pic: WCD



This a basic WCD popularized by teams like 254, 968, 1538 and many others.

It also features 1515’s modular electronics. All the electrical slides off of the robot, utilizing Wago mass connectors. The battery locks the E-board in place.

First, thanks for posting this. I really like the orange and black paint job; we might be doing something similar this year.

I’ve got a couple of questions about your implementation of the WCP DS. What center drop did you use? Why did you decide to put the gearbox pockets in your bellypan so far in? In the DT I’m working on, with a 3/16" drop, the pancake cylinders will clear the belly pan by a few hundredths. Also, I believe the DS comes fully anodized black, so you might not be able to make the gearbox plates orange.

Finally, if you’re doing a waterjetted bellypan, why don’t you put the electronics on it? Your slide out electronics board is certainly cool, but having it with the bellypan (where most teams put their electronics) seems redundant. Is the bellypan where you’re planning on putting your pneumatic system?

Just one thing on the DT, I can’t see but I just want to make sure you have the bearing blocks really well connected inside the tube. On a prototype last year we just had 3/8 plate on each side with spacers and they would wouldn’t always be lined up correctly.

Besides that the drive looks like a run of the mill WCD and I’m sure it’ll work if it’s made well.

As for the electronics, what’s supporting the PD board? It looks like it’s just on 1/8 polycarb. You might want to think about supporting it because it looks like it’ll bounce around a lot and that might looses up connections.

By the looks of your design I assume it’s welded together?
Looks pretty slick, can we get some more photos of the electronics area?

We work very closely with 1515, so I feel like I can speak a little about this drive. The mortorq electronics system is modular. It’s very nice to have, but quite heavy. Basically both Mathew and I have tried to get Mortorq to use a regular electronics(non-modular) bellypan, but so far they have been resistant to the change. This isn’t the final iteration actually though.

The bearing blocks(at least on this iteration) should be fine. They are the 973/1323 bearing blocks.

We are actually not using this bellypan. It was designed more for the aesthetic of the rendering and would actually be useless because it does not prevent torsion in the frame much at all (because of the typography in the center).

Instead, we are using a waterjet 1/16" ABS bellypan with a few large pockets rather than the conventional diamond pattern.

As to the electronics, 1515’s electronics for the past 3 years have utilized c-channel slides and either a reinforced corroplast or polycarbonate. We use WAGO X-comm modular terminal blocks to allow us to easily remove all the electronics in a matter of seconds. Is this level of modularity necessary, or perhaps even desired? No. However, it is a technique that has worked for our team in the past and we do intend to continue modularity in electronics in the future. It is something that our programmers and electrical students both very much appreciate as it allows them to work independently and free of debris.

The bearing blocks are very similar to the 973/1323 ones as Michael said, but with a different bolt pattern.

Please note that while this is a “standard” wcd frame, a much more recent iteration (except for the abs bellypan) is found here.

EDIT: Also, the WCP gearboxes are anodized black and colors in both this rendering and that of our latest revision are simply for the sake of the rendering. (I actually helped with the WCP renderings).

I’m interested to hear this. What was the root of the problem (ie, if stresses caused undesirable misalignment, what was the cause), and what undesirable effect did this cause? Also, could you describe your setup? What changes did you make in your 2012 drive?

I ask because we’re contemplating doing something very similar for our 2013 drive. Here’s a screenshot of the setup we’re thinking of: http://puu.sh/1H1fU. We would have 2 3/8" plates on either side of the tubing, pocketed so they fit over 2x1 tubing. They would be kept parallel by the 4 10-32 button heads running between the plates, the shaft itself, and the tensioning screw in each plate.

We had two 3/8 plates that fit halfway into pocketed tube and two bolts with spacers holding them together. Tensioning was done with a bolt from the end of the box beam to one of the two spacers. With the chain pulling one way and the tensioner pulling the other, the shaft ended up at a slight angle. It still ran fine and wan’t much of a problem but it probably put additional load on the bearings.

For the season we machined one big spacer that pocketed into each plate and partially held the bearing on each side. Because both bearings where in once piece they stayed in line.

Do you have to take the transmission apart to change a belt?

Those look like chains. Why 2 sprockets on the ends?

DampRobot, I reccomend looking at 973’s CADs and checking out their bearing blocks. They are super easy to machine and are 1 piece. The side plates can be made simpler if need be(that’s what we did last year), but if you have a waterjet sponsor they can do it too.

