pic: 3 CIM WCD Ball Shifter CAD

[nathannfm]

Originally Posted by Bryce2471

I think the WCP gearbox only has one web that goes vertically to the bottom of the CIM. That is what this configuration has as well. Here is a close up of the CIM mount:
https://scontent-a.xx.fbcdn.net/hpho...e9&oe=54D168FA

Ah, this clears it up, most of that webbing was not visible in the original render and that makes me much happier about the support of the CIM.

Originally Posted by Jared

The biggest change you should make is using the 0.75" boss on the front of the CIM to help locate the CIM. It'll increase the positional accuracy of the CIM by quite a bit, and it'll make the part even stronger.

This sounds like a good idea but I would caution that you should know the tolerances of that boss and the tolerances of the equipment used to cut the hole in the plate. We made our first waterjet part ever a few weeks ago with a 0.750" hole for the boss and suprise suprise it comes back and the CIM won't fit.

Originally Posted by Bryce2471

Here's a pic of it:
https://fbcdn-sphotos-f-a.akamaihd.n...d4841aad532276

Would this be all steel? I know the ball capture area is steel on the VexPro model presumably for wear reasons. Also, I know it would be pretty difficult to machine but I would recommend a fillet at the hex to round transition as that looks like its a pretty big stress riser.
Related to this component, if you make the hex shaft attach to the ball shifter with a pin or through bolt instead of making it one part it would make removal of the gearbox pretty simple. Just pull the pin, retract the shaft toward the outside of the robot and pull the gearbox either out the top or bottom.

Originally Posted by Chris is me

For those reading who want to learn, more on pocketing in this great video: https://www.youtube.com/watch?v=wGmsnD0KQMs

Also, just to comment on that video I prefer the "sketch fillet" tool to the 3D fillet tool as it crashes much less, trims your lines for you, and contains all your pocketing features in one "Cut-Extrude". Also, if it crashes you are already in sketch mode to fix it.

[asid61]

Originally Posted by nathannfm

Ah, this clears it up, most of that webbing was not visible in the original render and that makes me much happier about the support of the CIM.



This sounds like a good idea but I would caution that you should know the tolerances of that boss and the tolerances of the equipment used to cut the hole in the plate. We made our first waterjet part ever a few weeks ago with a 0.750" hole for the boss and suprise suprise it comes back and the CIM won't fit.

+1. Use the boss. If you just use screws, then the cim can wobble more than a couple thousandths and lower efficiency. The boss should be used.
We used 0.752" without problems last year, allthough it was sort of by accident- I plunged with a 0.75" end mill in place of a 5/8" and thought I screwed up. But it fit perfectly!
So plunging in with a good 0.75" endmill produces an almost-perfect hole, although boring or even better over-sized reaming would be preferred if you can manage it. They have 0.751" reamers on the market for a really good fit.

[Bryce2471]

Originally Posted by nathannfm

This sounds like a good idea but I would caution that you should know the tolerances of that boss and the tolerances of the equipment used to cut the hole in the plate. We made our first waterjet part ever a few weeks ago with a 0.750" hole for the boss and suprise suprise it comes back and the CIM won't fit.

Thanks for the heads up.

Would this be all steel? I know the ball capture area is steel on the VexPro model presumably for wear reasons. Also, I know it would be pretty difficult to machine but I would recommend a fillet at the hex to round transition as that looks like its a pretty big stress riser.

The vex pro website says that ball shifter shafts are 7075-T6 aluminum.

Related to this component, if you make the hex shaft attach to the ball shifter with a pin or through bolt instead of making it one part it would make removal of the gearbox pretty simple.

I considered this, but I didn't want to cut a negative hex into the end of the shaft.

[R.C.]

Originally Posted by Bryce2471

Thanks for the heads up.

The vex pro website says that ball shifter shafts are 7075-T6 aluminum.

I considered this, but I didn't want to cut a negative hex into the end of the shaft.

The pressed in output hex shaft is. But the actual ball shaft is steel.

[Bryce2471]

Originally Posted by R.C.

