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Pigeon-toed gyropod
A remarkably simple kneeless walking machine driven partly by motor and partly by gyroscopic reaction.
About this creation
Please feel free to look over the images and skip the verbiage.

Behold the "gyropod", a simple motorized LEGOŽ walker with a gyroscopically driven shuffling stride...



The onboard L motor just spins the flywheel and forces it to nutate (nod up and down). Reactive gyroscopic torques acting on the rapidly spinning flywheel do the rest.

As you can see at 0:47, net travel without the spinning flywheel and its large axial moment of inertia is nil. That's because the forward steps are actually gyroscopic precessions induced by the flywheel's forced nutations.

Taking the gyropod on a walk...



Look, boy -- a squirrel!

Operation couldn't be simpler:
  • Use full power to get decent travel speed.
  • Reverse the motor to reverse the direction of travel.
  • Pull gently on the "leash" to steer.
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Background

In 1981, noted American roboticist John Jameson introduced this "Walking Gyro" (good description at link in photo credit below). His goal was a dynamically balanced kneeless walker of the simplest possible design.


∧ Photo credit: Reuben Hoggett's write-up at cyberneticzoo.com.

A few years later, Jameson's concept found its way into at least 2 commercially successful walking robot toys -- one of them in the Tonka Gobot line.

Various DIY versions of Jameson's walker have also appeared, including Jeff Kerr's 3D-printed "Gyroman" (2015)...



and Bernard Perier's 2017 Meccano implementation...



But I have yet to find another LEGOŽ version. Granted, my walking gyro doesn't lift its feet completely off the ground like the others shown here, but at least it shuffles along at a respectable clip (~0.030 m/s or 0.11 kph). And let me tell you, even that took a tremendous amount of fiddling.

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Optional: Engineering notes

Goldilocks would have hated this project, as many parameters had to line up just right for the blasted thing to work at all. Most of the combinations I tried either rocked in place (as at 0:47 in 1st video) or fell over after a few forward steps.



Like Jameson's walker, the gyropod manipulates the angular momentum of a rapidly spinning flywheel to achieve the 2 essentials of kneeless walking:
  • Lift -- or at least deweight -- the feet and swing them forward, one after the other.
  • Stay upright in the process.
Like a human or chimp, the gyropod doesn't need to keep its center of mass (CM) directly over its ground contact to stay on its feet. Balance during walking is instead maintained dynamically -- but in a way far simpler than any living biped does it.

The onboard motor doesn't drive the feet directly. It just drives flywheel spin and nutation at the same time. An L motor offered the best combination of speed, torque, and weight for the job.



Since a misaligned motor delivers less power to the spin and nutation drives, I recruited 7 of the L's 14 attachment points to keep it from wiggling loose under the motor platform's reciprocating motion.





A crank on the motor shaft (bottom center) causes the motor platform to rock up and down as it turns. This rocking motion forces the flywheel to nutate (nod up and down) as it spins, and that in turn causes the flywheel to precess fore and aft. Chassis reactions to these flywheel motions lift the feet and swing them forward one at a time.



The motor platform pivots on a "pelvic" frame bearing the legs and feet.



As we all know, knees have many advantages. But they greatly complicate any walker, and Jameson was determined to keep his walker as simple as possible by doing without.

The legs swing freely from side to side at "hip" joints on the pelvic frame. A simple parallogram linkage forces them to swing together in a waddling gait essential to the gyropod's dynamic balance and travel.





Finding workable feet turned out to be the hardest part by far. The simple foot disks used on most walking gyros failed miserably, and so did countless bricks, plates, dishes, and sideways wheels.

The lightweight "bird feet" above emerged after hours of trial and error. The spring they provide seems to be important, and they have to be pigeon-toed to get a decent travel rate without falling over. Even more time went into trying to get the feet to lift completely off the ground, but a shuffling gait was the best I could do.

Of the many, many flywheels tried, this 68.8x36 ZR tire (44771) on a 56x34 medium racing wheel (44772) turned out to be the best performer. At full power, it takes ~12 seconds for the flywheel to reach maximum spin rate (~3,200 RPM), but walking commences ~7 sec after start-up.



Properly supporting the gear and flywheel shafts while minimizing overall weight (an absolute must here) presented a real challenge. Overhanging the flywheel turned out to be a viable solution.



Matching the flywheel to the transmission used to spin it -- and vice versa -- took many iterations. In the end, this 3-stage 1:15 overdrive worked best.



Due to the reciprocating motion of the motor platform, the gear shafts show clear signs of wear after only an hour of operation, but the gears themselves seem to be holding up well.

The freely rotating battery pylon used in the 1st video turns on an even cheaper version of this ball bearing platform by Sariel.



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Specifications

Construction:Studless
Overall dimensions:104x69x168 mm (LxWxH)
Mass:160 g (excluding battery and pylon)
Flywheel:Overhung medium racing wheel (44772) with ZR tire (44771)
Motor:Single L driving flywheel spin and nutation
Flywheel spin transmission:3-stage 1:15 overdrive
Max flywheel spin rate:~3,200 RPM
Min flywheel spin-up time:~12 sec
Max nutation angle:
Max step rate:~140 steps/min
Max travel rate:~0.030 m/sec = 0.11 kph = 0.067 mph
Electrical power:7.4V from external PF LiPo rechargeable
Battery mount:Freely rotating external pylon
Modified LEGOŽ parts:None
Non-LEGOŽ parts:None
Credits:Original MOC inspired by John Jameson's walking gyro
See also:Technic free (2-DOF) gyro, LEGOŽ spinning top folder

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Comments

 I made it 
  February 10, 2018
Quoting JWG 258 This is an interesting concept that should be explored further. Do you think two of these mechanisms side by side would allow a creation to move and steer?
Thanks, JWG! Yes, steering might be possible with differential power to the walkers, as walking speed does depend somewhat on motor speed.
 I like it 
  February 9, 2018
This is an interesting concept that should be explored further. Do you think two of these mechanisms side by side would allow a creation to move and steer?
 I made it 
  February 7, 2018
Quoting Nick Barrett Some pretty fine engineering to get that to work. Fascinating stuff and an interesting problem to solve.
Thanks, Nick!
 I like it 
  February 7, 2018
Some pretty fine engineering to get that to work. Fascinating stuff and an interesting problem to solve.
 I like it 
  January 27, 2018
I used two big motors for the dancing bottom of my "Dancing Bot" (and a smaller one for the head and arms). And he was heavy- weight! Still hoping... ;)
 I made it 
  January 27, 2018
Quoting Oliver Becker LEGO technic-magic from a master! Your great engeneering never forgets the FUN within a MOC and that's so wonderful entertaining, my good friend! I feel remembered of my naive efforts to get my "Robot" to dance: THIS would have been a great method to do! LOL But it's even more to get the bricks moved as to simply put them together... ;) Kudos! Maybe you make a bigger version with a little grip holding a goodie for Roxie: would she take it while the gyropod is dancing in front of her nose? ;)
Too kind, my friend! The part about the engineering is especially gratifying, as "interesting motions and visual effects with maximim play value" has been my mission statement for several years now -- hence all the tops. Great idea for a dancing dog treat dispenser, but with any more weight, the current version would stop walking. Still working on that, but I'm not hopeful.
 I like it 
  January 25, 2018
LEGO technic-magic from a master! Your great engeneering never forgets the FUN within a MOC and that's so wonderful entertaining, my good friend! I feel remembered of my naive efforts to get my "Robot" to dance: THIS would have been a great method to do! LOL But it's even more to get the bricks moved as to simply put them together... ;) Kudos! Maybe you make a bigger version with a little grip holding a goodie for Roxie: would she take it while the gyropod is dancing in front of her nose? ;)
 I made it 
  January 23, 2018
Thanks! The video's way too long, but I found it hard to cut footage because the thing was just too entertaining to watch.
  January 22, 2018
Excellent! I don't know why, but I laughed through a good portion of the first 2 minutes of your video, it's kind of funny to watch the little bugger go. : ) Very nice! ~~Logger
 I made it 
  January 22, 2018
Quoting Gabor Pauler Mmmm. Jeremy, this macine's movement is way too similar to the walking of my 3rd son, Gergo, who is a toddler now. Except that the machine does not leave pretty much everything broken into pieces under 3.5 feet height...
Ah yes, toddlers -- all new-found mobility and no judgment! To understand Gergo's need for destruction, you must first understand the thermodynamics of childhood. As you know, the 2nd Law of Thermodynamics states that the overall entropy of the Universe can only increase over time. Assembling a baby from disorganized atoms and molecules represents a huge local violation that must eventually be corrected. Male babies take this entropy debt to the Universe very seriously right away and start repaying it in earnest as soon as they are physically able. So little Gergo is just stepping up to his 2nd Law responsibility to sow chaos and destruction wherever he goes and as fast as he can. Girls, on the other hand, start repaying in earnest when they turn 13.
 I like it 
  January 22, 2018
Mmmm. Jeremy, this macine's movement is way too similar to the walking of my 3rd son, Gergo, who is a toddler now. Except that the machine does not leave pretty much everything broken into pieces under 3.5 feet height...
 I made it 
  January 22, 2018
Quoting Nirds forprez Lego fiddling at its best....
Very kind, my friend! Getting decent travel out of this seemingly simple little gizmo turned out to be =way= more frustrating than I ever could have imagined. Almost gave up several times. The bird feet saved the day.
 I like it 
  January 22, 2018
Lego fiddling at its best....
 I made it 
  January 22, 2018
Quoting Walter Lee It reminds me of how a penquin walks..
Me, too. Also, a walking duck in a hurry -- a common sight in our lakeside neighborhood.
 I made it 
  January 22, 2018
Quoting Sven ;o) You should build a penguin body around the whole construction ;) As always I really enjoyed watching the video. Great work my friend!
Very kind, Sven! A penguin body would be a hoot, but travel would grind to a halt under the weight.
 I like it 
  January 22, 2018
It reminds me of how a penquin walks..
 I like it 
  January 22, 2018
You should build a penguin body around the whole construction ;) As always I really enjoyed watching the video. Great work my friend!
 I made it 
  January 22, 2018
Quoting Didier B Jeremy, that's one of your weirdest creation ever! I like it. The walking movement is very interesting because it looks like a real living being walk and not a robot one.
Thank you very much, Didier! I love weird motions executed in LEGO, but credit for the basic mechanism goes to inventor John Jameson.
 I like it 
  January 22, 2018
Jeremy, that's one of your weirdest creation ever! I like it. The walking movement is very interesting because it looks like a real living being walk and not a robot one.
 I made it 
  January 22, 2018
Quoting Seaman SPb Cool!
Thanks, Seaman!
 I like it 
  January 22, 2018
Cool!
 
By Jeremy McCreary
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LEGO models my own creation MOCpages toys shop Pigeon-toed gyropod


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