TrotBot Version 3 takes its performance about as far as I can achieve with Lego, so I challenge any pioneers who are interested in taking TrotBot to the next level, to try and create a TrotBot with 3D printed parts.

Version 3 was robustly designed so that it could scale beyond Lego. However, that isn’t necessary in a classroom setting, so I made a simpler, half-cost version of TrotBot with 6 legs and a tripod gait. I’ll be using this classroom-friendly TrotBot in the walker class I’m teaching at a middle school this fall.

I’ve also posted plans for another classroom-friendly walker called Strider.

Two Classroom-Friendly Walkers

Hexapod TrotBot with a Tripod Gait

The part costs of this lightweight TrotBot are about half of the 8-leg version’s, and it’s easier to build. However, for it to be balanced like a tripod, the two outside front feet and the center back foot need to be in contact with the ground (or vice versa), so it cannot be turned tank-style like an 8-legged TrotBot can. Instead, I turned the TrotBot by tugging on the motor’s wire (which I reinforced with hot glue because Lego’s extension wires break easily).


Strider is my easiest walker to build. Its legs are based on a simple, 4-bar linkage, but to increase the step-height, the front and rear legs are linked such that the rear leg lifts the front foot and vice versa. Here’s a simulation of the linkage:

Here’s a LEGO version of Strider:

TrotBot, Version 3

TrotBot Ver 3, with increased strength and max speed

Performance Test Highlights

The main reason I added retractable toes to TrotBot was to lower the power required to bear its weight. However, my tests showed the toes also boost gait efficiency at higher speeds, allowing for faster gear ratios and improved turning and performance on rugged terrain.

Here are some highlights from the tests:

I’ve incorporated what I learned from these tests into TrotBot Ver 3’s instructions.

Testing TrotBot with a 10 pound load

Future Work

Lego is great for rapidly prototyping and testing ideas, and even when we were building our giant TrotBot in my garage we used Lego to innovate and test improvements. But, Lego’s integer-based Technic beams only allowed me to build a close approximation of TrotBot’s optimized linkage (which is simulated below). I’ve accurately modeled the leg parts in Autodesk, and I’ll eventually 3D print the parts to test how this optimized linkage impacts performance. If you decide to give it a go, please share your progress on DIYwalkers!