Scale: 1:6, 40cm tall.
Material: mostly polystyrene and steel (screws, etc)
Build time: long, I lost track.
It all started with this pencil drawing. Well, it really started when I read my first Perry Rhodan novels back in the days. One of the first volumes I read described an epic battle between legions of fighting machines, and I was immediately fascinated by the idea of autonomous machines doing their thing.
So fast forward to some 40 years later. The idea still resonates with me, although the intended application for such machines are more peaceful in my mind these days. Of course there is no model kit for the Arkonide or Terran robot, so I had to create the model from scratch (but this has never stopped me before).
The sketchy drawing glosses over many details that I made up on the spot while the model developed, but it served as a guideline throughout the process.
These are the building materials. The model is literally built from scratch in this case. The only prefabricated parts are screws, nuts, and washers; all other material is semi-finished goods. Here is the complete list:
Lots of tools are used while building the model. The most frequently used ones in this project were a paper cutter for cutting the PS sheet and a mini drill with various milling, drilling, and cutting bits. I always wear safety goggles and a mask when working plastic with power tools. In addition I use an old IBM mainframe fan for blowing toxic fumes and small particles away from the workplace.
A robot has lots of joints, so the first thing to do was to create some joints from scratch. This took me a lot of time and research. I looked for ready-made joints in all kinds of places, but eventually did not come up with anything that fit my needs.
So how do you create a joint from PS sheets? Pivot joints are easy, you put a small tube into a larger tube. Hinge joints are bit more complicated, though. This is what I eventually came up with. The sheet on the picture shows markings for the parts of one hinge joint (and the template used for making the marks).
In my first attempts I used a ruler and a circle cutter to cut out the parts, but I soon switched to a pair of tailor's scissors, which did an excellent job. Of course they lack the precision of a circle cutter, but so much precision is not really necessary, and I needed more than 100 of those parts, so a faster method was really appreciated.
The picture shows the parts of one hinge joint and the waste material left over after cutting them out.
The next step is then to line the parts up carefully and place them in a vise for drilling a hole through the center of the circular part. An M3 screw threaded through the holes serves as an axle for the joint.
Here is a half-finished joint in a slightly bent position. The halves of the joint can be moved around the axle and the friction of the discs causes it to stay in its current position. The friction can be adjusted by tightening the screw.
The slots between the individual parts of the joint are then filled with small rectangles of PS sheet. The picture also shows a piece of PS tube. The joint will be used to connect two such tubes to form a knee joint.
In the next step the ends of the joint are shaped with a milling drill. The joint then fits precisely into the PS tube. When fastening the joint with glue, the resulting joint will be a hinge joint or saddle joint, as used in the knee. When just squeezing the part into the tube, the joint will be a combined hinge and pivot joint, which can be used for the shoulders, hips, wrists, and ankles.
The first batch of joints was used for the knees and elbows. A cutting wheel is used to shorten the M3 screws, and the finished joints are glued into the arms and legs. Note that the elbow joints are smaller than the knee joints, but they use the same principle and the parts are similar.
I made some more joints for the wrists and hips or ankles before I got bored and decided to work on the torso next.
The torso is a rather complex shape that consists of lots of trapezoids and triangles. Here is a picture of the finished torso to give you an idea of the direction in which the following steps will be going. The torso contains the tubes for the head joint and shoulder joints and a hole for the waist joint. The latter is on the bottom and not visible in the picture.
The first step in building the torso is to make a box from PS sheet that serves as a support structure around which the rest of the part will be built. The picture shows the box and the bottom, center, and front plate in place. All plates are made from two layers of PS sheet, so they are two millimeters thick. This means you need a lot of glue and therefore good air circulation at the workplace.
Lower front and side plates in place. The hole in the center plate at the top is for the head joint.
The rear of the torso is not closed, because the waist joint needs to be installed here. The markings on the bottom plate indicate where the hole for the joint will be drilled. Note that the PS box serving as a support structure has been opened at the backside so that the waist joint can be accessed. Later I decided to demolish the support box completely, because the torso is very stable anyway and the waist joint is easier to install without it.
The PS tube forms the outer part of the pivot joints of the shoulders. The middle part of the tube will be cut out later to make room for the head joint, but it is glued in place in one piece in order to align it perfectly. Again, lots of glue and some support structure, because these tubes will carry the weight of the arms (plus whatever the arms are carrying).
