Given that the virus has limited the supply of parts we need, it's probably worth a quick update. As Rog mentioned in his first post, I'm assisting him in this build (Don't worry, we aren't breaking any social distancing rules. We live in the same house).

Over the course of the last week or so, Rog has cut the subject Jerry Can in half.

Before:

IMG-20200403-WA0001.jpg

After:

IMG-20200403-WA0003.jpg


From what I understand, the plan is to have the main chassis of the robot made from 12mm plywood (as it's what we have available) on the inside, then sandwich the Jerry Can around it as armour. The top bottom plywood panels would then act as reinforcement for the metal, while providing a stable and easily worked base to mount the electrics and bulkheads for the tracks.

Bottom half with plywood base:

IMG_20200404_135359.jpg


Bulkheads are 2x12mm plywood panels glued together:

IMG_20200404_160140.jpg


Now for where I come in. Tank tracks. The initial idea that Rog came up with was to use two bike chains and sprockets to fashion them, which seemed the most likely if we couldn't get anything straight off the shelf. Out of curiosity I had a look on Thingiverse to see if anyone had 3D printed something of the scale we needed. Turns out we were in luck!

IMG_20200329_195344.jpg IMG_20200329_195329.jpg IMG_20200407_080818.jpg

Somebody had designed a 3 inch snow track for a RC snowmobile, which is perfect for what we need. Downside is that it takes 2.5 hours to print one link.... and we need 40. That's not including cogs and spacers. I think I'm seeing tank tracks in my sleep at this point. We've been printing throughout the last week and we have enough for one side, which is what we will be using to test before we print the rest.

Material is PLA+, which isn't the most ideal material, but it's what we have the capability to print and we have lots of it lying around. To add grip, we are looking at using decorators sealant/silicone in to the track grooves. If that doesn't work, then screwing bike tyre in to the links will be the next plan.


Checking the length of the tracks:

IMG_20200404_130851.jpg


So that's where we are at currently. We took apart my old Aldi drill motors to make sure they work, but it appears that they have a 2-stage gearbox, which is much more awkward to design around. We're looking at replacing them with the 18V Mylek drills from Ebay, but the seller is currently away.

Another issue we are considering is that we still haven't decided on a weapon. Perhaps bodging a wedge or a push-plate on one side may be the easiest option, but we are open to ideas!