Wednesday, April 30, 2014

The Gong Show

I'm looking at making a hand gong for the upcoming production. They may not use it -- I may not even complete it -- but it provides an excuse to talk about the process of doing a "hero" prop.

The sequence is something like:

(Iterative) Materials and Methods research and experimentation
(Iterative) Construction/Testing

The Brief is the most top-down of the steps; this is where you take a hard look at the whole project and parameterize it; define how much you are willing to invest in time and money, whether it will involve new methods and materials, etc.

For this prop, the Brief is as follows:

Make a Chinese Hand Gong for use in upcoming production 

* Must be light enough for young actor to hold comfortably, but tough enough to withstand the rigors of stage use.
* Does not need to make sound.
* Should be realistic, not toy-like or obviously prop-like.
* And yet, should be oversized and bold enough in design to read from stage distance.

There's another pair of goals that belong in the brief as well, even though they are super-goals of the entire project:

* Should be fun and look good so I can have another prop build to my name.
* Should be good-looking enough -- and practical enough -- to sway the director into finding a way to use it.

The latter is because this gong is a key part of the direction I want to take the sound design, and if I don't do something like put a gong into their hands, they may not give me the physical action on stage I want to pin my sound effects into stage reality.

In any case, always include the super-goals when you brief a project. You need to understand why you are doing it and how it fits into your life and work before you can properly plan the assets to accomplish it.

Research: the intent here is to refer to the gongs of the Peking Opera orchestras. Which have specific types and names but at least one resembles marginally a common hand or hanging gong that is widely exported as an "ethnic artifact." According to research, it is just acceptable enough to pretend that a hand gong with the particular shape and pattern shown above is actually part of an operatic percussion ensemble.

Of course, in the operatic mode that particular gong is small -- for the styles I'll be representing most often in the sound picture, 8". They sell them up to 30", and 20" is seen in the pit -- but as accompaniment for quieter scenes, usually.

(One basic distinction that can be made is between "domestic" and "military" percussion, with the latter being used for all scenes of fighting and armies and so forth, and the other for basically everything else.)

(But we are talking about a variety of forms that evolved over 500 years of performance in many more disparate communities than there are nations in Europe with their own operatic traditions. And if you recognize the difference between Puccini, Mozart, and Wagner, you can definitely see that any blanket statement about "Chinese Opera" is bound to be incomplete!)

As per the draft stages above, research would usually end with a Plan. Often, a scale drawing. You will always research; even something created from scratch may be referring to artistic trends or functional forms. And much of what you learn is hard to commit to paper...but it helps tremendously if you can collate into one place (aka a drawing) all the key lines and dimensions of the thing.

In this case I'm not worried about it. The way in which the truncated-cone shape interacts with the painted ring is clear enough to be self-documenting. Instead this falls closer to being a formula; if I have one fixed dimension, I can derive the others from it.

I like to have two different minds during a project. I start with describing what the thing should be (if I had infinite time and resources), before I move on to what the thing will be (aka, what is practical to build.) I think it is a mistake to short-circuit the process by going immediately to how you can fake up some approximation, because it closes you off from discovering ways to make a better prop. Or whatever it is you are designing.

(I did this to myself as a lighting designer too; I would draw up a plot as if I wasn't the poor soul who would have to hang it).

The Materials and Methods is where you move across this divide. I describe it as iterative because you will have an idea, hit the stores or bend some metal or something, realize you can't find that material or that it doesn't look right, and move on to an alternate -- quite possibly, an alternate you stumbled upon while you were looking for the first thing.

For cheap props with flexible dimensions, the first stop is usually to see if there is anything already in the world that will fit the bill. You have to be exquisitely sensitive to real shapes, and not be mislead by simplified approximations of them. Far too often, real-world objects will have inconvenient details that are too labor-intensive to be worth attempting to alter or remove.

As a specific, I discovered some bamboo disposable plates that are close to the right shape for the face. They lack the thickness, however. So they would work pretty well if I wanted a lot of semi-acceptable gongs cheap. But the labor in adding a thick edge with the right curve may be enough that it is worth hand-carving the entire shape -- especially as the latter gets a more accurate profile overall.