The support structure for the head joint is glued to the remaining tubes after cutting out the middle part. The picture also shows the small plates through which the shoulder joints protrude. The center plates are only 1mm thick, because they are not very large and sufficiently stable this way.
Rest of the center plates in place and head joint support structure finished.
Outer tube of the head joint installed. The small plate in front of the torso will form its topmost plate.
Topmost plate installed.
At this point I decided to demolish the support box at the center of the torso. Not very easy, because there is not much space inside of the torso, but a pair of pliers and some deliberate amount of force got the job done. The hole for the head joint is actually unused, because its tube is shorter than expected. Once again it is a good thing that nobody will see the inside of the model later.
Top plates installed. These parts are two-millimeter plates again, lending some satisfying solidity to the model. Of course this also makes the model rather heavy. Hopefully the leg joint will be able to carry it!
Upper torso completed. The straight plates and the visible seams lend an oddly rugged and technical look to the model. It would be possible to make the seams look like welding seems when painting the robot, but I decided to go a different route.
The back of the upper torso is still open and will remain so for a while, because the waist joint is still not in place. Once the joint is installed, a removable cover plate will be put here, so the joint can be adjusted should it be necessary.
The upper torso after sanding. In fact it not only got sanded, but the seams have been removed with a milling drill and many edges and corners have been ground off. Now the techy sturdy look is gone and the torso looks more like some plastic part, but the more I look at it the more I like it. No use making a robot look more technological than necessary.
Backside of the sanded-down upper torso.
First container full of waste material (5×5×8cm container, that is). Waste includes a complete 13g-tube of glue so far, and I suspect that it will not be the last one.
The next part to construct was the lower torso with the hip joints. Of course the hip is really a ball joint with three degrees of freedom, so one hinge joint and two pivot joints are needed to simulate it. The base of the hip joints is a box made from PS sheet with a tube at its center, as seen in the picture.
I could not find a 30mm polystyrene pipe for the waist, so I used an acrylic glass pipe instead. Acrylic glass can easily be cut with a cutting wheel for plastics. The piece in the picture is all I needed, so I have almost 100cm left for future projects.
Of course acrylic glass is highly transparent and I do not want the waist of the robot to be translucent when it is finished. So I sanded the tube and inserted a curled-up piece of polystyrene sheet into it in order to make it opaque.
Fitting test, looks good. The axle of the pivot joint for the waist is an M6×40 hex screw that will be cemented into the lower torso. I had planned to fixate the upper end of the axle with a nut, a teflon disc, and a locking washer, so that it does not unscrew when the waist rotates. This turned out not to work, though. More on this later.
Step one of cementing the hex head of the axle in place: sheets of PS and lots of glue.
I cut off the extra material from the hexagonal box around the head. This may in fact have been a bad idea, because the extra material adds strength to the structure. Unfortunately this occurred to me only after the lower torso box was finished. Also in the picture: extra support structures around the tube for the hip joints.
This is the waist joint from the bottom. The hex box for the screw head has gotten a lid. The M6 screw goes through the acrylic glass tube and another piece of PS sheet that sits on top of the tube and makes sure that the screw is in a straight position. The piece of the screw that protrudes from the lower torso (not visible) will be inserted into the upper torso. The hole is in place and can be seen in the picture (although slightly out of focus).
Another fitting test. Still looks good. The hip box has gotten a truncated pyramid around the center tube. Another one will follow on the other side after the break. But first an interlude...
Building the dome of the head. I used a Chinese stone ball for a template and made a negative from modeling clay (which dried too quickly and cracked) and then a positive from the negative, which also dried too quickly, so I used modeling cement to fill the cracks.
If you have read other construction stories on my homepage, you know what is coming next: I used my Erkoform-D vacuum thermoforming device to make that part. The picture shows the finished part. A detailed description of the thermoforming process will be given later in this text.
I wanted a 2mm dome, but this is not so easy. Thermoforming two sheets of 1mm plastic at the same time will not yield a clean shape. Two separate spherical segments will not fit together. So I filled the inside of the segment with a mixture of glue and PS granulate. Granulate cannot be obtained in such little quantities, so I made it myself by cutting a grid into a piece of PS sheet and breaking it up.
The center and bottom parts of the head are made from curled-up arcs of polystyrene sheet. The center part forms a cylinder when curled up and the bottom part forms a truncated cone. The picture shows the (almost) finished head and the disc from which the segments were cut out with a circle cutter. There is some support structure in the head that consists of more curled-up PS sheets.
