Is this legal? Sorry about the quality by the way, I draw faster by hand then in paint :rolleyes:
The bumper goes inside the c-brackets, which are mounted on a piece of the kit frame. This is what’s currently on our robot, and it takes a bit of work to get big c-channel, so we’d like it to stay if possible.
However, I’m worried that it wouldn’t be considered “Robust” by the inspection officers, but I’m not sure. What do you think?
I’m not completely sure, but I think the bumpers will slide into the c-brackets and be pinned/bolted in place. What worries me more is whether or not the “kitbot” chassis bar is wide enough (up and down) to be considered robust. It feels robust, but even I admit that it looks kinda wimpy :rolleyes:
And I’d like to show a picture, but it’s kinda secretive…plus I don’t have a picture.
I don’t think so, namely because the c brackets may be called part of the frame, or because the connection will not be robust. Here’s a suggestion that has no gray area (It’s what we’re using on our robot):
Hope that helps.
(Ignore what I said before)
What exactly are the inserts to be used for? The c-bracket part of the frame is liable to change to fit rules. It’s the other part, the part the c-brackets are mounted on that worries me. Thanks for the suggestion though.
You would put the inserts into the plywood and put a bolt in through the opposite side. This gives you the ability to remove the bumpers simply by removing a few bolts.
Oh! That is a good idea, thanks. But what do you think about using the kit-bot frame as a holder for the bumpers? Is it strong enough?
Hay when you attach your bumpers to the robot, do you have to use the bolts like in Figure 8-1 in the rule book?
The specific wording is found in <R07-I>:
I. BUMPERS must attach to the FRAME PERIMETER of the ROBOT with a rigid fastening system to form a tight, robust connection to the main structure/frame (e.g. not attached with Velcro). The attachment system must be designed to withstand vigorous game play – nut and bolt fasteners are recommended. All removable fasteners (e.g. bolts, locking pins, pip-pins, etc.) will be considered part of the BUMPERS.
It is hard for me to make a decision on the drawing alone. The first thing I would question is whether this design allows for the 1" limit for hard parts in the bumper here…
N. “Hard” parts of the BUMPER (i.e. plywood backing, fastening system, and clamping angles) may extend up to a maximum of one inch beyond the FRAME PERIMETER. “Soft” parts of the BUMPERS (i.e. pool noodles and cloth covering) may extend up to 3½ inches beyond the FRAME PERIMETER.
The second would be the method of attachment as it applies here…
I. BUMPERS must attach to the FRAME PERIMETER of the ROBOT with a rigid fastening system to form a tight, robust connection to the main structure/frame (e.g. not attached with Velcro). The attachment system must be designed to withstand vigorous game play – nut and bolt fasteners are recommended. All removable fasteners (e.g. bolts, locking pins, pip-pins, etc.) will be considered part of the BUMPERS.
The third would be to check that the support structure is in fact entirely within the bumper zone.
And finally a quick check of the various Team Updates and Q&A responses pertaining to sizing, FRAME PERIMETER, and frame structure.
I am not sure that your design would pass the test on all of these.
Thanks for all the help everyone! Out of concern for the legality of our bumper system, we’ve decided to update our “bumper frame” per se to full sized c-channel. We’ll ensure we follow all the other rules as well. Thanks for the help, and good luck in these last couple of weeks!
Brock,
The C channel in the drawing link above is an issue with attachment and hard parts. A full length channel still has me concerned. Please read the bumper rule section completely.
Thanks. I’ll read the bumper rules carefully to make sure we don’t violate the hard parts and attachment rules. I feel like this awful picture isn’t exactly communication the idea correctly, so we’ll see. We’ll post the full robot next week, so there will be actual pictures.
