Missing O-rings: You learn things, even when you think you’re teaching

By Coach Doug | Success at a VEX IQ Crossover match depends on so many things, and you never expect it to hinge on whether there are missing O-rings.

We went to the Central Firehawks tournament this weekend at Longmont’s Westview Middle School. It was a great tournament, and extremely well run with help from Axel and the Innovation Center staff and students.

I was pushy, and sent a list of suggestions on how the fields should be checked based on previous experience—the bridge is so hard on the tournament volunteers and managers. There are hours invested in building it, and if it isn’t perfect it won’t work well. Axel and the tournament managers graciously thanked me for my pushiness, and assured me that they’d ask for help if anything came up.

So, learning while teaching?

All those emails that said “we’re experts in construction of the fields, and we’re happy to check them for you,” that’s being the expert. Turns out, I failed at it.

At a recent event with Team 974X, Chazak, they noticed that the O-rings were missing from the pegs on the walls. Their robot (and ours) relies on being able to reliably pick up balls from the wall and score them. When Chazak touched any ball, it fell off much too easily. They knew there was a problem, and figured out that parts were missing.

This weekend, hex balls were again falling off the walls with the slightest touch. We forgot about the O-rings.

We’d seen a great team notice the missing O-rings just a few weeks ago. Then at this weekend’s competition, an Innovation Center student asked me, “Did you change your program? Your bot is always more reliable than this!” during a programming skills match. All of the signs were there.

I never checked.

Last night, as we watched videos of this weekend’s matches, my daughter pointed out how easily the hex balls fell, even when barely touched (there’s a clip near the bottom of this post). She zoomed in on a video, and sure enough … it looks like the O-rings were missing. Even with all the clues, I never thought to check the problem—it was easier to write it off to nervous 3rd-6th grade drivers.

No missing O-rings? ✔ Check.

For our next tournament, we’ll make a checklist of the field elements that matter to our robot. This weekend (and our second instance of missing O-rings!) was a learning experience—even for this guy, who foolishly said “I’m an expert” before the event. I plan to talk to the team at our next practice: learn from your mistakes and do better next time. I even plan to take my own advice.

We’ve seen the best competitive teams over the last two years check the field and its elements every single match. We’re working to become one of those teams, both as we teach and as we learn.

Missing o-rings on the VEX IQ Crossover field can be trouble
What the O-rings and pegs look like when installed correctly
VEX IQ o-rings and pegs with a ruler for scale
Pegs and O-rings with an inch ruler for scale; they’re tiny but important parts!


This is the kind of behavior we’ve seen from hex balls that are attached to the wall on pegs with missing O-rings. The hex balls are much less stable, and normally well-behaved robots knock balls off left and right.

When hex balls are attached to the wall on pegs that include O-rings, it’s more difficult to knock them off unintentionally.