12 legged Lego Walker inspired by Strandbeest

[shroomzofdoom]

The specs:

- 12 legged walker

- Driven by 2 Lego Technic Large angular motors

- Powered by Buwizz 3.0

- 1 Technic L motor powers the deployable spinning Lego buzzsaw

- 1 Technic S angular motor to power the Lego arrow shooter

 

Sorry Lego purists, but I had to use some non-Lego parts in this design:

- 4.7mm aluminum tubes front run the width of the robot providing lightweight articulation of the legs in lieu of plastic axles

- Stainless steels axles are used throughout the driveshaft due to the inherent limitations of backlash and breakage caused by the Lego plastic axles

- Small nuts are threaded onto the upper leg pivots to maintain the connection as Lego bushes simply cannot retain the axles given the duty cycles.
 

Edited September 18, 2022 by shroomzofdoom
ARROW SHOOTER OPERATIONAL! New video

[Jurss]

10 hours ago, shroomzofdoom said:

I had to use some non-Lego parts in this design:

It doesn't look so heavy . OK, last model is pretty speedy, that could be the reason for lego not to hold a load.

[shroomzofdoom]

11 hours ago, Jurss said:

It doesn't look so heavy . OK, last model is pretty speedy, that could be the reason for lego not to hold a load.

Yeah, the speed causes the legs to basically fly apart during turns. Threading on nuts instead of using bushes at the top legs was a big improvement.

Each angular motor turns three cranks and driveshafts on each side (6 legs per motor). Without metal axles holding the leg sets together, the lash/windup would cause the timing of the legs on the outside to be out of sync,

Also, there is no Lego axle long enough for the two top rails. Piecing them together from segments wasn't structurally sound and there is too much flex in Lego axles. Aluminum tubing was far superior and ultimately allowed me to use 1M beams and pin connectors to maintain spacing, act like bearings, and keeping everything moving.

EDIT I got the dart shooter working last night and replaced the original video with all the features operational. It shows much better now!

Edited September 18, 2022 by shroomzofdoom

[gyenesvi]

That's an interesting and funny beast. Would be nice to see the mechanism (construction of the legs) in close up / slow motion though, to see how it was implemented in lego form (I have seen the Strandbeest in non-lego form already), to see those limitations that you are talking about. For example I don't understand why it needs so many legs, and why it needs to be so fast. Maybe without those features it could be built in pure lego form?

[shroomzofdoom]

10 hours ago, gyenesvi said:

That's an interesting and funny beast. Would be nice to see the mechanism (construction of the legs) in close up / slow motion though, to see how it was implemented in lego form (I have seen the Strandbeest in non-lego form already), to see those limitations that you are talking about. For example I don't understand why it needs so many legs, and why it needs to be so fast. Maybe without those features it could be built in pure lego form?

The one I posted above has 12 legs and is based on Ben Vagle's strider v3. He goes into great detail about the leg and crank construction and even provides parts lists. 

One of the main reasons to go from 8 legs to 12 version is that the more legs it has, the smoother and more organic the gait will appear. If you look at Jansen's work, some of the most organic movements come from strandbeests that have dozens of legs. 

Here's one of my original designs with 8 legs for comparison. Except for the aluminum tubing, this was all Lego (or knockoff) 

Another complication arising out of the transition from 8 to 12 legs is the crankshaft timing. To keep 4 pairs of legs in sync, they need to be offset 180 degrees. With 6 pairs of legs, the offset has to be 120 degrees. There are limited Lego parts with 120 degree angles that can hold up to high torque. The other problem with Lego triangles is that the axle holes in the center don't line up properly for this design. That led Vagle to unusually bulky designs and even (gasp) cutting Lego parts! 

My solution to the 120 degree problem was similarly heretical, but alot easier and more compact. I took 53.5 degree angle beams, doubled them to get to 107 degrees and lastly, used a heat gun to soften the plastic. 

The end result is hard to see, but highlighted here in yellow. 

While an 8 legged walker could be built mostly of Lego, a 12 legged one built 100% from Lego would be quite a challenge. And, of course I could've built it to slower but what fun would that be? :-P

[gyenesvi]

Thanks for the reference and some more detailed explanation! There's quite a lot of stuff to be absorbed related to this..