Before we get into the main mystery meat of todays entry, Id like to say that I had a fantastic weekend with my best mate in oxford, getting very very drunk on imported beer and playing hilarious boardgames. Strip poker (involving his girlfriend) was an unexpected bonus, although we were both at a distinct disadvantage having been drinking for seven straight hours by that point. Didnt even have a hangover on sunday when i woke up, and hauled my ass across london.
And so, sadly, it is much to my annoyance that the rest of my life isnt quite as superb as this weekend.
I am getting progressively pissed off with a little side project Im working on for my best mate (one i spent weekend with). Its actually a (much belated) birthday gift. Eventually, he says, its going to be a miniature sundial (probably a diptych dial) inside a case with a three leaf iris that works like a camera shutter.
And its this aperture thing thats giving me trouble, or I should rather say, the mechanics of it are. Since the point of this gift is to have something he can use in africa (hes going out there for six months working and teaching english in a school in ghana), Im trying to make this thing pocket sized, or at least reasonably so. It is this small size among other things, that is making things difficult for me.
Now I appreciate that not everyone has a mechanical mindset, so bear with me.
When i say aperture, i mean something that is similar, but not entirely like the aperture in a camera. The camera apertures are made of many little slivers of metal, meant to form a precise hole for a given intensity of light. In this case, they just have to meet, and essentially behave as if the lid of this thing were as solid as the rest of it.
Now, the internets is a big place, so I have managed to find something like the design that im tearing my hair out over. These images show a four leaf iris being opened, not a three leaf one, but the principle (and the mechanics) are very much the same.
Notice how the outer ring rotates with respect to the inner one? This rotation pulls on the links attached to one end of each leaf, which themselves rotate around a pivot (mounted in the edge of the opening) and the aperture opens. This rotation (of the iris leaves) is really all i care about, since this mechanism is pretty fucking bulky, as you can see, compared to the size of the opening. Ive been fairly harsh to myself, and trying to keep the dimensions of this thing small - about 80mm in diameter and maybe 40mm tall.
So, how do we solve this problem?
Gears! And more specifically, aspects of the epicyclic geartrain, namely that of making small cogs go around bigger, inside out ones, not unlike this:
So this is how we solve this problem. A large ring gear ( which effectively forms part of the casing) turns the smaller gears, each attached to a leaf, which turns, which opens, which means we completely do away with an absolutely massive, bulky thing, and instead becomes a very swish piece of smug bastardry on my part.
Scooore.
However, there are problems.
1) Gears.
Gears are actually a massive problem. HOOOOOGE. These gears are small, and pretty much entirely custom, despite a lot of google-fu on my part to try and get some of sufficiently dinky size to fit inside this thing. I am quite convinced that I may well have to get some custom made, which hopefully could be fairly simple, or sadly very expensive, depending on whether I can bribe someone in my university engineering department to make these things for me. All im really after, truth be told, is a flatbed laser cutter that can take stainless steel sheet of maybe 3mm thick and A4 sized, that takes a basic drawing format, but this leads us to...
2) Manufacture.
I cant fucking find one! Again, my google-fu has failed me. I can turn up so many metal fabrication places it makes my head spin, but these parts would take maybe an hour on the laser cutter in my high school workshop to cut. I dont need a cutter thats the size of a dining table, or can cut stuff thats as thick as my fist, I just need something of a little more power than the average bleeding lightbulb. This has wasted such a comedic amount of my time that I've actually been looking up my highschool's phone number to ring my old teacher whether he can cut it and send it to me.
GRAGH!
I want a star trek replicator. So I can make these bloody things, and then say "TEA! EARL GREY! HOT!" in a quintessential Patrick Stewart hom-aaaaage.
And so, sadly, it is much to my annoyance that the rest of my life isnt quite as superb as this weekend.
I am getting progressively pissed off with a little side project Im working on for my best mate (one i spent weekend with). Its actually a (much belated) birthday gift. Eventually, he says, its going to be a miniature sundial (probably a diptych dial) inside a case with a three leaf iris that works like a camera shutter.
And its this aperture thing thats giving me trouble, or I should rather say, the mechanics of it are. Since the point of this gift is to have something he can use in africa (hes going out there for six months working and teaching english in a school in ghana), Im trying to make this thing pocket sized, or at least reasonably so. It is this small size among other things, that is making things difficult for me.
Now I appreciate that not everyone has a mechanical mindset, so bear with me.
When i say aperture, i mean something that is similar, but not entirely like the aperture in a camera. The camera apertures are made of many little slivers of metal, meant to form a precise hole for a given intensity of light. In this case, they just have to meet, and essentially behave as if the lid of this thing were as solid as the rest of it.
Now, the internets is a big place, so I have managed to find something like the design that im tearing my hair out over. These images show a four leaf iris being opened, not a three leaf one, but the principle (and the mechanics) are very much the same.
Notice how the outer ring rotates with respect to the inner one? This rotation pulls on the links attached to one end of each leaf, which themselves rotate around a pivot (mounted in the edge of the opening) and the aperture opens. This rotation (of the iris leaves) is really all i care about, since this mechanism is pretty fucking bulky, as you can see, compared to the size of the opening. Ive been fairly harsh to myself, and trying to keep the dimensions of this thing small - about 80mm in diameter and maybe 40mm tall.
So, how do we solve this problem?
Gears! And more specifically, aspects of the epicyclic geartrain, namely that of making small cogs go around bigger, inside out ones, not unlike this:
So this is how we solve this problem. A large ring gear ( which effectively forms part of the casing) turns the smaller gears, each attached to a leaf, which turns, which opens, which means we completely do away with an absolutely massive, bulky thing, and instead becomes a very swish piece of smug bastardry on my part.
Scooore.
However, there are problems.
1) Gears.
Gears are actually a massive problem. HOOOOOGE. These gears are small, and pretty much entirely custom, despite a lot of google-fu on my part to try and get some of sufficiently dinky size to fit inside this thing. I am quite convinced that I may well have to get some custom made, which hopefully could be fairly simple, or sadly very expensive, depending on whether I can bribe someone in my university engineering department to make these things for me. All im really after, truth be told, is a flatbed laser cutter that can take stainless steel sheet of maybe 3mm thick and A4 sized, that takes a basic drawing format, but this leads us to...
2) Manufacture.
I cant fucking find one! Again, my google-fu has failed me. I can turn up so many metal fabrication places it makes my head spin, but these parts would take maybe an hour on the laser cutter in my high school workshop to cut. I dont need a cutter thats the size of a dining table, or can cut stuff thats as thick as my fist, I just need something of a little more power than the average bleeding lightbulb. This has wasted such a comedic amount of my time that I've actually been looking up my highschool's phone number to ring my old teacher whether he can cut it and send it to me.
GRAGH!
I want a star trek replicator. So I can make these bloody things, and then say "TEA! EARL GREY! HOT!" in a quintessential Patrick Stewart hom-aaaaage.
I work as a buyer sometimes for an effects company, and the company we always use for cutting is THIS one. I know you don't need a Mr Fusion style cutter, but you seem to be wasting a lot of time trying to find a small wind-up one. Sometimes it's just better to get it done!
Anyways, if you call them, speak to Mike Simpson if you can, and say Dave Thomas from Wolfman Special Effects department recommended you (if no bells are ringing at his end, say I'm a colleague of Jason McCameron), and just explain your situation. They're always pretty helpful, so might be able to recommend a smaller company.
Hope that helps.