The design is intended to be extensible according to your own requirements, using an industrial slotted framing system typically used to construct prototype machinery called 80/20. Precision-cut aluminum frame parts are intended for fabrication via abrasive waterjet machining services and can be assembled like a puzzle. Many parts can be sourced from your local hardware store or home improvement store. Some fabrication using common garage and shop tools such as drill presses, hacksaws, bench vises, and belt sanders is required, but there are no parts that require conventional machining such as milling or turning!
The final product is intended to highlight the level of sophistication available to modern makers and builders who may not necessarily have access to a conventional machine shop or collective such as a hacker / makerspace. Especially for students and minors, access to machine tools may be difficult or nearly impossible in our age of overabundant safety and caution. It is designed to show that the world of amateur and hobby engineering extends far beyond Home Depot and hardware stores - something which is generally unknown to many people who may be interested in pursuing engineering as a career, or aiming to explore it as a hobby.
This build will focus extensively on purchasing parts through online industrial supplier catalogs such as McMaster-Carr, specialty & hobby suppliers like Surplus Center, HobbyKing, and digital fabrication houses such as Big Blue Saw. Having access to these electronic resources, which really only became possible in the past few years, will facilitate students and hobbyists in producing higher quality and more awesome projects.
The resources alone, in my opinion, are all that most readers of this Instructable will need - it is often the case that many people who want to build things and know generally the approach they need, cannot proceed because of a lack of proper resources, whether it be tools or materials. In this case, this Instructable is perhaps more useful as another resource and technique guide, similar to my previous writeups on selecting electric vehicle power systems and building hub motors.
Step 1: History of the First Chibikart and Why I'm Building Another One
I first took interest in electric vehicles in 2007 when I built Snuffles the First, a whimsically named but extremely overpowered electric scooter - while I intended to use it as a campus cruising appliance, it was better off as a drag racer. Incidentally, Snuffles caused me to write my first Instructables guide on how to build small EVs. My focus in alot of these vehicles was using a custom designed miniature hub motor, for which I also wrote up a guide, to make even more compact vehicles and motorize things which previously were seemingly unmotorizable (or should not be motorized). Long story short, I ended up with several excess 100mm motor parts after testing the waters of production.
Chibikart 1 was built on a whim, to accomplish nothing in particular. In fact, the real story of the first Chibikart was to build a go-kart which fit into the front half of tinyKart, a similar go-kart project spearheaded by a friend of mine (and another member of the MIT chapter of the Collegiate Silly Vehicle Team), Shane Colton. Since I had pledged to not build another non-hub-motor vehicle before using up my sourced production parts, the choice of drivetrain was obvious.
Chibikart was a pretty big hit, I think, both locally and on the Internets, where for some reason it was hailed as the second coming of MarioKart. In the shop, we would occasionally take it for a ride around the conveniently circular layout of the building when we were at a mental block or in need of amusement.
BUILDING THINGS JUST BECAUSE
I believe that building just for the experience and adventure is a fully legitimate reason to embark on projects. Building personal projects for your own amusement is often dismissed by people as wasting time, which to me is a very disappointing attitude. Especially in engineering academia, there is a seemingly subconscious pressure to always be able to justify why something you are building is useful, optimized, commercializable, groundbreaking, etc.
I contend that no matter what the project, you inevitably pick up experience or new knowledge with each build which contributes to making even better work in the future - for yourself or otherwise. Immersing yourself in project work encourages thinking of creative solutions for problems when they inevitably arise - testing your critical thinking and analysis skills. By picking your own projects, you also invest yourself in them - there's nobody to disappoint or set a bar for you to barely clear, unlike directed 'class projects' or similar. You're only in it for personal gain, and that is a great motivator for many people.
For this reason, this new Chibikart actually does not bring anything that new to the table. All the methods, parts, vendors, and other resources described herein are in common use by mechanical project builders everywhere. Instead of linkdumping, though, I will present them in a format which introduces them as needed and in...mostly...logical order.
A NEW CHIBIKART FOR THE PEOPLE
One of the trends in Internet commentary regarding Chibikart 1 was that it was nearly impossible for anyone else who did not have extensive machinery access to build. Yes, I'm actually bothering to gauge what the Internet is saying in this case, because it was an insightful look into the attitudes of the "techie" and "gadget" crowd - many of the sites that Chibikart made it onto are populated by reasonably technical people, but in a direction which is distinctively not "Maker" centered.
