Robot speed limits?

This year was an exciting game that required robots to run full field cycles while crossing paths with their teammates and opponents. It led to some thrilling matches with heavy collisions. It was awesome.

That being said, it seemed like a tough year for G206. Is this solely because of the style of game? It was the first full field cycle game since the brushless revolution, and robots were being asked to reach high and far outside their perimeter. I do think it’s too easy to blame robots with a high CG, because there were also plenty of short robots inside their frame perimeter that got plowed over by a super fast cycling robot.

The post season discussion around 3 motor swerve modules got me thinking. Is there a limit to how fast these robots should be allowed to go? In the name of safety? In the name of an enjoyable competition experience for all? For the preservation of carpet and field elements?

I’m not suggesting a speed limit, just curious about whether anyone else has thought about this.

  • No limit needed, the natural limits of the battery are enough.
  • Maybe, but we haven’t reached those speeds yet.
  • Yes, and some robots have passed it.

0 voters


Traction’s a pretty substantial natural limit, too. You can’t accelerate much faster than gravity. no matter how much motor power you have.


Wow, I really appear to be in the minority here :grin:

This was a hard year for the G204/G205/G206 rule family. I think the brush-less motors are only part of the reason. We used to also have a limit on the max number of motors, as well as a limit on how many 40 amp breaker slots there were. (All I wanted in 2012 was one CIM for my shooter, but drivetrain had to use all 4 of them. I accidentally made a REALLY loud 4-BaneBot gearbox :rofl:)

The only thing I didn’t like to see this year is how frequently the younger or less mechanically advanced robots that kindly played defense per their alliance strategy in a match wound up dead on the field. This game was quite physical and many were not prepared.

No, I do not want to see a “speed limit” introduced, as it’s not enforceable. In 2006 the ball velocity was limited per the rules and tested as a part of inspection, but that couldn’t prevent anyone from Volkswagen-ing I suppose (no accusations). I also don’t particularly like the race-to-the-bottom to overbuy, sort, and condition the most optimal competition batteries for power-hungry robots.

Maybe this is a hot take, but I’d actually like to see a motor limit return in one form or another. Just hypothetically, maybe something to the effect of a limit of 4 Falcons, 4 Neo’s (full size), and 4 CIMs. You may substitute a Neo for a Falcon, and a CIM for either a Neo or a Falcon. Just spit-balling. It might encourage more mechanical creativity, like what 148 did with Tumbleweed in 2008.


I think the battery limit is definitely enough especially in games which require more non drive base current draw. Getting faster has been a natural progression of the sport and you can build a robot to be very stable. For example our robot at a few points was only on bumper fabric and it always went back onto its wheels. I don’t see why we should be limiting teams technically. Secondly I wold find it very hard to reliably enforce. Imagine the limit is 7 m/s. What are we using to allow 6.9 m/s but not 7.1 m/s. They will look the same to the human eye. I think refs have to already look at enough to start pointing radar guns at robots.


This is something that bothers me, too. If the battery is the limit it becomes a huge cost and inconvenience to teams wanting to use this competitive edge (and very wasteful).

I very much agree with this. I think the old PDP had it right with 16 slots. It made swerve come at a cost, and it encouraged clever mechanisms for sharing power between subsystems if a team wanted more.


Sure, but I think it is way more inspirational to see what teams are doing in all performance tiers of the competition with all the motor slots & power available to them. I enjoy watching the 2023 game significantly more than most pick and place games in the last decade, which I partially attribute to most robots being less held back by arbitrary limitations. Let teams cook!


Definitely don’t want radar guns, but I think you could get close enough with theoretical top speeds. There could be a calculator that all teams use (and is a part of inspection) where you input the number of drive motors, type of drive motors, drive motor gear ratio, nominal wheel diameter, and robot weight. If the calculator says you are good, then you are good. If you can find extra efficiency to beat the estimate, then that’s cool and you are rewarded with a slight speed boost over competitors.


Poof ball velocity was really hard to enforce in 2006, I’d prefer that if people want to meter speed they figure out a way to due it in hardware vs measuring speed. Although personally I’m ok with the current hardware limits we have right now.


I don’t think the rules should be structured in this way as FIRST typically allows for a mix of mechanical and software limits to meet the rules. Having a purely mechanical limit could stifle innovation.

One of the aspects of the field that drove the high level of contact is the field layout. The line connecting the game piece pick up area and the scoring area is laid out so that opposing robots have the longest possible run up (1/2 a field or more) and a nearly head-on collision with robots on the other side.

This year, we were behind by quite a bit. We ended up using our practice bot for our first 2 competitions while we worked to finished the comp bot. The practice bot was working so well that we discussed sticking with it through the season. But by the end of the second competition, we had significantly bent the robot frame and the arm mounting structure.

We swapped in the comp bot with steel reinforcements. Even that wasn’t enough. Many many of the top tier robots were swapping in large steel components on their frames for COG considerations. It also made the collisions even worse - more mass at the same velocity.

We were under 100 lbs at our first event. 105 by the end of champs with added structure. Our frame was 1/16th, and we have found the limits of that structure.

