Digging in the Dirt

The XR311 is painted up (not by me) and looks pretty good -- especially for the cheapest material Shapeways will print:

Unfortunately I can't offer that model for sale or download. But I did put the tires up for anyone to print, and re-organized my Shapeways store a little.



Went into TechShop today and tried out the billet of 7075 alloy I bought. Different stuff -- it was almost like first day on the lathe again. The main alloying element in 7075 is zinc, followed by magnesium. It is a high strength alloy -- comparable to steel in some of the tempers -- first developed for the Mitsubishi A6M "Zero" warplane. Corrosion resistance is worse than average, and machinability is considered only average. My experience with the stuff is that it made tough, springy chips that refused to break and were difficult to free. It looked very shiny when being cut, but left an obvious series of tool ridges even at extremely low feed rates. It also pushed up in cutting, leaving ridges at the ends of cuts.

So it was a good experience, but isn't going to wean me from the 2011 -- which is so machinable it is described as a "free machining" alloy. The primary alloying element in 2011 is copper, and it goes back even further than 7075; the 2000 series was known as Duralumin in 1904, when Alfred Wilm developed it at Dürener Metallwerke Aktien Gesellschaft. It is also an age-hardening alloy; left to itself, an object machined out of 2011 will slowly gain in strength until it reaches full temper.

What I was really hoping for was improved scratch resistance, but so no. The next alloy I'd like to mess around with, though, is 6061; practically pure aluminum (less than 1% of magnesium and silicon, plus a varying bit of iron, copper, zinc, chromium...) It is probably the most common general-use alloy out there, although one of its major strengths for general use is the high weldability.

What I'd really like is anodizing. But I'm going to have to live with powder coating (there's a class on Monday...if only I had sixty bucks to spare!)

Oh, yes. The machining. I managed only two finished grenades today. Outstanding orders as of this morning are six of the ones without springs, and one with a spring (which takes about twice as long to make). So about another hundred bucks coming in as the payments trickle in on this last batch. That will help.



Notice the snap lecture above? I've been doing that a lot. I set out to write a Tomb Raider/SG1 fanfic because I thought it would be fun. As of chapter 5 and about 20,000 words, I've settled down into a routine; spend a day or two looking up fun obscure facts, then condense them down into one or two pithy paragraphs.

Some scenes go faster, some take more. For a mere paragraph or two with Lara walking along a busy street in Cairo, I had to look up a huge volume of things, including colors and fare schedules of the rather complicated cab system, typical cat-calls (and a brief review of gender issues in modern Egypt), the filmography of two actresses and a little bit about the family of Alexander the Great, typical dress, the details on a nice outfit for her (no -- the shorts and turquoise top are not street wear!) and of course lots of maps and place names.

I'm overdoing it, of course. But its fun to have practically every scene an info-dump of the colorful and the obscure, and the readers seem to like it too...I have forty or fifty people following me already, waiting for new chapters.

Choice and Linearity

Not a particularly original thought, but I'm struck right now by how little influence the player's actions have on any of the games I've been playing recently.

The story in Tomb Raider 2013, for instance, unfolds not only regardless of what you do, but regardless of whether you even know what is going on. I fought the big guy on the ship without having the faintest idea who he was. Turns out, in some earlier confrontations you can chose to overhear the bad guys talking. The game actually and actively discourages this, however.

Now, that might have been a nice little mechanic. That you'd trade gaining useful information against the increasing odds of discovery (and the bad guys are a lot tougher to handle if you don't get the opportunity to silent-snipe them from hiding). Except that no action you the player is ever given is the least bit influenced by what you might overhear.

You can totally go through the entire game ignoring the conversations, skipping the journals, even fast-forwarding past the cut scenes. Because the only real "choice" ever made is to stop playing. (And the only active role you ever take is in playing well enough to get to the end.)

Half-Life 2 and Portal 1 and 2 also give you no meaningful choices. You can't chose to work with Wheatley, or leave him in charge, or leave the PotatOS in the bird's nest. It is rather amusing to view Portal in the meta-view; in-game Chell is renowned as never giving up. External to the game, there is no nonstandard game over. You can quit the game, but there isn't an option to send Chell to a corner and refuse to solve any more portal puzzles.

The meta is even stranger in Half-Life2. Freeman has a reputation as unstoppable killing machine. (Lara gets the same). Well, unless you are really, really good at shooters, you have been stopped. Multiple times. And restarted from a save point.

I know there are some games where internal choices matter. Bioshock, which I've just started, gives you at least two different game endings based on your actions within the game. And, for that matter, even the Civ series will play a different victory video depending on whether you won a diplomatic victory, or stomped the rest of the world into bloody submission under your iron heel (yes; the ending video is very much phrased in that way!)