Close-up of the almost finished head after sanding. Still missing: the face, the antennas, and the neck joint. In the background half of the finished lower torso can be seen.
You may have noticed already: pictures are not necessarily shown in chronological order here.
Another container full of waste material. In the background: the torso, the head, the arms and legs, some hinge joints, and the back cover of the torso (to the left of the container).
As mentioned earlier, the original plan for the waist joint was to put a teflon disc on the bottom of the upper torso, then a locking washer on top of that, and fixate it all with a nut. The idea was that the teflon disc would move freely against the torso. But it didn't. Apparently there was too much friction between the disc and the PS sheet on the bottom.
So I tried a few combinations with a teflon disc, a washer, and a piece of synthetic felt. What finally worked was: a washer at the bottom, then a piece of felt and then the nut. There is enough friction between the nut and the felt and sufficiently little friction between the felt and the washer, so the nut does not unscrew when the joint moves.
I could use superglue to fixate the nut in the waist joint, but decided against it. What I did instead was to make the back cover removable, so you can adjust the screw should it be necessary. Yes, there is a little gap there. Maybe I will fill it, or maybe it will look cool when the model is finished.
Another cemented nut and a socket screw. These will be used to secure the back cover in place.
Here is the back cover with the screw inserted and the nut glued to the torso. In fact the back cover sits pretty tight and probably does not need the additional fastening, but: better safe than sorry. And the socket screw looks kind of cool. Like an on/off switch or something. :)
This is the pivot part of the neck joint next to the mini drill used for fitting it and a piece of PS tube used for testing. The inner part of the pivot joint is fitted by first shaping it and attempting to insert it into the tube. Then more material is stripped from the inner part until it fits with just the right amount of friction. Unfortunately there is no way to adjust this kind of pivot joint later, so it has to be fitted very carefully.
The torso, head, and neck joint before putting them all together. The end of the joint that is opposed to the pivot part will be glued to the back of the head.
Done, and it looks much cooler than I expected. I like the clear shape of the head as it is, and I wonder if I really want to add a prominent face to it. But then there is a lot of time to think about that while building the arms, hands, legs, and feet.
One thing I wanted to get of of the way was the eyes. The plan was to make a transparent cover that goes from the left to the right temple and add line-shaped eyes under it with red fluorescent color.
I wanted to make the cover from acrylic glass tube. Cutting the tube in half lengthwise was easy enough using a cutting wheel, but bending it with a heat gun turned out to be much harder than expected. The part warped while bending and I never managed to make it fit really well. While experimenting I wondered if this kind of eyes would really fit well on the head anyway. In the end I decided to postpone the design of the face entirely.
So I turned to a rather mundane task: the building (or should I call it "manufacturing" at this scale?) of the rest of the joints. The picture shows a sheet with markings for 28 parts, enough for four hinge joints. In the background the joints already made can be seen: knees, elbows, and wrist and ankle joints. More joints are needed for the hips and shoulders. To the right of the sheet there are also two joints that did not turn out so well. Maybe I will find a purpose for them in a different project.
Third container full of waste material. Three joints already cut out, the last one waiting to be processed.
The hip and shoulder joints after drilling, threading, and gluing, but before cutting the M3 screws to their proper length.
All parts made so far: torso with head, arms, legs, six big joints, and two small joints.
At this point the entire project stalled for a variety of reasons, mostly back pain and procrastination. Designing the hands, feet, and face took a lot of time, mostly because I could not experiment much because my back was not in the proper shape for hunching over a work bench.
So the stuff to the right just sat there for almost a year.
After the break I started to design the hands. Instead of investing a lot of thought into it, I had a look at my own hand, mentally divided it into polygons, and immediately made some prototypes. The palm of each hand is made from five layers of PS sheet. Both palms can be seen in the picture: one under construction, the other already attached to the wrist joint.
Another close-up of the right arm, this time with the shoulder joint attached. Hand still unfinished.
Fitting test. Looks good. The arms seem a little bit long for human proportions, but this is really due to the perspective. Hand still unfinished.
Both wrists with palms attached, the upper one in its final shape after milling and sanding, the lower one still in its raw shape.
The right hand. The fingers are made from 3mm sprue runner and the thumb from 5mm sprue runner. Finger joints bent into shape using a candle, because a heat gun cannot focus heat on such a small spot. The flame got a little close sometimes, so traces of soot can be seen on the fingers. The space between the thumb and the palm was modeled using body putty and then polished.