I also looked at frisbees, which have the incorrect curve on the edge, and inevitably surface ridges that would be difficult to remove or hide. I could do a more generic sort of gong from one, but it doesn't have the specific shape of the Peking Gong.

The twin constraints of weight and strength are leading me away from MDF/bondo, and the constraint of cost leads me away from casting as an option. At the moment my best consideration is carved expanded foam that after being sealed will be coated in resin for strength.

Which leads into the final stage; where I start actually carving into some material and see if I am getting the shapes and the surface quality I want with an acceptable amount of labor.

Wednesday, April 23, 2014

All This and World War II

I finally got around to seeing Miyazaki's "The Wind Rises." Been watching an anime oriented around pre-war to World War II tanks. The past couple of days, I've been assembling models of Lewis Gun magazines. So of course this morning when I turn the radio to a random station, I get Big Band, Glenn Miller stuff. All of a sudden I'm swimming in period military nostalgia.

This week was also my CAD-CAM class. Which turned out less useful than I thought, but it is one of those things that is a lot harder to know going in. Basically, it covered a couple of entry-level commercial packages that create G-code from a file (2d or 3d).

The packages themselves are simple and nearly intuitive. The usefulness of the class was finding out that is how it is done, plus which parts of the process you need to know now and which parts you can safely skim over for the nonce.

So I didn't learn a lot, but I am now in a position where I can translate a computer-made design into something the ShopBot or the Tormach CNC mill can utilize. Which will be the next class. And my last free class; after that, I start paying real money.

A lad over at Instructables has been asking me to build a Holocron for him. I hate to disappoint anyone, but I have way too many obligations already due or past due. I very carefully am not taking any money for "Aliens" M40 grenades until I officially re-open that run (waiting on my new radius bit from McMaster-Carr now). But I did take money to revamp a sound system, and there's work I should be doing over there. Oh, plus two upcoming shows with elaborate sound designs, and I'm weeks late for my first one-on-one with the director of one.

Plus I need to fit in gym time, and find time to hassle the VA about my health care options with them, and Makers Fair is just around the corner...

Tuesday, April 22, 2014

Three Kinds of Rock

I've been reading a book about the elements. Or, perhaps more specifically, the periodic table ("The Disappearing Spoon," by Sam Keane). But that's not what inspires today's post title. Instead, it is the observation that in some of the earliest tools of the paleolithic, our ancestors still found it necessary to carry more than one kind of rock.

These days, even a big-box store can only scratch the surface of the available tools. I noticed this most when I was building scenery for the stage; you needed a monstrous number of different tools to even complete a single job. These days, I'm experiencing it most sharply while building props.

Not that I've given up sound design, or that sound design doesn't require a tool or two! In fact, I've got two exciting designs coming up, and I'm adding two new tools to my collection (a better software-based noise remover, and a Zoom portable recorder).

(More detail on that soon, so don't despair, people who came here for the sound design stuff.)

I was just at the hardware store today, strolling the aisles, and I entertained myself identifying the speciality indicated by the specific supplies on display in each section; glazing here, mudding beside it, auto body repair a little further down.

And then came home with a fresh sheet of MDF to work on what I hope will be a shorter project than usual; assembling some vaccuform Lewis Gun magazines.

Now, I really like TechShop. The span of tools, the fact you don't have to make sawdust in your bedroom, and of course tools that give me access to materials and processes I simply could not do at engraving acrylic, or lathing metal. But it was also rather satisfying to put my own small collection to good use again. Rough-cut some MDF with jigsaw, trimmed it properly with the scroll saw, cleaned the edges with a third-sheet sander. Drilled holes with the drill press. Glued it in place, and did some rough shaping with the Dremel.

But soon enough I'll take the project to TechShop as well. Because I can cut the other shapes I need from MDF, but it is faster and neater to cut them out with a laser. Or, soon, with a ShopBot...but I have at least two classes to take before that option is available to me.

Saturday, April 19, 2014

How Much is that Grenade in the Window?

