James Bruton's 4WD 'Pedrail' Robot Can Crawl Over Anything

Pedrail wheels combine the benefits of tank tracks and standard tires, and James Bruton's 4WD pedrail robot demonstrates the concept.

Cameron Coward
2 years agoRobotics / 3D Printing

There is a reason that almost every car in existence has round tires: they're very efficient. It takes little energy to sustain rolling. But a perfectly smooth, hard wheel only works well on smooth, dry surfaces. That's why off-road trucks have low-pressure knobby tires — they aren't as efficient, but they grip loose terrain better. Tank tracks take that idea to the extreme; they're great over rough terrain, but they are awful when it comes to efficiency. Pedrail wheels should be the best of both worlds and James Bruton's 4WD pedrail robot demonstrates the concept.

Pedrail wheels are quite strange to look at. They're round, which decreases rolling resistance and allows for somewhat efficient locomotion. But the entire outer perimeter of a pedrail wheel is lined with sliding legs that have pivoting feet. A guide on the wheel's hub keeps the legs from sliding all the way inward as it drives over an obstacle. The result is a wheel that steps and climbs up very rough terrain in a manner similar to a person walking up a flight of stairs, where a normal wheel would slip and slide.

Like most of Bruton's other robots, this model was almost entirely 3D printed. Most of the frame and body were 3D-printed and all of the wheel's parts, aside from bearings and fasteners, were 3D-printed, too. Electric motors with worm gears (for maximum torque) drive each of the four wheels. The motors are geared back up a bit with a belt final drive so the robot isn't too slow. Each wheel has its own independent suspension, which is a simple design based on two pivots and bungee cords. An Arduino Uno board controls the electric motors via two BTS7960 high-current motor drivers. Bruton can pilot the robot using his custom universal remote that we covered previously.

It's hard to declare with certainty that the pedrail wheels are better than tank tracks or standard tires, or if they represent a practical middle ground. But this robot seems to crawl over obstacles with ease, so pedrail wheels might be worth your consideration the next time you build an all-terrain robot.

Cameron Coward
Writer for Hackster News. Proud husband and dog dad. Maker and serial hobbyist.
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