I’m presuming that these are built from three planetary gearsets – one 4:1 and two 3:1. Does anyone know if this is correct and which of these stages is the final reduction?
I am trying to source a replacement gear set, and I again presume it’s the final stage that failed since that’s what common sense suggests. Banebots has very limited stock right now and I want to make sure I can find them something that has as many replacement gear sets as possible.
Also, if anyone happens to be sitting on a 42MM 36:1 gearbox, let’s talk about what it’d take to overnight it to Portland for me.
This isn’t for our team, for what it’s worth, so I have very limited knowledge right now.
one clue is that they specify this pinion for the motor, indicating that the first stage is 4:1. So, it seems likely that the second and third stages are 3:1. (the 27:1 gearbox specifies a 3:1 pinion)
Madison:
Are the secondary stages interchangeable with the input section? If so, Banebots has 48:1 gearboxes available, which have 3/4/4 (note that the Banebots site is wrong as to which pinion is required for the 48:1). If the team in need has the 4:1 pinion already, or orders one, could they use 1 48:1 to repair the 36:1 which is broken?
M
I’m pretty sure they’re interchangeable, but I don’t have one in front of me to check to be sure. We’ve got a 36MM gearbox lying around somewhere and the rest are on last year’s robot.
We’ve got some replacements on the way thanks to Adam and 973. I’m trying to solve the problem that caused the failure now, but since I’m largely guessing at what happened and the work is unsolicited, it’s challenging.
Madison, I’ve had a little experience with failures on the Banebot’s trannies. If you can describe what the problem is, the more detail the better, I might be able to help you determine the cause, and the solution.
Unfortunately, I only know of the problem through e-mail and only that a local team was looking for replacements for one stage of one gearbox. I’m waiting to hear back from that to see if we can localize the problem better and find the cause. My hunch is that the gearbox output is unsupported and side loading caused the final stage to seize and destroy its planets, but I’m not sure and may not find out until tomorrow or Thursday.
That is the exact cause I have seen over and over. Unless the carrier pins fail, not supporting the output shaft is the most common cause of failure I have seen.
Let us know what you find.
Hey, I’m Kyle Corbitt from team 1318. We’re the people who broke our gearbox.
First off, many thanks to Madison and all of you for helping out! We had hoped that someone would have these available, but I am simply overwhelmed by the level of support we’re getting from the FIRST community.
The gearbox broke late Monday night, about an hour before we had to ship the robot. In our brief postmortem we discovered that the final stage, as logic would indicate, was the one with the problem. In the final stage two of the pinions had sheared at the plate and all of the pinion gears were missing multiple teeth. Unfortunately, without my knowledge someone put the broken gearbox in the crate with the robot right before we shipped so it’s sitting in Portland right now, beyond further inspection. I’m not sure what failed first or caused the failure but side loading is a definite possibility. Our team will try to rig something up to improve that. Essentially, we’re taking our first stab at a crab drive setup this year and there’s a LOT of friction in the units. The banebots gearbox is used to turn the module.
Our current plan is to order two 48:1 gearboxes (one to use and one spare) as functional replacements and get them delivered to us at Portland. Thanks for the idea Madison, I have NO idea how we overlooked that alternative.
EDIT: Here’s a picture of our robot with one of the mentors working on it. You can see the BB gearbox with the FP motor at the point and the chain running to the wheel module. I also have CAD of the whole machine if anyone is interested.
In that low of a ratio, even stalling the motor won’t cause the final stage to fail like that. To cause the final stage to fail like that you need to put a side load on the shaft. The only thing holding that final stage in alignment is the output shaft, so if there is a side load it will cause those gears to get mangled.
Sorry to burst the bubble on that, I’d just hate to see a bunch of false hope in the 48:1s just fixing the problem and have them fail similarly.
Your team has produced an innovative design, and I’m sure you all will find a viable solution if sideloading is the root cause (as Adam’s insight supports). I’m sure you’ve seen the bearing blocks offered by Banebots for these gearboxes. We are using the smaller version (3/8 shaft) for our ladder sprockets, and are pleased with the quality of their construction.
Yes, we used the Banebots bearing blocks to support the 56mm big brothers of these that came in the kit last year. We’re working on a design right now. Thanks for the support!
