Houston, we have a problem

The team is working on getting the most out of their robot for a skill challenge tomorrow. Suddenly, the robot was having all sorts of problems. Upon closer examination the team found this. The zip ties and the nylon screws that were holding the base together did not break. They all held up to whatever stresses were being applied. The aluminum C-channel did not do as well. The C-channel did not bend or twist, but it actually broke. Has anyone seen this before?

Yes, this actually happened to a sister team’s arm C-channel.

Now that you know it’s being put under a lot of stress, consider doubling-up on C-channel for that spot (see image: 2 C-channels ‘inside’ each other and screwed together)

I’m said sister team. One minute, we are scrimmaging with barin, the next pop! bye bye arm! THE DAY BEFORE STATE.

Frankly, that beam was already on the strongest point of the metal. I would recommend either using steel or not letting it have the opportunity to bend: add some side supports to stop pressure on that point.

EDIT: We still blame barin. We were tangled when it broke off, so its always his fault. Look for #BlameBarin2k17 at Worlds!

I think the damage actually happened awhile ago, at one point I noticed the lift was crooked but couldn’t figure out why, later I realized the drive base was bent. I bent it back and it seemed fine. I guess the most recent programming skills run with 2 cubes at once was the last straw.

This happened to us between qualification matches a few weeks ago:


It was quickly braced with the coupler and robot went on to win the next match. After that competition the tower had to be rebuilt, paying much more attention to the forces and torques in the frame.

Boundary between c-channel segments is the weakest point. If you know that high torques are going to be present at the joint then, at least, you should put couplers into both c-channels to improve structural strength.

Stink Eye broke a Aluminum C-Channel on one of their claws. Didn’t realize it until we got to Crown Point. Luckily it was an easy fix.

The got it fixed and are working on getting consistency with their programming.

Way back in Toss Up, one of the C-Channels on our scissor lift broke the night before a competition on our programmer. I hear that it was quite a fun night.

Right now our sister team 3946C has a nice crack on one of the angle bars that connects the lift to the drive. It’s a nasty thing to look at. On my robot the hole that connects our claw to our robot cracked as well, but we reinforced the area with steel. I’ve seen this happen once in Skyrise to 1826 during a tournament before as well.

We just cracked the aluminum angle on our claw :frowning:

This was our arm…


And about 3 times as heavy.

Steel is heavier, but when you start doubling up the aluminum parts, then it’s not weight you think about, it’s cost.

We have broken both aluminum and steel c-channels that held our claw to the arm. Now we use two steels c-channels stacked in each other on each side, but since they are really short it doesn’t add much weight. The break might have been part of the reason we lost a tournament, since our claw was loosely zip-tied on after they broke.

It looks like you oriented it the wrong way. The long side should be perpendicular to the ground, if that makes sense. That way the long end of metal bears the burden.

I’ve never broken a cchanel. But I have snapped a HS gear perfectly in half