Right arm attached. The robot starts to look strangely human, even though its shape is clearly technical. I really start to like the white color more and more. Originally I had planned to use steel blue finish (because this is how the robots are described in the novels), but maybe I will use white instead. Time will tell.
Wrist and ankle joints with additional sheets of PS on their sides, so the pivot parts of the joints will fill the entire outer tubes and provide more friction. This is particularly important for the leg joints, because they will have to carry much of the weight of the robot.
Both arms finished and attached and now looking even more human.
There are 15 joints in the model so far. One hinge and one pivot in the neck (2), one hinge and two pivots per shoulder (8), two hinges in the elbows (10), one hinge and one pivot per wrist (14), and the big pivot joint in the waist.
The weight of the model is 156g so far. The leg joints should easily be able to carry that.
Legs with hip joints finished (left) and ankle joints semi-finished (right). The polygones in front of the legs will form the soles of the feet later.
Feet in progress with outer tubes of the ankle joints attached. Tubes are attached by milling a tube-shaped dent into the sole and then cementing the tube into that dent.
In-progress picture of the left leg. Hip, knee, and ankle joints are finished. A lot of last-minute changes went into the design of the legs. What is most obvious is that the knee has become wider. The knee joints were kind of wobbly when carrying load, so I attached some reinforcement rings made from 16mm PS tube to them. Still, the joints of the robot should only be manipulated carefully by grabbing the model close to the joint.
Then I had originally planned to just glue the ankle joints to the feet. However, this way the feet would end up on their edges when the legs are tilted inward or outward via the hip joints. So I had to add a pivot joint to the feet and the feet now have all the degrees of freedom of human feet. I will have to rethink the design of the feet, though.
Close-up of the ankle joint of the unfinished left foot.
Reinforcement rings sawed off of a piece of 16mm polystyrene tube. One ring in the foreground already cleaned-up. I will also have to make smaller rings for the wrist and elbow joints.
Close-up of the reinforcement rings on the right knee.
A lot of work, both design and building, went into the hands and feet. Here is a picture of the left foot after attaching the toes, but before working out the details.
There goes the second tube of cement.
Feet slowly taking shape under a lot of cutting, milling, and filing. Still a lot of work ahead: filling the front and sides with body putty, maybe even attaching some small sheets of PS to avoid large chunks of putty. The overall shape is pretty much final at this point, though.
Feet after finishing touches.
First time standing on its own. Perspective looks about right. The "real" robot would be 240cm tall (almost 7'9), have shoe size 58 (European, US 20), and glove size 13. The novels state a length of 250cm, but this includes antennas, and I decided no to attach any. A tall person (180cm, 5ft 11) would look at the bottom end of the chest plate when standing in front of the guy.
What's left? The face, which will cause me some more headaches, and painting. I have decided to paint the model in glossy white. Maybe semi-gloss. Lots of paint and thinner are on their way.
Until then I think we both deserve a break.
Head with center markings for the face. The eyes will have to have a concave backside in order to glue to them to the head. I have thought about vacuum-thermoforming them, but they are pretty small and milling a concave shape into their backside would most probably ruin them.
While working on the hands and feet, I have gained some experience with shaping parts with a milling drill, though, so this is how I intend to make the eyes.
This is the basic shape of the eyes, once again cut out with tailor's scissors. I do not have a circle-cutter that can cut a 3mm radius, and it would not be fun anyway.
Next step: bending the shape, so it can be attached to the head. I am bending the shape cold, because heating it would most probably distort it. The tools leave markings, but they will be filled and polished away later.
The eyes will be teardrop-shaped, so there needs to be some substance for modeling with a milling drill. As usual, this is done by gluing multiple layers of PS sheet on top of each other.
Eyes after milling but before polishing.
Eyes attached to the head. The human brain is very fine-tuned to recognizing subtle mimics, so positioning the eyes in such a way that they do not inadvertently express some emotion took some time. The auxiliary line is for centering the eyes.
Now for the mouth part, which took a bit of experimentation.
First attempt: thermoforming individual parts with a heat gun and then assembling them to form a "snout". That did not work so well. All the parts were distorted in some way.
Next attempt: cutting individual parts from a piece of PS pipe (background). Works better, but I was not happy with the shape.
