Tuesday, January 21, 2020

Milli (#2) - FrankenWorm (with Video!)

Milli is a bio-inspired Millipeded Robot and today's blog entry is titled:  FrankenWorm!

Rapid Prototyping
The best way to "learn quickly - fail quickly" is to using rapid prototyping techniques to test out ideas quickly and identify potential and real points of failure, design needs, and radical improvements.  Three-D printers are great for taking ideas and making them solid. An even faster way of rapid prototyping is "Frankenstein Prototyping", where the initial prototypes are built by using parts from other projects. In many cases, you just grab the part that is close to what you need and fasten it to the build.

Frankworm! Franken-prototyping the WildWorm Drive

Today, I am Frankenstein prototyping the WildWorm with 3D parts left over from previous projects. I wanted to quickly see if the rotating helix is going to be able to move the track treads of the WildWorm drive.

what is in the discarded print bin?

  • Motor frame - one of the chassis from the original Mojo
  • Battery holder - from an old RC car and RC Rover project
  • Motor holder - initial WildWeasle tests - holds a 'recycled' printer motor
  • Motor spindle adapter - from initial Centi tests
  • Helix Mount - Cam variation from the Mojo2 (he walks!) project
  • Horizontal Stabilizers - linkages from original Mojo project
  • Stabilizer linkage - v0 print of WildWorm track
...and this is why I don't throw away old 3D printed parts.

After finding the parts in the bin, I connected them all together to set up my initial tests. I just used quick fastening methods, tape, hot glue, twisted wire, and screws. It is meat only to learn what works, and what does not!  

Can you identify the parts in the picture??

WildWorm prototype test - Franken Prototype
Test Results
I ran the first tests with a weak battery pack, just under 5V DC. This was attached to a recycled printer motor that is rated 9-12V (I believe). I thought the motor had plenty of torque to rotate the helix without beating the assembly to pieces. -which was important at this stage.


The video shows the results of my initial testing.

First of learnings, yes this worm drive concept is feasible. The underpowered motor is just barely turning the helix, but the rotation is consistent enough to move the treads. The stabilizer will need to be tightened up to keep the tracks in a steady horizontal position. and the helix will need to be smooth, as well as the inside of the treads, in order to reduce the internal friction and sticking.

This test only proved that the motor with stabilizer will move the track in the correct motion. There are a lot of design learnings available, now I can iterate on these ideas and go for the next set of testing.

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