PiWars 2019 - The Chassis


Design Meeting

Today was our second PiWars 2019 meeting. It was very well attended, so well attended that I didn’t have enough work to distribute today. Thankfully discussion lead to some volunteering:

Discussion Points

  • Using Github & Gitea properly (Sam/Oly will teach)
    • Last year was the first time some of us used Git. We didn’t use it properly. This upsets Sam.
    • Don’t just commit to master.
    • Create a branch to work with then make a pull request once you’ve got somewhere with your branch.
  • Starting from scratch with the code.
    • We could use the current code as a base, but it’s ugly. The consensus was to start over.
    • Allows us to use Python3 for everything.
    • Docker discussed. We will give it another go. We will not be having multiple instances! (Damn you OpenCV)
  • Feasability discussed: We have time to do this - we have the old code if we really need it.
  • Body needs to fit the theme (Jake to do a design drawing - we’ll make it fit from there)
  • Controllers (dualshock4) (Jake)
  • New, more compact gun (Space Invaders) (Mike)
  • 3D Print Mecanum wheels (Alex)
  • Program OpenCV challenges (Alex)
  • Maze (currently unvolenteered)
    • To be fair: probably best we leave this until we know if the mecanum wheels will work for us.

Active Design


Yes, we did some actual work today. Not just talking about work. Oly and I transposed the chassis design from Sketchup to FreeCAD. We’ve agreed to make no major changes to the hardware of the robot… so our first mission is to completely rebuild the chassis of the robot out of better stuff (I know). The chassis of our 2018 entry looked, sounded and sometimes smelt like it was going to fall apart at any moment. It was 3D printed on a slow and untrustworthy 3D printer - it was under-extruded and in the end we just had to go with it. No! Not this year - this year we’ll have a chassis out of metal if all goes well. Oly has a CNC which we think might do aluminium…

  • Today we transpoed chassis measurements from sketchup to freecad for CNC-ing.
  • Will definitely do a wood chassis, aiming to do aluminium but it may break the CNC.
  • Oly to do actual CNC-ing in the nearish future after personal life happens.


Ok, no active design here… but i’ve looked on thingiverse and found these wonderful Mecanum Wheels which I know are too small. Next week:

  1. Find STLs/design appropriately sized wheels
  2. Slice STLs
  3. 3D print
  4. Blog about this mini adventure.