One does not get into Replica Props for money. At best, you can pay for your own habit. Tools, other props in trade, etc.

But being as this is a blog about eking a living out in the arts, I thought it might be interesting to show the economics of a replica prop "run."

I have now turned 12 prop grenades from aluminium and brass, and sold 9 of them.

Gross was $416 for the sales. Postage accounted for $62.50 and PayPal fees another $13.40. That leaves adjusted gross of $340.50 (assuming no losses or returns occur).

There's two different ways to account the raw materials. One is dividing the raw stock into how many pieces can be made from it. The other -- since some of the materials have to be purchased in amounts much greater than were necessary for the run so far -- is to attempt some form of amortization over the total predicted run. The same applies even more so to the tooling.

The raw metal falls into the first category. A $34 order from Online Metals is enough to make 8 grenades (assuming no mistakes). Which is only $4.25 each. The raw plastic caps are $30 for a box of 60, however, which is way more grenades then I would ever make. Even generously going three caps per grenade (one painted, one spare shipped to the buyer, and one lost or ruined), the divide-by-shipped doesn't accurately portray the cost to me. Ditto for paint and tape.

As a stopgap, assuming I close the run for good at 20, caps, the wrong size of caps (ordered by mistake), paint, tape, packing supplies, a size of metal I never used, etc. adds up to about $100 in stuff. Which is about five bucks per grenade, so a good estimate of costs of material is $10 per finished grenade.

Which if applied to the above would leave a theoretical profit of $250, but of course I already spent the materials for twenty or so. So in reality I'm ahead rather less than that.

This does not account for tooling, of course, and I spent over $100 on tools (lathe tools and drill bits). It also does not account for another of those interesting hidden costs; commuting cost. Each session on the lathe costs me $7.60 in BART fare, and that adds up when you realize my average is still down around three hours per grenade. I can usually get a couple hours above my reservation of four on a typical day at TechShop, which puts the "cost of labor" at about $5 per grenade.

So if I entertain the fallacy of a "typical" grenade, the monetary cost to me for each is;

$5.60 postage
$1.60 PayPal fee
$10 raw materials
$5 tooling
$5 work-related cost

= $27.20

For a suitably large number of grenades, I'd be bringing home $17.80 each, and that would effectively mean I was "earning" $35.60 each time I took BART out to San Francisco.

The musicians in the pit for the last show I worked were getting $45 a service. So this is not out of the ballpark, but it isn't exactly worthwhile wage.

My actual figures look both better than that, and worse than that. Looking backwards, I already purchased all that material and all those tools that are being so blithely "amortized" above. Which means I am out of pocket over $300 in tools and materials alone, plus it took a lot more trips to learn how to do it and get my process streamlined to the current state, meaning quite a bit more commuting costs than the above would lead one to suspect. Looked at this way the project is a pure loss.

But I achieved the original goal; to learn to lathe. I also have the tools, and a sense of accomplishment, and some social media cachet, plus I earned a free class (a $90 value on its own).

And looking at these numbers the other way, I already spent the money. Any grenade I build and sell at this point forward is essentially profit. Well, I still have to pay commute and postage and PayPal, but if I go in to the shop Monday, everything after the first $10 is money going back into my pocket.

So I've revised my offer at the RPF, and if I go on to also advertise at Aliens Legacy I'll have to offer the same terms; $50 shipped. That works down to $20 in my pocket for each one as I turn it (for a run of indefinite length and assuming ongoing replacement of tooling as it becomes worn). Or in the short term, a good day's wages every time I go out to spend six hours staring at a lathe.

Friday, April 18, 2014


The Holocron is done!

Unfortunately, grenades are far from done (here's the next six, just before they went out the door)

And I'm not really happy. It's odd. You could call how I feel about my work depression, but it isn't effecting me physically. There doesn't seem to be any such simplistic connection between my mental state and my physical state. On the latter, I'm climbing back up and have been to the gym more regularly, but I'm still not at that wonderful surge of physical confidence I had way back in December. I wish that would come again.


