So, this year our team is running a west coast drive with two of these gearboxes.
Given our limited access to precision machining, we attached them to the frame by means of a versablock, rather than the gearbox bearing block. This is, I believe, a supported mounting solution (at the very least, it is pictured on their website). In addition, we passed the two 10-32 screws that pass through the bottom gearbox spacers through the inner wall of our 2’‘x1’’ - but it is worth noting that these cannot actually bear that much load, as overtightening them causes the gearboxes to bind.
By the end of our second competition, both tapped holes in the gearbox plate for the 10-32 screws that attach through the versablock had completely stripped out, on both gearboxes. We were forced to replace them with 1/4’’-20 bolts. We hope that these will fare better.
So, if any other teams are using these in this way, watch out. And, if anyone from WCP is reading this, I would like to request that WCP either increase the strength of this mounting point, or else visibly discourage the use of versablocks for gearbox mounting on their website, so that other teams do not suffer the same problem.
1712 has used the Gearbox Bearing Block to mount our WCP single speed gearboxes in each of the past three seasons, and has done so without access to a mill. It requires a bit of careful planning, but can be executed on a drill press (or potentially even a cordless drill) without much trouble.
In 2015-2016, we used layout fluid, the scribing edge of a pair of calipers, and some math to place the locations of the holes to be drilled. First you determine the location of your center hole. From there you can score out a radius around that hole in the layout fluid. Then score out a line at the desired vertical displacement for the mounting holes (same distance from the edge of your piece to your center hole). Where the scored lines intersect is where you drill your holes. It was a bit of a slow and methodical process, but it worked.
In 2017 we simplified this greatly by taking advantage of the geometry of the VersaBlocks (as you alluded to). We marked our center hole, and drilled a pilot hole in that location. If you own a set of transfer punches, the rest is trivial from there. Center the versablock using a round bearing and the matching diameter transfer punch to your pilot hole (we used 0.500"). Then, with the versablock centered, use the appropriate transfer punches to mark the locations of the mounting holes (they are identical between the versablock and Gerabox Bearing Block). With all the holes marked, remove the versablock and drill each to the appropriate diameter for the Gearbox Bearing Block.
At one point (50th or so match of the season) one of the gearboxes started making the out-of-alignment noise. We inspected all of the teeth in the gearbox, and they appeared to be fine. We also verified that the CIMs haven’t shifted in their snowman holes, so it likely has to do with plate alignment. We’re still diagnosing it, to be honest.
It would be nice to have stockier standoffs on the bottom - even 1/8" wall tube instead of 1/16" would be nice. To avoid disassembly at this point, I think we’re going to make wooden braces between the plates, then use them to be able to clamp the outer mount bolts tightly without binding the gearbox. We’re also going to add churros to support the gearboxes against each other at the top, though I think it’s just meant as a slip-on brace rather than hard mount.
Did you email [email protected] with pictures of your part failure? That should be the very first thing you do - asking for help on CD is one thing, but contacting the engineers who made the product directly is going to better help you determine what happened than by asking a bunch of random people.
If you haven’t already, I suggest shooting them an email. RC and crew can be very quick to respond if you don’t wait too long to get to them.
When using the 3CIM products we always put standoffs between the motor sides of the gearboxes because that sagging is enough to cause misalignment and driving your robot around and 3CIM speeds is also enough to cause some serious damage without those standoffs.
Have you also looked at the type of wheels you are using and figured out if scrubbing is an issue? When the wheels scrub and the wheel attached to the output shaft pulls on the shaft during a turn that can cause some issues in the gearbox because of the alignment. Last year using pneumatic wheels showed us that issue.
We had shaft collars being spit out of the robot early this season because of scrub so we drilled and tapped every axle with a 1/4-20 bolt and a large cap washer on the end to keep the wheels on. We had a piece of #25 chain literally twist perfectly 90 degrees on us this season because we used those WCP alloy extra wide wheels. It looked like a joke puzzle. Would do it again 100% but with #35.
I had two separate teams at North Star this past weekend have issues with those “snowman” mounting holes for the CIM’s. Both used 12-tooth pinion gears, and in both cases the CIM’s had migrated to the outboard configuration (it was the second event for both teams) and they ended up destroying the pinion gears before they realized the problem. Fortunately, there were enough 14-tooth pinion gears sitting around in various pits to get them set up in the outboard configuration so they wouldn’t have that problem again. Personally, I hate those snowman holes when it comes to such a critical part of the robot. Give me something that isn’t going to move no matter how much I abuse it!
Very much agreed. We had this happen to us last year, and this year we are currently using 14-tooth pinions.
Given the issues we’ve had with the WCP gearboxes, we’re planning to try out the VexPro ball shifters this coming offseason, to see if we like those any better.
We knew this was a thing and ground down some metal bits to put in the void. Being able to select between 4 different speeds is definitely nice, but most teams don’t realize the extra steps/hassle needed until it’s too late.
All in all, I really like these gearboxes. We’ve inspected the dog gear & pin several times this season and found no issues, even after highly-stressful matches. This is the single-most critical point of season-ruining failure I’ve witnessed in any 2-speed gearbox. The key with the WCP DS is learning where to Loctite, using 14T gears (or void-fillers), and apparently standoffs between the two opposite 3CIM versions.
The one irritating thing about using 14T pinions is that they’re larger than the CIM boss, which means you have to press the retaining rings onto the CIM shafts once it’s already been installed on the plate.
Doesn’t that defeat the purpose of the retaining ring? If you’re using less force to press it on, doesn’t that imply that is the ring is no longer going to resist as much force?
I believe he means pressing the “lower” retaining ring on with the gear before mounting, then removing the gear (with the ring still left in place), placing the CIM on the gearbox, and then placing the gear back on along with the “upper” retaining ring. This means you only have to press the much easier of the two rings on with the CIM on the plate.
We found that problem with the 14t pinions as well. We ended up bypassing the issue by using a deep well socket to go over the ring onto the motor shaft and some light pressure on the arbor press. The socket presses down the ring while allowing the shaft to go into the socket. I cant remember what size the socket was but it is hard to get it wrong.
I can definitely see that. When we did it at the event, there was no way we were getting the gearboxes or the motors out of the robots, so it was really a moot point. Using the head of a socket wrench with an extension stuck in the end, you can usually get it in place and give it a couple of taps with a hammer to get the ring on. Makes it a LOT easier than doing it by hand, and helps ensure the ring goes on straight!
If that’s the case, yes, that’s exactly what we did in 2016 when using 14T pinions. It’s still more of a hassle than installing CIMs with the pinions and retaining rings already pressed on (especially in terms of pit maintenance).
The ring will resist less force. ‘Less’ doesn’t meant it will fail. The lateral forces of the gear down the shaft aren’t enough to overcome the retaining ring’s force if two conditions are met: 1.) The spacing between the pinion and meshing gear is correct. 2.) The bolts holding the CIM stay tight. With the WCP gearbox it’s very easy to maintain both.
We’re almost 5 raw hours into this drive train, including 58 matches. Including offseason, we have another 40+ matches to go. If we have a failure caused specifically by the retaining ring, I’ll be very surprised.