Rule R410 limits gaps between the bumper board to 1/4" apart or 8" in length. Our bumpers are supported by 1/4" brackets attached to our “frame” As such there is a (nominally at least) 1/4" gap between bumper and frame between where there are brackets. There is a bracket on each side of our swerve modules which puts the gap between the brackets (around the corner from each other) at about 9". If the swerve module was square this would seem not to be a problem, but the corner of the modules are radiused:
leading to a small area in the corner where the bumper wood is > 1/4" from the perimeter. And since the gap “sideways” is ~ 9" I am wonder if this is illegal and we need to put something in there to close the gap?
This seems like a good question for @Al_Skierkiewicz and @ChuckDickerson . Most swerve modules these days have some sort of radius on the corner, which is a far cry from the old C-base KOP drive train that was prevalent when bumpers were first introduced!
I agree that this is the critical segment of the rules, ?and also iirc new this year?, so it’s not surprising it has an ambiguity you could drive a tractor through.
I don’t think it’s reasonable to expect that this minimum 1/2" has to occur at the sharp corner of the robot, but there is also no tolerance given for what “each end” actually means. It also seems unreasonable for “each end” to be interpreted as “6 inches away from each end” or “quarter-points” type support.
As a first-line inspector working with today’s ruleset, if a team came to my queue with a 1/4" offset bumper system (which after fit tolerance usually means 5/16"-3/8" gaps) I would still pass them if they had a 1/2" wide support section within about 2" of the corner. I would be casually blind to any radii or chamfers involved at the very tip of the design. I would escalate to the LRI a team that was only tied in to the frame rails, like John’s design. The teams I turned a blind eye to might have a less fun experience at a future regional.
As a team mentor, if we showed up with our radius’d swerve corner prints (the profile matches the modules, just offset, so the radius is 1/4" larger) and the RI tried to keep us out of matches until the actual tip of the bumper corner was supported, I would respectfully escalate. In parallel I’d cut some aluminum angle and hot glue it over the radii to get the “support” all the way out to the true corner, and be mad about it the whole time.
@john3928 I think your best move while this processes is to print some spectrum-style swerve corners.
I will plan to bring some spares pre-printed to our Week 1 competition… working on posting files, makerworld wants me to post real photos of completed parts and give up my geolocation also all my real ones are at the lab right now, and I’m not there.
I’ve seen this asked before and I think Patrick was going to modify the plates for the mk4i so as not to leave such a large gap. Both of our sets of mk4is are the original ones with 8-32 bolts and larger gap. We’ve never thought about it and haven’t had or heard of any inspectors having a problem with it. If an inspector wanted to be prickly about it I would just ask for the LRI. Maybe we will just 3d print a spacer that fills that gap to be on the safe side.
OK, John first. If you added 1/4" spacers for mounting the bumpers, why didn’t you also add spacers in the corners? That eliminates any gap and also protects your swerve modules. You could curve the bumpers but that seems to be way too much of a fix.
As to the 1/2" rule at the end of every bumper that refers to the corners and satisfies the C channel ends of the kitbot chassis. The C channel is 1/2" wide. The “end” of the bumper is the corner because it is the end of a bumper segment. This is not a new rule and in fact has been around for many years. The reference to 6 inch support is for bumpers that did not fully surround the robot frame which changed this year. Bumpers must surround the entire frame and be supported by robot frame (structure) with no gap between segments larger than 1/2" wide. The support in the 1/2" of the end of the bumper for R410 is most certainly valid. That support prevents bumper failure at the corner. There are a variety of ways to design your robot to satisfy R410 using swerve modules that have a radius. As a matter of fact, I think a team would want to add frame to the corners of the robot to protect the swerve module from collision damage. There currently is not a rule that allows 1/2" gaps nor is there any specification that takes into account 2" on either side of a corner. Teams have been designing robot frame to satisfy this rule since swerve modules have become available.
What I had read “supported” to mean was that in a practical sense, the backing support must be at least 1/2" wide in order to provide sufficient backing / make a sufficient support. Note that because I’m understanding the 1/2" as the width of support, there is no dimension to the corner, which is what I substituted ~2" for as a reasonable distance to be considered supporting the end.
I’ve passed a bunch of teams that don’t meet this requirement, by the way. New, old, whatever, if the mounting system uses a multi-part design that meets at corners, the corner tolerance is the first thing that gets impacted and it has almost zero impact on whether it’s actually a well supported enough system to survive a match.
And this diagram should be in the rulebook if you want it to get followed.
Fig 8-8 does not do this requirement justice, having a 7" wide space be labeled “minimum 1/2” is not useful information.