Ran off four M40 grenades in two days. I had some problems drilling the holes, though, and that threw me off. I had the chance to make four identical and super-clean ones (which are all getting shipped to the same guy in Australia), but I ended up with a gouge in one, a damaged primer hole in another, etc.

And more orders are trickling in. I don't know if I want to put a stop to them until I have a better idea (or forever), or to keep lathing and see if I can work out better ways to build them. I've incorporated a number of enhancements in the tooling process that is leaving them with a cleaner finish and more dimensional, plus taking less time to cut. But I still need more; the cost to me is not insignificant, and the time spent is starting to be a distraction from other tasks.

I only built a grenade as a project to learn how to use a metal lathe. It has rather ballooned out from that! I've sold 9 already at the RPF, and I'm looking at orders for seven more if I chose to accept them. But I ship as soon as they are ready, so I'll never have a really big picture of a bunch of them (the above is the five shipped today, plus two spares, my original -- in a green cap -- and the one-piece prototype).

On the Holocron, the lights are less bright than expected, and the lid fits less cleanly than desired. The lid didn't fit at all for a bit there. Drat those silly manufactures of neodymium magnets -- can't they just ship monopoles like I wanted? So I had to pry one magnet out, flip it over, and re-glue it, and that always spoils what otherwise might be a pristine surface (in this case, far from, anyhow).

The capacitor I finished up with is too small, and it does lose its place in the program if jarred excessively. You can just barely hold it in one hand and do the light show uninterrupted.

On the theater rebuild, I spent all this week doing props instead of working there. I started in on nice wall-mounted boxes for the Clear-Coms (instead of XLR taped to the walls) but foolishly got the wrong gender of box front. It works fine, but it is annoying. Also, there's broadband hiss (RFI) getting in the new monitor mic. Given the quality of the gear, it should be a pristine signal. But the cable run picks up AM radio and I can't seem to filter all of it out.

And similar complaints. But at least one prop is completed. And if I put a hold on grenades, I'd have a little time to do things like gym, house cleaning, designing the next two shows...and maybe even sleep and eat sometime as well.

Monday, April 14, 2014

Rotating Perspective

The Holocon software is finally running. Since I had four individually-controllable RGB pixels, it just seemed too much of a shame not to animate them. So I wanted to write a routine that "spun" (that is, a chase circuit) with a pulse superimposed on that, with a color shift superimposed on that.

Took forever to work it out. Yesterday, I managed to board BART out towards TechShop without my grenade plans (or a book to read) or even a pen. And worked out the software routine I needed in my head.

(This being the internet age, once I arrived at TechShop I logged in to one of the freely available workstations, navigated to Instructables and after searching out my own Instructable on the grenade, scribbled down the measurements I needed on a scrap of paper.)

The big thing that made the routine finally simple enough to write was realizing the LEDs were changing too quickly for me to bother with actually fading the chase part up and down. Between the hysteresis of the light, and the persistence of vision of the eye, just blinking them in a 25%, 50%, 75%, full-on pattern would be sufficient.

Now I just need to solder up a "naked" ATtiny circuit and hook it back to the rest of the Holocron. The last part will be figuring out how to close the lid properly. And once that is done, I can finish the Instructable and earn another class.

Another bit of perspective. I had to use a different lathe than the one I normally reserve, and I found to my dismay it was a bit out of alignment. I was pretty much ranting about how bad it was; over five thous off of plumb (measured over three inches from the face of the chuck out along the workpiece). Using the three-jaw chuck, I had a wobble at the end of my billet that was on the order of twenty thou.

Yeah. About that. A thou is a thousandth of an inch. The worst error the lathe was throwing at me was maybe 1/32nd of an inch. Put another way, the lead on my mechanical pencil is bigger. Even using the edge of the lead, I could not draw a line with the accuracy I'm usually shooting for with the lathe (2-3 thousandths of an inch).

Friday, April 11, 2014

Grenades and Tanks

I just sold and shipped one Pulse Rifle grenade and I have a happy customer.

I'm still enjoying myself doing the machining. I've always liked working with metal, and having access to the tools that can really carve into the stuff is something I've wanted for a long time. I've also been checked out on the milling machine, which will eventually open up even more fabrication options for me.

