by matthiasm, published
An eight-legged big spider robot.
The design goal was to create a legged robot that is large enough to walk regular stairs and strong enough to lift simple loads. It also had to be simple enough to use regular RC-srevos and could be cut with my minimal CNC machine.
The build process is documented here:
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CNC-machined from 3mm ABS foamboard, this thing is pretty impressive once all eight legs are moving. You will also need a lathe to create the axles and a few platic parts, a powerful servo controller for your 24 high-torque servos and a powerfull battery pack.
The dxf files all fit onto A4 (European standard size for paper, a whee longer than "Letter" format) simply because that is about the maximum size my Isel can handle (cute, huh?).
"boden" contains the floor part of the body. The holes in the middle are big enough to let you insert a racing pack style battery through the bottom. The parts that look like skates reinforce the lower axle hold and are inserted into the slot from below. The purple hexagons are only cut half depth and hold the head of the hex screw that makes the axle.
"cross" contains a bunch of cross sections that are glued in an X-shape into each upper leg. These cross section greatly reduce torsion and make walking much easier to calculate.
"joints" are all parts needed to create four hip joints. These are quite hard to build right, so be patient and do a few test builds before finally glueing everything. Again, the purple lines are half-depth and hold a standard ABS disk which serves as counterold to the joint bolt. The small purple circles are for sinking the heads of the screws that go into the servo disk. Remember that you have to build four clockwise and four counterclockwise joints!
"Legs" contains most parts for a single leg (add the cross section from "cross"). The skinny parts again are reinforcements an should be glued to the end of the upper leg (8 per leg).
"Middle" contains the middle section of the robot. The holes next to the servo cutouts are designed for a plastic rivet to hold the servo.
"Poles" contains all - um - stilts would have been a better name - that connect the bottom, middle, and upper section of the body. Careful! Therer are two kinds of pieces, one with a slightly set back cutout to allow full motion in the hip joint. Don't mix these up.
"Ribs" has more parts for the body for enclosing the battery bay and the controller cutot.
"Top" contains the top shell of the body.
All parts should fit tightly. If you find that cutouts and notches are wrong, you must verify your assembly. All these files have been tested and built. Please reference the photos.
You will need additional parts for the axes and servo mounts. And of course, the cutouts were designed for a specific servo, so you'll have to find a servo which is very similar in size. I will try to put more information here soon.