Rugged, highly mobile, infinitely modifiable solar-charged bot chassis
If you are looking for a mobile, outdoor platform for your next robot project, or perhaps a chassis for use in a RoboMagellan or similar robotics competition, you need to check this platform out. The MINDS-i Rover is all new and we find it to be of significant value. The initial inspiration for this platform came from Mike Marzetta, president of Altek and also of MINDS-i, a company that specializes in injection molding, injection mold tooling, precision machining and painting and finishing. Mike/images/drupals inspiration in forming MINDS-i was to provide kits that would enable hobbyists to create anything envisioned/images/drupal to create interchangeable parts for bringing inventive ideas to life. The Rover kit makes us believers! Mike brought to this design a wide range of materials including polycarbonate, acetal (a copolymer relative of delrin), glass filled nylon and ABS plastic, among other materials, all to tune the design for extreme durability.
The MINDS-i Lunar Rover kit is self-recharging via its included solar voltaic panel and travels off-road with ease. The stock 7.2V 1800mAh NiCd battery can be fully charged by the panel and onboard solar converter in under 90 minutes in the I midday sun (1.2A at 8.2V). The kit comes with an inexpensive brushed 05 can motor and Pro-Line Masher 2000 all terrain truck tires and has plenty of spunk to leap off curves, roll over bumps and climb rough terrain. It is designed so that you can easily mount your own motor system to the drive system if you want to up the mobility ante. It is a true kit/images/drupalyou build your own differentials for each set of wheels, all of which pull this critter forward. Although this review just looks at the chassis, the MINDS-i Rover is also available packaged with the PCS
Edventures Brain microcontroller with free code for autonomous exploration (to see a similar implementation, scan the barcode to watch a video of the Rover controlled by a VEX microcontroller at the Carnegie Mellon Robotics Academy!).
There are three versions of the kit in every kit; these include a leaf spring suspension setup, a 4-link suspension, and a ladder-bar suspension chassis. You pick the setup you prefer, and you can easily modify it as there are extra parts in the kit. The result is a robust, tough, eye-pleasing platform that runs well and that you can hack at will. The kit comes with all the tools you will need, including Alan wrenches, a Phillips screwdriver and more.
It is based on a clever plastic snaptogether system that uses three basic sizes of inserts that have two basic parts. A black cylindrical insert slides into a gray cylindrical housing, then you rotate the black insert clockwise a few degrees using the included screwdriver-like tool to lock the insert. These inserts lock parts together and come in two flavors/images/drupalone with lengthwise ridges to rigidly lock
beams together, and one with a smooth outer surface on one end so that an interlocked beam can swivel about the insert. You can therefore design-in rigid construction with fixed angles or flexible connections that can move rotationally or accommodate any odd mounting angle.
There is a tiny lip near the tip of the insert locking tool that enables you to grab an installed insert and easily pull it out/images/drupal just unlock the insert and add some counter-clockwise pressure and pull. This chassis is as easily disassembled as it is assembled. The kit includes many rugged, hard plastic beams with various numbers of holes. The chassis of the Rover is made entirely from these beams, which are locked together by the cylindrical inserts. We asked Michael Marzetta
how he came up with the three chassis designs in this robot kit/images/drupalhe said he gave the parts and pieces to a few young engineers at MINDS-i for brainstorming (Kriston, Levi, and Tim), and that they get the lion/images/drupals share of credit for this ingenious first generation robot rover chassis. Mike himself invented the inserts that hold it all together/images/drupalwhich I think was a stroke of genius. Let/images/drupals take a look at some lessons we learned building the Ladder Suspension variant.
CONSTRUCTION TIPS & TRICKS
In the initial packaging of the kit, myriad beams and parts arrive in a wide variety of plastic bags. Take out the small parts/images/drupalthe inserts of various sizes/images/drupaland put them in organized plastic cases like those used for beads or you can use empty egg cartons, and put the beams together by size on your work table. Beams come in a variety of lengths with from two to 15 holes that will receive the inserts. If you don/images/drupalt organize the parts, the build time will double owing to having to search out pieces in a sea of parts.
The initial draft of the manual shows the build steps using a picture of each step with a key, on the left, to the parts used in each step. The beams were not labeled with respect to the number of holes so I counted the holes per beam in the manual illustrations, and labeled the beams by hand before assembling a part/images/drupalI then knew which size beams to fetch and the size was on record. MINDS-i plans to label beam sizes in future releases of the instructions.
The several metal bolts and screws in this kit anchor into holes in dense plastic that are not tapped. The toughest to screw in, and you have to get it right the first time to avoid any cross threading, are the screws that bolt the interior gear in the differential to a plastic base. Best to wear a pliable pair of leather gardening gloves to get a firm grip on the Phillips screwdriver while you firmly grasp the housing to which the gear is being mounted. After you have assembled the differentials and built them into the chassis undercarriage, make sure that they still turn freely by twisting the output shafts by hand. Early versions of the kit had some instances of diffs freezing up if their cases were locked down
too tightly during assembly, but MINDS-i says this issue is now handled. Also be sure to rotate the diff case itself when mounting it in its retaining bracket so that its output shaft points at the electric motor when the front axles are mounted to the undercarriage (see photo)/images/drupalthis step, number 32 in our manual, was not clear.
In the review kit, I had to remove flashing from some of the insert exterior housings and from the ends of metal threaded rods that screw into servo linkage ball link cups that mate to steering arms. Also, small button-like inserts called thread adapters fit into some of the beam holes. Some fell out while I continued assembly/images/drupalI used CA glue to get them to stay put.
Finally, when you are joining the front axels to the undercarriage that holds the motor, make sure you use the shortest of ridged inserts provided for that purpose. Only eight are provided, four for the front axel and the other four attach the rear axel subassembly. Everything else goes together like clockwork/images/drupal give your self a few to several build sessions for assembly.
We built the ladder suspension setup and drove it over some rough terrain and had no disappointments. It is well adapted for this job, and effortlessly jumps off a roadside curb or tears over rough ground. We tumbled it, flipped it onto its back,
drove it off ramps and repeatedly picked it up grabbing the very rugged solar panel, the undercarriage or the wheels and it never complained and remains as good as new. We give this highly customizable robot chassis two thumbs up.