This Instructable is for all the Makers, Halloween enthusiasts, Engineers and Tinkerers.
Background: I have been a participant in the annual Auburn Community Festival for almost my entire life. It is a harvest festival with many competitive categories such as pumpkin growing, baking, costume contest and scarecrow building competition. This year (2015) I created a robotic exhibit of a huge crow over 12 ft long and with a 12 ft wingspan. The crow is chasing and eating a scarecrow which is a bit ironic, I named the exhibit "revenge of the crow". The crow had LED eyes, pneumatically controlled mouth, turning neck, a double articulating wing, and a tail that oscillated up and down. The scarecrow on the ground had double kicking legs that seemed to be fending off the mammoth crow. This Instructable will show how I created this robotic crow so other may do the same or modify and make it better. I made this crow entirely out of recycled materials, except for a few parts I bought off Amazon.
During this project I did a lot of experimenting to find out what worked for this, however you may need to do experimenting as well to find out what works for you. This Instructable is based upon general help and doesn't go into very in-depth detail, of course if you have any questions, feel free to message me.
Step 1: Frame and Body
Frame and Body: This is the construction of the basic frame and outline of the crows basic shape. Keep in mind that this entire process was experimenting and finding out what works. I originally was going to make the frame out of EMT (electrical conduit), but PVC turned out to be much more malleable and easier to work with. The fame does look a bit rough because I was pressed for time, but it is pretty sturdy.
1. I started out by welding a metal post with feet on it for support. This must be strong because the weight of the crow can get up to 150 LBS or so. Also the crow I made was about 10 ft tall and had a lot of stress on the base.
2. I next made the bottom support for the crow. This is a piece of EMT that was welded to the post made in step one. (Careful when welding galvanized metal the fumes are hazardous!) This was the basic shape of the bottom of the crow and needed quite a bit of time to get bent to the desired shape. From here on out, this is the foundation of the crow.
3. Forming the "ribs" out of PVC. Originally this was going to be made from EMT, but PVC proved to be faster and easier to form to the desired shape. I heated it with a blow torch and then bent it, each rib took about 10 minutes to make. I connected the ribs to the frame with metal wire. You are going to have to play with this, forming the body was the most difficult part for me. I looked at pictures of crows online, and this helped. I paid special attention to the body proportions while trying to keep everything proportionally realistic.
4. The beak is what I did next. Again was just experimenting. I found that PVC outline with chicken wire topped with a few layers of paper mache worked well. Finally I gave it a top layer and smooth texture with a layer of duct tape. I will paint this later on. Be sure to make this such that the bottom beak pivots close to the center of the head.
Step 2: MAKE IT MOVE!!!
After the frame is mostly built, I moved on to making everything move. This included the pneumatically controlled beak. The LED eyes. The turning neck. The dual articulation wings, and the tail oscillating. I know this does not look very aesthetically pleasing, nor is it prideful work but I was pressed for time when doing this crow so I cut as many corners as I could. When installing the cylinder, motors and LED's be sure to run all your wires and tubing down to the ground.
1. Eyes: For the eyes I got old trailer lights that were hooked up to 12v. These were easy to install and were pretty bright. Enough to be seen during the day. I did what ever I could to get these lights where I wanted them. This included using duct tape, and paint string sticks. Don't forget to addict wires and run all wires all the way down to the ground via attached tot he main post the crow is made on.
2. Beak: For the beak I wanted to have something that snapped close rather than oscillate open and close. So what better than pneumatics? I started off by having the bottom beak pivot with just my hand moving it. I adjusted the fame and head until I liked the way it looked. I then figured out how much throw I needed so I bought SMC NCMC075-0400 off Amazon. It worked perfectly. After it arrived I created a pivotable bracket for the back end of the cylinder and connected the piston to the part of the beak that I left attached for this. It always helps to look at the pictures. So far the beak could open his mouth but not close it very easy so I added a simple spring to retract the mouth. Be sure to run you pneumatic tube along with you wire from the eyes.
3. Oscillating neck: I wanted the neck to move so I set up a very simple 12v motor (6RPM) with a simple crank. I attached a segment of metal wire to the end of the crank and the other end to one side of the neck. This was very subtle movement but it worked.
4. Dual Articulating wings: This part was probably the most fun to create. I wanted real life motion rather than just a single set of wing. I used Autodesk's Force Effect Motion app to design the wings. It was really col to learn how to use. So I made a quick plan as to how I was going to make this. It was mostly made up on the stuff I had laying around my house. I used a piece of plywood as the main back to support the motors, chains, and wing mechanisms. The wings themselves were made from PVC and metal as the main upper spine. I started by ordering two lazy susan bearings off Amazon. I then created wooden gears out of plywood with one gear having an axle attached that would stick out about a foot. The wooden gears were then bolted on to the lazy susans with were then bolted to the main plywood back. This entire mechanism is hard to describe so look at my pictures hopefully those will describe it better. For the wings to be moving, I used two little 120v AC motors set up inline with each other via a heavy duty chain. These motors get extremely hot so I had to put two heatsinks and two fans per motor to keep them cool. These motors were attached to sprockets which drove a chain, the chain was attached to a sprocket met on the gear axle that was made earlier. I then added a heavy duty bearing to help support the alignment of the axle. Check out my pictures for more explanation. The wings moved at roughly 6 RPM
5. Oscillating tail: The tail oscillating was first created with a PVC frame that had a pivot point about 8 inches from top. I then connected a metal rope with the same mechanism for the neck. Just a simple crank made the tail go up and down. This again was done with the use of a 12v motor. Its speed was roughly 20 RPM
Now would be a good time to test everything. If there is a mistake it is best to fix it now. For testing the pneumatic beak, I had a compressed air tank inline with a 24v air solenoid that would pressurize the cylinder making the beak close.
Step 3: Feathers for Flight
The crow feathers were made from cardboard that I got for free. Cut out in the rough shape of a feather, painted black then zip tied onto the crow. To keep the feathers close and tight to the body I used brads to pin feathers to other feathers. This was the most time consuming part by far, but it was very easy work. I had to put on each individual feather by hand one at a time. Thanks to the help of my family I was able to get this crow done in time! I owe them big!
Body Feathers: The pattern of the feathers was made to resemble a crow, so I started at the back of the crow towards the tail and preceded to work my way towards the head overlapping each feather. This was done so the feathers would overlap each other in an "aerodynamic" way to resemble the bird feather pattern.
Wing Feathers: The win feathers were a bit harder to keep up, especially when they started to move and flap. I attached the cardboard the the wings with zip ties and used brads to secure them to each other.
Step 4: Making It All Run.. or Fly for That Matter.
I used a simple 12v battery to run the LED eyes and the 12v motors. I attached a 24v inverter to give my pneumatic solenoids power. A bought a little 1000w generate off Amazon (I know Im an Amazon freak) to run the 120v wing motors.
For the pneumatic beak I had a 5 gallon portable air tank pressurized to about 120PSI (I would regularly refill this tank). A pressure regulator brought the pressure down to 30 PSI which is what the cylinder could run on. I then had two 24v solenoids that controlled the pressure of the cylinder. One was to pressurize the cylinder, the other was to release the pressure. The solenoids were ran from an Arduino which was powering a relay board by JBtech I got off Amazon. The Arduino code was very simple it would just switch the signal to these two solenoids every 1.5 seconds or so. (I added a variety) but always keeping the solenoids power opposite of each other. For example never having both off and both on at the same time, when one switched on, the other would switch off.
Thats it folks, if you have any questions or confusion just message me, I would love to help. If you make something off this shoot me a picture of it, I would like to see it. :)
I would like the thank my family for helping me get this done in time. and thank Auburn Recology for donating some recycled stuff to create this beast.
Goodluck, share and have fun.