robot rules mean. I agree with the above post. This is not new. This has been an issue for over a decade and FIRST has made ZERO attempts to clarify this for over 10 years which means it has not been a problem. I also agree that you don’t want to look for problems, but if there is something touching touching the bumper in the requested spans then that’s it. FIRST needs to be far more specific with bumper support if that want to fairly enforce what counts as support.
Refs wear Black and White Stripes or Yellow and Black collared shirts if they are in command of the other Refs.
Refs do not care how your bumpers are mounted, refs only care that they stay in place. Refs care if you break rules in a match.
Inspectors wear bright yellow hats, and sometimes black vests.
Inspectors care about how your bumpers are mounted, and will advise you if they are worried they won’t stay in place. Inspectors don’t care what your robot does in an actual match.
Referees, Inspectors and Judges are all different, do different things, and are handedly color coded. Please lets try to use the proper name for the proper job so we do not confuse new members to the community.
16 Likes
It’s healthy weight that’s down low anyway. I will not fault a team for making something that has mass down low.
2 Likes
Skip to about 8:30 in this video and you can see a few different ways we have handled this in the past. You can do the closed wheel well easily as pictured above by other teams or you can run angle/tubing across if you wish to open up the wheel well.
We also did this last year from our build season thread to upgrade the design and this worked wonders for us. We did not even add the stiffening brackets shown by the end but if you wanted to get those, they are simply off the shelf tube plugs and gussets for the whole system.
1 Like
It’s why I quoted the word “Ref”. I didn’t think it was important enough to post about because often times FIRST is very confusing with their terms. Why is the HYBRID station on the floor this year? What is it a hybrid of?
it’s a hybrid of a CONE NODE and a CUBE NODE- as in you can score either game piece in it, while all the other NODES are game piece specific.
1 Like
I have to disagree here, the rules are not ambiguous and in fact are very specific. 8" max unsupported as per the rules (R410) and pictures shown above. As to WCD, WildStang has used it in the past and we add structure between the wheels to satisfy the rule ( as shown above in the second drawing by nuclearnerd). I am not a fan of the structure that is at the top limit of the bumper as it allows the bumper to rotate during collisions and damage the drive wheels. Flexible material like a piece of lexan or a simple aluminum bracket do not satisfy the R410, “BUMPERS must be supported by the structure/frame of the ROBOT (see Figure 9-9)”.
Above all, your inspection team wants to see you play every match you can. We desperately want to insure your team has a good event and that means having a working robot. Your LRI has years of experience watching and inspecting robots, use them as an asset.
7 Likes