And this is out first year with the corner biased swerve modules, which were a significant investment for us. So our thought for the rear was to build as strong a bumper as we could but NOT connect it directly to the swerve modules so that impact forces were never transmitted directly to the swerve modules.
with these modules there is no frame tubing for 4.5" on each side just a pair of rather frail looking horizontal plates and a vertical space in the corner:
this lead me to believe that R410B (measuring around the corner at ~9") was going to be our issue:
and it is, but as was previously brought to my attention here, R408F/R410 is likely a larger issue, as I previously understood “end of segment” to mean where wood ended, the red arrows here, I did not realize that the corners, green arrows here, were also segment ends):
As we still don’t want to connect directly to the swerve modules, I guess we will be “cantilevering” some plates from the tubes out to the corner:
OK, neff, I think you have it. We know from experience that if the bumper is not supported by structure in the last 1/2" behind the plywood, the bumper will fail in some way. The plywood will delaminate or the rest of the bumper will take stress that will affect it’s integrity. (often failing at the mountings) If you look at C channel from the edge, you will see it is 1/2" wide and the full height of the C channel. That is support enough for the end of the bumper segment. In the case of a standard frame that meets at the robot corner there is significant structure to support the bumper segment. We also know from experience that a gap greater than 1/4" between plywood and robot frame will also cause the bumper and/or the frame to fail. That is why those rules are in place. The whole object of bumpers is to keep teams playing. If a bumper fails and starts leaving debris on the field, then it is bad for all six robot. If a bumper fails and that causes robot damage, then that team suffers and all of the subsequent alliance partners also suffer.
John, yes you are correct to try and protect your investment. What better way to protect them than to have them covered with a bumper system that does not fail. With just a small addition you can satisfy the the 1/4" gap, supply the support at the end of the bumper segment and take full advantage of the bumper to protect your robot and swerve modules. Yes the cantilever shown would work, are you thinking a complete corner as a single piece? A two to four inch wide angle bracket that extends vertically to all three layers of the module would also work. The choice is yours. You want to protect your modules and everyone wants your robot to play and not have the bumper fail. Please look at Fig 8-7, while it is showing how the bumper can be formed in the corner it is also showing the full backing of the frame and plywood meeting in the corner.
Would you really consider that “structure/frame” (R410)? If the intent is to protect the modules, I’d want the bumpers supported so the corner can’t flex, and with how hard robots hit each other, I’d think twice about relying on a 3d printed part like that to survive the impact transmitted through the bumpers.
Honestly, I’ve always found the use of “structure” there to be really vague – I’d say pretty much anything solidly connected to the rest of the robot that doesn’t have some other obvious function (like a motor or a radio) is part of its structure.
All this debate on the exact reading of the rules is and their intent is weird for me considering how I’ve designed bumpers. One the one hand, we have a .15” gap around our tube frame to allow for 1/8” gusset plates without having to worry about rule interpretation too much, but the actual mounting points and structure on our bot are designed to avoid ever having forces go directly through the wood and into the outer tubes. Instead the bumpers largely float around the bot and are intended to take the brunt of collisions absorbing some energy and transmitting forces to very specific points of the frame while most of the frame should never contact bumper.
Real bumpers have cloth folded up in the corners in a way that is difficult to show in CAD. Not to push any rules, but just reality of fully covering the bumper in fabric and making a neat tight corner with fabric. This stuff tends to fill imperfections.
I tend to go the other way. We generally aim to spread the load out and transfer it to the frame tubes rather than concentrate it into the attachment points. Spreading the load out on the bumper let the noodles spread out the impulse load. different ways to eat the pickle.
This is what we did previous to this year, previous to swerve – a secondary frame of 1"x1" encircled the robot above the actual 2"x1" frame and the bumpers mounted to the 1"x1"
Patrick, given that plywood is flexible, I can’t see how you expect that the bumper will absorb all of the energy of a collision without transmitting some, most, all of it to the frame. The design of the bumper system intends that transfer of energy to take place such that the energy is dissipated and spread by the bumper system. Gaps greater than 1/4" or voids in the frame longer than 8" as shown in Fig 8-8, will concentrate that energy.
You mentioned passing other teams in other years and wanted to see if you recall seeing similar things. This is our first year utilizing swerve corners (and a swerve drivetrain in general) and we decided to just copy what other teams have done in the past with these 3DP corners to satisfy R410. Getting some apprehension knowing that some of the designs I’ve referenced use these corners and yet still have a >1/4" gap from segment ends (i.e., bumper backing inner corner). See image below of another team’s previous year bumper corner.
Team is considering adding a sharp corner to satisfy R410 but maybe we’re overthinking this. Seems like there is a lot of ambiguity in bumper rules (which are being talked about in other threads/discussions) in which we didn’t have to worry about before, formerly being a primarily KOP chassis/tank drive team.
In practical terms, the fabric will bunch up in the corner and make it hard to shove a 1/4" go-gauge in there so you might be OK from day one.
In enforcement terms, in previous years I wouldn’t have dreamt to enforce a 1/2" of support by measuring that support from the corner of the bumper the way Al has indicated in this thread, and have happily passed teams with standard corner supports of approximately the radius you indicated beause they offer a broad support surface that firmly secures the bumpers for at least 1/2" near each end.
Unfortunately for your point, I am but a lowly first line inspector with no real power, and now have the unbridled pleasure of knowing that I am expected to try to shove a piece of quarter inch stock in the corners of team’s bumpers/frames. SVR is going to be wonderful.
also all my real ones are at the lab right now, and I’m not there.