I think what brought this on is it is a continuum. And that the railroading can seem less onerous depending on how it is done and what is done. Gordon Freeman finishes Episode 3 having effectively kicked the Combine off Earth, and both he and Alyx are still alive.

Tomb Raider 2013 ends up with Roth dead, as well as a whole bunch of other people who didn't necessarily deserve to die. Especially those who died at your own hand; and unlike Half-Life, you can't bypass more than a handful of them. There's no equivalent to gunning the engine and fleeing past the metrocops instead of choosing to fight them. Instead you have to slaughter 98% of the people you meet because if you don't, they'll shoot you in the back as you run past.

(The map is also more linear. Even Half-Life2 -- which is quite linear -- gives you options to bypass concentrations of troops. Tomb Raider 2013 not only gives you only a single path, in well over a dozen instances it places you in the middle of a fight during a cutscene before giving the controls back to you.)

I don't know why the illusion of helping to construct the story is so much thinner on Tomb Raider 2013. But it is. And that makes a poorer game.

My Game Protagonist

Yeah, I've been playing a lot of Tomb Raider. The 2013 "Innocent Lara" is problematic in some ways, but outside of her behavior in a few cut scenes I've been able to mesh with the avatar.

Games -- more so, I think, than television or movies -- are often approached with a level of appropriation. One plays (or watches) while constructing a head canon of one's own. It isn't always possible; sometimes the disjunct between one's own understanding of the world, the logic and the emotional logic of the story, can't be reconciled with the nonsense being shown.

And some time I'd like to unpack more what the 2013 reboot does with gender roles, race, violence, and how its treatment of these areas meshes (or fails to mesh) with the story.

But not at the moment.

The protagonist I'm thinking of at the moment starts as your typical reluctant hero. She had an idea, what was to be an academic investigation of limited scale. She got much more support and interest than she expected, but instead of bailing, she stepped up to the plate to do the work necessary for this much extended scope.

And faced the usual obstacles of a hero's journey. A veritable storm of harassment and threats. It seems at times a whole little world is being thrown into turmoil as she continues to work. And yet she doesn't lessen her standards or let the opposition harden her. She continues in the best tradition of the reluctant hero to question herself, to critically look at every step in her process, to meticulously document and to make sure that she is doing the right thing.

And thank you, Anita Sarkeesian, for doing this. It shouldn't take a hero just to start the project of building a proper critical groundwork so we can get to really improving games. But it does, and thank you for being strong enough -- externally and internally -- to do it.

Vee Hick Cull

The "Morrow Project" XR311 print arrived from Shapeways. It looks real good, even in the cheapest of the available materials (the white nylon). I didn't expect the tread on the tires to show as well as it does. In any case, I'll post some pictures once it gets assembled and painted up.

I'm pushing on contract and hourly right now, as bills are coming due and the next show doesn't go into tech for several weeks yet. So not a lot of time for props or electronics projects.



Successfully replaced another jack on a Sennheiser body pack. It's a pain because the circuit board is so tight, and the traces are fragile. I had to carefully cut apart the old jack with dykes and de-solder the stubs of the lugs one by one. I have at least one more to go through, plus the easier tasks of antenna and LCD, but the big labor is a pile of damaged Countryman B3's. I'm hoping I can return at least some of them to service, but they are all aging.

I may have imagined it -- no way to do a double-blind -- but when I finally washed out the elements the principals were wearing on Shrek, it made a big difference to the sound. Yes; you can actually rinse the Countryman elements in water. Or in alcohol, which is what I do. Do give them time to dry out properly, though!



Meanwhile, the crazy budget system I assembled at another theater made it through the first Theater Camp without problems. I still need to label and document. Downloaded a couple of installation diagramming software packages, but the level of detail I need for these end-users means I'll probably have to do the docs in PhotoShop. Or Inkscape, which is the shareware option to Illustrator.

A Rolls MA2355 is fed by a dedicated microphone (Crown PCC160) and drives two legs of monitors; one in the booth, another in the dressing room. This is completely independent from everything else, but at some point I'd like to link it up to the ClearCom for Stage Manager announcements to the dressing room. (This may be as simple as a length of cable).

The primary system aggregates through a Rolls rack mixer; this pulls in a pair of inputs dedicated to the FOH mix position, a pair from the firewire interphase of the sound effects computer, and front-panel jacks for iPod and dynamic mic for use during rehearsal and by the Theater Camps. On the remaining work list is to cut a plexi shield that will deny access to anything other than the latter two inputs to casual users of the space.

