![]() ![]() How to cut round pieces from a plastic sheet? I first cut a smaller square piece from the sheet. ![]() The 2 mm sheet felt rigid enough in my hands when I tried it before buying. But of course it shouldn’t bend or break. I wanted the lid thickness to be as small as possible for magnetic couplings. The plastic sheet placed at the front of the cylinder. It cost 5 euros in a finnish hardware store Biltema, link: I bought a plastic sheet made of styrene-acrylonitrile, also known as SAN. I really dodged a bullet there, because I later found a chart that says more than 30% concentration of ethanol is not recommended for ANY use with acrylic. I didn’t see any cracks or clouding, so I used it in a few small places to clean the cylinder. I decided to try car windshield cleaner (ethanol alcohol, probably 50% concentration), first on scrub pieces. I read some debates online whether you can use alcohol to clean acrylic or not. I first though about using a nail polish remover (acetone), but after I used it on the first lid, the plastic lost transparency. You couldn’t remove the stains with soap and water. I first used gloves that left smudge on the cylinders. It also stains easily and is difficult to clean. ![]() I quickly got some scratches on it and started using soft fabrics underneath the table/stool when working with it. These were to be used with the lid.Īcrylic plastic is sensitive material. I used a hand saw to cut 2 cm pieces from the smaller cylinder. The right one is shorter as I’ve already sawed two pieces from it. Therefore I increased the diameter to 11 cm, just to be on the safe side. In this drawing everything would fit but with little room for error. With this information I draw a sketch with 10 cm outer diameter. The lid sealing takes 2 mm and the hull thickness is 3 mm. For the lid sealing I will use a piece of a smaller cylinder that is attached to the flat lid. Some clearance is needed between the magnets. For left/right turn I first envisioned using a linear magnetic coupling, similar to Submarine 3.0, but in the end I changed it to a 24-tooth magnetic coupling. What is the minimum diameter? Magnetic coupling for the main propeller will take 4 cm, as I intend to base it on a 40-tooth Lego gear, like in previous subs. So, I decided to make a cylinder with flat ends. Not optimal for speed, but fast enough in hindsight. The back also needs to be flat for the large magnetic couplings I’m going to use. But also, I want an on-board camera to the front, so the front has to be flat. As narrow as possible to increase movement speed. I couldn’t even imagine building the thing, solving problems and checking everything is ok before dive if I couldn’t see inside. It cannot bend or compress under pressure, otherwise I’ll lose buoyancy, like with the Submarine 2.0 soft lids. But this time I wanted to try something different. Both worked ok, especially the IKEA snap-on lids were easy to use. In previous submarines I used IKEA glass food containers and a plastic lemonade pitcher as hulls. ![]()
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