Gearbox Standoffs & Electronics Mounting on WCD

What’s up CADers!

I was designing some WCD just to get better and quicker at it, also for fun :stuck_out_tongue:

I tried using AndyMarks Evo Shifter (3 CIM), since it could be a good option after the kinks have been fixed this past year, and I noticed the mounting holes interfere with the chain if you are using a < 22t sprocket (#25). 22t sprockets are fine, but when chain is wrapped around them, it has a larger diameter than 2", which means that it hits the bellypan…

Here are some pictures of what I am talking about:

Hidden boxtube and wheel Here you can see that the 22T sprocket barely clears the standoffs, but chain clips the bellypan at the bottom

In these pictures I cut out slots in the bellypan where the chain goes, but that means it is being held only by the ends, which isnt good. I was wondering how you get around this, last year we added an extra plate that goes onto the boxtube and basically converts the gearbox mounting holes to whatever we want, which worked but were heavy, since they were 0.25", and took up width on the chassis.

My second question is putting holes in the bellypan for electronics mounting. Currently what I do is lightning the bellypan first, layout the electronics in the assembly with mates, add material where needed for mounting, then use external references (The Assembly) to put the holes so if I move the electronics in the assembly, the holes go with it. But this is reallllly inefficient and it takes a long time to add the material for each mount, then make the proper cuts. Does anyone do this differently or have a better process for this?

Thanks in advance!

With a WCD, I assume that you’re running the center wheel lower than the outside wheels. On 1836 we typically lower the center wheel half of the desired drop, and raise the outside wheels the other half. This means that you have more than 2" to fit your sprockets on the outside wheels, and the middle shaft should have a slot in the gearbox anyways.

Now, simply to fit your sprockets is not a great reason to do this alone, and many teams (including 1836) have run 18t or even 16t sprockets on drive without problems.

+1 on using 18t or 16t sprockets; that will make the bellypan/chassis much stronger as well.
Apart from that, looks good to me. Your bumper supports are somewhat inadequate, and you may want to copy something that other teams do involving box tubing or something else a bit stronger. 254 is a good place to start for ideas.

I might have made it unclear in my original post, but the issue I had with the 16 or 18t sprockets was that they clip the gearbox spacers that mounts the gearbox to the boxtube. See here:

(Changed Pitch Dia to that of an 18t Sprocket)

So 16 and 18t sprockets don’t fit, and the 22t sprockets hit the bellypan.

We’ve run far weaker bumper supports before (both with and without metal frame on the bumpers) and it worked plenty fine when doing full robot/half robot bumpers.

I was thinking more of inspection (we’ve had variable results from wimpy supports before). Interesting that you’ve had good results from them though.

To OP: why not just move your spacers a bit so you can have the stronger bellypan and smaller sprockets?

How can I “move” spacers that use mounting holes from the gearbox…? The spacer simply provide the right distance from the gearbox to the boxtube so the bolt can clamp correctly. I might be missing something, but I dont think you can just move them?

The standoffs here are probably good for a few thousand pounds in compression.

Sometimes inspectors need educating during the process.

What is the ID/OD of your spacers? I’m sure some teams have used these gearboxes with a WCD, so there must be a decent solution. Andymark designers know what they are doing, and with so many teams using 2x1 West Coast Drivetrains there must be a solution. Maybe someone who has used these gearboxes before on a competition robot can speak to how to mount them.

You could use the 221 17t double sprockets inside the tube as another option.

Other WCDs avoid this problem by running the sprocket inside the gearbox instead of outside it. Make the spacers holding the gearbox together longer, and put the gearbox right against the drivetrain frame.

If I were an inspector, I would be more concerned with the spacers wiggling vertically than their ability to take hits. Those spacers look like they could come loose after taking many hits and leave you with wobbly bumpers. Did you do something to counter that, or did you find that they simply didn’t come loose?

Using that reasoning no robots that use fasteners should pass inspection.

We rarely ever have bolts come loose.

We used standoffs in 2016 that we’re far stronger in compression than the tube they bolted to. I’d wager our supports we’re more adequate than 90% of teams.

Although we used boxtube supports like you mentioned originally this year, I was confident that with some blue locktite, it would be able to hold up to any T-Bone we get during a match, we do half bumpers so the front and back hold the bumper really well, I thought this could cut down machining time and maybe even be more effective for side hits.

As Bailey posted above a second before ^^ :stuck_out_tongue:

So what I’ve done is just made a plate that goes right onto the gearbox plate that just changes the hole pattern, this seems pretty ridiculous but its the only logical thing I could think of, Chak’s suggestion requires making all new shafts and spacers, and taking the gearbox apart, which could be a whole day by itself , so I think this makes a bit more sense:

Let me know if you think there’s a better solution!

I find it odd that the Evo gearbox is hard to make WCD compatible. Can a 16t sprocket not fit inside the gearbox?
Adding new spacers should only take a few hours assuming a complete gearbox at start. Considering that you need to assemble it from scratch anyway, you might as well just cut a couple longer spacers in the lathe on day 1. Your adapter plate isn’t bad at all, and actually might make mounting the gearbox easier, but it’s kind of a weird way to do things.

I agree its weird but it would be a quick thing to make in build season and it solves it pretty well. You said the gearbox has to be put together, when we purchased our Sonic Shifters this year they came assembled, how do you know if it comes as a kit or not?

Here’s picture of the pretty much finished drivetrain, I mounted electronics, and Ill figure out where pneumatic’s go once I finish the super structure.

I’d be very hesitant to put the main breaker where it is. That spot on the corner can be really easily hit with a missed shot etc. (dependent on your superstructure of course), and doesn’t make much sense given your battery and pdp placement. It’s nice to limit the wire length between battery, main breaker, and pdp for a number of reasons, and it seems like there should be a better spot somewhere for the main breaker to go. Other than that, looks solid!

What is the function of the big holes on the crossmember? They seem to be lined up with your drive rails, but I’m not sure what they do?

looks like bumpers would protect the main breaker there.

Also that hole might be for a screw to tension sliding bearing blocks.