Gearbox for mechanism or appendage

[asid61]

$100 for this is a very good price, although I'm wondering how you're getting past the cost of what I assume is a 2 stage planetary transmission. Best of luck in your endeavors.

[MrForbes]

Look up eccentric gearbox...it's not planetary. I'd love to see the insides of this....

[Travis Schuh]

Do you have estimates on backlash and efficiency numbers?

[billbo911]

Originally Posted by MrForbes

... I'd love to see the insides of this....

Originally Posted by Travis Schuh

Do you have estimates on backlash and efficiency numbers?

Excellent questions.
Any chance you can provide these?

[Andrew Duerner]

Good questions.

The backlash is somewhere around 1-3 degrees.

As for the efficiency, I really don't have the right equipment to measure that right now. It is abs plastic and it's not melting, if that's saying anything.

Attached is a picture showing whats going on inside. The gearbox ended up being pretty simple, kind of ironic considering the path it took to get to this point.

-Andrew

[Michael Hill]

Do you have any maximum torque figures?

[AdamHeard]

How can we buy one?

[Tottanka]

Originally Posted by AdamHeard

How can we buy one?

2nd that.

[Richard Wallace]

Originally Posted by AdamHeard

How can we buy one?

Try Harbor Freight. Link to old thread. Other link.

[Paul Copioli]

This gearbox is known in the industrial robotics industry as an epicyclic gearbox and is very common in robots that require low backlash and high gear reduction.

A couple of business and technical points:

1. There are MANY patents on this design. Several of them have expired but a few key ones still exist so do a patent search before selling this.

2. This design looks to only have one stage going in a single direction. This will induce severe oscillations that cause torque ripple which are detrimental to high load arm applications. There are ways to solve this but it adds significant cost.

3. In order to get acceptable efficiency the oscillating gear must have a very smooth surface finish. Grinding that surface is a must or I would not use it. Plastic gearing for this will severely limit the load carrying capability.

That's all I can think of now.

Paul

[Andrew Duerner]

Michael, I torqued the gearbox unpowered with some lever arms until it broke apart. I would estimate that it reached around 50 ft-lbs.

Adam, I built a website, I'm a mechanical engineer so no making fun of it looking like its from 2004, I need to go through the rules on mentioning trademarked names or just delete them, after I do that I'll post the website address and they can be purchased through the Paypal payment system with a credit card.

Paul, I did some patent searching, I couldn't find anything that the design violated, If you know something in particular that may be a problem I would welcome any information. I haven't experienced oscillations besides having to counterweight the input cam/oscillator. Plastic gears do have their limits, obviously I wouldn't recommend this for an industrial robot, but for FRC robot that needs to run for limited amount of time, I believe it can work.

-Andrew

[Nate Laverdure]

Cool project! Very cool that you'll be able to sell them.


It seems like whenever I talk about 3D printing at work (that's all the time), someone always suggests that I use printed parts to make my own metal castings. It seems easiest to do something like lost-ABS investment casting, taking advantage of ABS's low melting point.

Seems like this would be the perfect project to try this out. Where you have mating surfaces, you could add additional thickness and clean them up in a mill to get closer to the requisite surface finish.

[ajlapp]

These drives are very cool...I've been working to create a useful one for about three years.

I haven't released a unit for FRC because of the immense challenges.

I won't detail them here, but I will tell you that we have a "large" box of failed iterations.

I've attached a picture of a 400:1 unit with a 2.5" OD and an 8mm CIM input.

Here is a video....these are from May 2013.

http://youtu.be/tJoWlCDmaLg

[Mike Marandola]

Originally Posted by MrForbes

I'd love to see the insides of this....

I second this. This looks pretty slick.

[asid61]

Originally Posted by MrForbes

Look up eccentric gearbox...it's not planetary. I'd love to see the insides of this....

Oh whoops, I missed that part of the description. Planetary seems more "normal" to me for large reductions.