Should Bumper rules change?

FIRST General Forum
1

With the age of Swerve in full effect right now robots are faster than ever and with that we are seeing some unintended results with drive trains and bumpers.

Pictures from this thread

Are showing that both drive trains and bumpers are being torn apart and damaged more than they have been in the past, with metal frames being heavily bent and torn despite bumper protection and teams having to rebuild their bumpers multiple times per season. With the new Krakens and Neo Vortexes coming in 2024 we are likely to see faster drive trains and more pictures like in the thread above. With higher speeds comes more impacts and collisions and damage and bumpers coming off of robots.

So with that being said should bumper rules change to accommodate ever changing drive trains and if so what changes should occur?

Some ideas that I have off the top of my head are

  • Different Materials for Construction
    Rationale: instead of strictly wood and pool noodles perhaps maybe expanding the materials to just require a hard backed material and a absorption material

  • Increasing the weight limit
    Rationale: allowing more weight allows teams to add on more support to their bumpers which can help reduce the amount of bumpers that fall off

note: I’m not advocating for any of these changes in any official way these are just some thoughts I came up with

1 Like
2

Step 1: See how the 4-motor restriction plays out.
Step 2: See how 2024 game looks.

Step 3: Look at the bumper rules and see what needs adjusting.

With that said, the primary goal of the bumpers has always been to reduce the pain of impacts, not eliminate it. Part of the reason bumpers are mandatory is that if they weren’t, offense teams would probably have wedge-sided robots just to make sure they could get in and out without taking too much damage. (This was, in fact, an issue back in 2005. When bumpers of this design were made specifically legal, albeit optional, in 2006, sloped sides were also banned.)

With that said, I would actually suggest the following: Toughen your drivetrain rails. If you aren’t using 1/8" aluminum or stronger, you are going to get beat up, bent, and broken. (“Stronger” may be in terms of thickness, material, or material shape.)

Beyond that: Softer bumper material, larger noodles, or thicker padding on the bumpers. Require hollow-core noodles.

Increasing the bumper weight limit has to come out of the robot weight limit, due to the 150lb of robot being, er, mighty close to OSHA limits, shall we say?

As far as bumpers coming off: Usually, from what I’ve seen, it’s wood screws to the brackets tearing out, or someone didn’t fully pin them on. The former is a design issue (and I would say that having a rule about through-bolting the wood is going to be darn near unenforceable, even if it is put on the books); the latter is a change speed issue most likely.

21 Likes
3

I agree with your post.

Hollow core has me questioning. Yes it would be able to compress more than solid core and therefore absorb more impact, but wouldnt that also mean a greater/faster chance of deformity, requiring new bumper sets to be built?

5 Likes
4

Echoing @EricH let’s wait and see. Rev made a slight design change of the Rev ion which is the primarily affected drive train tubes. I don’t think it will fix everything but it will help.

5

My prediction, 2024 drive trains on average will be higher power then 2023, despite the the 4 motor restriction. The release of Krakens and Neo Vortex makes it easier to put more power in the drive train and will more then offset the teams who have to go down to 4 propulsion motors. The only thing it does is stop the 3 motor swerve module development race, keeping the power from getting even more out of control.

6 Likes
6

Would electric current/rpm limiter work?

7

It seems like a lot of bumper damage and damage inside the frame perimeter happens when one robot rides up over another robots bumpers.

I wonder if it would be a net positive to increase bumpers to 3 noodles high and increase the bumper zone from 7.5" to 10"

With the current bumper rules its possible to only have 1 noodle of overlap which can lead to robots climbing other robots easily. With 3 noodle bumpers this becomes basically impossible.