This feeds a DriveRack PA+, which does the absolute minimum system tuning; a little notching in a graphic EQ for gain, a gentle corrective parametric EQ, and delay for the rear speakers (which I'd like to replace, and move further forward to make proper fill speakers out of).

I've also got another rack mixer in there which is not yet connected, but is designed to bring together a second pair of firewire outputs with a second pair of feeds from FOH, to allow both access to the front fill stage monitors.

Still, just this (plus putting in hardwired boxes for the ClearCom runs, adding a Furman to the rack, and a few other details) already cost over fifteen hundred. The bucks add up quickly with sound.



Those bucks went to the theater. My own bucks stretched just enough to pick up a little fabric and repair my futon cover, but not enough, yet, to have any PCB's fabbed off. My browser is still filled with tabs on power MOSFETS and 5-watt LEDs, but that project is going to remain stalled for a little longer.

Science!

Being a physicist is apparently one of those things that is always on. I read in various personal material -- blogs, autobiographies, anecdotes, etc. -- that physicists are constantly aware of the physics going on around them.

This is not a unique attitude. I light the stage, and do sound design for it. I've tried to draw comic book art, and I build and render scenes in 3d. These, and more, are all referenced to observation of the real world. And that means any time I'm out walking, I'm also out analyzing; what made that sound? Why is that shadow that color? What are the depth planes of this scene? 

This is almost back-of-the-mind noticing, mind you. You don't go around with a notebook out, stumbling into things as you try to record your observations. You just, plain, notice. 

And since I've rekindled a (strictly amateur) interest in science, I find myself applying that tool as well.

A couple days ago I wandered into the kitchen late at night and filled a water glass without turning on the lights. It was easy to do, but why? A little experiment the next day showed that the key was the material and shape of the glass. Here's how I reconstruct; the turbulence of the water sets up an oscillation in the tuned resonator that is the sides of the glass. As the glass is filled, the length of the resonator becomes shorter. Since each halving of length is perceived as a doubling of the octave, the perceived pitch center rises exponentially.

Presumably, the pitch appears to be rising swiftly, accelerating, towards a point where it can't be perceived as a tone any more. And somewhere a little short of that, you turn off the water.

The free-air wavelength of a 10 KHz tone is over an inch, though. So what you are hearing is clearly not the air column, but the vibration of the walls of the glass. Which are stiff, and just as making a guitar string more tight increases the pitch, so does making a resonating material stiffer. I tested this with plastic, glass, metal, and ceramic vessels of similar dimensions, and on first blush it does look like that describes the phenomena accurately enough.

On Friday my metal arrived for the next crop of grenades. I bought a stick of the tougher 7075 alloy to experiment with. But what if the label comes off? How can I distinguish it from the 2011?

Isn't it obvious? I held one of each by one end and tapped them lightly with a piece of metal. The harder alloy had a higher pitch.

One of the things that so fascinates me about physics in the "real world" is both how close to the surface it is, and how deeply complex you quickly get out of what are relatively simple rules. Because real materials are complex; they are compounds, they have grain, they have non-simple cross-sections, they connect.

So something as simple as observing which surface exposed to sunlight gets hot, is both a simple and obvious exercise in absorption versus radiation, but also can be unpacked into greater and greater detail as you consider interaction between layers, conduction, whether convection cells are forming in still air directly above the surface, etc., etc.

When you get down to it, much of the behavior of a simple reaved block has to do with levers and friction forces. Friction is what makes short fibers into a rope, and friction is what holds a nut on a bolt. Of course, if you unpack those friction forces, you find yourself in a maze of mechanical interlocking and compression forces and Van der Waals and so forth...

(But at the same time, there are very basic physical laws -- rather, mechanics -- going on that can confuse the untrained. Difficult enough for some to understand that a block trades off length for force; if you are moving twice the amount of rope, you are lifting half the amount of weight (plus overall friction, which goes up with the number of elements in the system). Tough for a lot of people to realize that if you lift a weight, the load on the pulley is twice the weight. You have to add the forces; one force for gravity trying to pull the weight to the ground, a second equal force for the rope keeping that from happening. If you don't understand the basic underlying principles, you can put yourself at risk.)

This is why there are so many jokes about physicists complaining that physics describes the entire universe, and specialities like, say, marine biological acoustics is just detail. Thing of it is, these details are so very, very tough to work out from first principles, you really do need the entire framework of the other sciences, with their laws and rules of thumb and categories (however well or poorly those line up back to the underlying physics).

And that's also why you can get close with an approximation -- like the water glass model above -- but recognize that this simplified model will not track that closely to the real behavior. In fact, it can go entirely wrong...

A Little 3d

"Little" as in 1:6 scale --

This is a mesh from my upcoming Poser set, printed out in the "Frosted Detail" material, aka a UV-hardened acrylic polymer printed with the MJM process.

