pic: Introducing BarBox: My First Attempt at Gearbox Design

[bardd]

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[jman4747]

I like it so far especially for a first gearbox I just wanted to add that you could aquire CAD files for vertualy any standard gear at rushgears.com and a good practice also is to go to some place like mc master carr's web site, VEX pro, or granger find stock gears to base your designs off of. Also I had a question about what your reduction was and how heavy this box is?

[bardd]

Originally Posted by jman4747

I like it so far especially for a first gearbox I just wanted to add that you could aquire CAD files for vertualy any standard gear at rushgears.com and a good practice also is to go to some place like mc master carr's web site, VEX pro, or granger find stock gears to base your designs off of. Also I had a question about what your reduction was and how heavy this box is?

Thanks for the tip, I'll look into it when I get the time for alterations. The gearbox is 2.7lbs, I'll try and make it lighter.

[cbale2000]

Originally Posted by bardd

The gearbox is 2.7lbs, I'll try and make it lighter.

Trading out the middle portion of the gearbox frame for a polycarbonate version might save a bit of weight.

Honestly I never understood why so many gearboxes (like the toughbox) use metal enclosures between the plates considering its probably the most structurally insignificant part of the whole thing.

[HammadB]

While I don't know which gears you're using specifically and thus their bore sizes, maybe try a smaller gear size on the second stage. You could obtain the same reduction using AM 14 and 28 tooths etc and make the box more compact and a tad lighter.

Additionally replacing the enclosure with some standoffs would retain structure but save considerable weight.

[magnets]

I'd recommend replacing the metal enclosure with some standoffs, then if you need to, put thin lexan shields around it. Also, the CIM motor shaft isn't supported on both ends, so you don't really need the outer plate to be that big, and you could make it about half size. Also, you could probably get away with making some holes in both plates, depending on their thickness.

I can't tell from the image, but it looks like the CIM is held on by two screws. It's a better idea to make the top of the CIM flush with the plate, and cut a 0.75" hole in the plate for the top of the CIM to sit in.

[KrazyCarl92]

From an interchangeable part standpoint, why not have the hole for the CIM shaft/boss in the side plate be on both side plates? This way, you can make 2 of the same part per gearbox and have more flexibility if you need to replace anything.

[Chris is me]

How are you making the metal piece in between the plates? Machining all of that from solid seems like way overkill for what a couple of standoffs could do.

If you want an enclosed design easily, you could take a page from the Toughbox Nano and build this gearbox out of tube stock.

[bardd]

Originally Posted by HammadB

While I don't know which gears you're using specifically and thus their bore sizes, maybe try a smaller gear size on the second stage. You could obtain the same reduction using AM 14 and 28 tooths etc and make the box more compact and a tad lighter.

I couldn't find a gear combination that can use smaller gears without altering the ratio too much. Unfortunately 14 to 28 can't work, both because in that case the output shaft will intersect the 50T gear on the first stage, and because there's no 28T with 0.5" hex bore. There is a 29T one, but still too small.

Originally Posted by magnets

I can't tell from the image, but it looks like the CIM is held on by two screws. It's a better idea to make the top of the CIM flush with the plate, and cut a 0.75" hole in the plate for the top of the CIM to sit in.

The hole exists. You can't see it in the picture though.

Originally Posted by KrazyCarl92

From an interchangeable part standpoint, why not have the hole for the CIM shaft/boss in the side plate be on both side plates? This way, you can make 2 of the same part per gearbox and have more flexibility if you need to replace anything.

The output shaft sits on two different bearing sizes (0.875" in the back and 1.125" in the front), so the front and back plates have different holes for the bearings too.



Most of you recommended standoffs, I'm going to try that. I'll try and make holes in the plates too. Christ- ehh... Open profile version will be coming early.

[bardd]

Made some changes, introducing BarBox 2.0:

New weight: 1.75lbs



Thanks for the tips everyone!

[Redo91]

One other thing to think about when designing your gearbox is how you would mount it.

[bardd]

Originally Posted by Redo91

One other thing to think about when designing your gearbox is how you would mount it.

It's a bit similar to how you'll mount a toughbox. You attach the bottom four screws to a channel with fitting holes, and have the shaft go through another hole in the channel. There are other ways to do it but that's the way I wanted to mount the gearbox so that's what I designed for.

[Adrian Clark]

Originally Posted by bardd

The output shaft sits on two different bearing sizes (0.875" in the back and 1.125" in the front)

Why is this necessary?

And a note on standoffs: It's very hard to find .375 OD tube with #10 clearance ID. Rather than buying .375 rod and drilling it out I prefer to buy .0625 wall with .375 OD and put .0625 deep counterbores in the plates to capture the standoff. Makes things much lighter and simpler to make.

[R.C.]

Originally Posted by Adrian Clark

Why is this necessary?

And a note on standoffs: It's very hard to find .375 OD tube with #10 clearance ID. Rather than buying .375 rod and drilling it out I prefer to buy .0625 wall with .375 OD and put .0625 deep counterbores in the plates to capture the standoff. Makes things much lighter and simpler to make.

Ditto,

If your turning down the back guy currently to .375", you might as well save yourself time and just lathe it down to .500".

I know it might be lighter to go that smaller bearing but honestly, its much easier programming/making 2 of the same part then it is 2 different parts.

Adrian,

We do about the same thing, buy .375" OD Tube with a .235" ID. 1658T41 - McMaster. We go parting crazy and you can make a lot of spacers in no time, especially on a bar feed . We use this material for the gearboxes we make. Do you really need the cbores? We've noticed its incredibly harder to assemble gearboxes that way.

-RC

[MichaelBick]

Originally Posted by R.C.

Ditto,

If your turning down the back guy currently to .375", you might as well save yourself time and just lathe it down to .500".

I know it might be lighter to go that smaller bearing but honestly, its much easier programming/making 2 of the same part then it is 2 different parts.

Adrian,

We do about the same thing, buy .375" OD Tube with a .235" ID. 1658T41 - McMaster. We go parting crazy and you can make a lot of spacers in no time, especially on a bar feed . We use this material for the gearboxes we make. Do you really need the cbores? We've noticed its incredibly harder to assemble gearboxes that way.

-RC

I agree that counterbores are harder to assemble with and unnecessary. What we've been considering for next year is buying aluminum 6063 .375" OD tube with .145" ID and still machining it out. While we will have an extra step, the ID will be closer, the hole will be centered throughout, and our drills will not gum up because we are taking out quite a bit less material. However I'm worried about the 6063 aluminum. I've heard it is a bit less strong than 6061 and more gummy. I'm assuming it will be fine but if anybody else does this I would love to know.