FRC Team 2168 Outboard Drive Gearbox Concept

[kbrowncny]

Released 1-6-17

Files Available On GRABCAD

https://grabcad.com/library/frc-team...rbox-concept-1

[Andrew_L]

Very nice. I noticed you went the double inverted cylinder approach to shifting. I considered that method a while back, but found needing two cylinders per side to shift wasn't worth it. An alternative that I've found working quite well is to put the shifting in the first stage (or second if you use a 3 stage). Doing this can make flipping the cylinder very simple.

Another option you could do is just leave the shifting cylinder on the inside, and deal with the fact that it's so low in the frame that it's unlikely to affect anything (1323 did this in 2016 to great success, our boulders rolled right over our shifting cylinders [and other electronics] and right into our shooter without a problem).

[kbrowncny]

The cylinders are $12 on McMaster cant beat the price and it saves room.

[Aren_Hill]

Just out of curiosity, why didn't you full constrain the CIM pilot nub? Your Center-Center on that gear mesh is now set by screw hole tolerances, for no benefit I can see.

Just curious, looks nifty.

-Aren

[kbrowncny]

The base extrude sketch for the mounting plate locates the CIM nub. That includes the +0.003 PD increase for gear mesh. That sketch is built off tangent circles inline. That sketch locates the center for the bearing holes, idler gear, and CIM nub. There is a +0.005 for CIM mounting (it takes into account powder coating). The second extrude cut on the main CIM mounting plate locates the CIM mounting holes at a 2in C-C off of the nub location.

Is there a better way to do this? I am self taught at Solidworks and I may not know the most efficient way to do something, but I can definitely manage sketches, circles and lines! We are always trying to improve, comments welcome

[Ari423]

Originally Posted by Aren_Hill

Just out of curiosity, why didn't you full constrain the CIM pilot nub? Your Center-Center on that gear mesh is now set by screw hole tolerances, for no benefit I can see.

Just curious, looks nifty.

-Aren

Originally Posted by kbrowncny

The base extrude sketch for the mounting plate locates the CIM nub. That includes the +0.003 PD increase for gear mesh. That sketch is built off tangent circles inline. That sketch locates the center for the bearing holes, idler gear, and CIM nub. There is a +0.005 for CIM mounting (it takes into account powder coating). The second extrude cut on the main CIM mounting plate locates the CIM mounting holes at a 2in C-C off of the nub location.

Is there a better way to do this? I am self taught at Solidworks and I may not know the most efficient way to do something, but I can definitely manage sketches, circles and lines! We are always trying to improve, comments welcome

I think what Aren was saying is when the gearbox is actually assembled, the only things keeping the CIMs from moving away from the center are the two screws per CIM. The tolerances on the cocentricity of the screws' bolt circle and the output shaft is not as high as that of the .75" boss around the output shaft. You already have half of the boss surrounded, so it should not be very hard to extend that all the way around the boss. Then the CIM boss will constrain it, instead of the screws. It will also help keep the CIM from wiggling when changing directions, which changes gear spacing and can ruin an otherwise good gearbox.

Aren please correct me if I'm misinterpreting you.

[Joey Milia]

Have you powder coated gearbox plates before? Thats not usually good practice because of how thick and inconsistent the thickness is. Usually they're left raw or anodized.

[asid61]

Looks interesting. The inverted cylinders look like a good idea to save space, and if they're cheaper than $40 for a Vex cylinder, go for it! I think 192 did something similar last year.
The little connector plate is also nifty. Saves you the trouble of using those big Vex/AM ones for sure.
Agree that you need to surround the little 3/4" CIM pilot boss completely. Furthermore, I've heard it's good to have material all around the face of the CIM to support it and stop it from flexing away.