Custom gearboxes

[craigboez]

You could invest in all those reamers, or just one boring head. Its a lot more versatile and a lot less spend on tooling.

[mglucido]

I see that most teams are adding the 0.003" to the center-to-center gear distance. What's the best way to calculate the starting center-to-center from which to subtract 0.003"

- Inventor Gear Calculator? ... Which seems fairly straightforward
- Something better?

Thanks,
Michael

[IndySam]

Originally Posted by mglucido

I see that most teams are adding the 0.003" to the center-to-center gear distance. What's the best way to calculate the starting center-to-center from which to subtract 0.003"

- Inventor Gear Calculator? ... Which seems fairly straightforward
- Something better?

Thanks,
Michael

(gear1 / 40) + (gear2 / 40) + 0.003

(50t / 40) + (30t / 40) + 0.003

1.25 + 0.75 + .003 = 2.003

[apalrd]

Originally Posted by mglucido

I see that most teams are adding the 0.003" to the center-to-center gear distance. What's the best way to calculate the starting center-to-center from which to subtract 0.003"

- Inventor Gear Calculator? ... Which seems fairly straightforward
- Something better?

Thanks,
Michael

(number of teeth on gear A + number of teeth on gear B) / (2 * dp)

For AM gears DP is either 20 or 32, usually 20.

FYI, for a given c-c distance, any combination of gears with the same combined number of teeth will fit. E.g. 25-40 will fit in the same c-c distance calcualted for 20-45.

[mglucido]

Thanks Andy and IndySam. I was just working through the pinion relationships to understand IndySam's magic number of 40 and my calculation was off by 20 (on which Andy shines a bright light!).

Thanks!

[billbo911]

We are fairly new at building custom gear boxes. his is our first year using Hex shafts in them. Aside from the lack of availability of .5" Hex bearings currently, it looks as though we will also have a need for sleeve spacers in our box. The VexPro Delrin Hex spacers are out of stock currently as well.

So, the question is, what do you use to create sleeves for your .5" Hex shafts?

[thefro526]

Originally Posted by billbo911

We are fairly new at building custom gear boxes. his is our first year using Hex shafts in them. Aside from the lack of availability of .5" Hex bearings currently, it looks as though we will also have a need for sleeve spacers in our box. The VexPro Delrin Hex spacers are out of stock currently as well.

So, the question is, what do you use to create sleeves for your .5" Hex shafts?

Assuming that the spacers are just spacers and nothing more, you can get round stock/tubing and bore the center out to ~.580" for hex to slide through. Personally, I like ABS plastic for this, but you can use a bunch of different stuff.

Also, the ~.580" dimension isn't THAT critical, but it's something worth trying to hit. The point to point dimension (effective OD) of a .5" Hex is ~.577" so that extra .003" or so just makes everything go together smoothly.

Or if you really wanted to, you could get round stock/tube, bore it out to .5" ID and run a broach through it.... If you're just making spacers, putting a hex into them is kind of a waste since they're not torque transmitting.

FWIW, the same method will work in a pinch for making a hex bushing as well. It's not the 'right' way to do things, but if you've got a low load application that needs to be hex and you can't find a bearing or a bearing won't fit, it's worth looking into.... In 2011, the team I was on ran a 1/2" hex shaft with the points turned down to an effective OD of .5625 and then ran that shaft through a delrin bushing on a roller claw. Just something to keep in your back pocket.

[sanddrag]

For spacers, we use 3/4" diameter black delrin rod from McMaster. I second the recommendation to drill it to slip over the hex. We've tried broaching them in the past and the delrin springs back making a really tight fit. We've had to run the broach through 3 or more times to get them to even go on.

[ToddF]

We made our own using our Makerbot.


We also made custom gearbox covers.

[billbo911]

.580" ID.
.75" rod bored/drilled out.
3D print your own.

Excellent, I think we're good to go!

Gotta love CD!!

[artdutra04]

Be careful with 3D printed spacers to ensure they are only used as spacers and not a bearing/bushing surface. If any part of the 3D printed spacer acts as a bushing, it will melt and fail.

I have always been a fan of using using Delrin rod to make spacers, partially because it is low friction and partially because it machines very nicely. McMaster has both solid and hollow Delrin rod, so if you have access to a lathe, Delrin spacers are fast, cheap, and easy to make.

[mglucido]

I just wanted to drop back into this thread to express my appreciation for all the great info here. You all helped us learn how to build a gearbox to gang two CIMs and one miniCIM and gear it appropriately while spanning the correct distance for our lifting mechanism to function.

It was our first custom gearbox and everything just fell into place after studying this thread carefully.

Thanks everyone!
Michael Lucido
Team 2838

[xSAWxBLADEx]

You could use these to reference. Great gearbox's!
http://wcproducts.net/wcp-00100/