So, the idea is to make something that can evolve over time to become as close to indestructible as possible; each time it gets into a fight with a spinner and a weakness is exposed, I'll try to refactor that weakness out. Hence the name (actually borrowed from a 'sculpture' by the surrealist artist Man Ray): "An Object to be Destroyed".
Initial plan was to 3d print a body frame and screw on polycarbonate plates top & bottom . Having played around with it in Fusion and printed some tests however, I realised this introduced too many weak-points, as well as making it harder to prepare a stock of spare parts. So eventually I decided to go fully printed - but to try using one of the tougher nylon+CF filaments for all the body-work.
Given the price of exotic filaments, I want to get the design as close to finished as possible first. To that end, I'm using some so-called "premium" but actually "really not very good" blue ABS that I bought dirt cheap from the HobbyKing bargain bin some time ago. Although I wouldn't dream of using it for a real robot, it's proving useful for prototyping. Here's the latest prototype for Object 2B Destroyed, shown with only one of the wheel protectors fitted (if weight allows, I'll make that a full-length side protector, so it's easy to replace after a spinner catches us broadside):
Wheel diameter is 21mm and the body is about 13mm thich, so the whole thing sits pretty close to the ground. The row of holes at the ends are for bolting on a 1mm thick titanium sheet wedge and I'm planning to sandwich some 2mm thick neoprene foam between that and the plastic, to help absorb impact. Might even experiment with little wedgelets at one end for optimum acetate-busting - certainly got enough room to spare on the length. One big improvement already on most of my previous designs, is a separate battery compartment hatch, which means only 4 screws to undo to access the LiPO!
Next step was to print it up in something tougher. Options for Nylon + Carbon Fibre fil are currently a bit limited (without shipping it over from the States) but in the end I settled on something called "PA12 + CF5" from Fiberlogy, bought from 3d-Jake. Unfortunately. although the filament seems pretty good, the spool it came on is a nightmare; much too fat to fit in the air-tight spool holder that came with my Up 2 Mini printer. One thing one hears over and over again about nylon filaments is that they suck moisture out of the air like nobody's business and instantly become unusable... so the first job was to build a new spool container. Here's the result:
It's just a "Lock & Lock" plastic food box, to which I've added a simple 3-d printed spool holder and a nozzle for the filament & bowden tube. Though I say so myself, it's actually a great improvement on the Tiertime original (that thing on the left) - takes a full sized 1KG spool, it's even more air-tight and just as easy to load. Did a couple of simple test prints earlier, using the default ABS settings (270c hot end, 90c bed) and seems fine so far. Separating the print from the top support layer was a faff but absolutely no issues with warping or layer separation. First attempt at the full body is now printing - so in a few hours I should know whether Object 2B Destroyed is going to be a thing!
