My team is looking at getting a new kind of shifter this year. The two we’re currently looking at are the WCP DS three cim gearbox and the Vex Ball Shifter, both with the third stage. We’ve heard about some issues with the vex aluminum shaft wearing down and haven’t found anything on anyone else using the WCP before. We would like if we could easily attach an encoder to whichever we choose. If you’ve had experience with these and can share your experience it would be very helpful.
Both the WCP DS and the VEXpro ball shifters are good quality.
Only the VEXpro ball shifter has a 3rd stage
The output shaft of both gearboxes is made from 7075 Aluminium that is anodised. There shouldn’t be any problem with the shaft wearing down when used correctly such as in a WCD. The shifting component either Dog or Ball can wear though.
The VEXpro ball shifters allow encoder attachment while the WCP DS does not. If you are planning to use a WCD this is not a problem as the encoder such as a grayhill or a CTRE mag encoder can be mounted to an outer axle. If necessary a CUI encoder, First choice 2015 and 2016 can be mounted to one of the CIM motor shafts of the WCP DS using this great thing http://www.chiefdelphi.com/forums/showthread.php?t=138750&highlight=WCP+DS+encoder
While the WCP DS is designed especially for use in a WCD. The main difference is the type of shifting, the WCP DS is a dog-shifter while the VEXpro ones use a shifting ball. There have been a lot of discussions on this topic on CD previously.
I haven’t heard of the Vex shaft wearing down except briefly in 2014. They have improved it since then so that it no longer wears.
As stated above the encoder attachment is nice. If you have a lathe sticking an encoder on the WCP one is quite easy either by modifying the gearbox upper shaft or on the drive axles. I would just go with whatever is cheap (assuming you can get over the encoder stuff).
First of I love seeing people recommend my stuff. Second of be careful because I do belive the first choice variety of CUI encoder is the 101V (need to check that) which is right angled making it harder to use. Also the WCD gearbox verison requires machining to the pinion or you need to use andymark pinions.
That said for gearboxs I would go with WCP DS, why well I have heard of teams wearing the ball shifter out over a season. After a season with DOG shifted we are planning to reuse internals because the are still in good condition.
I’ve checked on the FIRST Choice website 2016 and it’s the AMT103-V, I’m not sure about 2015.
The AMT103-V is almost identical in size to the AMT102-V, the problem is that the encoder output pins are perpendicular to the encoder face, rather than parallel in the AMT102-V. I’m sure it’ll be able to work if necessary, but the CIMcoder housing may have to be thicker to account for this, which would result in more output shaft being used up.
Sorry I meant 103V I knew it was on of the two. Don’t want to hijack this thread. PM if you would like to talk about what would and would not work with the CIMcoder.
DOG shifting has a much better track record than ball shifting in my experience with FRC. Between the WCP and the VEX I’d use the WCP for this reason. (I know that an all steel andymark supershifter can last half a decade or more. Depending on your resources this may be a worthwile 3rd option, heavy and expensive though.)
The ball shifter is quite a lot more versatile in that it can be more easily used outside of a WCD style drivetrain.
The WCP gearbox integrates into a WCD much more nicely (no 3rd stage necessary unless you want to run massive wheels). My experience with the ballshifter using the 3rd stage and versablocks is not very good. There’s a lot of load on 4 #8 screws which tend to loosten and are a pain to tighten. YMMV.
reiterating the encoder comments
We can give you the pros and cons of each gearbox and our opinions on them but it’s up to you to weigh these factors and ultimately decide.
Use caution if you mount the encoder to the first stage of the WCP. This injects a dependency on the pneumatic setup and the ‘default’ gear in code just to get accurate counts. The real danger is that someone swaps the tubes on a single solenoid setup so that the physical ‘default’ gear is swapped, yet no one thinks to change code before testing autonomous. The result of that (from experience) is that the robot will go way further at a very high speed, and the bookshelf at the other end won’t survive. :rolleyes:
My experience is with super shifters and ball shifters. 1310 got super shifters in I believe 2011 (maybe earlier) and have used the same internals in every year except last. On 865 we used ball shifters in 2014 and by the end of the season they were definitely showing signs of thorough wear. These characteristics have been parroted by nearly everyone I’ve talked to.
FWIW 2220 used ball shifters in 2013, and, aside from some assembly goof ups from us, they performed quite well on that robot, which also saw use through 2014 as a demo bot. I drove that bot at demos quite a few times and never noticed a significant performance drop, but then, I had my hands on it after three tournaments of competition. We definitely abused those gearboxes, and they held up quite well. Right now the ball shifters are probably what I’d get if I wanted shifting.
Not trying to invalidate you experience, but just providing a counterpoint to help avoid an echo chamber.
Which components were wearing down? Keep in mind that the plunger was changed from 7075 aluminum to 4140 steel after the 2014 season.
During autonomous I don’t think anybody will shift gears, and even during teleop shifting occurs in a fraction of a second.
You bring up a good point about switching tubes (those rookies…) but I would think that would get cleared up relatively fast. Also if one ran their auton in high gear that would mitigate any damage.
The gearboxes were still good enough for demo purposes so we never took them apart afaik.
Dog style engagement has a much larger contact area with much more positive geometry. I have yet to encounter someone having serious durability issues with them since the supershifter dogs were beefed up. The ball shifter is an excellent product but I wouldn’t buy one expecting to reuse it the way I would with a dog shifting gearbox (especially the steel supershifter). YMMV.
How did you know there were wear problems? We had issues with the shifter to piston linkage, but never with the shaft itself.