Introduction: Russel, the RC / Robotic Zombie
Hi! Meet Roadkill Russel. Russel was just a boy who loved his tricycle, and like most children, trick or treating. Until one fateful Halloween night! Now he roams the street at night no longer seeking candy, but human flesh! At least that is his backstory. I like to name my projects and develop a back story to help me bring life to them and to truly create something where there was nothing before. This Instructable will be going over the steps and process that went into this project and what went into developing Russel. It won't be a complete step by step. That would be too large of an Instructable to write and quite honestly harder for me to put into words than me actually building Russel. I have many skills, so something had to fall by the wayside, and for me, typing and spelling are definitely two of them. But doing these Instructables will help me with both of my weaknesses and hopefully help others expand their skills too.
Step 1: Getting Him Rolling
I chose the tricycle part of the project to start with. This is the part that I was the least sure of how things would go. I knew how I intended to do it but still had questions on the nuts and bolts of how. I found the trike on Craig's list for $35. You can still buy them new for twice that but I liked this one, it had some wear to it. For the drive system, I bought a used cordless drill motor. You can usually find them in thrift stores for cheap. I paid $10 for one. You want the motor and planetary gearbox. Remove the drill chuck first before taking the drill apart. I learned this the hard way and had to spend a lot of time putting the planetary gear set back together. I mounted the motor and gear set to a "U" channel the same width as the trike's base. I used a 6 inch by 3/4 inch steel shaft and taped one end to match the thread pattern on the output shaft of the drill motor 1/2- 13 and the other end of the shaft was taped at 3/8- 16 to mount the wheel too. I also welded a tab to fit between the spokes of the wheel to lock it from spinning freely, then I turned the shaft on a lathe so a bronze bushing would fit over it. This will be the right drive wheel. I didn't want the drill motor supporting the weight of the whole project. So the motor was mounted more to the center of the channel. Then a tab was welded to the outer end of the channel with the bronze bearing pressed in it to support the 6 inch by 3/4 shaft. On the other side, a stand off was welded in with a coupler nut on top to support the left wheel. This wheel rolls freely. Make sure the wheels follow a straight line. If not it will roll funny, if at all, or be off balance. After removing the original wheels and the shaft on the base of the trike; I welded the three struts of the bike to the base so the bottom side could be ground flush to better mount the new drive assembly. The whole drive assembly mounted in the "U" channel was now bolted into the lower deck of the trike. If I need to service the drive assembly it can come out in one piece. The new wheel track is now about 1 1/2" lower than it used to be. I used a Hobbywing speed controller for the motor drive. Most speed controllers or ESC are for brushless these days and can't be used for a brushed motor. Their ESC has a built-in voltage shut off option for use with lipo batteries, and you really want this for lipo batteries. I had to order it direct from Hobbywing. At this point, the trike could drive itself when attached to an RC controller.
Step 2: Steering
The next big thing! How to steer it? From the conception of this project I knew I didn't want to steer it with any sort of external arm or gearbox. If it was to be steered by an arm it would be his own. I thought, in the beginning, it would need a large liner servo in the body to do the job. But in the end, two high torque servos one in each bicep linked to the forearms on both sides worked quite well. Using a solid shaft with a ball joint on the end gave it a nice push/ pull action. Both servos are metal geared with aluminum arms. But before any of this was done I welded up what looked to be a stick figure body from 3/8" tubing. Basically a backbone with shoulders, hips, a stub for the neck and a base to bolt to the trike seat. Also, 1/4-20 stubs where welded sticking out of the hips. I used 1/4" ball joints for the hips, knees, shoulders, elbows and wrist joints. Using the same tubing as the body for the arms and legs, Helix coils where taped and installed into the tubing to screw in the ball joints. After installing them I discovered both the shoulder and shin bone mounts needed to have a swivel in them or the legs and arms would bind and lock up. The bottom of the feet also needed to be able to rotate around the peddle shaft. For the foot mount, I welded a 7/16 nut to the bottom of the shin bone/pipe and drilled it out to 1/2". This allowed it to rotate around the peddle shaft and had enough slop to keep things moving smoothly. The shoulder and shin swivel I drew for you a diagram. After linking all of this together it was hooked up to the RC controller and out to the street to test, and confuse the neighbors. I'm not sure which one of those I enjoyed more.
