I'm Back!

Was feeling awful for a good three weeks. Yesterday woke up like it was Saturday; like I'd been pulling long hours all week and finally had a chance to sleep in; that sort of "still sore and kind of weak-feeling, but basically feeling refreshed" thing.

Went out to the city and spent ten hours at the lathe. Was taking my time, but being efficient; cut fourteen new primers so I'd have a small stock of them, fitted the guts in two bodies, and then went and cut two more full-function grenades from scratch. Even with the loss of efficiency in doing them serially instead of in parallel, took less than two and a half hours each. 

And still had a spring in my step when I returned (with a heavy backpack filled with aluminium stock, metal working tools, laptop, and a thermos full of coffee.)

Somewhere in there I roughed out possible layouts for the Duck Light. That thing is still bugging me. For me, the platform works, because I can program and I have the ISP to access a minimal AVR. Well -- there's a potential solution via the XBee node, to include in the serial command set to the Duck Light commands that will re-write constants held in flash. 

Still, the very flexibility of the thing is my boon but the downfall in making it really useful to non-programmers. I'm building a tool that allows me to create a lighting look for each specific project as it comes up. I can really only think of one option that I can hard-program so it is a mere button-press or the quick soldering of a jumper away for the end-user who doesn't program, and that's making a lantern (and even then; the power of the complete platform is I can tweak the color, the depth and rate of the flicker, the length of the fade, even the brightness.)

Sigh. Even if I make up a remote programmer wrapped in a GUI that is friendly to the end-user, it wouldn't handle the hardware end. Even something as simple as adding a capacitance sensor, or a microphone input hard-coded to a DalekEye circuit, means jumpers, or dip switches, and of course adds to the number of components on the board.

(For that matter; I really need to allow space for an accelerometer/accelerometer breakout in the footprint. Which, like the XBee, is an expensive part so it doesn't want to be hard-soldered as part of the basic package.)

The Arduino Problem

There's probably another name for it. I think of it in terms of the Arduino shield, however.

When the first Arduino board was made, due to either mistake or some rationale which has long been forgotten, one of the headers was offset by about half a standard pin space.

This meant that protoboard doesn't fit on top of an Arduino with standard headers. And that meant that ever shield (aka the stackable daughterboards which fit on top of an Arduino and add functionality) had to echo this error in pin placement.

So what happens when the next edition of an Arduino board comes out, or a third-party wants to make a compatible? If they want to remain back-compatible with the existing shields, they have to reproduce that same pin spacing. The Arduino board is basically stuck with it, and the longer it goes uncorrected, the more difficult it would be to correct.



I'm in a similar spot with my grenades. I was noticing today as I was cutting tape for the tops that my hand-ground 3/32 grooving tool has shrunk to close to 1/16th. And there are a couple places where I may have been mislead by my earlier research, or that I find aesthetically compromised; the button should probably be shorter, the "crimp" further from the base, the grooves deeper. And I really should have worked out how to give the blue and green caps a different visual look.

Plus, there's multiple places I've learned better ways to machine, or necessary choices. Like adding a "tape slot" to the solid-body grenades, or like the changing angle on the "crimp" so it can be cut without scratching the metal of the base.

But I'm already shipping second orders to previous customers. So I have to keep as much of the look of the very first production run, in order that they continue to look like they are identical. And as much as possible, matching the look of the other major fan-made runs, so one cosplayer can get away with wearing a dozen cold-cast grenades from another builder on his webbing, and using one of mine as a "hero" prop.



I'm still tinkering with the process. The last two full-function ones took 2.5 hours each from start to finish. I'm leaving the compound rest at 15 degrees through the process and only moving the turret twice. As another trick, I clamp the bits into the tool holders at an angle (I can get away with stuff like this on aluminium!) That way, I can leave the tool holder aligned for grooving, and make several of the tool changes without losing zero on the DRO.

I'm still finding little tweaks. I just realized today I need to break the internal edge of the through-hole; what happens, is when I press the plug in the front of the grenade is very slightly deformed. And in some, the rough, sharp edge of the front of the hole now pinches the button and scratches it when it is pressed.

I've also realized that pushing a "dead" tool (that is, with the lathe stationary) into the metal to find zero is a bad idea; I'm leaving tiny pock-marks on the piece.

And so it goes. I'm eager to stop lathing these, and move on to something different.

Falcon to Eagle to Pigeons

I may have to back-burner my Tomb Raider fanfic "Day of the Falcon." (Falcons so far; Horus, the falcon-headed Egyptian god, the Tribute of the Falcon of the Knights of Malta, and a rival tomb raider calling himself Juan Carlos "el" Halcon...)

I'm trying to throw together the 0.5 version of the Duck Light, despite funds being tight for ordering parts. Started laying out the PCB in Fritzing, which may actually work for my needs, but I've been meaning to learn the free version of EagleCAD. Oh, yeah -- and there's a nice-looking open-source freeware option called KiCad that is worth checking out.

