pic: CV Robotics WCD 6wd Drivebase Prototype

95% complete render of our 2015 Prototype drivebase

Wheels are custom, polyurethane tread
No welds, only pop-rivets
Comes with the new Glossy CIMs :stuck_out_tongue:

This render is missing hexshaft, hex holes on wheels, chain, fillets on gearbox pocketing, and has some miscellaneous holes in the 2x1. Also, our electrical components are omitted.

Why are you not using Versa Blocks?

They might be using the COTS WCP ones or one they machine in house. Its dark so I can not tell much. We used versa blocks last year and are switching to the WCP version because…

  1. We wanted to enter a new field this year with machining. Something as simple as slots for them is a good practice that is not super complex.
  2. It gives a MUCH cleaner look.
  3. Although super minimal, it saves space and some weight.
  1. You can mount things right above the slots easier

Sorry I meant the WCP Versa Blocks. It does not look as if they are using them, however i could be wrong.

I think a waterjetted bellypan only makes sense for a handful of teams (and it’s still wastefull then…)

Garolite or 4-6mm high quality plywood are plenty strong, and easy to mount electronics too.

My personal preference is the wood painted black.

the water/laser time put into a bellypan can cut out several systems worth of parts elsewhere on the robot.

Looks great guys!

And I wonder how many people went looking for Glossy CIMs after seeing this post. (Guilty.) :stuck_out_tongue:

Bingo, the Versa Blocks take up extra space and change the profile of the extrusion. We are using WCP Side Bearing Blocks in this drive. Sorry about the black parts, this render was the only one I had on hand.

We have a shop that’s offered up their CNC Plasma Cutter. We plan to cut it, then check tolerances to see if it’s good enough for use. If it isn’t, our fallback is to use one of our schools CNC routers to machine a wooden bellypan and paint it black.

I got a few PM’s about the glossy CIM’s. Regrettable to report, but they don’t actually exist

I cannot stress enough how important it is to test new fabrication methods before the season. In 2013 I tried to cut a bellypan out of .090 5052 Al on a plasmacam machine, a machine I had never used before. When I came to the shop and showed the staff what I was making they told me it wouldn’t work, and they were right. As I was cutting out the profile the sheet began to warp, I had to give up shortly after I started because the sheet bent up and hit the torch. This is exactly what I was warned would happen.

Before you take the time preparing to go to your sponsor and make the test parts I recommend you talk to an operator first. They will know the machine and it’s limits and can tell you if your parts can be made on their machine and even give you tips on how to design your parts to be easier to cut. The main things you need to convey to the operator is the materiel, its thickness, and the complexity (run time) of your parts. With that information they should be able to tell you if they can cut them without the sheet warping.

There a several teams with in house CNC plasma cutters, you should be able to find them with a quick search. I would recommend talking to them as well, they can provide you with valuable insight on how to best utilize a plasma cutter for an FRC team.


Looks nice guys. Will you have a prototype on your Bunnybot robot or will you be using another drive train? For last year’s Bunnybot competition, we field tested our first swerve modules on 2471-A. It was a valuable system for us and I recommend it for you guys if you have the time and budget. Of course, a gen 1 swerve drive is bound to have a few kinks to work out, but you never know. It’s just a tip.

If you do insist on having a machined bellypan, make yours lighter. We shoot to have ours be around 1.5 lbs for an 1/8" thick sheet of 6061 aluminum. I noticed the strand thickness on your bellypan is much thicker than the thickness we usually design for, so you could probably go a lot thinner than you currently do.

A useful tip
[spoiler]Note: We design with a total strand thickness between .15" and .17", which when done without forethought could result in warping and loss of torsional strength. Do what works well for your team. Don’t just do something because we do it (Central Valley people are crazy :wink: ).[/spoiler]

I’m assuming you are choosing to use a custom transmission because it fits your resources better than a COTS one, though if it doesn’t I could always lead you to some sources about why COTS transmissions are a great solution.

All that aside it looks like a very promising design that will serve you well should you choose to use it for the 2015 season.

Why did you guys decide on using chain instead of belts?

I hadn’t considered that it would warp, thanks for pointing that out! I’ll look into it. Our sponsor wasn’t sure, they are primarily a steel outfit.

I neglected to mention that we are building this drive right now, the 2x1 entered machining yesterday. Unfortunately for swerve drives, we subscribe to the “swerve is never necessary” ethos. Even though I think your drives are pretty brilliant.

The strand thickness was fairly arbitrary, we weren’t sure how thin we could go and still have torsional strength, looks like we can scale it down a fair bit (though not to your level…yet)

I’d prefer a COTS gearbox over this one, but we use the gearboxes to teach advanced CNC code to students. All of the CNC code used to mill these gearboxes is handwritten. The only other advantage to this gearbox for us is it sits much lower than a WCP or Vex gearbox in the frame. Personally, I’d like a 2-stage gearbox (16.8 FPS is high) w/ shifters, but team history precludes that effort for the time being.

It simplifies our drivebase, with belts we would need tensioning blocks and would also run the small risk of snapping a belt. We ran our drivebase without chain tensioners last year, and that’s carrying over because it worked so well (71 matches, still within tolerance).

If you are not tensioning your chain, then why do you have bearing blocks instead of just placing the bearings in the tube? If you have milled slots in your tubing and bearing blocks like you mentioned, it is a simple addition to have cam tensioners added in that could easily stop a potential problem from happening. They’re no work at all for a season-long reassurance.

To be honest, we weren’t sure how the cantilevered shafts would affect the 2x1 bearing holes. Last year our shooter utilized 2x1 with bearings mounted directly into the 2x1. Over the season, the pressure caused the holes to ovalize. The forces aren’t equivalent, but the construction is. I linked a pictureof our shooter mechanism (JVN Cam).

I wasn’t aware you could add cams to thistype of bearing block

Look at 2791’s recent drivetrains. I’m sure Chris Picone can elaborate more on their processes, but they run a C-C WCD variant without blocks and haven’t experienced any problems that I’m aware of.

And those cams were invented for that kind of bearing block. :wink:

Those blocks are designed to be put in slots and moved by cams. That’s exactly how our drive worked last year. If you use the blocks, it doesn’t hurt to slot them and make them slide.

EDIT. Andrew beat me to it.

This is why I love Chief Delphi, I feel stupid for missing that :eek: … Thanks for pointing it out

I learned that a month ago, and had the exact same feeling.

Are CIMs glossy or am I clinically insane… :confused: