Large-Scale TrotBot
Some more images of our bamboo TrotBot demo at the maker faire can be found here, and you can find an overview of our version 1 wooden scale up here.
TrotBot Ver 1
"In my opinion, there's a lot going for the 'mechanical' world, albeit anachronistic in this day and age of electronics and computers. The mechanical problems arise particularly when scaling up - vibration, heavy weight, material costs, etc. It is far easier to 'fine tune' a design in compensating programming. However, I've also seen code where, most likely due lack of fundamental understanding of the basic principles, spent more time compensating for an initial bad design than getting the real job done. There's a lot to be said for simplicity and parsimony."
Reuben Hoggett, creator of the Cybernetic Zoo, commenting on our TrotBot scaleup attempt
If anyone else is crazy enough to attempt scaling up TrotBot, then you probably should build it in a 12 leg version. You would need to add feet, so maybe explore shock-absorbing feet, perhaps like the feet used by the Mondo Spider in the video below. Also, notice how Mondo's feet were designed to slide, which helps to smooth Klann's speed, and also makes tank-style turning feasible for large mechanical walkers - at least on smooth terrain.
"In my opinion, there's a lot going for the 'mechanical' world, albeit anachronistic in this day and age of electronics and computers. The mechanical problems arise particularly when scaling up - vibration, heavy weight, material costs, etc. It is far easier to 'fine tune' a design in compensating programming. However, I've also seen code where, most likely due lack of fundamental understanding of the basic principles, spent more time compensating for an initial bad design than getting the real job done. There's a lot to be said for simplicity and parsimony."
Reuben Hoggett, creator of the Cybernetic Zoo, commenting on our TrotBot scaleup attempt
If anyone else is crazy enough to attempt scaling up TrotBot, then you probably should build it in a 12 leg version. You would need to add feet, so maybe explore shock-absorbing feet, perhaps like the feet used by the Mondo Spider in the video below. Also, notice how Mondo's feet were designed to slide, which helps to smooth Klann's speed, and also makes tank-style turning feasible for large mechanical walkers - at least on smooth terrain.
Or, perhaps small inflatable tires that could rotate a little could both smooth TrotBot's gait somewhat (like Prof Joseph Shigley's shock-absorbing inflatable tire-feet), while also improving tank-style steering? Of course, a lot of prototyping would be required to dial this in!
While the active heels and toes we added to LEGO TrotBots improve performance at small-scale, they would be much harder to add at large-scale. For example, the "heel" linkage's connection to the leg's inner beam works well at LEGO-scale with its high strength-to-weight ratios (where the section of length 2.55 connects above the section of length 2.64 in the image below), but our 450 pound wooden TrotBot put a lot of stress on the leg at that joint, and we had to reinforce it with a truss.
Plus, the heel and toe linkages add mechanical complication and friction, increase the number of parts required, have inertia effects which add to vibration problems, etc.
Below are the bar lengths of the large-scale TrotBot we started building out of bamboo - which we never finished since bamboo's variable geometry can require a lot time to turn it into precision parts, plus the joints require reinforcing so that the bamboo doesn't split. Please note that the triangle's bottom right angle highlighted in pink is not 90 degrees, but is 109.475 degrees.
Or, perhaps small inflatable tires that could rotate a little could both smooth TrotBot's gait somewhat (like Prof Joseph Shigley's shock-absorbing inflatable tire-feet), while also improving tank-style steering? Of course, a lot of prototyping would be required to dial this in!
While the active heels and toes we added to LEGO TrotBots improve performance at small-scale, they would be much harder to add at large-scale. For example, the "heel" linkage's connection to the leg's inner beam works well at LEGO-scale with its high strength-to-weight ratios (where the section of length 2.55 connects above the section of length 2.64 in the image below), but our 450 pound wooden TrotBot put a lot of stress on the leg at that joint, and we had to reinforce it with a truss.
Plus, the heel and toe linkages add mechanical complication and friction, increase the number of parts required, have inertia effects which add to vibration problems, etc.
Below are the bar lengths of the large-scale TrotBot we started building out of bamboo - which we never finished since bamboo's variable geometry can require a lot time to turn it into precision parts, plus the joints require reinforcing so that the bamboo doesn't split. Please note that the triangle's bottom right angle highlighted in pink is not 90 degrees, but is 109.475 degrees.
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Bamboo is incredibly lightweight and strong in tension and compression, but its variable geometry can require a lot of time to turn it into precision parts, and the joints need to be reinforced since bamboo splits easily
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