Sunday, February 16, 2020

Milli (#5) - It's crawling now

The Prototyping of milli is moving - as well as Milli, its self!

The focus since the last post was to find and fix any binding parts of the tread tracks. I have located a specific tread that was not flexing properly, due to it being part of the v3 design and connecting to a v4 tread. I am using screws to act as 'pins' in the track to connect treads together. This is not a good practice as the tread of the screw can bind with the tread. however, if significantly bored out it is permissible at this stage of development.

Milli OpenSCAD - for 3rd prototype test 16 Feb 2020

The other change was to adjust the design of the horizontal stabilizing arm.  This arm converts the spinning helix motion to a moving sine wave. Thus it is essential to the design. Changes included shortening the arm by 8mm and increasing the opening by 4mm. I also noticed that the first tread was binding with the arm, and adjusted the tread to move more freely.

Milli - ready for static testing, full tread length, 18v battery, messy desk(!)

The result - the track moves freely!  At least in the initial trials when I applied 18V to the motor it worked well. I then removed the frame holding the chassis and a quickly put together a simple axle and wheels. This was made by a thin rod and some plastic gears salvaged from a printer. I used alligator clips to hold the wheels in place. I put the robot drive on some carpet for friction and Viola! - the worm drive works!!

Next steps:

  • Find that nagging binding point seen in the video
  • Thinking on the chassis and covering. How the heck am I going to get a battery on it?
  • New tread design with increased movement
  • Ability to move on smooth surfaces


  1. That is just so incredibly cool! And a little spooky. Looks like it could go really fast too. Borrowing from natural designs is a beautiful thing.

  2. Thanks Tom! I am working on some 'peds' (feet) for it now. The spooky factor is awesome.