On the other hand, dimensioning has been an ongoing struggle. I've finally settled on a tenth of an inch smaller in diameter and that chambered in an Airsoft shotgun replica. But length is still an issue (and was for the movie; despite the official claims, only three rounds would actually fit in the real prop.)

I've been reflecting just how many things I had to learn to get where I currently am on the lathe. I was also reminded recently just how much there is yet to learn. But that will be another post. I want to mention an odd yet very watchable 2012 anime I saw recently.

"Girls and Panzer" is about one year of a sports club at an all-girls high school. The name of the sport is given in the anime as "Sensha-do" and is variously translated by various media; I like the cleverness of "Tankwando" myself but the official translation uses "Tankery." Yes; it is about mock battles using lovingly restored W.W.II era tanks.

It doesn't sound like it could possibly work. It sounds really silly. It is silly. But it does work. Somehow, it is a really fun show to watch.

Yes, a lot of it is the usual meat and potatoes of anime set at a Japanese high school; friendships, friction with families, trouble fitting in, etc. And it does follow much of the familiar sports club script of the underdogs going into the nationals with the very survival of their school at stake (apparently the national schools administration was browbeaten into agreeing that if Oarai High School makes a strong enough showing in that particular extra-curricular activity, they will continue to be funded.)

But it also breaks with one of the traditions of much Japanese manga about certain sports (particularly martial arts) and most traditional activities, as well as with a cross-cultural tradition common to way too many shows in general. In the first, there is no stern instructor, none of the self-abasement, none of the rote learning. Although the students of Sensha-do very much respect the traditions of their sport, it is never presented that there is only one correct way of doing it, and it is certainly not presented as the protagonists having to move beyond their pride and learn the correct ways.

This is almost lampshaded. When their instructor shows up for the first day of practice, she gives the teams a map and says, "Get in, drive to these spots, then start shooting." They have to figure out how to start the tanks on their own -- one team by riffling through a manual, another by frantically Googling it, and at least one by having handy a tank fan who has really, really studied the subject previous to this.

In the second, the "gambatte" routine is downplayed. Too often, in Western works just as often as in Japanese (and I'm looking at you, Disney), the key to victory is having enough "heart." Of wanting enough, of trying anyhow, etc., etc. In "Girls and Panzer" the key to victory is often as not reading the damn manual.

Sure, they also come up with the usual maniac plans of such things, and there are also several key moments where the most important thing is to rebuild their trust in the team, and have hope they can continue on. But for all of that, it is shown over and over that merely wanting it a lot doesn't magically make things go right. You need to put in the work -- of practice, and of study.

This is a very strange universe. The entire idea of tank combat as a high school sport is ludicrous, and the anime doesn't help any with the Academy Ships (entire towns with their central high school built on top of massive aircraft carriers). Whatever is the educational equivalent of OSHA fled the scene gibbering long, long ago.

The show also passes the Bechdel test. Laps it, even. Only one named male character ever shows up, and the conversation about him is very short. Really, very few men, and very few adults, show up at all, and those that do don't do much. It is as I said a strange universe.

In any case, language is another part of the fun. For no particular reason, one of the amateur sub groups chose to throw in a bunch of gratuitous German. Now, of course "Panzer" is used as the common term for "armored vehicle," and the phrase "Panzer vor!" appears frequently, and one character says "Nein" once. And the ampersand in the official titles is transliterated on those same titles as "und." But the subtitlers just went ahead and replaced many of the occurrences of common, idiomatic Japanese with equivalents in German.

I thought my German was better than my Japanese (I don't know either language, not particularly) but I still usually caught the Japanese first. Japanese being such a contextual language anyhow, it makes a certain sense that "Hai!" can be translated as "Ja!" or "Jawohl!" or "Gute!" (and several other variations as well. But the translation is really reaching when a character comments on an explanation just given -- simultaneously with taking out her contacts and putting on glasses -- and the translation of the Japanese all-purpose syllable "Ja" is translated in the subtitles as "Alles klar."

