05-26-2010 12:26 AM

sdcantrell56

Re: pic: 3 Motor Single Speed Gearbox

You can definitely use the CIM mounting holes as the transmission stand offs. This design overall looks good. You could look into using delrin plates instead of aluminum to drop a bunch of weight for the same amount of machining. Also think about how you are going to mount the transmission as right now there are no mounting holes.

05-26-2010 12:28 AM

sanddrag

Re: pic: 3 Motor Single Speed Gearbox

I would not recommend Delrin plates. Holding tolerance is more difficult, and they flex, causing gear wear issues.

05-26-2010 12:34 AM

Re: pic: 3 Motor Single Speed Gearbox

We did a gearbox with delrin plates, and the gears wore about twice as quickly as our aluminum boxes.

Also, assembling the box with the motor bolts is quite doable, but makes assembling a bit of a hand gymnastics exercise.

Edit: A bit of a suggestion: If you can recess the standoffs to allow the box to 'snap' together, it makes assembly much easier, and makes aligning parts much quicker.

05-26-2010 12:48 AM

Brandon Holley

Re: pic: 3 Motor Single Speed Gearbox

Looks really nice thus far. You may want to search cd-media for our 2008 drivetrain. I designed it to be a 6 motor (4 CIM, 2FP) single speed drive system with 4.75" wheels. Just something comparable to look at.

If I am interpreting your question correctly you were asking about clearance inside the gearbox. Be sure you give yourself some clearance for tolerance stack up. If you don't, when you tighten everything up your gearbox could be seized up, or you may even damage your bearings.

The motor screws are completely legit to use as a method to hold the gearbox together.

Keep up the good work.

-Brando

05-26-2010 01:12 AM

Lil' Lavery

Re: pic: 3 Motor Single Speed Gearbox

Why not use a 1/8" plate instead of a 1/4" plate?

05-26-2010 01:21 AM

AdamHeard

Re: pic: 3 Motor Single Speed Gearbox

One advantage of 1/4" plate here is it lets you put the CIMs real close to each other without the bearing popping through and hitting them.

05-26-2010 01:45 AM

NickE

Re: pic: 3 Motor Single Speed Gearbox

If you're gonna mill the plates, you're gonna need some exterior fillets. If you're gonna jet them, you're probably fine, but I still like having the fillets there for cosmetic reasons.

Having counterbores for the standoffs certainly keeps everything more ridgid, but i would say makes assembly much more difficult. Lining up every standoff with its corresponding hole can be quite a challenge (which would probably become even harder with these being the motor mount screws). If you're gonna include counterbores for the standoffs, do not do it on all six standoffs. Even with just four counterbored standoffs on our gearboxes this year, it was still quite a challenge to line them all up.

05-26-2010 01:49 AM

Chris is me

Re: pic: 3 Motor Single Speed Gearbox

That's pretty much the only reason, and I wanted two identical plates. You can't put 3 CIMs on the gearbox with this ratio without overlapping the bearings.

05-26-2010 07:14 AM

Collin Fultz

Re: pic: 3 Motor Single Speed Gearbox

The Team221 WildSwerve modules use a 1/8" bearing shim so that 1/8" plates can be used. They work pretty well. I'll see if i can find a picture.

Also, I wouldn't use the motor mounting holes as the gearbox plate holes, mainly because I like those motor mounts TIGHT and sometimes gearbox assembly bolts need to be loosened a little bit so the gearbox can run with less internal friction. I suppose that may be a personal bias though and not a requirement.

One other thing to think about: How would this mount onto the frame of a robot? The machined plates look cool, but how would you mount it? That's probably too much of a robot-specific question to fully answer right now but is worth thinking about.

Looks good. Keep up the hard work.

05-26-2010 06:42 PM

Tom Line

Re: pic: 3 Motor Single Speed Gearbox

Since you have 2 stages there Chris, I'd evaluate the gears you have available and try to shoot for center distances between the second gear stage shafts that will allow you to swap out for a couple different gear sets. Much like the final stage on the super-shifters allows you to modify the gearing by swapping 2 gears. This is FAR easier than changing the spur gears on the 3 motor outputs, and will allow you to modify easily should you ever want to drop a FP or CIM and need a slightly different torque.

05-27-2010 12:44 AM

Chris is me

Re: pic: 3 Motor Single Speed Gearbox

Right now the distances between gears would accommodate a standard Toughbox ratio, but the placement of the motor / spacers interferes. The use of a standard ratio was far from intentional though.

05-27-2010 05:20 AM

artdutra04

Re: pic: 3 Motor Single Speed Gearbox

We've also used 1/8" shims with 1/8" sheet metal plates in our gearboxes for the past two seasons. We use a single #8-32 button head screw and PEM nut to hold them in place. Here's a photo: