Introduction: Make a RC Robot for a Movie
Back in May of 2005 I received a phone call from colleague at Colpitts Design. He was approached to build a puppet for feature film. They were looking for someone to make remote controlled robot character to play a part in an upcoming movie.
It was described as a walking biped robot about 3 feet tall and they wanted to start shooting in about 4 weeks. I would have loved to make a biped walker but we all thought it might be a bit ambitious given the time, budget and resources, so Peter and I agreed to pitch a two legged rolling robot.
After I hung up the phone I put together a lego prototype to propose a simple method of locomotion. We shot a video and sent it to the art department. The next morning we were given the go ahead to start building.
Step 1: Full Scale Prototype
While the Art department was making final refinements to the design we spent a couple of days making a full scale working prototype.
We started by drawing up some parts on the computer and cutting them out, while at the same time looking at various motors, gears, servos available to make this thing move. To have the tork we wanted to drive the hips and wheels we decided to use windshield wiper motors that we drove with custom made control boards and a potentiometer connected to the drive shaft to turn it into a big servo. We took off the cast gear box and machined our own to allow us to design our own mounting face as well.
For our first test we wired everything into a plugged in power supply, later that would need to be changed for something self contained.
Step 2: Concept Art
For this build concept art was provided by the films art department. A number of renderings and concept sketches by Bartol Rendulic came our way and finally he provided us with projected view drawings for this robot. I say finally not to sound like it took a long time, Bart draws like a maniac and we were getting updated and revised drawing every day or two.
Notice here the robot was named Steve Maqueen at this point of the project
Step 3: 3D CAD Modeling and Renderings
Now that we received approved drawing with projected views we were able to bring those sketches into Solidworks, resize it to the correct scale and begin using that as a guide to model the parts.
I have made the drawing available to download so you can view it as an edrawing. If you don’t have an edrawing viewer, get one here for free.
The CAD data served us in many ways. First off screen shots and renderings could be sent to the art department for approval, but more importantly for us it allowed us to build accurate parts that looked almost exactly like the drawing and rendering we were sending to the client.
Once we had a few key components modeled up and approved we started making them. A 3 axis CNC mill did a lot of the work for us. Some of the frame work for the body required only 2D cutting so for those aluminum plate was cut using a CNC water jet cutter.
Step 4: Making Parts
Some other fabrication techniques used to make this included Thermoforming a.k.a. Vacuforming These parts were small enough for us to do ourselves using a simple frame to hold the plastic and was heated using an old household oven. We happened to have a very good vacuum pump and tanks so we used them, but I have experienced a lot of success using a workshop style vacuum cleaner. (vacuform in your kitchen Instructable to come) The moulds or blanks used for the thermoforming were machined out of MDF.
For other more detailed part that we did not want to machine we rapid prototyped using SLA back in 2005 this was a little more exotic then it is these days.
Step 5: Kit Bashing
Gack, is a term used to describe all the non functional bits that strangely enough makes a prop, set, or puppet look functional.
I like mixing real manufactured parts with the ones we make, not only does it save time and money, it complements the other parts to make them look that much more real. It really helps to know of places where you can go to find this kind of stuff in the quantity and variety to make the trip worth while. I am careful to avoid single items unless I am positive I can get away with only having one of them. It is always good to have extras around or know that you can get more if you need it.
Step 6: Bringing It All Together
At this point all of the electronic and mechanic have been mostly sorted. All that is left is a little fine tuning. This stage really comes down to final assembly and dressing the puppet up with mostly non fictional detail. Here we are adding parts that have been purchased from a variety of sources, hardware stores, automotive, medical, industrial suppliers. For this style of build it is important to included parts that look familiar, defiantly earth based, NASA surplus looking mechanics. One thing I try to do is to not use obvious bits of hardware that the view can pick out, and if I have to, I try to us it out of context to help hide it.
Step 7: On Set
Here it is on set. At times it took two operators to bring this to life. One to operate the legs on 4 channels to make it walk, turn and pitch forward and back, while another person would control the arms at the shoulder, elbow and wrist which used 6 channels.
So that's that. Make a robot puppet in under 4 weeks.
It was fun to make, don't remember seeing the movie though.