Step 3: Getting a Head, for Russel.
On to the head. This was one of my more perplexing parts of this job, and not for the reasons you might think! The heads dimensions! For the body, I just cut all my own measurements by half. This works for the body but not the head. Children's bodies are smaller but their heads are not all that much smaller than that of adults. Our eyes are the same size from birth to adulthood; our skull develops and grows around them. So their heads are smaller but not by as much as most of us might think. The zombie head I did for "Making a silicone jacket mold" was originally for this project but after putting it on the body instantly knew it wasn't right. After getting measurements from my goddaughter, I realized how off I was and those cheap plastic skulls they sell for Halloween were just about right on the money. So I hot glued the skull to a 2" x 2" stick and mounted it to a board and started sculpting. I used Roma plastilina clay to sculpt the head with the glass eyes set in place. The head might be a little larger but no one is complaining. After I finished the sculpt; a plaster mold was made. Then three layers of a suitable RTV silicone was brushed in to make a skin. In between layer 2 and 3, I embedded a layer of pantyhose material for strength. The mold was in two halves so before bonding the silicone halves together into one skin; three layers of fiberglass cloth and resin were laid up into both halves. When the resin dried I pulled out the fiberglass parts but leaving the silicone still stuck to the mold. Then the fiberglass parts are trimmed and glassed into one piece. Now the skin is bonded together with more silicone. When the silicone is cured you will have a one piece rubber skin you can pull out of the mold.
Step 4: Building the Robotic Head
The head's animation. Those fiberglass head parts are now what I will refer to as the shell. Sometimes I'll split a headshell front to back but in this case, I wanted more of a skull cap style for servicing. The shell is the confines that I need to work in, so all the servos to drive his movement have to fit in there. Usually, the head rotate would go in the body but for this project I wanted the head to be all self-contained, In case I needed to service it, I could, just by removing a few screws and unplugging it. There are four movements that are in the head, rotate L/R, nod U/D, mouth and jaw grind. Keeping in mind even hi torque servos can only do so much I tried to keep the pivot point as close to the center mass for balance. Two servos where mounted to 3/8 inch tube, this will be the center point of the head. Below the two servos is a plate that will serve as the pivot point for the head nod. One of the servos will operate the nod and the other the head rotate. This will mount the head to the body, the 3/8 inch tube will slide over a 1/4 inch steel shaft welded to the neck/body. A control horn is clamped to the top of the 1/4inch shaft that is cut to be 3/8 inches longer than the 3/8 inch tube with the servos attached to it. This both keeps the head in place and once the servo is connected the head will now rotate. Next, after getting a rough idea where the headshell and the robotics will be, a plate that will attach to the head nod pivot is made. This will also be how the headshell is mounted to the robotics so this plate needs to fit inside of the headshell. This plate will also be where the jaw pivot will come from and where the servo for moving the jaw will also be mounted. All of this needs to stay inside the confines of the headshell and be placed in a manner that will allow all of your movement to work together through their entire range of movement. Don't cut out the jaw or any other headshell parts that will be moving till you have them attached to the robotics. Once all the robotics are working and not colliding with one another it is time to mount all the moving parts. The head nod plate the jaw pivot plate/arm or whatever it called for and any other movement you were able to fit into your head. Now you can start to cut the headshell into its various parts, slowly removing excess fiberglass so no movements bind. Most of the heads mechanics are made from aluminum and some brass. I used aluminum from some old stage lights we had taken apart for recycling. The prebent 90's and other angles where cut with a band saw to new shapes for mounts and drive linkages. The nice thing about doing this is the aluminum is already annealed and rehardened to shape. Bending aluminum yourself gets tricky to get all of these things right and could lead to broken and weak parts. One thing I have also learned over the years is when you are making anything move, be it a servo, hydraulic or pneumatic whatever, set it up so there is a physical stop or have the move stays within the full throws of your actuator. I have seen way too many people say " I'll just limit it in the program". The computer or person operating it will either glitch or monkey with it trying to make it better. The end result is sometimes catastrophic or at the least, it will keep coming back for repairs.