These are people who may have some knowledge the latest processors and chipsets Apple is using in the iPad, or may have some glimpses of the engineering processes involve therein. Some of the sites even post pretty engineering and science heavy content at times, like about the latest 3D printer or swarming quadrotor death-cloud. But what they haven't done is picked up tools and made something. They're not stupid - just they have not been exposed as much to the gritty underbelly of engineering, the machines and people who eventually make iPads.
But the statement about Chibikart 1? Totally true. Those hub motors are nice custom-machined assemblies that have been through 4 or 5 different revisions, and even if I just handed someone all the parts and drawings, they would have to either get access to machinery, learn how to use it, then stumble through much of the same pitfalls as I did just to get one working motor. Or they can spend $3500+ to hire a machinist or shop to make them, and that's just the mechanical parts. A123Systems will definitely not sell you one of those custom 33v lithium ion batteries I used.
THE RISE OF DIGITAL FABRICATION
But say I took away the hub motors and sweet custom battery and replaced it with hobby model airplane motors and commercial Li-ion packs. Then all of a sudden Chibikart becomes very much accessible indeed, the reason being that it actually uses very few traditionally machined components.
"Digital fabrication" is one of those neologisms that has come from the weird design space intersection between engineers and futurists. Along with similar terms like "personal fabrication", it symbolizes the ability for designers to create products on-demand and bypassing the traditional system of toolmaking, assembly lines, design cycles, etc. to arrive upon a working, perhaps not production-ready product in short order. Personal Fabrication is the more specific form that defines "designer" as anyone who wants a custom product or thing. Basically, it's instant design gratification available to anyone. Parts are made in immediately useful or near-net-shape forms by machines which can be reconfigured to make many different parts in short order.
The most common processes which fall under this label are computerized 2D processes - laser cutting and waterjetting - and 3D processes which require minimal operator intervention, such as 3D printing and scanning. Traditional multiaxis CNC machining is usually not considered, because it still takes a trained machinist with years of experience to set up a CNC job quickly and effectively. But the 2D processes have been well-optimized to work for anyone - laser cutters are generally plug and play and accept many 2D graphics formats, waterjetting is much the same, and 3D printing is just like 2D printing (if you don't insist on building your own).
In the past few years, people have taken formerly high priced premium services like laser cutting, waterjetting, and 3D printing to the market. Nowadays, there exist services where you literally send your 3D model to and it comes back a week or two later as a finished thing. Examples of these services includes Shapeways and i.Materialise 3d printing (i.M being the somewhat more upmarket version), and Big Blue Saw for waterjetting and laser cutting. All of these places will give you instant quotes on the spot based on your uploaded model. Are we in the future or what?
You can do alot with just 2D parts, actually. They can be arranged in creative ways, usually involving some kind of wooden dinosaur model kind of right-angle joints, to create functional mechanical structures. They may not have the fit and polish of a new car, but that's not what we're after here.
THE FALLING COST OF ELECTRIC VEHICLE PARTS
Even five years prior, in 2007, building your own custom electric vehicle was still quite difficult. Small ("personal") vehicles especially; which seems strange until you consider that electric forklifts and golf karts and other large rideables have been around for years, and that is where you scrapped parts out of if you were putting together an electric car or bicycle!
During the past few years, the advent of dedicated small-EV parts companies and businesses dealing in low-cost motors, controllers, and batteries has made it easier than ever to build your own small rideable contraption. Part of the reason is the meteoric rise of electric model aircraft component power and energy density at the same time that prices have fallen nearly an order of magnitude - the nitty gritty details of this are covered in my "Scooter power system" instructable.
THE BOTTOM LINE
Given the availabilty of 2D precision-cut metal parts and inexpensive repurposable parts that can be used for vehicles, I thought it was the right time to produce a design which is substantially more accessible, but in roughly the same form factor, as Chibikart 1. The build itself would be intended to be nothing too spectacular, but the concepts and resources presented in the process of would be of benefit to those seeking to build their own vehicles, or mechanical projects, but who may not confident in their knowledge or just need additional places to get parts. This vehicle would have no "unobtanium", or Unobtaining Machines, as I call it, used in the build, and all parts must be sourceable from commercial vendors with an online ordering portal or are very common IRL (e.g. hardware store or hobby shop).
Build one and challenge me.