As I built up my Ultimate Bit Char-G project, I watched other people around the world stack up battery after battery on their little cars in the aim of making them uncontrollably fast in a straight line on a perfect, flat racing surface. So what did I do? Decided to pull an about-face on the world for my next project! Instead of going for speed, I went for torque. Instead of going for race-surface traction, I went for something unheard of in the world of Bit Char-G's -- articulation!
Follow along as I strive to build the world's first 1/100th scale R/C truck, a dual-motor, low-geared, hill-climbin', terrain-tacklin' Bit Char-G that doesn't try to outrun anyone... it just runs over them!
(Updates are posted in reverse chronological order -- the latest & greatest shows up first.)
8/16/02 -- part 3: It's starting to come together! I test-mounted the cab and it looks great to me. I also took the truck for a test drive, and the articulation is working quite well. It looks like a short centipede as it goes over irregular surfaces. It also climbs more than a 30% grade with no run-up, and will stop on a hill without sliding down. So far, so good!
I'm going to attempt to get still more articulation out of the truck next as I start stacking up batteries and attaching body panels.
Stay tuned for periodic updates. I already have inspiration for my next super-micro project!
8/16/02 -- part 2: Alrighty then, after a brief lunch/Speed Channel break, I got back to it. I attached the three main functional segments (one axle per segment) to the flat chassis using medium CA glue, and immediately started checking out the articulation. At first it was not all that great, so I trimmed the flex points on the carbon fiber until I was happy, and here's what I ended up with:
The electronics decided to stay with the center (thorax!) segment for logistical reasons. I used the rear (abdomen!) segment's stock motor leads to jumper over to the forward (thoracic) motor mount tabs (whaddya know, it's an entomology lesson!). I also ran an extra set of wires out from the battery compartment to later attach a 2nd battery in parallel for extra runtime. I may use still more batteries later for additional weight.
8/16/02 -- part 1: What do you say we start with some hacking? Literally! I had no reservations about taking the saw to a crippled car to recycle its parts! No mercy! Opening up the guts involved simply removing the body, unclipping the top cover, and snipping off the motor leads close to the PCB. I also pulled the battery out for later reuse. Witness the ferociousness:
In the second picture, you're looking at the new chassis stock from the side. There are no Photoshop tricks -- this single-layer piece of carbon fiber is not even as thick as the nail of my thumb. I trimmed it into a rectangle of the correct width, but excess length (better to be safe than sorry) to mock up the major elements. After this came a few hours of very, very fine Dremelling. The patience required to make the tiniest adjustment almost made me lose my mind.
I was only able to build most of this truck from scratch in part of one day by planning ahead and gathering all of my materials beforehand. Inspiration for the 3-axle layout came from ThorBob's 6x6 project "trial truck." In my early tinkering with Bit Char-G's I had learned the internal anatomy fairly well, and quickly saw that the rear section made for quite a nice little powered axle module that could be easily freed from the electronics and thick mess of wiring. The vehicle is so small, I didn't want to invest too much time and money into it, so I decided very early on to use a flat chassis plate with flexible sections inspired by the H-plate on Kyosho Mini Z's (a very old idea, I have come to find out). I don't remember how or why it came to me, but a piece of scrap foamcore carbon fiber trim left over from the original Ultimate What The? chassis attempt would prove the perfect starting point. All I had to do was separate one of the outer layers, shave down the foam, and voilla, a single-layer sheet of epoxy-laid carbon fiber roughly the thickness of two human hairs!
The truck would need to move slowly to navigate over rough terrain, and I would need a lot of torque. I had a miniature Ziploc bag full of unused 1.0 motors, and these would be just the ticket. For even more low-end grunt, I bought two Tomy gear sets to use the lowest ratios they had.
For cosmetics, I was considering using an HO-scale truck cab and making a custom rear cover for it, but one of my Choro-Q (tiny Japanese pull-back-and-go) vehicles, a Japanese TV station field control room truck, cried out, "Use me! Me! Memememe!" This would at least give me a good forward cab, if not a sleeper/storage cabin to go with it. Finally, for tires, I absolutely wanted more appropriate than stock slicks, and a couple Bit Racer tire sets yielded a nice outfit of block-pattern treads (bluish in color though they are).
Of course, also important were two Bit Char-G chassis from which to build the whole truck. I got one almost for free when a local customer completely broke the steering in his and I gave him a few bucks of URC Store credit for it, applicable to his purchase of a brand new replacement. From that chassis, obviously, I would use the rear end for the 3rd axle. The other chassis would come from my fleet of demo cars.
It took awhile to get all of these items, pulling together some from local shops, some from eBay, some from my dealer in Hong Kong, but all of it was piled into a small corner of my large home office desk, and when the time came, it was all ready!