I would not be against putting an upward limit on the amount of wattage teams are allowed to put into their drivetrain. It might help address the carpet damage issues and robot damage issues.

Another solution might be to reduce the maximum breaker size to 30 amps.

The breaker idea is somewhat problematic, as clever teams will easily circumvent it with adaptive amperage limits to allow full current for shortage durations.


I can appreciate this perspective, but I will respectfully disagree. For me, inspiration isn’t tied to robot performance. Though this is subjective and I can see how it helps curb appeal. To play devil’s advocate for a minute, it is said that constraints are good for innovation.

Now, whether this is a good or bad constraint is debatable of course. I’m all for letting everybody cook, so long as we’re using what’s already in the kitchen. :grin:


You sir are forgetting that you can exert more downward force than just gravity allows, just wait until someone starts taking designs from F1.


Perhaps there’s room to allow for improved bumpers? Pool noodles can only take so much shock off of a collision. Something like Sorbothane (or similar) “pool noodles” might help here, or allowable alternate constructions/materials.


But what about the massive stockpile of pool noodles we have all built up over the years!!

But seriously that’s a good idea these robots are going to kill each other.


I agree, and based on my latest round of battery testing results, I am suspicious that 18Ah AGMs are slightly worse than they were circa 2017, due to inflation/shrinkflation.

What if we leveraged the existing PDP/PDH current measurement system to put a peak power and total energy limit on the robot? Display remaining energy on the scoreboard; make it a part of the game. Have the announcer question whether team 9999 is going to have enough energy to complete their endgame. Give an RP for completing a task with more than X energy remaining. If it doesn’t work out, turn the limit off for the next year.

Of course, there are problems with this idea too. Brushless motors would give a competitive advantage, since they are more efficient than brushed, so there might need to be a motor efficiency compensation (hopefully implemented by the manufacturers, not the inspectors). Some teams will buy a several PDHs and find one whose current measurement system reads 1% low. A CD thread will be posted with the grand list of gearbox efficiency tests. Rolling resistance/loss in wheels could become a spec. Regenerative braking will be argued over.


FIRST needs to rethink some of their playing field design and robot-robot interaction rules with the advent and quick adoption of brushless motor. I reflected on this in my post in the Lessons Learned 2023- The Negative thread:

I think this may have been the most brutal and violent game since 2014. In the divisional playoffs the meta switched towards getting into these high impact collision to disrupt the opponent or force them to drop a game piece. On Einstein, the rivets holding the belly pan up on one side of our frame sheered off, and it was sagging a good inch; our bellypan was literally about to fall out from under the robot. We also had intermittent CAN issues in our drive’s network whenever we took a big hit. The higher levels of this game were absolutely brutal on robots, and we’re lucky we did not physically break during the playoffs.

Rather than implementing speed limits, I think it would be better adjust the playing field to include more penalty zones and limit cross-field high speed interactions. In 2014 we had a rule about intentional high-speed ramming to discourage purposeful damaging contact. I could see a similar rule being implemented in addition to playing field layout design to discourage high energy collisions. I’d also like to see referee training on G206-like rules. There were some instances where a robot’s high CG was more of a culprit in the tip than the opponent robot, but the opposing robot got credited with the tip and red card.


Our pool noodles are all cracked at this point and no longer springing back as much.

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“Maybe this is a hot take, but I’d actually like to see a motor limit return in one form or another”

Absolutely. My personal opinion on this would be to bring back the CIM motor (or equivalent motor such as a Neo or Falcon) count limit.

FRC has gotten a little to easy to design for, especially when you can throw a high power+high torque motor at everything if you really want to.

I believe that this (CIM count) would level the playing field a little bit too. The teams that don’t have the money to throw a Falcon at everything would definitely benefit from this as the high resource (mainly money) teams would have to work with the same “cheaper” options that their lower resource competitors have to work with.

Another benefit, it would reduce the cost of operating an FRC team a little bit too. Although not by a whole lot. The cheapest motor +controller option I am aware of that is encoder compatible is the Baby Neo + Spark Max, which is 118 per pair before tax. The VEX+CTRE equivalent 775 or Bag+Talon SRX is 120 per pair. If you don’t need an encoder a 775 or Bag+Victor SPX is 80 per pair. A single falcon is 220 per unit and a Neo+Spark Max is 138 per pair. A potential price difference as low as 18 to as large as 140 $.


Absolutely not. In FRC, money is easier to come by compared to experience. Teams with more experience would revert back to PTOs and other complex solutions to eek out any bit of performance. Teams with less experience (and often the ones with less money!) would still struggle AND be limited by these same rules. Rules like this seem like they might level the playing field but really exacerbate inequality within the program (similar to the argument that the bag levels the playing field because it hurts 95 percentile teams, while it had a disproportionate negative impact on < 75 percentile teams).

The whole conceit of the program is that we use competitive robotics to build skills and inspiration in students. Students getting to see what they spent the season on working and performing well is significantly more experience than the inverse in my experience.