My team is playing around with HDPE to see if we might ever use the material for robot parts. Meanwhile we’re prototyping a swerve chassis, and are concerned about the motors taking a hit. So we used the old cutting board to make a rough concept to protect the corners. The discussion came up about whether the HDPE would be considered part of the perimeter (assuming constructed and fastened much better than in the photo) or it would be considered something not a part of the perimeter. The perimeter definition is: fixed, non-articulated structural elements of the ROBOT contained within the BUMPER ZONE.
What do you think - would something like this pass inspection or not, assuming the bumpers were constructed so it was inside the bumper zone?
I would consider the HDPE as defining the frame perimeter. As to passing inspection, I don’t have enough information. It appears to me that the HDPE is thicker than 1/4" so my first question would be is the portion not protected by the HDPE longer than 8" (see rule R410 and the red arrow below):
If so then you can’t have bumpers across that region w/o adding support for them. If you are just doing corner bumpers, as long as they and the HDPE are at least 6" across, that would also work.
Thank you all. Most likely if we created a “cage” to protect our motors it would be from 1/8 or 1/4" aluminum, and mounted to the top of the 1x 2, and not HDPE, although we like the increased impact resistance of the HDPE. And instead of using an old, discarded cutting board we would purchase HDPE stock from somewhere. If we did something like in the photo we would definitely have any gaps >8" filled with the hdpe or something else.
We mainly had a question about whether something like that would be part of the frame or not.
As others have stated, your HDPE panels, as shown, will be defining your frame perimeter and it appears likely that there will be a greater than 8" between the HDPE panels at each corner, making the bumper mounting illegal.
It would be best to use more than one screw to attach each HDPE panel to your chassis. It would also be best to use a piece of aluminum angle to attach the two HDPE panels to each other so that they brace each other against impacts. Adding a third panel on top would make it very solid and prevent the panels from being caught on parts of other people’s robot that intrudes inside your frame perimeter.
New cutting boards from stores such as Walmart can be a good source of HDPE and would save you the effort of finding a plastics wholesaler willing to sell you a small quantity.
This is correct that those panels likely define your frame perimeter. The easy fix is to add more HDPE or other material that’s the same or slightly smaller thickness in more places along your aluminum rails so there are no longer any gaps larger than 8’ between any two pieces.
That is the easiest fix, IF you have room to spare with the perimeter; there’s also attaching them on top of the frame rails so they aren’t defining the perimeter.
Most teams shouldn’t be building max frame perimeter robots anymore (for most games, 2017 and some other are the exception). So for most teams that is easiest fix. It also allows you to easily mount other gussets and side panels outside of your aluminum rails. We use 3D printed parts in the corners of our MK4i’s to accomplish this very thing (bumping our frame perimeter corners out a 1/4") and many other teams have begun doing the same thing.
I was referring to the units. An 8-foot bumper gap is easy to build shorter than.
I would actually say that it’ll also depend on thickness of the plastic. 1/2" thick times 4 is an extra 2", which if you’re close (for “reasons” including but not limited to not knowing any better) could be problematic.
The swerve protection panels should be accounted for up front in the design. Teams that go over the frame perimeter limit by adding such protection panels need to improve their design process.
All teams should be designing such that there is some clear margin from any limits in the rules as a form of risk management.
When doing inspections, I have come across teams with frame perimeters that were 1/4" or 1/8" below the limit as well as right at the limit. In all of those instances, I could not see a clear reason why they could not have designed their frame to be 1-2" under the limit. When asked, they all stated that they used the limit in the Game Manual as a design goal.
Yes it defines the frame perimeter. Not a big deal as long as you are under the maximum frame perimeter. Just shim out the interior section where you need bumper support. Bob is your uncle.
You are going to need to attach like them like they are going to be absorb big hits and tie them together. Not a rule, but u will be sad if you don’t.
