Raptor2 - Running Biped With Steering[MOC]

[MaxBrix]

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.

 

[jorgeopesi]

We are close to see a Lego functional ED-209, very good work.

[caiman0637]

Nice! This is really quite cute and impresive.

[howitzer]

Very impressive. I love that it only has one motor and apparently no sensors at all.

How many non-Lego parts are there? I can see some springs and controller/power source but is there anything else?

[MaxBrix]

18 minutes ago, howitzer said:

Very impressive. I love that it only has one motor and apparently no sensors at all.

How many non-Lego parts are there? I can see some springs and controller/power source but is there anything else?

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.

 

 

[Void_S]

4 hours ago, MaxBrix said:

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.

 

 

I believe (for purists), the rubber "feet" can be also made of 2l rubber liftarms.

As for the model itself, these self-balancing things are still a kind of magic for me! Great to see our magicians doing something unusual 

[MaxBrix]

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 Shuttlefan]

This looks more impressive - and more realistic - with every iteration. It seems to me like it's unsteady partly because it's losing traction - perhaps some extra weight in the head and tail could help to dampen the "bouncing"?

[MaxBrix]

On 4/23/2021 at 3:17 AM, The Shuttlefan said:

This looks more impressive - and more realistic - with every iteration. It seems to me like it's unsteady partly because it's losing traction - perhaps some extra weight in the head and tail could help to dampen the "bouncing"?

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.

[iLego]

On 4/21/2021 at 12:38 AM, Void_S said:

As for the model itself, these self-balancing things are still a kind of magic for me! Great to see our magicians doing something unusual

Exactly my thoughts. I am able to somewhat understand the typical mechanisms in vehicle MOCs. The axis of motion is fixed and it's possible to visualise how things are happening. But these kind of MOCs are beyond me ... they are like magic. The movement is happening in so many dimensions at the same time, some intended via the mechanism and some unintended due to part tolerances. Its very hard to visualise what all is happening and how to improve it further !!

I suspect the number of replies on this thread is not the true indicator of the interest level. Its just that it's  hard to give constructive suggestions. There are probably a lot of silent admirers for this kind of work