We have gotten questions about the size of Lightweight robots maybe changing along with the switch to the small ball. Specifically we have been asked if the LWL robots will have to shrink to 18cm. All robots will be the same size for 2026. We said this when we were asked and we will keep it that way in the rules for next year. It did get us thinking however because the reason for our decision (and this was confirmed to us by teams at the rules discussion session at the RoboCup tournament in Salvador four weeks ago) was that it was quite hard and also noticeably more expensive to build 18cm robots for open league and we didn’t want to put another hurdle in for lightweight league teams trying to go to Open League. So the question becomes:
should we change any of the robot sizes? We have been thinking about the following options (there are of course many more combinations, tell us if there is one we didn’t mention that you think should be considered):
Keep everything the same
Keep OL at 18cm, change LWL to 18cm as well - probably makes things quite hard for OL teams
Keep OL at 18cm, reduce LWL to 20cm - shoudl be doable because all LWL robots have one or two centimeters of empty space already
Increase OL to 20cm, reduce LWL to 20cm - would allow keeping a LWL bot when going to Open League and generally making OL bots easier to build
Increase OL to 22cm and keep LWL the same size - basically like Nr. 4 burt with bigger robots - generally smaller robots make the field “bigger” so there is more space for moving around an manneuvering
Which of these options do you like best? Do you think one of them but with different size numbers would be better? Do you have an entirely different idea? Please give feedback below.
None of these changes would happen for the 2026 season. Any decision that we make will be announced early enough for the 2027 or 2028 rules so everyone has enough time to prepare
Additonally I have a question for you about those who remember the transition when Open League went from 22cm to 18cm step by step over a couple of years: Would you say this made it easier or harder to adapt? Because I can imagine it is a little bit easier to engineer but also nobody actually wants to re-do robot mechanics completely every year and I’ve been told by some teams that they went straight to 18cm early - not sure how representative that is though.
Going step by step was helpful
Going step by step was not helpful
Going step by step would have been helpful if there was no covid
I’m writing from the perspective of a coach with very little experience in Soccer.
With the current size, I feel that the teams are rather limited in parts selection. This discourages them from exploring new designs, and there’s a strong tendency for them to just stick with whatever worked in the past.
I agree, esp. for Open League we have seen a SSL-like design (pancake BLDC motors, often Maxon, sometimes with gearbox sometimes without) - although we are only in year 4 after covid and engineering has improved a lot from 2022 to 2023 to 2024 to 2025. Would you say you would be more likely to have more Soccer teams if the size was changed? If not what else would be needed for your students to be able to do soccer more easily?
As a coach I experienced the reduce of the size from 22 to 18 a a very good decision.
As David said, it makes the field “bigger”.
I absolutely disagree that this reduces the choice of parts.
We bought 38Euro brushless motors from chinese ttmotors that are 16mm in diameter and “long”, but they just did not touch each other in the middle. We also used 22mm brushed motors from ttmotors that cost only 17 Euro.
Both including 16:1 planetary gearboxes.
It is a bit harder to fit anything into the 18cm robot, yes, but this leads to better robots as you cannot “just put in everything” as you were jused to do in lower leagues.
So I voted for “18cm in open” and “22cm in LWL”. That keeps the difference between the leagues.
The open league should stay much harder to build and play as it is the highest league there is at all.
So the tendency to explore new designs is encouraged when switching leagues.
Greetings
Roland
As a junior mentor heavily invested in robotics education. I have been thinking about this topic since the open call meeting a few days back. I highly value the educational challenge the open league presents to lightweight participants having to go from 22cm robots to 18cm robots. From my experience the biggest challenge for teams transitioning is redesigning the drive system. In the past years it has lead to very interesting custom gearbox designs. While it is not easy, as any real challenge, many teams including the team that I mentored myself were able to do it, and more importantly had a blast while working on it.
In terms of the costs of building a 18cm robot, the drive system would be the biggest hurdle. But as @stiebel mentioned there are affordable motor options out there but you have to take the time and effort to explore your options. Designing your own unique drive solution should also be encouraged. I came across a TDP of a SSL team from 2023 that made a drive system using 28 dollar brushless outrunner drone motors.
Solutions like this could also be used in the Open League, it would not be the first time that a SSL TDP would inspire junior teams leading to great achievements.
Another talking point is the transition from Open League junior to SSL major. The 18cm limit is in line with the SSL league, making it easier to bring (unfinished) projects and ambitions from junior to major and continuing Robocup in that way.
My perception of the open league is:
A league that is a level above the lightweight league in which you have to level up your electrical, mechanical and software skills in order to compete.
A league with more experienced competitors
A league that fosters better gameplay due to the smaller robots and the need of more advanced camera systems.
A league that reaches university level robotics
In my opinion it all comes down to the question: “What educational values do we want the Open League to pursue?”. Answering this question should set the bar to what extent the Open League can be made more entry friendly for the lightweight teams.