The pressed in output hex shaft is. But the actual ball shaft is steel.

Interesting. Is the small shaft that engages the balls steel as well then? I find it hard to believe that they would use one steel and the other aluminum.
Also, here is a picture of an updated version that uses some of the suggestions posted in this thread:
https://scontent-b-sjc.xx.fbcdn.net/...e4&oe=551455E2
Thanks for everything so far. Questions and comments are still welcome of course!

[R.C.]

Originally Posted by Bryce2471

Interesting. Is the small shaft that engages the balls steel as well then? I find it hard to believe that they would use one steel and the other aluminum.

The small "plunger"/shifter shaft is currently AL, might see an upgrade in the Future?

[Bryce2471]

Originally Posted by R.C.

The small "plunger"/shifter shaft is currently AL, might see an upgrade in the Future?

Lol
Do you know if vex did any tests that suggest the ball carrier needs to be steel?

My team built a ball shifter for our shooter last year. (I'll admit it's a different situation) We experienced that the ball carrier had the least wear out of the three shifter components.

[Mike Marandola]

Originally Posted by Bryce2471

Lol
Do you know if vex did any tests that suggest the ball carrier needs to be steel?

My team built a ball shifter for our shooter last year. (I'll admit it's a different situation) We experienced that the ball carrier had the least wear out of the three shifter components.

Some teams saw extreme wear on their plungers this year.

[Bryce2471]

Originally Posted by Mike Marandola

Some teams saw extreme wear on their plungers this year.

I know. I addressed this issue earlier.
I was not referring to that part in this instance.
the part I am talking about currently is what surrounds the plunger.

[Mike Marandola]

Originally Posted by Bryce2471

I know. I addressed this issue earlier.
I was not referring to that part in this instance.
the part I am talking about currently is what surrounds the plunger.

Ah. I just realized that.

[Chris is me]

Originally Posted by nathannfm

Also, just to comment on that video I prefer the "sketch fillet" tool to the 3D fillet tool as it crashes much less, trims your lines for you, and contains all your pocketing features in one "Cut-Extrude". Also, if it crashes you are already in sketch mode to fix it.

I sometimes (often) fillet in 2D, but the advantage to this that I've noticed (especially if you save right before you attempt 3d fillets) is that you can suppress / delete your fillets, adjust your original design, and your pocketing is more likely to still work after the fact than if you trim and fillet in the sketch layer. It also takes a bit more work / time.

Seeing the support of the CIM in more detail makes me more comfortable in it - I guess it's just my personal preference to have a member follow the outer edge of the CIM to best support the face. You're probably good to go with what you have.

[Bryce2471]

Originally Posted by Chris is me

Seeing the support of the CIM in more detail makes me more comfortable in it - I guess it's just my personal preference to have a member follow the outer edge of the CIM to best support the face. You're probably good to go with what you have.

I'm sure that adding a member would increase strength, but after the revisions I posted, I think it would be unnecessary in this case.

[Cory]

Originally Posted by nathannfm

Also, just to comment on that video I prefer the "sketch fillet" tool to the 3D fillet tool as it crashes much less, trims your lines for you, and contains all your pocketing features in one "Cut-Extrude". Also, if it crashes you are already in sketch mode to fix it.

To each their own, but I would consider this very poor practice. It makes the part much less transparent to anyone else who may need to work on your design and is far less flexible, as mentioned by Chris.

If you need to fix fillets, like Adam displayed in his video, you can use the fillet tool to do face fillets that will bridge the intersection of faces where two fillets intersect. Then you don't need to sketch anything.

[Jared]

Originally Posted by asid61

We used 0.752" without problems last year, allthough it was sort of by accident- I plunged with a 0.75" end mill in place of a 5/8" and thought I screwed up. But it fit perfectly!

Excellent point. I made all our gearbox plates last year to somewhere between 0.750 and 0.751, and only one CIM motor we had fit. We found it interesting that our CIM motors that were 8-10 years old fit perfectly in the 0.750" plate, but the news ones all seemed to be a touch bigger.

[JorgeReyes]

What gear sizes did you end up using on this gearbox?