Finally I decided to vacuum-thermoform the mouth part. In the picture there are two molds. The left one will eventually be used, because it fits better on the cone-shaped lower part of the head.
Here is the finished vacuum-thermoformed part. For those who are interested, here is the process of thermoforming in much too great detail.
The mouth part in place after a lot of filling, milling, and sanding. Now that the robot has a face, I think it also needs ears. And maybe antennas. Then it needs loudspeaker holes in the mouth, but I need to get a 2mm drill that fits in my minidrill first, so this will have to wait a little longer.
Ears made from a bit of PS tube and multiple layers of PS sheet. You know the drill by now. No pun intended.
Ears after milling and sanding.
Then the robot needs a speaker grille in the place of the mouth. This is done by drilling lots of 2mm holes in a small part of PS sheet. PS is best drilled with a wood drill but, at least where I live, you get 2mm wood drills only with a hex bit attached. Fortunately, this is easily fixed with a cutting wheel.
The robot's head with the ears, speaker grille and antennas (made from steel nails) attached. My goddaughter insists that he looks cute now. That is a matter of perspective, though. See further below.
Close-up of the lower legs and feet.
Close-up of hands, arms, and lower torso.
Close-up of the head and torso from the perspective of a tall person (well, action figure) standing close to the machine. Still looking cute?
The last container of waste material. A long journey comes to an end. When I started to cut out the sheets for the first hinge joints, I did not think I would ever get that far.
Here he is, 1/6 scale, 40cm tall with a weight of 224g, awaiting painting. I will have to do some experiments with the paint first. How much thinner? Priming or not? How to paint the joints so that they are still movable, etc.
Time for a break.
And, yeah, he does look kind of cute. Nothing wrong with that! :)
Disassembled for the last time (hopefully) for painting.
Paint is glue with pigments, therefore painting joints is a bit tricky. Especially the hinge joints have lots of surfaces that can stick together, so they have to be mobilized regularly while the paint dries. I started with the leg joints. The legs are fixed in a vise while drying, so the joints can easily be moved. At times the joints moved harder than I had estimated, but in the end almost everything went well...
But then, of all the joints that could break, the neck joint did. The joint was a bit tight to begin with, and the morning after the day I painted it, it refused to move and all wiggling and bending did not help and in the end it broke.
This joint is the one that is hardest to replace, because it was installed when the head was not yet finished. So I will have to come up with some other way to fix it.
The head with the left-overs of the old joint milled away. Fortunately the inner part of the hinge came out without any trouble. In front of the head there is one of the spare joints I had made. Not yet finished, but well on its way.
New neck joint still under construction. This time it will be painted before installing it.
Neck joint ready to be installed. This time mobilization after painting went well and the new joint moves smoothly. There is a slot in the upper part of the joint. The part left of the slot will go inside the head and the right part will be attached outside. This sounds simpler than it is, because the joint has to be perfectly straight (or the robot would tilt its head to the side) and the slot is a bit too wide (by design), so a few tiny PS sheets have to be inserted to fix the joint firmly in position.
Done, and looks pretty good so far. The fitting test will have to wait for a while, though. See below.
Interlude: paint on the lower torso drying. Spot the other parts of the robot! My goddaughter says this look brutal, especially the torso hanging upside-down. Well, it is a temporary state of affairs.
Left to do at this point: painting the upper arms, upper legs, palms, soles, and the head.
Head fitting test: looks good! Head coated in two layers of white
and awaiting painting of the eyes. Speaker grille holes painted black
for increased contrast. Ears Antennas covered in masking
tape for protection from accidental painting.
Painting was kept very minimalist this time. Originally intended was a steel-blue finish with dark red fluorescent eyes, very much like the depictions of the fighting robots in the Perry Rhodan universe.
But then something more peaceful came to mind, and the robot ended up with two layers of white with some black accents. Almost an entire can of white (14ml) was used, and almost a full bottle of of thinner/cleaner.
Awaiting final assembly.
And it is done.
Lots of lessons learned during construction, lots of things I would do differently now, but I doubt that there will be another. The pivot joints in particular are not very smooth, which makes the hinges and hence the entire model rather fragile. You have to move the joints very carefully.
Goddaughter says she looks pretty female now. Is it the color? Or the big insectoid eyes? (We study lots of insects and most bees and wasps you see are females.) Anyway he/she/it turned out more beautiful than I ever imagined.