Animatronic Cosplay Wing Mechanics
Introduction: Animatronic Cosplay Wing Mechanics
Out of all the costume animatronics projects I've taken on, this was by far the most challenging.
Animatronic wings present a lot of problems for costumers- weight, power requirements, movement, and durability all have to be taken into account. They are just flat out hard to make. This small mechanism was created for an Asuna Sword cosplay to allow four wings to lift up and fold back- using only a single servo with as little as 4.8V power. The baseplate measures just 7" wide.
Here's a video showing the mechanism moving four polycarbonate wings. The total wingspan is about 62" and the movement is unusual as the character's wings don't have a defined pivot point- they appear to "float" as they raise up and fold backward.
Here's a video of just the mechanism moving. You can see how the lead screw drive moves the wing base pivots and how the radius arms move the wing mounts.
The goal of this project is to help others with their moving wing projects- think of it as a recipe guide. If all you need is to make wings move up and down this will show you how to make a really compact linear drive. But if you want a folding movement then you're covered too!
Be sure to click on each image as there are notes!
Let's get started!
Step 1: Tools and Materials
The tools for this are pretty basic. You can get by with a bandsaw, drill press and files. Having access to a lathe makes making custom pivot parts a lot easier but it's possible to design around that.
The belt sander just makes cleaning up parts go a whole lot faster than having to file everything by hand. :)
For materials I used:
Various thickness Aluminum plate/sheet
Brass tubing
Steel rod
Music wire
A LOT of 6-32 socket head cap screws
Small brass washers
6-32 set screws
4-40 socket head cap screws
1/4-16 ACME lead screw and nut
Hitec HS-7955TG servo
5K potentiometer
Step 2: Mechanical Design
The design of this mechanism didn't happen overnight.
The Asuna Sword character has beautiful translucent wings so I knew right away the wings needed to be made from a rigid transparent material. Unfortunately that meant they would not be super lightweight. You have to think of a wing as a big long lever that you are trying to pick up by the very end. The more leverage you have and the lighter weight the wing is, the easier it is to move.
Say you have a 30" wing that weighs 5 oz and you have it mounted on a pivot. Servo torque ratings are typically listed as oz/in, meaning that the stall torque of the servo might be 180 oz/in. 997
That means with a one inch long lever the servo will stall just as it tries to lift a 180 oz weight. Now you never really want to max the servo out as it can easily be damaged if it stalls (typically burns out the control circuit) and as you approach the stall rating the power draw goes way up. That 30" long, 5oz wing represents roughly a 150 oz load to the servo when it is mounted directly to the servo output shaft (yes the weight is distributed over the entire wing length but it's a close enough approximation.) While the servo can lift the wing it certainly won't be very happy doing it- it will have a hard time controlling the wing movement (especially when lowering the wing) and it will probably burn out trying to hold the wing up.
This is what I learned when I built the first mechanism. Originally I had eight servos- each wing had a lifting servo as well as a folding motion servo. This was later reduced to six, as I only needed two servos to make the wings fold back in unison. I made wings from laminated plywood for testing and sure enough the servos couldn't control the movement properly. This led me to the idea of using a lead screw to raise the wings.
Lead screws are great. The beauty of a lead screw is that it works kind of like a wedge. With very little input force you can lift a large weight- and it will stay put. This part is super important as it greatly reduces the power requirement of the servo. You can remove power from the servo and the wing will still stay raised. Lead screw mechanisms are typically packaged as a linear actuator or linear servo- the lead screw, motor and controller are all combined together in a nice contained unit. There is a lead screw calculator located here. Just plug in the lead screw specifics and your load and it will tell you the motor torque requirement. The specific type of lead screw can greatly affect how your movement works. 215