2073 is looking into WCD, feedback requested

[TikiTech]

Howzit!

We started using WCD last year and really like the performance. So unless the game dictates otherwise we will be using it again, though possibly a hex frame 8 wheel WCD.. I posted earlier
..
A few things.. Top render has the transmission constrained on the wrong side of the drive rail.

You will be better off not using the versa blocks on the center and just drilling your center hole to use the WCD gearing block.
http://www.wcproducts.net/217-3634/

You will also need to drill a few holes on the drive rail for the bolt heads on the transmission plate to nest into. This will allow the transmission plate to rest against the drive rail giving much better support. You can run a dual sprocket on the transmission to drive each of the outer wheels.

I suggest #35 chain. We have been using #25 but last year we had to tension the chain more often due to our use of the WCD 3 CIM dual speed transmission. (great transmission by the way)

Also factor in a chain/belt cover. Nothing is worse than an electrical wire getting in there. Most of the time an encoder is mounted to one of the outer wheel shafts. Plus the judges like things to be safe!

I am sure I will think of more after I post this..

Good luck with this, looking good!
Aloha

[Michael Corsetto]

Bill,

We should arrange an in-person design review in December. It would be a great experience for both teams. We're not too far away after all

-Mike

[billbo911]

Originally Posted by Michael Corsetto

Bill,

We should arrange an in-person design review in December. It would be a great experience for both teams. We're not too far away after all

-Mike

Excellent idea! I know we plan on meeting with your team leadership to discuss CCC, maybe we can coordinate both things happening at once?

Everyone else, THANKS!! Please continue the feedback!

Great observations and suggestions so far. Correcting these details will go a LONG way to make this a successful endeavor!

[JesseK]

It looks like this setup only mounts the WCP gearboxes via 2 #10 bolts. Could you or your students provide an exploded view, or a close-up view, of the gearbox, rail, intended bearings, and all bolts around one side of the bot's center wheel? Making the rail transparent or semi-transparent would also help.

[billbo911]

I'm working with the student who created this to get his CD account set up so he can respond directly to these questions. The team is out of school this week, so communications are a bit slow. I hope to have him up on the board later today.

Originally Posted by JesseK

It looks like this setup only mounts the WCP gearboxes via 2 #10 bolts. Could you or your students provide an exploded view, or a close-up view, of the gearbox, rail, intended bearings, and all bolts around one side of the bot's center wheel? Making the rail transparent or semi-transparent would also help.

Thanks for the request JesseK, we will work on getting that up ASAP.

[AustinSchuh]

Looks like you have ~1" between the bumpers and the wheels. Consider pushing your wheels out a bit further. That'll give you more room inside the base for your electronics.

Why not stand the battery upright? The bumpers will extend to the top of the battery anyways, and you gain a bunch of space back.

The 20/30 amp fuses are hard to get to and see. Move the radio up a lot, or somewhere else.

Considering that the electronics will change next year, can you get models of them and try fitting them into your base instead? That'll be more valuable (and they are smaller!)

[R.C.]

Bill,

The things I would change:

-Don't use a full versasblock per gearbox, use 1/2. And mount the gearbox so the face of the gearbox is flush.

-Use the WCD 2 CIM DS and ditch the belts inside the tube. Go to 18T sprockets and run chain, you'll be much happier. If you still want to run belts, I would read some of the posts/docs on here about tooth size and width of belts.

I would comment on the electronics layout but Austin has me beat!

[chrisfl]

Do you have the center wheel dropped lower? If so, how much lower? I think I have seen some teams that did not drop their center wheel, how much of a difference is this? Is it beneficial or not? For those that did not drop the center wheel, would you recommend it?

[billbo911]

Originally Posted by chrisfl

Do you have the center wheel dropped lower? If so, how much lower? I think I have seen some teams that did not drop their center wheel, how much of a difference is this? Is it beneficial or not? For those that did not drop the center wheel, would you recommend it?

The current design has a .125" drop.

Many of the suggestions here have been incorporated into an updated version. I will see if I can get the improved version up soon.

[R.C.]

Originally Posted by billbo911

The current design has a .125" drop.

Many of the suggestions here have been incorporated into an updated version. I will see if I can get the improved version up soon.

I'd recommend using colsons and then shaving down the center wheel till happy with your drop. We started out with 3/32 and ended up with 1/16 or none.

[billbo911]

Originally Posted by R.C.

I'd recommend using colsons and then shaving down the center wheel till happy with your drop. We started out with 3/32 and ended up with 1/16 or none.

Did you find 1/8" gives too much rocking of the chassis?

By intentionally shaving down the center wheel, which usually wears down fastest anyway, aren't you introducing a different effective FPS from the center wheels than the front and rear wheels? I know this is done on purpose with some 4x4 vehicles to increase traction on surfaces that will allow slippage, like sand or gravel. Are you suggesting to do this as a way to determine optimum drop, or something else.

[TikiTech]

Originally Posted by R.C.

I'd recommend using colsons and then shaving down the center wheel till happy with your drop. We started out with 3/32 and ended up with 1/16 or none.

^THIS ^

We started with 1/8" and kept it. By championship it was worn close to 1/16th and ran like a champ.. Though might of been that WCP 3CIM DS transmission...

With the deformation of the carpet and the Colson wheels, it was ready to go at 1/8" !

I will get the CADs up over the long weekend.. like the end of it because the weather is great!

Aloha

[billbo911]

Thanks everyone who gave suggestions and comments. This is almost becoming a "Design by Community" project.
Here are two new renders. Most of the suggestions have been incorporated now. In the oblique projection, we noticed the tension cam is on the wrong side of the block. Ooops! It is corrected in the overhead render.





Full Res images here and here.

[TikiTech]

Originally Posted by chrisfl

Do you have the center wheel dropped lower? If so, how much lower? I think I have seen some teams that did not drop their center wheel, how much of a difference is this? Is it beneficial or not? For those that did not drop the center wheel, would you recommend it?

If there is no drop center you will run into scrubbing (robot hopping from the outer wheels having too much traction to allow smooth turning). I have seen the use of Omni wheels to resolve this on a non dropped WCD.

1/8" drop is the norm for the center wheels. If you keep the weight centered well enough, spinning around is very easy! As mentioned, even when weight is not centered, on a drop center drive the robot will rock to one end and essentially be 4wd with a short wheelbase, which will turn much easier with less scrubbing than 6wd non drop..

Yeah robot doughnuts!

Aloha!

[RandeJ]

We're also looking at WCD this year and doing something similar to your setup. We are mounting the gearbox with the WCD mounting block and then using chains & sprockets to get to the other wheels. Pic show concept - brown items are the chains (not belts).

Definitely planning some sort of chain guard/cover.