The WCD is a chain drive. It looks like belt because chain made in solidworks is a solid piece. I’m not sure why the extra sprocket is there and a spacer would probably be in it’s place.

Hi, I’ll go on a big tangent that will talk a little about why I design with big gearbox pockets.

One thing that we on 2733 learned the hard way with our first WCD was that everything needs to be easily removable. Our bellypan didn’t have large enough cutouts in it to accommodate the transmissions when we were trying to get them out. Our second version (used at Bunnybot this year) had cutouts that were as big as we could make them without compromising the rigidity of the frame. It saved weight and friendships :wink: .

The basic rule for us: the pockets are cut to measure at least the length of the transmission (tip of shaft to end of the cylinder or motor, depending on the mount) plus one inch.

This is a fantastic lesson for all in this thread, not just WCD drivetrains even.

It’s usually far easier to service drivetrain components for the bottom instead of the top. Then you can build whatever you want on top without worrying about service. Fully removable gearboxes are also nice because you can work outside of the machine entirely, and you always want to be able to completely replace critical assemblies with spares without possibly forgetting a washer (or bearing :).

In fact, with recent drivetrain development, we’ve heavily prioritized bottom access to key components, especially chassis maintenance points. When game mechanisms get added on top, it’s too hard to access many of them from the top.

Michael is right, those are “chains”. I actually made this one in Inventor though. The second sprocket is, embarrassingly, a case of laziness. Now that I use SolidWorks, however, I use a configuration for the sprockets so that each wheel/bearing block assembly only has the single appropriate sprocket.

Also, in the current revision, the shafts are chamfered at the end as per the WCP Design.

Thank you for the suggestions regarding opening up the bottom. I will make sure to leave clearance pockets for maintenance purposes.

I take your point about the 973 blocks being easy to machine, but I just can’t get around the fact that there are 3 pieces that need to be machined instead of 2. I guess my question comes down to this: why do the bearings need to be in one piece, and if they aren’t, what happens? Joey’s response seemed to be that although this can cause the wheel to be out of alignment, nothing terrible happens.

On the other hand, if two piece (rather than 3 pieces) are hard to keep aligned, and this misalignment will significantly impact performance, a 973 (or 254, for that matter) style bearing blocks are the best option. I just wasn’t really aware that this could be a large problem, and want to make sure that we don’t make any drivetrain decisions that we’ll regret next year.

Sorry for hijacking the thread, I just want to learn a bit more about the ins and outs of WCD bearing blocks, like the ones featured in this design.

Or you could just do GT2 belts, C-C +.003-.006 and not worry about it? :stuck_out_tongue:

The advantage of pressing both bearings into the same bore is that they’re definitely lined up straight. You don’t need them to be perfectly in line, but then you’re going to wear out your bearings much more quickly, you’re going to sap efficiency, and if its bad enough, the whole thing will seize up. You’ll be able to see and feel the improvement of having the bearings in the same bore, but if its just impossible for you to do it that way, it can still work, just not was well

Just to note, 696 has always done two separate bearing blocks machined from 1/4" x 2" flat bar held inline by nothing more than the axle through bearings and 4 bolts and we’ve never had a problem. Much less machine time and material cost. Although, we may go for the fitted-tubes style next time, just to try it out.

Alternatively, you could make your bearing block out of a single piece of 1.25" wide by 2" high at 1/8" thickness tube, available at onlinemetals:

I know it’s 6063 aluminum; our drivetrain was made with the stuff last year, and it was just fine to machine.

Bore your bearing hole and a couple of screw holes, and then lop off the top of your tube to make a C-channel like piece. Slide it onto the robot, tighten down your screws, and you’re good. Our team used the system on previous robots before we moved away from the cantilevered drivetrain design; while I cannot personally attest to its effectiveness, as it was before my time, our mentors recall the solution as doing a fantastic job. Since we intend to return to cantilevered drive this year, we have of course revamped the design; a screenshot is here:

https://plus.google.com/u/0/photos/113039244236921832063/albums/5827806817806165217/5827806823682841202

All the advantages of imbedding your bearings in a single piece, without having to make three different bearing block pieces. I thought it was genius when I first saw it, and the material is readily available.

Seems like a pretty fantastic idea altogether. :smiley: Have you considered using rod ends instead eye bolts for tensioning? I might be misunderstanding how your system works, but the eye bolts in your CAD seem excessively large compared to the bolts being pulled.