As soon as I saw how grumpy and irritable Chopper was I knew I needed to build one of my own. Chopper is a mash of many junk parts so I wanted to use mostly scrap parts to build mine. There are no official sizes so I used a template sent to me by an Astromech.net user who took measurements from the Chopper built by Lucasarts for promotions of the Star Wars Rebels series.
I'm planning to use the S.H.A.D.O.W. controller system with Playstation Navigation controllers. The Navigation is a small controller that is easily hidden.
At the Rogue One premiere Chopper experienced a failure of a shoulder bolt that nearly caused a catastrophic crash. So, the entire month of January was spent beefing up the shoulder linkage and redesigning his stance to use a better center wheel. Here he is a Pensacon 2017 and everything worked perfectly.
You can see his new stance and wheel here. He glides effortlessly now and his runtime increased from 5 hours to over 8. By the end of day one he was running strong on the original set of batteries. I barely noticed any slowdown.
Chopper recently attended his second convention of the year. I've applied some of the weathering to his paint and started on the dome electronics. Unfortunately I blew up the LED lightstrip because I was in a hurry. A quick and dirty replacement was a red reflector from my classic Mustang's taillight. It didn't light up but it didn't look horrible.
At some point during the convention an odd R2/Chopper hybrid was created.
This convention had a lot of open floor space so I was able to keep Chopper mobile nearly the entire convention. He ran about 5 hours straight and still had just enough power to get him to the car for the drive home. Mark's R2 was running a single 12v LiPo and got about 4 hours of runtime.
Please pardon the mess. The electronics portion of Chopper was thrown together in the span of a week so it's a wiring nightmare. It won't stay like this.
The Arduino Mega (which can't be seen in this image) runs a bluetooth dongle that connects to the PS3 Navigation controllers. I used a single controller for Chopper since there is an issue with dome jumps with two controllers connected. Since I'm using a power wheels drive motor and gears for the dome drive this jump is a real issue. The motor goes from 0 to full speed in half a second and can not only scare kids it can damage Chopper.
The Arduino connects to a Syren10 for the dome drive, a Sabretooth 2x32 for the foot drives, and a Sparkfun MP3trigger for sounds. The AMP is a Sure 2X25. I power the droid with 2 standard 7Ah batteries connected in parallel since I want the run time. Chopper recently went to his first convention and I was able to get about 7 hours moderate use from this configuration. I consider moderate use as mostly stationary but with a lot of dome movement and sound.
Chopper's "face" is what most people are going to see first so I wanted it to look correct.
So, of course, the first thing I did was incorrectly mask off the eye plates to be painted yellow.
Thankfully it was a recoverable error.
The saucer was 3d printed in 5 parts and assembled. The assembly lines still show up. I'm hoping with some weathering they will fully disappear. The antenna is from a broken router I found in the junk pile at work.
The motor supports for Chopper also support the drive wheels so they are constructed of aluminum with steel spacers. The motors and wheels used are from E-100 Razor scooters. They were purchased from Ebay.
In the image below you can see that I accidentally gave Chopper two right "feet". This was corrected later that day.
It wouldn't be Chopper without the little greebles that make him look like a pieced together droid.
The pipe detail is going to hide an emergency kill switch. I learned from K-9 that catching and shutting down a runaway robot is not easy when the off switch is inside. The cover is held closed via rare earth magnets so I can pull it off quickly and get to the off switch without pulling off his rear cover.
Chopper's center leg isn't a footshell like R2D2 and other droids. It's just a single large wheel on a caster. The hardest part was finding a caster/wheel combination that worked. I eventually had to build a caster around a wheel that I liked. I'm testing that now. So far I've had minimal issues from the assembly.
The caster tracks properly as the droid turns. However, just moving him by hand resulted in a nasty face-plant. I'm looking at positioning the batteries to help compensate.
After a lot of trial and error I decided to 3d print the legs. The main skeleton is a piece of 1 by 1 steel tubing so the 3d print is just a detail and not a support material. This way I was able to lower the infill and save material.
The 3d model turned into a print once I sliced it properly. My first prints had issues because the filament I was using was low quality. I ended up using them anyway with some smoothing with an ABS slurry.
After many hours of printing I was able to assemble the pieces into two functional legs.
The steel supports bolt onto the main body. This enables me to disassemble Chopper to the point where I can transport him in the smallest of vehicles. He even fits in my DeLorean.