image
image1036Ă—563 64.8 KB

10 Likes
8

So this is likely technically inaccurate. While most people think “softer is better” the real answer is that there is a spectrum of stiffness vs. the energy to be absorbed, and there is a more and less ideal stiffnesses. Do the thought experiement. You are going to strike your hand on a table. Given the same relative thickness, if the material is too soft, it won’t slow your hand, you will strike the table, and hurt your hand. Too stiff, and essentially it feels like you are just hitting the table. The spectrum of ideal solutions would be compressible where the stiffness is tuned in such a way that the ForceDisplacement = the desired amount of kinetic energy to be absorbed. Constant force energy absorbtion is tricky. it usually requires some sort of mechanism and strategy. Also, if improperly sized, will bottom out and cause a sharp impulse. A different strategy is to to absorb the energy via increasing force like a spring. For that the force increase with displacement or F=kX (k being spring constant, and x being displacment). The energy = 1/2Kx^2. This type of system tends to work well when the impact is not super defined, and the progressive displacement helps absorb more and more energy towards its end of compression. You can also do variable geometry of the springy cushioning element so that the more it compresses, the more it engages. This can allow for a softer initial and stiffer final force, or even more progressive. You will see this on furniture bumpers or castled snubbers on suspension bushings.

The reality is, if we want to absorb more energy, we should probably go thicker with the bumpers, and we might need slightly stiffer material. A lot of the damage to the noodles is happening due to crushing. If I wanted to design bumpers to be as similar as possible to current design, but absorbe more energy, I would like push for the slightly larger diameter solid core noodles. I would also then look at putting a stiffer smaller diameter material in the gap against the board. I’ll try to put a figure together.

12 Likes
9

I like the look of the profile for a 3-noodle bumper, but having such tall bumpers would likely invalidate a lot of over-the-bumper intake designs, making a bumper gap more necessary and prevalent. This would consequently reduce bumper coverage across all robots in aggregate.

6 Likes
10

Yeah it really depends on the game piece I think. 2020 balls might not be doable over the bumper but 2019 or 2022 would probably be fine.

11

To me, contact inside the frame perimeter is a bigger problem than frame damage. Knowing that hits are getting harder, teams can beef up their frames (thicker wall tubing, 2x2s instead of 2x1s, etc.) to make the drive base more robust. But after the Clippard explosion at IRI in 2022 and the frequent damage to wiring and electronic components over the years, I think we should focus more on protecting the guts of the robot from contact and not just the frame.

So, one thing that I would like to see is the option of making taller bumpers (equivalent to 3 pool noodles). I wouldn’t make this mandatory and it would not be needed on all sides of the robot. But, if teams were allowed to make taller bumpers on certain sides of the robot, it could help to protect the electronics and pneumatics inside the frame perimeter from impacts from other robots. The taller bumpers would not be able to extend any closer to the ground than the existing bumper zone, but could extend above the existing bumper zone.

I’d also like to see the ability to integrate other shields (wood, polycarb or even metal) into the bumpers extending above the existing bumper limits.

I think you could do a lot of this within the current weight limits for the bumpers. I can’t remember the last time we were anywhere close to the max bumper weight limit at inspection. But increasing the bumper weight limit a bit might not be a bad thing either.

I know that it is possible to integrate shields into the robot design without needing to change the bumper rules. But, i think it would be good to not force teams to chose whether to spend their weight budget to protect their robot vs spending that weight on mechanisms. The bumper rules are a weight allocation that the team must spend on protecting the robot. Giving them a bigger budget and more latitude to integrate more protection seems like a no-brainer.

3 Likes
12

Im almost certain hollow core makes the issue worse. the goal of bumpers is to increase impact absorption time, therefore reducing peak gs seen during the collision.

if the bumpers are to soft/deformable the bots will still be at a high rate of speed once you have fully compressed the bumpers. once fully compressed the remaining energy is transferred to everything else.

If the bumpers are to hard they themselves transfer to much energy to the rest of the chassis before absorbing a significant amount of energy.

