During our last match today, we lost one side of our drivetrain, and were unable to drive around. When we took apart the BaneBots gearbox, all 5 of the pins in the carrier plate had come out of the carrier plate, so that the output shaft spun freely. :eek: This is with the new hardened carrier plates, in a 2-CIM 12:1 gearbox.
Has anyone else had this problem?
I did notice that when I put the new plates in that they were really just pins stuck inside a through hole, unlike the other plate which had pins in a partial hole. Thanks for getting this out, now it ours fails I’ll know what’s wrong with it.
Banebots, in a hurry to get these new carrier plates out, had to substitute a standard pin that they could easily obtain in place of their own, longer pin. Therefore, the pins are a bit shorter. I guess the lack of engagement inside the hole is allowing the pins to back out in operation.
I suppose teams should press the pins back out and use some press-fit loc-tite to retain them. That seems like the easiest solution. Any team with an arbor press should be able to take care of it in a few minutes.
There was one report of this problem from a team at St. Louis. I believe the team was 525. Hopefully someone from that team will provide more details.
From what I heard this happened to our team (I’m a programmer, but I think this is what happened.)
We have pictures of the carrier plate somewhere…
I wasn’t there when it happened, but we apparently lost the pins on the other side this morning. We had been playing a lot of defense. Unfortunately, there’s no good way to check for the problem without taking apart the gearbox, and when it fails, it fails completely.
We had noticed difficulty making left turns sometimes, and backing up made the problem go away. This might be a warning sign, but we need more evidence to prove it.
Yes. BOTH of the BB transmissions on our robot failed during the course of one regional. They failed in exactly the same way and likely cost us a qualification round. We had the second one fail on us during the QFs. Fortunately, because of good planning and an amazing display of teamwork, we were able to swap out and install an spare transmission assembly in between matches. Our drivetrain is a 6 wheel-drive using the KOP wheels with the center wheels lowered.
Well, I guess we won’t be using these transmissions next year.
We will pull them out and rebuild them for our next 2 competitions.
Does anyone know the precise diameter of the pins?
I think if we insert a short pin into the top of the planetary gear, this may prevent the longer pin from coming out, in addition of course to putting some thread locker on the ends of the long pins.
Team 1323 had one of our transmissions lock up. We were running the two CIM adapters to the kit banebot transmission with a new carrier plate and the spur gear in the center had pushed the inner carrier plate out and was making the Global Gears bind. Team 1778 in the pit next to us had this happen twice with two different Transmissions and they were only running one CIM to them. Anyone else have this problem
We had the same problem - the pins came out of the new carrier plates and one of the planet pinion gears stripped. I posted a long explantion on this Our Banebots Experience thread.
We had this happen in testing. Locked up so bad couldn’t turn it with a 5" wheel on it. Single CIM, 40lb bot, slippery surface. Took it apart, greased, put back together, ran like butter.
Yes, it has happened to us, multiple times. Those carrier pins shoot out after less than an hour of driving on our robot- and we are simulating competition defense. This really is not good.
Yes… In NJ we took them to the machine shop and had them spot welded. That seemed to hold them for the rest of the regional. I don’t know if that fix will last.
My biggest concern here is that we’ve replaced a predictable failure (increasing backlash until the double d fails) with an unpredictable failure (pins pulling out of the carrier plate). If this is the case we have made a bad situation worse and almost makes me want to consider keeping the weaker carrier plates.
I’ll get them pics up tonight for all to see.
Basically in the high stress situations inside the transmissions, the pins holding the carrier plate to the gear array slipped right out of the plate. Slip fit pins anyone? 
Not good.
That was our fix, and I’ll post a pic of that as well for reference.
it’s my understanding that the pins on the replacement plates are shorter than the originals…has anyone tried simply taking the pins out of the original plates, and putting them in the new plates?
maybe that’s too easy…
I think the problem is not short pins, it’s over sized holes. The pins do not interfere sufficiently with the holes, so they walk out under load. Fatter pins won’t work because their diameter has to suit the planet gears, so the only fixes are to (1) remake the plates or (2) somehow retain the pins in the existing holes; some have suggested using Loctite, others spot-welding. The latter has proved reliable enough for one event, so far.
edit: I have heard one additional suggestion. Since the pin holes are actually tapered, larger on the gear side of the plate, it might be possible to press them through so that they extend on the opposite side and thereby make the fit more secure. Then the plate could be installed “inside out”. Don’t know if that would help – the spot welding idea seems better to me. /edit
are the pin holes tapered before the transmission is put to use? maybe they get tapered as the pins move around?
anyways, the pics I saw of the new plates show the pins are not pressed in all the way, and I believe this is because the pins are too short. every team has(had) the original long pins…don’t cost nothin to try them…
On the spare carrier plate subassemblies I saw at St. Louis (AFAIK there should be spares available at each event) the pins were pressed in flush with the back side of the plate. We tested one by applying light hammer force to a punch and it popped right out. We gaged that hole and measured that pin diameter, and concluded that at least some of the holes have insufficient interference fit to the pins. It is true that the measurement of hole taper was made after removing the pin, so that may have had some effect; however, the same taper was apparent in a “new” part and in one that had failed after short use.
I noticed the new plates have a letter stamped into one side (was it a K ?). Does anyone know what this means?
Anyway, this may be the perfect application for Loctite 680 retaining compound. It is great stuff. It took a torch and an arbor press to get off a gear on a CIM that was a slip fit on that had a drop of that stuff on it. Just make sure surfaces are relatively clean. (no grease).