So I made one of these before but it was a cheapie low budget foam job- now it's time to do it right.
This build is a special project I'm doing for a friend. I didn't make the helmet- I'm just making it move. I will say that the helmet that was sent to me is one of the most gorgeous movie prop replicas I've ever seen. It's an absolutely stunning piece and it's dead on accurate. Once I'm done the helmet will be shipped back to the owner for proper finish work and painting. Although it is to be a display piece it is wearable just like the movie helmets.
The helmet will have moving head, light up eyes (dimmable), opening eye iris and properly moving fans. Everything will be radio control just like the original movie helmets. I may write up a complete tutorial when I'm done but there will for sure be a short video series about the construction. It's a really exciting project and I'm thrilled to have the opportunity to work on it.
Here's the eye iris I'm using. They measure 37mm OD x 5mm thick- perfect size! Full open to full close requires rotating the pin lever 90 degrees. Because they are identical, in order to operate them properly the right and left servos need to rotate in opposite directions. The way I've designed it the pin lever is fixed and the iris body rotates- it's housed in a machined cup that rotates in the bearing mount. Pics of that soon...
More work done on the Horus head. Machined new eye cups from Aluminum. Each iris is held in place with three 6-32 set screws. Still need to attach the head pivot mechanism, iris locating brackets and eye LEDs. It’s a perfect fit in the head casting… no room to spare!
The iris apertures are available from China via eBay but you can find them in the U.S, from companies like OptoSigma and Thorlabs. The trick is finding one with the correct dimensions and we just lucked out with an eBay find as they were a lot less expensive than sourcing stateside.
I make all of my Aluminum parts using a Taig benchtop lathe with a milling attachment. For making relatively small parts it’s one of the best, most versatile tools there is. Taig equipment is very high quality and you get a lot of bang for your buck- great support for it too. Check out www.cartertools.com.
More work done. Still a few small bits to iron out and then I'll get to work on making the fans move. That's a tiny 10-32 ball link in the photo- it's threaded into a 3/8" rod and the rod has a collar with a set screw that holds it in place. The collar is positioned at the top of the main helmet body and moving the rod in the collar allows you to adjust the distance between the body and head castings to get the spacing just right.
As it turns out the servo mounting plate assembly is a tiny bit too wide- I'm going to flip the servos 90 degrees and shorten the servo arms in order to make it fit properly in the main helmet section. I could use the current setup if I changed the servo arms and used smaller end links as it would allow me to position the servos closer together but the smaller 4-40 nylon end links have a tendency to break under higher loads. I hate it when things break so a quick re design is necessary.
LEDs and driver board showed up today. The LEDs are 3W (silly bright) and the driver board is a Sparkfun FemtoBuck. The FemtoBuck is a constant current LED driver board that can accept a PWM signal to dim the LEDs.
Finally getting back to work on this! Wired up the eyes tonight and holy crap are they bright. They're perfect.
My old variable power supply died so I quickly put one together using parts I salvaged from circuit boards in my scrap bin. For a power source I used an old power brick from a HP printer. At some point I'll probably break down and buy a proper bench power supply...
I had a bit of trouble getting the eyes to dim properly. Yep- I let out the magic smoke. While getting ready to do a test with the radio transmitter I accidentally reversed the power wires to the FemtoBuck and smoked the driver chip. I ordered a replacement AL8805W5 chip, removed the blown one using a hot air tool and soldered the new one in. Note to self- ALWAYS use polarized connectors!
As soon as I was back in business I set about making the RC radio receiver signal work with the FemtoBuck. The FemtoBuck is able to dim the LEDs by applying a voltage range of .5V to 2.5V to its control pin. The problem is that my RC receiver doesn't output a compatible signal so a fix is needed.
Arduino (Pro Mini) to the rescue! At the beginning of this project I thought I'd finally build something animatronic without an Arduino in it but the little bugger managed to work its way in there...
Using this code the Arduino was able to take the output of the receiver and turn it into something useful-
const int inputPinA = 2; // The pin connected to the RC receiver's servo output A const int outputPinA = 3; // Output PWM pin A
In several scenes in the movie Stargate you can see how the fans on the sides of the Horus and Anubis helmets rotate in a progressive manner, with the upper fan moving the greatest amount and the lower fan moving the least. It’s a really cool effect and the set of three fans on either side of the helmet was made to move using a single servo. It’s a really compact mechanism.
In order to replicate this I created a kinematic model of the mechanism using a free program from Autodesk called ForceEffect. This is an awesome bit of software that allows you to plot motions of all kinds of linkage mechanisms. I would have killed for software like this back in the day (20+ years ago) when designing suspension mountain bikes as I used to plot kinematics manually. The original helmet mechanics used helper springs to overcome the high leverage ratios- I have the benefit of modern digital servos that are much more powerful than the analog servos used when the film was made.
Here's the assembled mechanism. Note that the schematic shows the left side of the head and this is for the right side of the head. Still have a little bit of relief machining to do and drilling the fan blade mounting holes.
Here's what the mechanism looks like with the fans attached-
And it's finished! Got both of the fan mechanisms installed yesterday- really tricky to get them aligned properly. I also changed the way the head shell mounts to the head mechanism. I'll shoot a build video this weekend that shows all of the movements and how it all works.