The legs and shipping plugs are press-fit and allow a limited amount of posing -- when I decide on the final pose I'll put a few drops of glue on them.

The coins, incidentally, are 1-baht from Thailand. I keep a little pocket change from everywhere I've visited.











Meanwhile, the grenades are rolling off the lathe. This is from early last week, before I went in and finished the four bodies you see there, painted up the top of the second solid-body, and shipped them all off to customers.

Since someone at the RPF finally asked, I've been painting up caps (and solid-bodies) in the three colors seen in the actual movie (blue shows up on a couple of uniforms, and there's one green in the scene in the control room when Newt picks it up).

Actually, according to third-party documentation, the HEAP and "Bounding Betty" types are supposed to have different-shaped safety caps. Me, I'd have more than color to distinguish one from the other, because you might be trying to fumble one off your web gear in the dark.

(Plus, and this is a mistake you wouldn't expect from Cameron, blue should really, really be reserved for training and simulation materials. And reserved, too, for that specific powder blue that indicates inert dummy rounds.)

In any case, molding custom caps would be a pain, printing wouldn't work well (smaller tapers and gentle curves suffer from stair-stepping), so that kind of leaves injection molding. Which I technically could do, since TechShop has both injection molding machine and the CNC mill to cut the molds with.

But I'm going to put my energies on learning powder coating instead.

The more you know...

...the more you realize you don't know.

Finished four M40 grenades yesterday. Six hours at the lathe. Now, some of that was just me being a little rusty, but it is still a labor-intensive prop.

This morning cleaned them up for shipping. Here's what has to be done after all the machining is complete;

1) Fit the primer and superglue it in.
2) Clean off the excess glue.
3) Break the edges and remove scratches and jaw marks with 400-grit and 800-grit paper.
4) Hand-buff the whole thing with 0000 steel wool.
5) Apply a light coat of sewing machine oil.
6) Wipe down carefully with clean rags and paper towels.

And of course:

7) Trim a mocap (HDPE pipe cap) to .740"
8) Cut off the label.
9) Sand the trim and top flat
10) Buff the entire cap so it will take paint
11) Apply two coats of Krylon Fusion for Plastic (or Tamiya Olive Drab 2, depending)
12) Carefully cut a 3/32 wide strip from a roll of white vinyl tape
13) Apply the tape 3/32 from the edge and trim to size
14) Spray the entire cap with two coats of Krylon Crystal Clear gloss

I figure that adds another two hours per grenade. Meaning it basically takes a day to make each one.


Anyhow.

Here's a typical step; drill a 15/64" hole, lathe a piece of brass rod to the same dimension, and part off. Simple enough?

Not really. Drill sizes are nominal; it may or may not be .234" as advertised. Worse, drill bits chatter. The outside of the hole will be a larger dimension than the deeper parts, by several hundredths of an inch.

And when you part, the parting blade pushes up material. So even if you try a test fit (which I did), the primer may -- well, did bind as I tried to insert it into the finished grenade.

This is why I'm now lathing the bodies to 2-6 thous larger than the finished dimension until all the grooves are cut and the knurling done (which is even worse for materials displacement). Then a final pass to take off those little raised edges. It is more difficult to do with the primer, since that is a mere .2" long. But I need to figure out how to modify the process in order to add this step, or compensate for this problem.

And this? This stuff here? This is the meat. This is the difference between learning a tool or a method, and getting practical experience. This is the mostly undocumented ground knowledge that goes away when a generation retires; the reason why having the "blueprints" to a Saturn V doesn't allow you to just start building a new one. The difference between being a graduate of Google U and being able to struggle through a mostly-right answer, and being an actual professional in the field who solves questions like that daily (and has gained a gut instinct on what is right and what is wrong and where the traps and pitfalls lie).

Oddly enough, I had some of this conversation as I was cleaning up last night. Which started when I was sharing laments with another TechShop member about not following up on the CNC SBU.

TechShop gives you an SBU (Safety and Basic Usage class) before you are allowed access to a tool, but this is like a 101 class, a survey; it orients you to the field. You need to spend a lot more time before you actually achieve some competence.

But here's a thing -- like a lot of learning, you need to follow up. The SBU includes a practicum, and you finish feeling like you at least know how to turn the tool on. Well, you do -- at that moment. Give it a couple of days, or a couple of weeks, and that knowledge will fade.

This is why it took me a full day on the lathe just to get back to making cuts. And why I expect the same thing will happen on the mills (CNC and manual). Because I didn't jump back on immediately, which means I'll be in the same situation of trying to remember what seemed so easy to remember during that four-hour introductory intensive.