PotatOS Project Part 2

[PART 1]

[Sorry for the lack of pics in this post! Completely forgot to take pictures of the electronics on their own except for the bad one of the sound board! Hope you enjoy the rest of the post!]

Now where was I…

Last time I was talking about priming the potato and getting it all the one colour. That worked a treat, there were a few imperfections and raised lumps I hadn’t noticed that I got sanded down. I did not, however, want the potato to be perfectly smooth. It’s very tricky to do natural organic random dents and knicks in a man made potato, but I decided while I didn’t want massive lumps, bumps and chunks I didn’t want it to be pristine. If it was pristine, it’d look extremely fake. I’m being graded on this project as if I was making a prototype for a collectors piece or collectors toy so it’s allowed look plastic but not too plastic. Little hard to explain I guess but I don’t want it covered in dirt like it was just picked out of the ground either!

Anywho, I got my potato primed and sanded a few times until I was happy. I had ordered some Smooth-On OOMOO 30 silicone from Kaupo.de and that is when disaster struck. The original plan was to do a two part block mold of the potato, and then slush cast it so I had a hollow version to fit the electronics into. It seems I didn’t order enough for one side, let alone two and I didn’t trust my instincts and poured anyway. The silicone didn’t even come close to enough, and it was an extreme waste! I had removed a lot of the negitive space by packing in some extra clay, but then the mold walls ended up a bit too thin.

Pro Tip: Trust your instinct and don’t mold when you’re extra tired!

Now while the silicone didn’t work out, and when I pulled the potato from half the mold it was a little too transparent to make a plaster jacket for, I have to say OOMOO 30 is really nice stuff. It’s advertised as a silicone that is so fluid that it doesn’t need a degassing chamber, it does it all itself!  there was not an air bubble in sight on the inside of that mold! I was really impressed. Most of the Smooth-On range is just mixed 1:1 by volume which is dead handy! OOMOO 30 cures in 6 hours, but there’s an OOMOO 25 that curse in just 75 minutes for those than need their mold pronto. I don’t think I’ll be trying that one for a while, it only has a mixing time of 15 minutes and I’d hate for it to start curing while I work. I’ll get better at mixing quickly, then we’ll see.

The potato was resting in a chunk of clay because I was doing a two part mold, this was packed in to about halfway around and then silicone is poured ontop. Ideally when that cures, I flip it over, remove the clay, clean the silicone and add some release agent before doing the second half. That didn’t happen so I had to pull the potato from the lump of clay it was resting it because I was terrified the damp would do damage to the model. I’m not sure how well primer takes to sitting in moist clay for a long period, but I’m certainly not going to test it now.

So, while I wait for more silicone to arrive, I decided to give the electronics a shot!  Shane kept me company while I was working on these as he had a little more soldering experience than me. I also find I work well in the company of others, especially other people that I can bounce ideas and questions off. Even if the person doesn’t know the answer, just hearing it out loud or saying it can be enough for your brain to turn around and tell you you’re being silly, or say, well why not give it a shot?

As I said in PART 1, I was never good at electronics in school. We learnt a fair bit in physics, but because I was relatively good at the nuclear physics end, that usually got me through exams ok. We don’t learn electronics in college unless we teach ourselves so this was going to be an exercise in that. It is probably due to my lack on knowledge that plan A didn’t work out to well, so plan B was implemented. If anyone out there reading this has any ideas or sugestions on the electronics they’d like to toss my way feel free to add it to the comments below.

After a lot of trial and error
and way to much money (shall definitely be investigating seriously cheap online electronic stores next time) I have a soundboard that has 2 push buttons for the outside of the potato (one for the red dot on her eye – and one for the small one on her computer chip) that are wired to the soundboard. It’ll be more like a toy or collectors item this way – push button A for phrase 1 and push button B for phase 2. The soundboard has a little mic in it so I can record directly from my laptop and runs on a 6V battery. I also got a speaker from an audio kit because the soundboard didn’t have it’s own. I’ll have to make a plastic tube for it to help with the accoustics but it seems to work rather well. there’ll be 2-3 LEDs around her eye and everything will have an off switch too.
Oh speaking of her eye, there was a bit of a Health and Safety issue in the college still so instead of laser cutting out 3 discs of 5mm MDF and one of 1.5-2mm, I had my dadteach me how to use his router and cut out my own. This was a little awkward because the eye piece is only 65mm in diameter, and the router much prefers to cut big things.  We made a template that was about 60mm in diameter by using a hole saw drill bit. This was because the guard on the router that edges it around the template, would add an extra 8mm or so to the diameter. After the circles were all cut out, I was able to glue them together and sand them back down, nice and evenly, to 65mm using what was basically a vertical lathe constructed from a drill press, a drill, and a metal bar with my circles clamped down the end.


Once the 3 larger discs were sanded I filed down
 the grove in the eye piece that goes across the lower circles. It’s about 1mm deep and 1mm across. My squared needle file was the perfect size for it. I then added the smaller upper circle that was also cut using a hole saw drill bit, and filed a little hole where the red button is going to go. This’ll be cast and slush molded so it’s hollow enough to fit various electronics underneath. Because it was still a little rough on the edges I added some red putty smooth it out before priming.

I gave the eye a quick sanding with very fine paper to get any small blemishes out, and re-primed so it had a perfectly smooth finish. The very centre was still a bit lumpy from the glue I used to attach the smaller disc, but because that was going to be removed from the final cast, it didn’t bother me so much. The next post will show how I molded this eye piece and the main potato.

[PART 2.5]

2 thoughts on “PotatOS Project Part 2

  1. Pingback: PotatOS Part 3 | 3C Creations

  2. Pingback: PotatOS Project Part 2.5 (Molding and Casting) | 3C Creations

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