We were planning on doing something similar with our bumpers, and having seen this we’re carefully considering the rules again, which led to a few questions from our handy local inspector 
First, a picture of our idea, as accurate as we can be with pictures is attached, showing both a side view and a top view. now, a description:
We use C channel that is slightly larger than the kit-bot frame on the bumpers. It’s attached to the bumpers securely (most likely with two bolts/tee nuts per section of C channel). When we attach it to the robot, the C channel fits snugly around the frame, with holes for bolts to drop through vertically to secure it. Due to the snug fit and the bolts holding it in place, the bumpers are securely mounted, with no wiggle room - i believe this would meet <R07> I.
The C channel would be Aluminum, less than 1/4 inch thick. Since this is snug against the frame (with holes drilled out of the frame to allow incursion of the bolt heads holding the C channel to the bumpers), the total depth of hard materials would be less than 1 inch (3/4 of plywood and, for example, 1/8 of aluminum). This would meet <R07> N.
However, we aren’t sure about <R07> M - specifically the statement that the bumper has to be supported along its full length. Our robot design would make it difficult to have C channel along the full length of the bumpers - most likely we would have 2-3 sections maybe 3-5 inches long. Would the resultant 1/8 inch gap between the plywood and the frame, in sections where there’s no additional C channel, be permitted? A simple solution to this, of course, is to build out the frame in those “unsupported” sections an additional 1/8 inch, which would provide a flush mount for the bumper (pictured in the attached image as red). Our feeling is that 1/8 inch is well with in the designed flexibility for plywood of this type, and such a gap would pose no structural hazard to the frame or bumpers. In fact, you might end up with a gap that big from simple warping of the plywood.
We ask this with the full understanding that you aren’t the GDC, and if asked to the GDC we would get the canned “we cannot comment on specific designs…” response Since at least one other team is considering this, we figured posting our concerns and possible work around to remain within the rules could help the community.
Eagle (what is your name again?)
The rule you reference refers to robot structure that backs up the bumper. i.e. the part of the frame not shown in your drawing. The design criteria include the backing, knowing full well a 150 LB robot at any speed would be able to break or severely weaken the 3/4" plywood. ( I think Dave Lavery showed a picture of a of the damage from a robot hitting the wall last year.) With robot structural members behind the bumper plywood, the whole system provides what the GDC expects would protect the robot during most legal game play. Using the C channel in your drawing for attaching the bumper is a good way to attach the bumper, but the structure is still part of the rule. In your example, the 1/8" gap caused by the C channel would not compromise the 3/4" plywood as it is compressed against the frame.
In this year’s game, contact with other robots on the bump will cause some interaction to occur at angles not encountered during games on a flat field. That being said, bumpers mounted only in the middle with no backing robot frame structure will suffer from these non-parallel contacts. Bumper/robot damage would be the result.
Ahh, i understand your concern now. As it turns out, we have a little, but probably not enough, backing to the bumpers outside of the basic kit-bot frame. The wheel mounts, for example, provide some of that support, but only on the lower half - and currently we don’t have anything supporting it above the center line.
We are planning on making some “roll bars” to go over the top of the robot, and those could supply some of the structure you indicate. Would you recommend having a horizontal bar along the top/bottom of the bumper for the full length of the bumper, or would some vertical supports (spaced maybe a foot apart, used as part of the roll bars and thus reinforced to take the impacts) be sufficient?
I don’t think anyone on our team has considered these types of off-centered impacts, thanks for bringing it up.
~Jon
Jon,
As you pointed out in your previous post…
<R07> M - specifically the statement that the bumper has to be supported along its full length.
This is the rule your inspector will be confirming during inspection.
Jon,
May I suggest you consider the attached image. In addition to providing increased vertical support, it removes any ambiguity as to where your frame perimeter is defined.
Regards,
Mike
Mike,
I am not sure that even that implementation can handle the contact we will experience.
Al,
Your posts are making me slightly nervous. I understand this game will result in some impacts we are not used to seeing in FIRST. However, it seems that in your interpretation (being an inspector, and a great inspector at that 
) is almost any implementation of a single beam along the back of a bumper will not be robust enough. Now in your opinion would you approve the 2 previous design/sketches posted in this thread for inspection?
-Brando
