shifting gear box recomendations

Our team is looking at purchasing a shifting gear box to run a low high torque to a high speed output.

We have used sonic shifters in the past and were happy with those. Anyone have any other recommendations for another type or brand?

Go teams!

Vex ball shifter: 2 cim or 3 cim

West Coast Products dog shift: here

Vex is more inexpensive but IIRC WCP is lighter. Also, Vex is sealed whereas WCP is open. Beyond that I don’t have too much experience but I do know that both are quite popular among FRC teams.

You can find a full list here:

Our team has used the AndyMark dog, Vex ball, and WCP dog shifters in the past.

It really depends on the contest, Recycle Rush for example was really a single speed gear box year. We focus on the spread, and the tire speeds that we want and not so much the vendor. Wide open fields tend to favor top speed, where congested fields tend to favor acceleration rate. Each gearbox has unique mounting points, and envelopes that need to be considered as well.

A few comments on each.

AndyMark Sonic Shifter - Pretty battle tested design with some steel gears. Stock case is quite heavy. We would water-jet custom plates and uses spacers instead. Available in a 2.56 and 4.0 spread. Multiple options for encoder types and mounting. Four 3rd stage ratio options per spread. Simple to custom machine an output shaft.

Vex Ball Shifters - Used for one year with no problems. You can use the 3 CIMs gearboxes with 2 CIMS. Available in 2.06, 2.16, 2.27, 2.65 3.68 spreads with a four of 3rd stage kit options. Limited to their gear driven encoder setup (Grayhill or US Digital shafted). Custom machining a third stage output shaft slightly more challenging. Only sealed design.

WCP Dog Shifters- We used the DS Flipped Version last year. It was a first year gearbox and required a little creativity at times. The Flipped version has 10 different spread options from 1.28 to 4.05, and 8 3rd Stage ratios available. A lot of choices, but most are not useful to typical 4" to 8" tire sizes. Custom machining an output shaft is straight forward. Lots of encoder mounting options.

We typically make our own output shafts out of 7075 Hex stock. This allows us the option to reassemble the gearboxes later as a COTS part for use in other years.

Unfortunately, I cannot recommend the WCP 3-CIM dog shifter. We used it last year, and had a plethora of problems:

  1. While it is supposed to be possible to mount it to the 2x1 with a VersaBlock instead of the gearbox mounting plate, this is prone to failure as the 10-32 bolts strip out the holes in the face of the gearbox.

  2. This could potentially be mitigated if it were possible to use the outer gearbox bolts (the ones that go through the spacers) to reinforce the mounting, but tightening these (at least initially - see later elaboration) causes the gearbox to bind.

  3. The plates are flimsy. The gearbox as a whole notably “sags” over time, and the top CIM (which is mounted on a cantilevered section of plate) can sag enough to cause minor problems with the quality of the pinion mesh as the shafts end up out-of-parallel. This can be mitigated somewhat - the whole-gearbox sag by additional mounting, and the individual motor sag by placing a spacer between the motors - but this is a pain and should not be necessary if the thing were better-designed.

  4. The flimsiness of the plates results in gradual plastic deformation in the plates over the lifespan of the gearboxes. In particular, the forces from the dog seem to have caused the inner plate to have “ballooned.” Ironically, this wear on the gearbox served to alleviate the aforementioned binding issue by providing more slop on the shaft - but I do not like relying on bugs cancelling each other out.

  5. The positioning of the shifting cylinder is unfortunate. The cylinder itself is not so much a problem, as the pneumatic fittings that must go in it - they end up frighteningly close to the ground. We’ve lost a whole bunch of them this year to slight irregularities in the drive surface.

I have had good experiences with WCP’s 3-CIM single-speed gearboxes before, so the relative lack of quality of this particular product is disappointing. We will be trying VexPro’s alternative in the near future.

We use the Andmark EVO-shifters (2 CIMs), they seemed to work well enough - at least, after we replaced the defective part. The screw did come loose a few times, we ended up super-gluing it or something*.

*I’m not part of the pit crew

While looking at find robot parts I noticed 221’s gearbox.
Does anyone have more info on the SuperLight SuperShifter Transmission?

Definitely Vex Ball Shifter. The support line for Vex is pretty reliable. We had an issue at a regional due to human error and Vex offered to one day ship us a part before playoffs.