pic: 3 CIM WCD Ball Shifter Second Edition

[R.C.]

Originally Posted by Oblarg

This. A thousand times this. This is my biggest issue with the WCP single-speed gearboxes; it's incredibly annoying.

I'm not following here, the issue with Bryce's gearbox is that all 5 standoffs mount to CIMs so you can't keep the gearbox together without motors. The WCP gearboxes use two bottom bolts and 2 integrated into the CIM so it doesn't have this issue.

We normally do this (not our robot) and put in CIM's later. You had the gearbox fall apart in a similar WCD setup?

[Oblarg]

Originally Posted by R.C.

I'm not following here, the issue with Bryce's gearbox is that all 5 standoffs mount to CIMs so you can't keep the gearbox together without motors. The WCP gearboxes use two bottom bolts and 2 integrated into the CIM so it doesn't have this issue.

We normally do this (not our robot) and put in CIM's later. You had the gearbox fall apart in a similar WCD setup?

If you use the bottom two standoff bolts to mount to the frame (non-WCD designs, such as a modified AM14U, are not necessarily compatible with the through-tube bearing block), then taking the gearbox off of the robot and taking the CIMs off of the gearbox does, indeed, cause the gearbox to fall apart.

Past that, simply removing the bolts to the CIMs with the gearbox still on the robot causes the spacers to fall out, which can be a massive pain if they're not in an easy-to-reach spot.

[R.C.]

Originally Posted by Oblarg

If you use the bottom two standoff bolts to mount to the frame (non-WCD designs, such as a modified AM14U, are not necessarily compatible with the through-tube bearing block), then taking the gearbox off of the robot and taking the CIMs off of the gearbox does, indeed, cause the gearbox to fall apart.

Past that, simply removing the bolts to the CIMs with the gearbox still on the robot causes the spacers to fall out, which can be a massive pain if they're not in an easy-to-reach spot.

Gotcha,

Wasn't thinking of a non-wcd case. We normally leave the bolts in the same spot and that keeps the spacers there, but this again is a WCD case.

[Bryce2471]

We normally do this (not our robot) and put in CIM's later. You had the gearbox fall apart in a similar WCD setup?

Out of curiosity:

Why is doing this useful?
Why couldn't you do this with the gearbox design that I posted?

[R.C.]

Originally Posted by Bryce2471

Out of curiosity:

Why is doing this useful?
Why couldn't you do this with the gearbox design that I posted?

We like the ability to do that so we can add CIMs in later/makes wiring a little easier without CIMs in the way. Also much much lighter without the CIMs in so its easier to handle etc..

The reason why I'm not a huge fan of using all bolts connected to CIMs is during assembly you either:

a) Have to assemble with CIMs to hold the gearbox together or
b) Put it together and put nuts in the back, then when putting in CIMs having to take each nut off.

Nothing crazy revolutionary but could make your life easier.

[Bryce2471]

Originally Posted by R.C.

We like the ability to do that so we can add CIMs in later/makes wiring a little easier without CIMs in the way. Also much much lighter without the CIMs in so its easier to handle etc..

The reason why I'm not a huge fan of using all bolts connected to CIMs is during assembly you either:

a) Have to assemble with CIMs to hold the gearbox together or
b) Put it together and put nuts in the back, then when putting in CIMs having to take each nut off.

Nothing crazy revolutionary but could make your life easier.

That makes sense. I agree that it would be a slight inconvenience. Although I like the idea of using the CIMs as standoff nuts because most of the forces on the back plate come from the CIM mounts, and because it lightens things.

[asid61]

Originally Posted by Bryce2471

That makes sense. I agree that it would be a slight inconvenience. Although I like the idea of using the CIMs as standoff nuts because most of the forces on the back plate come from the CIM mounts, and because it lightens things.

It would be a pretty big inconvenience IMO. Gearbox assembly is already hard enough, as I learned last week.
It doesn't hurt that much to add different mounting holes for the cims. Plus, then you can use a system like what 192 used to tension gearbox belts this year to allow for different pinions to be mounted.

We tried assembling WCP gearboxes. It took us around five hours to assemble two gearboxes due to some unforseen issues. It's a great gearbox design for teams with little manufacturing resources. But some parts, like the sping washers, are really annoying to work with if you have enough machining resources to make it fit properly.
Also, R.C, if you are reading this, there was a slight error in the instuction manual. A 1/32" spacer is explicitly stated to be a 1/16" spacer in the instuctions. Not sure if that's our problem or something wrong with the manual.

[R.C.]

Originally Posted by asid61

We tried assembling WCP gearboxes. It took us around five hours to assemble two gearboxes due to some unforseen issues. It's a great gearbox design for teams with little manufacturing resources. But some parts, like the sping washers, are really annoying to work with if you have enough machining resources to make it fit properly.
Also, R.C, if you are reading this, there was a slight error in the instuction manual. A 1/32" spacer is explicitly stated to be a 1/16" spacer in the instuctions. Not sure if that's our problem or something wrong with the manual.

Assembly should take around 20-30 minutes a gearbox, we used 4 3 CIM WCD gearboxes this year.

I'm not a fan of the spring wave either, it'll be replaced out to a solid washer in the future here soon...

I'll take a look and your more than welcome to email me here. Please email me what gearbox you were using and which manual etc.. That way we can take care of the typo.

Thanks

[asid61]

Originally Posted by R.C.

Assembly should take around 20-30 minutes a gearbox, we used 4 3 CIM WCD gearboxes this year.

I'm not a fan of the spring wave either, it'll be replaced out to a solid washer in the future here soon...

I'll take a look and your more than welcome to email me here. Please email me what gearbox you were using and which manual etc.. That way we can take care of the typo.

Thanks

In the future I'm sure we could do it faster. First time is the hardest, I think.
I will shoot you an email just as soon as my team has its next meeting.

[Chris is me]

As others have mentioned, bearing bore gears and shoulder bolts will save you some weight and bearings. You can even bore out a smaller gear to accept smaller OD bearings.

It is non-trivial to ensure that the idler gears mesh with both pinions and the large cluster gear at the same time. While the outer CIMs can freely rotate, the middle CIM meshing with both idler gears will lock their orientation relative to each other, and if this combined orientation does not line up with the large cluster gear, the gearbox will not work. It is a lot less elegant to do it this way, but two motors on one idler and one motor on the other idler would be a bit safer and more tolerant of misalignment.

about the above - sorry, misunderstood gearbox initially. I see the gears on the right idler gear now, for some reason I thought another shaft was buried in there. In this case, I would just like to comment on the use of a 12T CIM pinion as an idler - this may not work well particularly if the pinion is aluminum. A lot of force going through a tiny gear. That's not to say it's impossible or not doable, just be careful.

Personally I like this design a lot better than the previous revision. The extra gear is a thing, yes, but the design is more symmetrical, compact, and in many ways simpler. Just seems more elegant to me.