As top speeds the bumpers need to become harder to deform and have more dampening. I personally think the easiest change would be requiring solidcore noodles and potentially changing size to 2.75 or maybe even 3 in diameter. not only would this increases damping but the larger diameter would allow the dampening to occur over a distance of 3 inches vs 2.5

LOTS of assumptions below this is to just get a vague idea of impact Gs seen by the robot assuming all deformation occurs in the noodles and they fully compress and absorb the impact perfectly.

acceleration seen by a robot collision with an immovable object at 20fps assuming the impact is perfectly absorbed over 2.5 inches ( current bumper noodle diameter)
29.7 G

3 inch noodles
24.8 G

I think you can compare our current bumpers damping to a car suspension that is under damped and hits the end of travel on the suspension regularly. I think our current noodle options are just too soft to fully absorb this kind of energy before they “bottom out”.

1 Like
13

I don’t think the 4 motor restriction will do much to decrease bumper damage. Anecdotally, most of the damage done to bumpers has come from standard swerve bots using 4 drive motors. I think a bigger factor is just game design - games with open fields and crossing paths like 2023 will inevitably result in really hard collisions. A motor limit won’t change that.

6 Likes
14

This comes out to approx. 3000lbs. IF absorbed over the 2.5 inches. A pool noodle is done absorbing way before the 3000lb. which leaves a force more like a rubber mallet than a cushion. This is why most noodles turn to mush.

The first fix, from a bumper standpoint, is a different material than the noodle, but off the top of my head, I don’t know what that would be that is economical.

The easier fix is to use the “demolition derby method of safety”. Add congestion to the field that slows everybody down.

1 Like
15

The trick is to do that without restricting visibility. In some of the past games where teams couldn’t see the other robot coming because of the lack of visibility, we often saw some pretty dramatic impacts.

1 Like
16

Also lack of driver vision will NOT slow us down going point to point with april tags. By end of season this year. we had a live path gen with field obstacle avoidance(static game elements not robots) that drove more aggressively then our driver. it was only limited in acceleration to prevent wheel slip. it took full advantage of our L3 topspeed. as more teams get proficient with april tags this will become more common.

4 Likes
17

Didn’t the (original) 2020 game do a decent job of that? The middle of the field had the speed bumps while the trench was flat but required teams to slow down enough to line up. I know teams often prefer to remove these impediments in favor of speed and easier driving (see 2020 and 2023 cable protector bump), but maybe they have some other value?

2 Likes
18

My knowledge of material deformity is low, and I’m not sure exactly how much it matters, but does it seem to anyone else that there is a non-negligible amount of negative space in the profile of a bumper? Would filling in that space with some other material (packing peanuts, stuffed animal stuffing, etc) add any benefit? If they are even produced, would it be beneficial to move to a different profile noodle, such as a square profile?

19

I like the idea of a 3-noodle-high bumper option but I don’t expect anything like that to be implemented in 2024; that kind of change would need to be telegraphed well in advance, since teams are allowed to reuse bumpers year to year and likely already have materials in stock (my team already has our plywood cut to width).

Hollow noodles are demonstrably worse than solid core, this has been shown time and again. If a rule change could be made that would positively change the quality of noodles, it would be to allow the higher-quality standards of the construction industry “noodles” (actually known as Backer Rod). These have a more consistent quality from what I have seen and are made of the same material; they’re just not sold as “pool noodles” and are thus technically not allowed. This is an arcane and pedantic rule and should be changed.

The 2023 game only had 12-motor swerve on less than a half-dozen robots and as such the damage we’ve seen wasn’t a result of those levels of power for the most part; the upcoming rule change is prophylactic. The game for 2024 might have a much slower field (I’m expecting stairs and platforms), which would make most of our hand-wringing unneccessary, but the larger problem of fast and powerful robots driven well will remain for a future game with a flat and open field, and our current bumpers will need to be improved before then. Not that “fast and powerful robots driven well” is really a problem; I much prefer this to fields of robots that don’t move.

16 Likes
20

This rule along with others like not being able to reuse small 3dp and so on…I don’t really mind if they are bent. In the past we’ve bought straight from the supplier “foam rolls” which then companies rebrand to pool noodle. I don’t think there’s inspectors out there doing core samples on your bumpers.