Step 5: Controling the Beast
Now that I have the tricycle working and a working head How do I control it all? The tricycle is controlled by a standard RC controller. Not too much different than the set up on an RC car. The battery pack is in the torso along with the RC receiver the wires run down the body and then through the trike frame. The ESC to run the drive motor is in the trike base. I did this because it is better to run the signal a longer distance than the voltage, plus the ESC will get better cooling there.
The head runs independently on a Pololu Mini Maestro controller. These controllers are great and I can't say enough about them. They have brought new life to many of my old projects that sat dormant for decades and opened the door to many more. From Pololu's site https://www.pololu.com/product/1352, you download their programing software, watch their little programing tutorial and away you go. The only trouble I've had with it is syncing it up with audio, but I have seen youtube clips doing it so it should be possible. There are two electronic project boxes mounted to the backbone in the torso one for the batteries and one for the two controllers and the sound card. I plugged servo extension wires into the Mini Maestro board and ran them up to the neck. this is where they meet the servo plugs for the head along with the speaker mounted in the neck. The sound card runs on a loop that is triggered by the Maestro board. At some point, I might set up the RC receiver to trigger the Mistro board but at this point, his head and sound start the moment I plug the battery in.
He runs on a 3s 2200mha lipo (12V) for the tricycle but also can run two 3s 2200 in parallel to double his run time. To be honest, I actually have no idea how long he will run for with this setup, I have never run him long enough to find out. I did have to add a second 2s 1300 to run the head I kept getting glitches running it off the 3s 2200 with a voltage step down chip. I would have preferred to use the 3s setup but in the end, another battery didn't mater weight wise.
Step 6: Getting Dressed Up and Ready to Roll.
Now that I have all the mechanics working it is time to make him look like a real boy. The body is made from foam from an old couch cushion. I start with the body and work my way out. An electric carving knife works great for cutting the foam. a razor works good for smaller detail stuff or hollowing out arms and legs. Liquid nails works well to bond the foam and Velcro together. The arms and legs are cut at the joints to help with his movement and to keep him from bulging funny. Everything is Velcroed in place to keep it from moving out of place. For added shaping and smoothing of the body and arms, I used a right angle die grinder with a 36 grit sanding disk. The 36 grit sanding disk works great but it can dig in very fast if you're not careful, if you're grinding on the end of a foam part, make sure the orientation of the grinder to be sanding off the end and not into. Using a finer grit sanding disk doesn't work as well and usually only gets hot and starts melting. The Spider-Man suit I bought at a thrift store for $5 and it already had all the muscle suit built in so this helped a lot. Always try to get your anatomy as close as possible. You may not offhand be able to describe how it is supposed to look but everyone knows when it is wrong. We don't always pay attention but we are surrounded by it every day.
At this point, I painted the head and hands with a silicone paint only doing a small bit of the blood. I sprayed the glass eyes over with a very thin pigmented milky whiteish yellow lacquer paint to give him a dead look. With everything together and complete, I give costume some aging with a beige acrylic paint in an airbrush. I do the same with the shoes and gave them some scuffing too. Once I liked the aging it's time for the blood. I made the blood with Lexal caulking, thinning it with paint thinner and adding red ink dye to color it. Lexal caulking will stick to the silicone and everything else and stay glossy. I add the blood to the head wounds, wig, body, and shoes. I even took the shoes and added blood tracks on the back step from when he climbed back onto it after his fatal accident.
There are still things I would like to add to him. A small bike head light that would flicker and a small blue dimmable led aimed back at him to bring a little more creepiness to him in the dark. Maybe a bike bell set to the RC controller. Motion or noise sensors so his head turns to face the commotion automatically or drops him into a more aggressive program. Maybe even a little sister Roadrash Rachel? Who knows what the future holds.
I hope you enjoyed this Instructable and it could help bring life to a project that has been roaming around in your head.