MaxBrix

I haven't, but I think It is possible. I have hope it will be solved. The holes don't really have to be cut but it might get hot.

This is my brushless M-Motor modification. I have used it in a few models and it hasn't self destructed yet. It is pretty good if you don't mind using an RC radio. I also have some Lego compatible servos so the combination makes it easy to build with Lego and use a good radio.

My sixth and fastest Robot dog. https://youtu.be/MC8_yIHKBOc

One unedited shot Walking up Stairs.

Just a happy accident.

Big Dog 5 gets lateral hip motion for a 30% speed increase. Progress continues. Still only one L-motor, no brains.

Thanks, It seems like the realism is an unexpected outcome of trying to make it work better. Weight is my enemy. I have to find another way. It could eliminate bouncing with a flat footpath but that would require one foot to always be on the ground. Running requires bouncing.

Ankles and Hips. I am working toward Raptor 3.0 by experimenting with a leg that flexes side to side and linkage to control the foot path so that it travels under the center of gravity with as little tipping as possible. The leg has to move forward without colliding with the other foot. The lack of springs at this point makes me sad. 3.0 will need to be larger to make the linkage placement more adjustable. It needs a higher step and grip adjustment also.

The feet are made from wire shelf rubber caps with the tip cut off with blue silicon tubes from a whisk inserted through the hole into an axle connector. I personally don't consider the non-Lego radio/ESC/Battery any different than a Buwizz, Arduino, Sbrick or other 3rd party solution. 350mah 2s 35c battery, 10 amp ESC, Radiolink r6 FG receiver - The total weight is 39.1 grams. That tiny weight helps a lot with getting the feet in the air.

Lego Raptor2' moves like a dinosaur by swinging it's head while walking like a real biped. The head not only balances but pushes back on the torque from one leg pushing on the body which usually causes the model to twist back and forth. The tail swings freely absorbing side to side torque. The tail's harmonics cause a delay that keeps the tail on the high side of the walker. Weight far from the center of gravity acts like a tightrope walkers pole. Steering is controlled by a small change of speed altering the bounce of an imbalanced gate. One leg's stride is maybe 1mm longer. When the motor moves slower the air time is less so the stride becomes effectively lower. The change of speed needed is very small. The wider a biped is the more stable it is with both feet on the ground. the narrower it is the more stable it is with one foot in the air. If the CG is low the model the model is more stable standing. If CG is high it will fall less quickly in an imbalanced position. This the first Robo Raptor.

Boston Dynamics Big Dog 4 (Speed Dog). I am trying out a new leg linkage design that has more stable compliance so it can handle non-smooth surfaces. It is also my fastest Big Dog.

Sorry for that first reply. Although smaller that wasn't the same transmission. You want a smaller 2 speed and smooth switching transmission. I rebuilt it smaller as per your request and made a video. Here you go.

This one is the smallest. The down side is that the low gear is slightly less efficient. The upside is that it acts like a CVT by mixing two gear ratios.