The purpose of this thread is to create a list of ways climbers have broken possibly resulting in robot damage to help keep functional robots at competition.
We had a functioning climber on week 5 that hooked on the rope with some bolts. However the bolts broke after some use so we decided to switch to Velcro. So far no issues with the new climber.
2910’s climber has broken in several ways now, each time differently.
Our first time, the robot barely got off the ground before the chain started slipping (luckily our ratchet held).
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The second time, we had the ratchet going the wrong direction, so even before we touched our rope our motor mount sheared out. We had spares, so we swapped it out and tried again with the ratchet set correctly.
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After successfully climbing, we noticed that the whole structure started twisting because of the torque the motor was putting through the system. We then put an overkill aluminum plate on one side.
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After that, the rivets on the bearing mounts on the final shaft which grabbed the rope sheared out, which we replaced with bolts.
All of this produced a super beefy mechanism which will now probably break our versa-planetary gearbox before we break anything else. :rolleyes: but it works.
Chain started skipping and now we’re looking at a directly driven solution. We also accidentally ran it backwards, and our COTS solution to ensure that the climber couldn’t be back driven made the motor mount bend out of place.
Same with ours. We just stretched our gear winch system and shaft brackets with a block of wood and it hasn’t worked better!
First time around, we didn’t have enough gear reduction (calculation was fine, but assumed a smaller drum diameter than we actually had). It stalled after just tilting the robot, the we smoked either the motor or the gearbox, not really sure which.
Then, with a larger reduction, our #25 chain started skipping violently and stretched out. Now we have two loops of #35 chain.
Now, we just have some cases where we want more reduction when we catch the rope on one the grabber fingers, so we’ll be upping the reduction again and adding a ratchet.
For reference, our climber is a pretty simple velcro winch system with a velcro-covered strap (sewed) as a rope. For those interested on more detail, reveal video here: https://youtu.be/uj4vVY62pd8 At the week 0 scrimmage we attended yesterday, our practice bot’s climb failed twice.
The first was due to the rope snapping during the climb. This is because the rope we used was structurally compromised from a previous prototype climber that had a tendency to poke small holes along the strap while climbing. We had used this rope to climb plenty of times before, but bad luck had it that the rope failed while at the scrimmage. Luckily, we only fell a short distance. The only thing we broke on our robot was part of our fuel intake mechanism that was supposed to be made of polycarb, but it turned out we had accidentally used acrylic.
The second time it broke was due to the fact that we climbed too high up the rope (the bottom part of the davit and button were not present on the scrimmage airship). At the top of the rope, one of our climb motors hit the side of the airship and snapped off. Thankfully, as we were using versaplanetary v2’s for our gearbox, the point of failure was on the motor mounting plate. Neither the motor or gearbox was damaged, and a quick replacement of the mounting plate make the climb fully functional again. This failure only occurred for two reasons: 1. We were higher than we would normally have to climb, meaning that the slant of the airship walls made the walls closer to the robot than it normally would have been. 2. Our climb motor was exposed without protection (you can see this pretty clearly in our reveal video, which was filmed with the practice bot). This fix was already planned before the mechanism broke, as our final robot is going to have protective side panels that double as sponsor plates.
Thankfully, no huge failures or major design flaws. Just some unlucky breaks.
We had a pretty good climber and only had to make some minor adjustments. Then the other day running out competition model it quit working. We are almost positive that something is broken in the gear box.
We fabricated a custom winch drum out of polycarb tube from mcmaster and hex hubs made out of UHMW rod. The torque stripped our hex hubs internally and we had to take the whole thing apart 2 days before stop build. Hopefully we can get the new scheme built and tested tomorrow.
I (see: flair) touched it.
We smoked our climber CIM. When we weren’t climbing. Our winch “drum” is on an arm and has a ratchet so it only goes one way. When we reverse the rotation, the torque lifts the arm to the stowed position, but it does have a tendency to fall out.
We put in a limit switch so that when we weren’t climbing and the switch was released, we could apply a short bit of rotation to bring it home. The programmers implemented the first and last part, but not the part between “and” and the comma. The motor was stalled all during shakedown driving.
We had our ratchet going on in the wrong direction and accidently made the climb button a toggle button. We weren’t sure what was going on until our bag motor started spewing smoke.
As a test, we left the robot hanging overnight. The adhesive holding the Velcro covering on the spool came free.
We reinforce the adhesive with tie wraps.
The rope crossed over the 1/8" ABS side plate and crushed it. The robot still climbed, it just took longer. Those ABS plates have since been replaced with 1/4" aluminum. We won’t be crushing those.
Put some red locktite on our versa planetary motor set screw and it dripped down to the motor shaft and face. During a break it must have had time to set and suddenly our climber was bound and motor gave a tiny puff of smoke. Lucky it was easy to diagnose and easy to fix (thanks to vex making the GB easier to disassemble now).
We’ll probably just rivet it to the spool
Out rope (velcro strap) got caught in the gear of the climber and got snipped. robot dropped 2 feet and screw up the chassis alignment. nothing else broken. Chassis has since been realigned.
Redesign the climber. Now use regular rope. No more rope pinching.
We drew it in 5 minutes and hoped for the best.
https://drive.google.com/file/d/0B59jpIFTgv8cNmxocDFjVGJwMGM/view?usp=sharing