Oddly enough, a quote from Guderian himself is spoken in the anime in what sounds to my ears as ordinary Japanese, but is properly given by the subtitlers as "Nicht Kleckern sondern Klotzen!" Yet, they completely miff the famous McAuliffe retort to a request for surrender (during the Battle of the Bulge), rendering it as, "They sure are nuts."

The translators leave alone a nice translation of Caesar's,"veni vidi vici" into idiomatic Japanese (at least I think it is; I only understand the "mitte" that begins it), but the same character's other foray into the classics, "Festina lente," is transcribed exactly.

This language fun is shared by the characters; the first time "Panzer vor!" is uttered by one, another swivels around with a shocked "Pants are for what?" At least, that's the subtitling; my Japanese is not up to understanding the rapid-fire idiomatic reply of the original anime. But the "subtler" joke is that the Japanese use British, not American garment terminology here. Which possibly makes later scenes with their cries of "What would panzer be doing in a parking lot?" and "Where are the damn panzers?" even funnier.

The cast really gets into it with the "Russian" school, though (all the various schools that field Tankwando teams are Japanese, but they chose to put on a show of various national stereotypes. The "American" school sets up camp -- in a blink-and-you'll miss it bit -- with folding tables, boxes of K-rats, a jeep, and Coke in the old-style glass bottles.)

One of the voice actresses is a Russian Language student, and during the big tank advance they SING "Katyusha." And then to add frosting to the moment of awesome, the same character reprises part of the song as a lullaby to her sleeping commander. My musical day was made even before the "German" school advances to the music of the Wehrmacht marching song "Erika." A song I partially learned myself during work on "The Sound of Music."

And I've made a botch of describing this thing. As I said above, it doesn't seem like it could possibly work, or be anything else other than silly, but it was very much worth watching.

And was perhaps one of the things that helped me recover from the slump of this past week. I'm still not back up to full strength, but at least I'm back to lathing, and I've got Holocron code spinning around in my head, too.

Saturday, April 5, 2014


It started when a talking snake began to tell me about God.

This is not a good thing. I'm not sure it is ever a good thing. In this case, it was every single channel of the stage snake -- which I'm trying to use to run proscenium microphones, monitor microphone, band needs, and drive speakers, too -- picking up a LOT of AM radio.

I tried the usual; checking the ground. Checking all the wiring for continuity and cross-talk. Walking the route of the snake to see if it was running parallel to anything bad. The only thing that did anything was lifting ground at the booth end, and that is not acceptable (if for no other reason than we need to run phantom powered microphones off it).

So did some reading up, and, yes, it does happen. There's a bit of an elephant in the room, though; for all the discussion on all the forums about what you should do to fix things, nobody seems to notice that the vast majority of cases involve foil-ground snakes. Me, I think that foil and drain combination makes a great capacitor, and that's got to have something to do with it.

Especially since a second snake, with woven shield, has an almost undetectable level of noise in the same building.

Well, that snake is the only one with the capacity we need. So back out there today with parts for more experiments. Clamp-on ferrites did nothing. From a quick analysis of the problem frequencies, I need eight wraps or more and the cable is a bit too stiff to manage that.

Adding capacitors to ground on both signal lines did help. Perhaps even enough to make the snake usable. But that means I have to take apart every single connector on the fanout, and add these caps. Plus ensure I have "shield" to chassis ground by wiring the connector shell to pin one on that end.

I ran a completely independent cable for the most critical need; the stage monitor microphone. And, well, THAT is picking up RFI as well. In the case of that mic line, seems a broader spectrum of noise, basically a white noise, with the same powerful AM station right down at the bottom of the band rising above with various rants about how Richard Dawkins is a horrible mean man and so on and so forth.

When I get back in, I'll add filter capacitors and test the ground lead on that line as well. But it all depresses me quite a bit. The theater's managers were as frustrated as I was with how hard it is to work in there and what a mess the sound system was. So we got the funding for me to clean it up. But I'm in there doing more temporary wiring (because there is a show going into tech and I can't afford to bring the system completely down while I work on it). And stuff like this happens; my brand-new wiring is showing some of the same problems I battled on the old system.

