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Renosis

ChatterBox Teeth - Wind-up

by Renosis Apr 28, 2011
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You need to add some force for the spring to work against so its energy doesn't dissipate in an instant. If you lift up one of those toys with wheels, the wheels zip around and lose all their energy in an instant. Perhaps a length of clock spring supporting the jaws open would provide enough force to keep the spring going longer.

UPDATE:

I haven't given up on this project. I have changed the entire design to be in OpenSCAD! I am also working on a parametric Geneva Drive.

The Teeth model has since changed, because I could not get this model to open in OpenSCAD. The change is for the better.... believe it or not, the new teeth loo
k SO much better!

Observe:

http://www.flickr.com/photos/58101887@N02/sets/72157626570003611/http://www.flickr.com/photos/5...

Those are some pics of the new teeth with comparison to the old teeth. The new teeth are great, they look even more realistic! It almost looks like you can pull each one out with a pair of pliers!

See:

UPDATE: We are going to be uploading new files soon! We have added some additional gears. Also I need to change the winder axle, I don't know what exactly happened. But the ones in the picture are so much sturdier than the recent ones I have been printing. For some reason the tabs that the winder key slide into have been breaking off rather easy. So, Either I need to print that the clock spring main axle gear thing with 100% infill or I need to do it slightly differently. It needs to be very sturdy, because ALOT of pressure gets put on the winder.

Yeah, you have to be careful with springs... they can be lethal!

http://www.boingboing.net/2011/05/01/horology-considered.htmlhttp://www.boingboing.net/2011...

:-)

Awesome project! :)

If you can't shrink the gears, why not enlarge the teeth‽

Or apply weight to the top teeth so there is more negative torsion on the spring.

Well, the teeth already take up a good portion of the build platform already and I kind of wanted to keep them the size of human teeth. But, a huge set of teeth that chattered would be great, maybe someone should come up with a derivative.

We are currently working on a gearbox that may work. We'll see what happens, then we might have to try other things.

Proposed gearbox based on MakerBlock's gears: http://www.thingiverse.com/thing:8148http://www.thingiverse.com/thi...

Chatter Gear Box
by syvwlch

Awesome! I will try these out when I get off work. I commented on the thing, so I'll keep this short. This makes you a collaborator!

Happy to contribute, but what I did was very easy... cramming that into the design is going to be the hard part! :-)

By the way, I am totally stealing that wound-spring power source for some future clock, if someone doesn't beat me to it... ;-)

Yeah, I designed it months ago, so it is in sketchup. I plan to remake in openscad so others can use the geneva drive in other projects!

Whoops! Most updated SCAD file for the gears is here:

http://www.thingiverse.com/thing:8144http://www.thingiverse.com/thi...

ChatterBox Teeth Gears

What is the fill on the teeth? Increasing the mass of the jaws should increase the period of the chomping.

As a last resort you can probably reduce the width of the spring.

What about modifying the spring? Or how about adding something that rubs against the gear from the side to slow it down? Like a brake? Just add enough tension so that the gear still turns but not as quickly...

That's an idea, but I think I ran into a problem with this type of approach when I was experimenting with springs. You see, there is a dramatic difference between the power it takes to open and the power it takes to close the mouth. So, if we tension the gear to have enough power for one, it is not going to be the right power to do the other. I could be wrong though. Maybe I could try a few different ways to do this.

But I really think the best idea is to add more gears to regulate the speed. This is the approach most wind-up toys take and I think it is the answer. The problem for us is building a gear box the right size and shape, and we are lucky we have gotten this far with that. What we need is someone who
is up to the challenge and is really good at designing gear boxes to collaborate with us and help us win the MakerBot United Competition!

An old-school trick for robot arms (whose torsos remain approximately upright) is to counterload the shoulder with a spring approximately equal to the weight of the arm and the anticipated load. Then the motor has a more symmetrical job to do and need deliver only half the torque (albeit in each direction).

Perhaps spring-loading the jaw would make your gear-tensioning enough more symmetrical to be less of a challenge?

I actually tried using springs, but my approach wasn't very scientific. I have no idea what amount of tension the springs I used produced or how much force would be needed to even things out. As you can imagine, the results were less than stellar. All in all, the springs just ended up making it require too much force to get the teeth open. I used extension springs, and I couldn't even get one open cycle out of it. So, I nixed all the springs and have gotten to where I am now. The teeth do chatter, but they need to be improved!

What about a rubber band instead of a spring?

Well I'm not sure if you could make it small enough, but if you could some how make up a watch escapment gear that might slow it down. It might make it too slow perhaps if you could get it down to size.

Yes, we have thought of doing an escapement, but thanks for the suggestion. It would be just too hard to get it that small. We have watched all sorts of videos and read all sorts of stuff on clocks and watches. The pieces are just too intricate to do.

