WCP DS or Vexpro BS?

Last season we used the 3 cim BS from vexpro, we loved them. We really only have one complaint; over the course of the season, we noticed more and more sag. We DID have a cross support between both transmission also. It wasnt that big of a deal…until we noticed scrape marks on the bottom cim from dragging. But we are looking into the WCP 3 cim DS, what are peoples pluses and deltas? From when you first got them till after a full season.

We used the 3 CIM Ball Shifters this year. We did make two small modifications after some issues we had last year that were quick during assembly. The first was we pinned the output shafts in after our experience last year with the loctite in the press fit failing and them falling off several times. The second was we put loctite on the screws that held the encoder standoff plates in. Last year we had them come loose overtime and by the time we noticed they ruined $100 worth of grayhill encoders. To access those screws you have to disassemble the whole gearbox which was something we never wanted to do after the robot went in the bag.

We also swapped the encoder gears for the replacement ones as the originals were slipping.

With those two modifications we’ve never had to touch them through six competitions and hours of demos and they have been the most reliable two speed gearboxes I have used.

I did notice some scrapping on the bottom CIMs however I don’t believe it was caused by the gearbox sagging as the rest of our lexan bellypan (which sits lower than the CIM) is also covered in scratches. We did span between the gearboxes using some AndyMark Churro tube. Something to keep in mind is with a 3 CIM shifting gearboxes it is a lot more weight your are suspending off the side of your drivebase that can bend overtime and cause the sagging.

When we were originally deciding what to use we were debating between the WCP 3 CIM SS, WCP 2 CIM Shifters, and the VP 3 CIM Ball Shifters. We knew in a defensive game we wanted a high and low gear which eliminated the single speed. We liked the Ball Shifter because it was an enclosed unit and the final factor was the fact that the VP 3 CIM Ball Shifters were $50 cheaper than the WCP 2 CIM Shifters (which is why we weren’t even considering the WCP 3 CIM Shifters). When purchasing over $1000 in gearboxes for two robots, saving a few hundred dollars was nice.

I have used a version of the WCP 3 CIM Single speed and the 2 CIM DS for the past few season and the work great. With a West Coast Drive setup they drop right in, and with WCP selling all the other WCD parts custom 6/8 wheel drive has never been easier. We have had no problems with ours over dozens of matches.

For an COTS option there isn’t anything else I would do.

Did you guys use the versa block on both sides or just the ouside? I have heard people talking about bolting the transmission straight through the 1X2 chassis rail and into the outside bearing block. Any thoughts on this?

It is more common in a tradition West Coast Drive for the transmission plate to be bolted in contact with the 2x1 frame rail on one side with the bearing block on the other. That being said it can be done with a block on both sides if you really want to, but you’ll have to have some good reasoning for doing so.

Hmm, Ronnie are you referring to the Ball Shifter with your question or the WCP shifter?

The WCP products are designed to house the sprockets between the plates
Single Speed Assembly in WCD configuration
Dual Speed Assembly in WCD configuration

The Ball Shifters are completely enclosed, so the sprockets need to be on the outside of the gearbox and also have some spacing away from the chassis rail itself. If you can solve that without an inner bearing block in the rail, then you don’t need the inner bearing block.

Generally speaking, a single shaft should only be loaded between 2 precision bearings. The more bearings you add, the more chance the bearings are precisely lined up in their mounting leading to inefficiencies.

The WCP gearboxes use only two bearings on the output shaft - one is on the inner gearbox plate, the other is on the outer bearing block (there is no inner bearing block). Spacers on the hex shaft keep the sprockets in place along the axle. This allows the outer plate of the gearbox to be direct-mounted to the chassis rail as Andrew described.

Thus I believe if you’re asking about the Ball Shifter, your question can be reduced to whether or not you can replace the bearing on the output shaft with a spacer, and then move that bearing to the outer bearing block. In theory I see no problems with this, yet I also don’t know how the Ball Shifter is mounted.

I only know this because I did some pretty thorough research on the WCP SS gearbox in WCD configuration since it’s the only WCD-designed gearbox that VEXPro has in stock at the moment and we want to prototype something this Fall.

No we did not use the versa blocks because we used a plate drive system this year. The construction was similar to the 2014 kitbot but with our own custom sideplates from 1/8in 6061 aluminum, live axles, and the 3 CIM VP Ball Shifters with mounting holes for the WCP line of gearboxes since we left ourselves open to try different gearboxes if we needed to.

All we used for mounting was 4 bolts that attach the 3rd stage to the main gearbox with the axle extending across to a bearing on the opposite plate.

The plate the gearbox mounts to has a cutout that allows the gearbox to be removed from the underside of the robot without having to slide the entire gearbox into the center of the robot (slide it out of the bearing on the far plate and it comes right out). The blue and red parts are just PVC spacers to keep the wheels and chains lined up. We color coded them blue (0.25in) and red (0.55in) so between two robots all spacers are the same and easy to identify. You can see the cutout I’m mentioning where the red spacer on the middle wheel meets the gearbox.

Picture 1

Picture 2

My I was wondering how people liked the WCP DS but we used the BS and experienced the sag with them. That being said, we used both bearing blocks. I will be looking at mounting the 3rd stage of BS directly to the 1x2 tonight. I can’t remember off the top of my head but I’m going to guess since it has the versa pattern on it, I should be able to directly mount it with only a few holes. That would more than likely greatly help the sag we experienced. Reason for asking about WCP DS was because I would like to use them in a WCD this fall. I also see it as a plus that the chain/belt runs are below the gear assembly instead of the external 3rd stage we had with the ball shifters.

If you do a west coast drive with the COTS stuff that WCP/Vex sells (including the WCP DS) you will be very happy. Personally I prefer 25 chain over the 9mm HTD belts (if you look at the Gates Manual and do the math this makes sense).

I haven’t seen one but I feel like I show throw up a cad model I have of a COTS WCD. To use the versa rails with the DS it’s basic drilling/boring. You need to make precise-ish slots to use the WCP WCD Bearing blocks, or just a big hole if you want to do go with the versa bearing block.

If you are unfamiliar with the nitty gritty details of building a wcd look around on CD and you will find lots of information. As with everything there is a right way to do it, and a wrong way to do it.

We did a WCD last year with the versa blocks and we loved it. I don’t know if i’m just not observant or they just posted them but those bearing blocks from WCP are something I didn’t see. Hopefully I can get my hands on some to test with this fall. Save money and they aren’t as bulky. Thanks!

They were on the VEXpro and WCP website all of last season.




I guess I was so happy about the versablock I overlooked them :cool: haha

Our white paper on building a belt driven Vexpro VersaChassis with 3 SIM ball shifter may be helpful.