Oh, yeah. And the grenades are already selling. There's been just enough interest to scare me a little. Good thing I put a hard cap on the first run, but even then, I am one grenade away from having to race into the shop and lathe some more off.

Plus, I have to do a lot more of those stupid caps. I like the look, more-or-less, but it is a lot of finicky labor to get the plastic caps trimmed and sanded and painted up.

I did finally get around to taking screen shots off the Aliens DVD, and comparing them with my current drawing. And, yeah, there are a few places where my accuracy suffers. The rear slot, which forms a sort of "shank" between the brass end and the crimp that presumably marks the back of the actual grenade should be wider. And the front slots should be narrower, and have a v-shaped bottom.

I happen to like the flat-bottomed grooves, but I'm tempted enough to build another grenade with the new findings and see how I like that one. Another downside, though, is that most fan-made grenades have also had the flat-bottom grooves.

I've also been thinking about a different aluminium alloy. 7075 may be a little more scratch resistant, although I suspect anodizing is the real trick here.

There's also been interest at the RPF in one-piece grenade models (without detatch-able caps or working buttons). And, sure, spray paint would work on those, but this also seems like a good opportunity to try powder coating. One more class at TechShop to try to schedule in!

All in all, it is making me feel very tired.

Thursday, April 3, 2014

Please, Sir, won't you buy a grenade?

I've now built five grenades. So of course now is when I go back to check references, pull screen shots from the Aliens DVD, and see if the current dimensions will actually chamber in a real shotgun (the answer being; "more-or-less.")

I've also committed to building more of them. At least I have some options going forward. If for some reason I end up making more than ten or twenty -- unlikely as that may be -- it turns out the Tormach CNC milling machine at TechShop has a rotating table for the fourth axis. So you could more-or-less use it as a CNC lathe.

Really, though, the basic body shaping is simple enough to do the way I'm doing it. Even a template wouldn't save significant time; I just read the numbers straight from the plan through the DRO and make the cuts. It takes a little time to shape the body due to having to change tools, and a little time just to take down as much metal as has to come off (you can't just hack it off in one pass), but the significant time expenditure really appears to be the internal workings; the part that gives it a spring-loaded button.

For grenade #4, the press-fit plug was slightly undersized. When I started shaping the rear of the grenade the plug began to work free. I tried to bang it out from the button end and mostly succeeded in scaring the body of the grenade with the jaws of the vice. So I drilled it out, which worked a lot better.

I was actually able to chuck the damaged grenade by just the rim, using the four-jaw chuck, and I gingerly took a few thousandths of an inch off. Which cleaned up the worst of the vice scars, and now you can barely tell it apart from the others.

Grenade #5 I managed to create start to finish in under three hours. I was working a wee bit too quickly, though, and ended up cutting the button almost 2/10 of an inch too long. This is another difficult spot in the grenade; the exposed length of the button is determined by the depth of a blind hole drilled in the unfinished body, with any errors in that long drilled hole compensated for by adjusting the distance to the corresponding shoulder on the button. In the case of grenade #5, I added the error instead of subtracting it. And I was in too much of a hurry to measure the button before I seated the plug.

Which is a long way of saying the average construction time still has to be estimated at around five hours each.

I did one for fun. I did a second one because there were some errors in the first. Any more, I do for strictly mercenary reasons. So I have no compunction about wanting to get paid for my time. Depending on how I chose to amortize the tooling I bought just for this project, and by what number to divide the (large) minimum order of plastic caps, the fixed expenses work out to $14 to $23 per grenade.

Pricing out the labor cost of mailing, communicating with buyers, dealing with returns, etc. is beyond me. If I was pressed, I'd estimate another $5 to the assumed costs. And $6 postage within CONUS.

That leaves the rest as more-or-less hourly. Or as a "service," if you want to calculate musician-style. This number doesn't break $10/hour until I hit sixty bucks a finished grenade. And that's just the metal-work; the plastic cap adds a not-insignificant time investment on top of that.

So as much as I'd like to come down to $45 per grenade, I don't think I can do it.