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

Tuesday, February 4, 2020

Milli (#4) - Prototyping the Wild Worm Drive (New Video)

The Milli project is an effort to build a bio-inspired (math inspired?) robot capable of traversing surfaces that are problematic to other robots (such as loose gravel, shag carpet, and muddy bogs, etc).  And to make it look really cool. ;)

The results of the 2nd prototype are much improved, you can see from the video that the prototype has the correct motion and considerably less friction.

Currently, I have printed 23 links in the track tread.  There is an additional load to rotate the helix, but applying additional voltage the motor resulted in enough torque to spin the helix. (at 18V it is very quick).

Next steps will be to create a rear stabilizer to dampen the effects of the spinning helix.