Every wind-up toy I have ever broken has worked just on gears alone (well that and a cam). So, the only route I see is to design a gearbox that will produce just the right amount of friction to slow the spring down without stopping it. We tried and tried. But this is really my first time trying to
design gear boxes and such. I mean, I understand how they work and what needs to be done, I just can't practically do it.

I could just steal a gear box from some other wind-up toy, like I did the clock spring, but I really wanted to limit the amount of non-printed parts to a few m3 bolts and nuts
and the clock spring.

It's not so much about introducing friction as it is changing the number of chomps per windings of the spring, like changing speeds on a bicycle, there is some magic gearing ratio that will make the thing work... but as you pointed out, it's hard to make a gearbox that small.

@syvwlch

Exactly! I just need to introduce more gears. The problem is, it was hard enough for me to introduce two gears and make this thing work in its current state. I have 0 experience with gearboxes and gears. Pair that with the limited space we have here and the inability to make gears small enough, an
d you end up with what we have here!

And so, I've posted it as WIP. The teeth do chatter, but they need to chatter longer and we need a talented person to help us accomplish this. I am going to continue trying things, but in the spirit of the competition and collaboration, I wanted to openly invite
anyone who wants to join in and make this work. I just really don't think MakerBlock and I will be able to get it to work the way we want it to by the 8 PM CST deadline on May 1st.

Try a worm gear! Basically, one of your gears looks like a screw shaft. You can easily get 40:1 or higher ratios out of just one pair of gears.

The print quality of those teeth with the 2 colors is so awesome!

Thanks,

Ya, the original idea was for me to just release the teeth, by themselves. But then, I thought we could go one better and make them chatter. I was originally going to go with a servo, which would make the project so easy! But, I thought, nah, they gotta have a key and they gotta WIND UP! So I want
ed to do it classic wind-up toy style. Unfortunately, we weren't able to make them work as good as we wanted them to. And the deadline is fast approaching, so we posted them as WIP. I am hoping someone can come up with a clever idea or a REALLY GOOD gearbox that will allow us to get a little more '
time' out of the chatter.

The amount of blogging this will get tomorrow is going to break the internet.

I'm sure you have thought of this already, but why would it not be sufficient to increase the gear ratio between the turns of the spring and the turns of the geneva wheel? Wouldn't you be able to simultaneously increase the duration the spring runs (measured in chomps, as it were) and increase the torque required to move the teeth... both of which should slow the teeth down.

No?

Well, we added two gears... Big Gear on the spring, small gear attached to large wheel controlling the teeth. It had absolutely no effect on how fast the energy was released from the clock spring. It did increase the amount of times the mouth opened and closed though.

It just opened closed 21 times instead of 7 times or so.

We might be able to add more gears or make a larger ratio, but there is a limited area to work with and we can only go so small with the teeth on the gears due to the limits of printing.

Usually with these wind-up toys, the gears are very
very tiny. Here is a comparison:

Wish there was an edit button. What I wanted to say in the middle was:

It just opens and closes 21 times instead of 7 in the same exact 2 seconds it takes for the spring to unwind.


Anyway, the gearbox is the answer. All the wind-up toys only use gears and a cam-shaft. But they have such small gears and can fit it in such a small package. The entire Gear-box for
most of these toys fits like 6 gears in an object the size of one of my gears.

Yeah, I know your pain there.

Any room to stack a bunch of those gearboxes in series? Smething like this, but at the scale of the gears you were able to use:

http://www.thingiverse.com/thing:7379http://www.thingiverse.com/thi...

Modular Gear Reducers
by mirk

I actually downloaded that as one of my first experiments. Of course, as you said, in its natural state it is too big. I also tried the planetary gear box 246:1 by Emmett, here:

http://www.thingiverse.com/thing:7390http://www.thingiverse.com/thi...

Of course they would have to be scaled down to get them to work. I have trouble with designing gear boxes and I am lucky I got this far. I was hoping someone with more experience building gear boxes could get in on this Collaboration and help us win the comp
etition and reap the benefits with us!

1:246 Gearbox
by emmett

Lol, I didn't realize I was up against your clock and two tank tread robots.... Stiff competition! Pretty sure your clock has got it in the bag, which is great, because I think it deserves the win more than any other design!

I still really want to get these teeth working though, regardless of competition, I hope someone decides to either collaborate or post their own better derivative!

Well, your chatterbox teeth work better than the clock does at the moment... ;-)

Emmet's planetary gearbox (the 246:1 thing) already uses some tiny planet-gears, so shrinking it would be harder than just stacking a few more pinion-wheels like the ones you already have.

Not that will be easy, either. You designed this in Sketchup, right?

Yeah, most of it is designed in sketchup. I started this project before I knew anything about openscad. I plan to redesign most of it in Openscad. Yup, the planetary gear box can't really get any smaller.

Basically, I'm proposing to use a gear-box to slow things down. Sorry, that was less than clear.