In re learning software packages, I still haven't gotten facile with Blender, which means I'm starting work on the Jubal Early with Carrara. Sigh. I've been introduced to the slicing and tool path tools I need to turn it into g-code the CNC milling machine can use, but that's going to be a learning curve as well.

I'm very worried I won't have enough time to properly repair microphones before I have to start Feeding the Birds -- aka mixing Mary Poppins. And I'm renting out my own gear over the same time period, which at least will relieve some of the financial stress.

And the KP/-31 receiver is still sitting on my desk. Which isn't bird-related at all, sorry. I read through a thread at a gunsmithing forum and that just underlined how many operations there are to machine the thing from scratch. 3d printing would also be expensive, and the shapes are wrong for CNC milling (not all in one piece, anyhow). Very possibly making a master model and casting that would be the most efficient, despite my worries about the strength of the result.

So I'm looking again at welding. I'll take a grinder to the parts and see how that goes first...

Minimizing

I'm in the cash flow hole right now. Contracts are started, but the first checks are weeks away. I hate being so low in cash. Makes me want to curl up at home with the lights low and hoard food instead of eating it.

The Jubal Early build seems plausible. I'd be surprised if more than a half-dozen people went for one, though. And the tool-up is a couple hundred bucks and 40-60 hours. Even right here at the start of it, it would help my 3d design if I had the Pachmayr grips to measure. But those are $36 a pop. 

The M40 grenades are a better story that way; I have enough metal to finish the current orders.

I'd still like to come up with better ways to do them. I did some research on the fourth axis of the Tomach CNC milling machine. And, actually, there's an even more clever trick; I've seen a guy chuck the stock in the head, and clamp the tools to the workbench, turning it into a sort of poor man's indexing CNC lathe.

But the set-up time for any of this is simply too large, in my opinion. The two things that would save the most time on these would be to have enough tool holders to properly use the quick-change tool post, and to have metal in lengths to where I could re-chuck and assembly-line it. 

Might actually make sense to cut billets to length and center drill them, then work between centers; at which point I could use a template or a saved set of tool offsets in the DRO.

In any case, there's good argument for moving on to props that cost more (even if just in terms of raw material); because even if the markup stays the same, 20% of $250 goes a lot closer towards paying for the next month of TechShop membership than 20% of $45.

Hrm. I just realized there's a couple of alternates to TechShop where I might be able to use a wire-feed welder. With some sacrificial blocks of aluminium or even wood, I might be able to grind out and re-weld the Suomi. Because as attractive as machining from scratch is, that's a heck of a project.

(One downside to welding is that crosses the Federal firearms line again. Unless I very carefully destroy some of the receiver in the weld process to make sure it can not seat the full-auto bolt.)

Just to be silly, I investigated what Tomb Raider 2013 plays like if you completely ignore the entire "salvage" mechanism, and make no effort to maximize skill progression either. That did make the battles a bit tougher -- the boss battles are quite annoying when you don't have anything but the base Dodge/scramble, for instance. But I got through to the radio tower in one hour, and through to the helicopter in about two and a half hours. Skipping through the cutscenes also saves, I dunno, maybe twenty minutes there as well.

Oh, yeah. And got through the major battles with the base, unmodified pistol (no salvage, remember?) Which also proved annoying, as it is significantly less damage and even head shots don't take down many mid-game mooks. I got killed a time or two, but mostly made it through the big set-pieces on the first try. Which is still better than I'd doing on those dratted QTE's.

In the last of this thematic topic, I'm still working up the circuit for my Duck Light, and pretty much determined it is going to be largely (if not entirely) SMD even for the prototype. But I'm thinking it may be worth doing a quick through-hole version right now so I can offer it to the design team on the next production. Except, of course, for the whole not-enough-cash-to-purchase-pcb's-this-week problem.

Where's Henry Ford?

Actually, I'm not sure I'm even up to Winchester. No luck in assembly-lining the grenades -- each one is still a manual process and each one is a little different.

Went in today. First task was to find a way to hold one from the other day that I'd forgotten a cut on. And then I cut too deep. Drat.

Ran off a second solid-body and was starting to get into the groove. Set up for the finishing pass, threw on the half nut for a powered feed -- and engaged the cross-feed instead of the longitudinal. Drat. Fortunately, this time I knew I could rescue the piece as long as I didn't re-chuck it. So turned it into another full-function body. Of course, that meant bringing out a bunch of other tools, and pretty much killed the assembly line.

Then ran short of metal. Was just enough on the last bar to finish the order if I was clever. I wasn't quite clever enough. Did two passes in the wrong order. Set up for a left-handed cut, got the power feed set correctly for that. And going "backwards" must have thrown me, because when it came to the moment where you throw off the half nut and take up the motion smoothly with the traverse wheel...I grabbed the wrong wheel. Drat.

