Semi-Animatronic Wing Prototype 01

I'm using real feathers on an owl puppet for a stop-motion animation, so I wanted a way to animate without having to touch the feathers. I've also never made an animatronic mechanism before, so it was a great opportunity to try it. This works, but it's just a prototype. I have plans for a more detailed design that should make the flapping more realistic, allow for different kinds of movement, and be controllable from a distance with a cable system.

Comment by StopmoNick on May 1, 2014 at 5:34pm

That's a great start, but as you say, there are different kinds of movement.  The main thing is that a wing going up folds slightly, then opens out on the downbeat.   I animated several shots of a flock of batwinged creatures flying for someone's film last year, all done manually, and have done one test of my raven puppet flying, so I know exactly how tedious it can be for something that is repetitive most of the time.

There is a mechanism I've seen for a walking leg that might work for a flapping wing.  It needs 2 parallel bones in the upper arm section, one just pivots at the base, the other is driven by a small crank that rotates in a small circle.  Needs a drawing to make it clear.   But maybe you know what I mean.  Here's a crude sketch of a simplified version anyway.  Actually you would probably have 2 parallel bones for the upper arm and the forearm, then a single one for the hand/feathers, but the principle is the same.  I may have the crankshaft rotating in the wrong direction, I need to actually make something and fiddle with it to be sure.  For the other wing you need it to have it's own crank going in the opposite direction, but if you make those flywheels a pair of gears that mesh, you would get that happening.  What happens is that the wing tip actually rotates in a big circle, stretching out longer on the downstroke, and folding in on the upstroke.  It's actually like a Pantograph - a drawing tool in the ancient pre-computer era for enlarging a drawing by racing over it.  Changes in the distances between pivot points can vary how much the small circle at the base is enlarged to the bigger circle at the tip.

Comment by Mike on May 1, 2014 at 6:56pm

Thanks Nick, I think that diagram will be very helpful. You wouldn't happen to know what those cables are called that are used in animatronics would you? From what I understand, they're almost like a coax cable, flexible but firm, and you can pull wires through them without them crinkling up? I've been looking online, but I haven't had any luck finding out if they're specially made, or if they can be bought.

Comment by Zaid on May 2, 2014 at 12:02am

you can use bike brake cable's I think, unless Nick knows of something specifically made for animatronic work.

Comment by Don Carlson on May 2, 2014 at 2:07am
Heyyy, that's pretty nice!
Comment by StopmoNick on May 2, 2014 at 2:45am
I have used bicycle brake cable, but it is a bit heavy for small jobs. For smallish animatonics I used multifilament steel fishing line for the inner cable, and curtain wire for the outer sheath. The curtain stuff is a tight spiral of steel wire with a plastic coating on the outside.
But a couple of years ago I needed something much finer for a legless lizard - looks like a snake, about 12 - 15mm in diameter, and needed cables to turn it's head left and right, and a longer section of neck up and down. I discovered some very fine cables at a hobby shop, used in radio controlled model aircraft.
The outer was a yellow plastic tube. If I remember, tomorrow I can look in my studio to find the brand name and actual dimensions.
Comment by Mike on May 2, 2014 at 10:24am

Thanks guys. Wow, bicycle brake cables is a fantastic idea! They're not incredibly expensive either. I wonder if there is a name for that type of cable. It looks like "fixed cable" might be close, but no luck finding anything but more bicycle brake and shift cables under that name. There must be a place that makes different gauges. Something close to the thickness (thinness) of a 16 gauge aluminum armature wire would be perfect.

The idea would be to cast a resin body with all the notches and grooves needed to house springs and gears and such, controlled by thin wires inside of a cable, and to run that cable out of the armature through a K&S shaft and into a control box.

Comment by Marina Papa on May 2, 2014 at 12:15pm

Here is the "harpi" di Daniel Svensson, he worked quite a lot on its armature and animation.

http://www.stopmotionanimation.com/photo/harpi?context=user

Comment by Simon Tytherleigh on May 3, 2014 at 9:19am

The proper name for these cables is Bowden Cables. As Nick says, they are often used in radio-controlled aircraft in small sizes, e.g.

http://balsamart.co.uk/store/index.php?main_page=product_info&c...

You can also get some good end linkages from this sort of supplier to connect to your control device.

Going a step further, using mechanical servos might make the action look very abrupt, as they don't tend to have an ease-in and -out. You might be able to incorporate some elastic, which would ease as it gets slacker, although it might not be as controllable. But elastic might give the feather spread Nick mentioned as the wing goes up, without needing separate controls.

It looks good. It'll be interesting to see it as it develops.

Comment by Mike on May 3, 2014 at 9:36am

Thanks, Simon! That helps a ton! 

I hadn't planned to use any servos for the same reason you'd mentioned, plus I haven't learned enough about electronics yet to feel confident about that rout.
That's my Summer project, animatronics 101! 

This will be more of a mechanical build, with manual controls like dials and sliders to pull strings and turn gears and such. Like an automaton without the wind-up key.

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