pic: 4 Speed CIM Gearbox

Inspired by this thread, a 4 speed, 2 CIM gearbox. Uses two dog gears to shift between reductions of 21.9:1, 14.2:1, 10.2:1, and 6.6:1. It’s will weight about 10lbs. The model is not quite finished yet, but it’s close enough to see what’s going on.

I’ll refrain from the usual “4 speed is unnessecary bla bla bla” as you don’t seem adamant about using it for season.

In the context of designing a 4 speed, it looks good. Pretty simple, pretty clean, and if that weight is with CIMs (which I think it is) and witch the correct weight set for the CIMs (2.75lbs), it’s not that heavy.

You could lighten those plates up a bit more. If you want me to cheese them up, give me a pm. http://www.chiefdelphi.com/forums/showthread.php?t=68968 is a link with an example of the type of cheesing I’m talking about.

It looks good.


Similar to what 968 did in 2004 and 2005 but theirs used a chain to link the two segments instead of gears.

Looks good. :slight_smile:

AM Gears? Very Nice Job on the Cad, lighten the plates out like Vivek said. Also, see how much weight you could lose using AM aluminum gears and circular lightening pattern.

He may be using plates that aren’t aluminum, so cutting a lightening pattern may not be a good idea.

Also, aluminum gears may not be strong enough in this application; it’s something he would need to calculate to know for sure.

A lightening pattern in the gears would be a good idea as well.

Hmmm, never thought about that, THE RAWC uses 1/4" Delrin I think.

How well does the Delrin hold up. Originally I had planned the plates to be Aluminum, but the Delrin sounds like it would be a neat idea, especially since it would mean less machining.

Another thing, would it work to replace some of the gears with brass? I heard that brass gears are supposed to work in, providing a better mesh. I am thinking of replacing most of the gears with aluminum/brass if that will work.

In some ways Delrin can be more of a pain. Standard drills and end-mills tend to load up when machining Delrin. Even strong flood coolant won’t clear it sometimes. We’ve found a continuous compressed-air stream on the tool is needed. Also, the material often doesn’t come perfectly flat from the supplier. This and its inherent flexiness can cause some gear mesh issues. Threads tapped in it aren’t particularly strong, requiring special PEM nuts for anything that screws into it. The weight benefits are nice though.

Bad idea. Steel gears will mesh just fine. Throw another .0005-.002" between their nominal center-to-center distance to make sure of it. In my opinion brass is far too weak and soft for applications in FRC drivetrains.

Aluminum gears can be quite successful if done properly. It is A LOT of work though, and requires a very specialized and dedicated sponsor shop. The 968/254 gearbox from 2007 is a fine example. Read about it here.