pic: Single Speed Gearbox Iterations

[rcmolloy]

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Very nice gearbox. Is it a direct drive? Just curious - what was its intended purpose? Was it just for fun, or designed for future use?

Keep up the awesome work! I can't wait to see the 3D model!

[DampRobot]

What motors is this for? It looks like it's some sort of CIM or two BaneBots setup...

[Andrew Remmers]

What size wheel does it drive to get that speed?

- Andrew

[Richard Wallace]

Originally Posted by Joyride_67_1902

What size wheel does it drive to get that speed?

I'm guessing a 4" wheel, directly driven by the gearbox output, at full (normal) load CIM speed (4320 RPM according to the CIM data sheet) -- so ( 4320 / 5.74 / 60 ) * pi()/3 is about 13 ft/sec. Free speed would be faster, about 16 ft/sec.

[rcmolloy]

Richard pretty much clarified everything up from a technical standpoint. I still can't believe he grabbed that much from the crowded drawing. Thanks for clarifying up the math. I felt like I was a bit off somewhere haha.

It's a 2 cim box if you can make out the mounting holes that are perpendicular to the plane that the intermediate shaft and pinions are sitting on. I'm sure the cims will stay in that orientation as of right now but that may change with another iteration down the line.

The gearbox was created because of bordom and my want to increase my design ability. AdamHeard and I are really working close on honing in my design skills this year and I just decided to start throwing stuff at him to check out. This box wasn't terribly difficult to make but it still helps me since this is the first 2D layout that I have pretty much completed up to 90%.

[Richard Wallace]

Originally Posted by rcmolloy

...this is the first 2D layout that I have pretty much completed up to 90%.

Nice job.

Keep throwing stuff at Adam Heard, you will get really good at this.

[JVN]

You can get that entire reduction in 1 stage. Lighter, simpler, more efficient.

12:72 will work with a 4" wheel, and actually gets more reduction than you have right now. (12:69 would be right about where you are currently.)

I always use a 12t or smaller on my CIMs because it allows us to put the gear on the CIM before installing it through the CIM 0.75" pilot hole.

Instead of spending money on COTS gears, you could go find a local shop who can make you some custom aluminum 72-toothers for cheap (or free). You're not going to need a whole lot of gear, should be nice and light.

-John

[Mk.32]

Originally Posted by JVN

You can get that entire reduction in 1 stage. Lighter, simpler, more efficient.

12:72 will work with a 4" wheel, and actually gets more reduction than you have right now. (12:69 would be right about where you are currently.)

I always use a 12t or smaller on my CIMs because it allows us to put the gear on the CIM before installing it through the CIM 0.75" pilot hole.

Instead of spending money on COTS gears, you could go find a local shop who can make you some custom aluminum 72-toothers for cheap (or free). You're not going to need a whole lot of gear, should be nice and light.

-John

Quick question from this; because we like to be able to put the gear on the CIM before we put it in the gearbox, I bored the CIM mounting holes to about .9 so a 14th would fit though it; so does it really matter that you use a .75 pilot hole?

[IanW]

Originally Posted by Mk.32

Quick question from this; because we like to be able to put the gear on the CIM before we put it in the gearbox, I bored the CIM mounting holes to about .9 so a 14th would fit though it; so does it really matter that you use a .75 pilot hole?

The idea behind using a .75" pilot hole is to help align/center the CIM, which has a protrusion at the base of the output shaft that is also .75" in diameter.

[Mk.32]

Originally Posted by IanW

The idea behind using a .75" pilot hole is to help align/center the CIM, which has a protrusion at the base of the output shaft that is also .75" in diameter.

I understand this but is it really necessary?

[R.C.]

Originally Posted by Mk.32

I understand this but is it really necessary?

Mark,

I highly suggest it. The thing with the .75 hole is that it supports and locates the CIM. We've had older robots have the CIMs come loose and sometimes even break bolts because the bolts took all the load. John is spot on with the .75 hole.

We use the 14T gear still. We just slide the CIM in with the spacer and put the gear on and add the push nut/retaining clip. Its not that much time (30 seconds more).

-RC

[Cory]

Originally Posted by Mk.32

I understand this but is it really necessary?

No, but your gearbox will perform much better (with less effort) if you do.

[JVN]

Originally Posted by Mk.32

I understand this but is it really necessary?

As said by others... it is not a good idea to locate the motor using the motor mounting screws. That little .75 pilot hub is great because it helps ensure good center-center distance.

Aside:
I don't see any reason to use a 14t over a 12t. Whatever gear math people are doing which says 14 is better than 12... I haven't seen it, and I like to think I've played with these numbers quite a bit.

-John

[Mk.32]

Cool, thanks for the tips.
definitely use the .75 CIM hole on my next boxes.