Oh, and finished the day destroying another chunk of brass stock trying to part it. At least this time I figured out a better method; just cut a v-groove where the part should happen, and hack-saw it off right in the lathe.

Next set, in progress; the solid-bodies need to be painted, the two full-function need the spring-loaded buttons installed. Unfortunately, all the primers I ran off yesterday are a trifle large; only two of those in the bag were useable. The two grenades on the right are mistakes; my original (at the old dimensions), and the one I tried to rescue and failed.

The one thing I can say is I'm starting to like that 7075. It is very springy; I have to adjust to the tools springing back on me, and dealing with chips on the rough passes is still a problem. Also, it is so tough I can't really dig the knurling in as deep as I'd like on the grenades. But on the upside, with the right feeds it makes a very shiny, hard surface. It feels tougher, and even weighs noticeably more.



I've been looking at the Suomi some more. The plasma cuts they made through the receiver left some pretty large gaps. Just welding isn't enough; I'd need to do filler welds to bridge those gaps. And it also made a total mess of the threads where the end-cap goes.

But machining is no simple task, either. There's a lot of complex slotting for the magazine well, and some big chunks of metal that need to be constructed for that, too. And it seems impossible to do without welds -- which means getting checked out on MIG, and then getting enough practice in to do them clean.

The Men Who Stare at Gats

I was given a project some months back. I said I'd know more about its feasibility when I'd had a chance to lay out the parts I have and stare at them for a while.

I stared at them today.

This is a de-militarized KP/-31 "Suomi," a Finnish-made submachine gun introduced in 1925 and used in World War II. The "de-militarization" consists of -- as you can see from the photograph -- using a torch to cut the receiver into little bits.

My task is to make a new receiver. Not, I hasten to add, a functional one. In fact, there's some nice little laws I'd run afoul of if I made more than 80% of a functional receiver and sold it or was otherwise recompensed for the work. Figuring out where that line lies, and making sure what I build can't accidentally be fired, is going to be part of the problem.

So how to it?

There are two basic strategies (both of which are also applied by gunsmiths who do intend to end up with a functional weapon at the end). The first is re-weld. This might be the fastest, especially as I have no need of the special jigs and resulting accuracy of the gunsmiths. I just need the parts to more-or-less fit.

The other is a new receiver. And where I part company with the gunsmiths is in materials. My first impulse was to sculpt the entire thing and cast it in resin. I might even be able to take some impressions from the existing scraps (or negatives from the parts that mate with them) in order to save on hand-sculpting.

The best argument for sculpting is that it is the most iterative process. At any point, I can add more material back in; there's no risk of cutting too deep and ruining the piece. The biggest downside is lack of strength; the necessary shapes include some very thin portions, and the weight of the barrel and the pressure of the trigger assembly are going to put a lot of stress on them.

Which leaves metalwork. The shape is too complex and the bounding box too large to make subtractive methods optimal, as much as it has a surface attractiveness to simply CAD the entire thing and CNC it out of a single block of aluminium.

And additive methods bring back some degree of iteration; you can work on a sub-assembly without risking the entire piece.

In the real weapon -- and also in the "80% kits" that used to be commercially available (they seem to have dried up), this is how it is done. The "tube" and "sidewalls" are machined separately, then welded together.



So that's my working assumption; take a tube that's as close as possible to the required ID, lathe it down, cut the rear threads, mill out the lugs, mill ejection port and a long slot along the bottom. Then cut into a slab (or several pieces) of flat stock to create the sidewalls, the part that hooks into the stock, and the magazine well.

Press-fit is not going to work here, though, so aluminium welding, and then clean-up of that. That's a lot of work. And a lot of the cuts and holes are necessary because so much of the receiver is exposed; is the look of the gun. And they have to be right to fit the existing parts that show externally, like that trigger group. There's also a question of how to treat aluminium so as to fit in with the look of the other metal.



There may be a third route. It might be possible to simulate the look of the receiver and support the other parts of the gun with rods and careful bits of water-soluble glue. I'll have to stare at it longer, but at the moment that isn't looking very plausible.

In any case, it doesn't seem the best "first project" for the mill. It might actually be a little easier to tackle this thing:

This is one of an excellent run in pewter-cast of the pistol used by the character Jubal Early on Firefly. Not my favorite design, but apparently there are enough people interested in one to justify looking at trying to build a few. It looks like a natural for CNC, with a little traditional machining to open some of the mating slots and tapped holes.

Well, I still have seven grenades to go to fill the current orders. That's at least two more days of machining, plus painting time. Pity I'm not making enough money at this yet to pay for next year's TechShop membership...

Keep them spinning

I feel like I'm backsliding on machining. Does not do much for my confidence in finishing that submachine gun...or doing a limited run of Jubal Early's for sale at the RPF.

I've got several orders of solid-body grenades to finish. Those do go faster, but I'm still at almost two hours (with set-up and clean up) each. So I tried a couple of tricks to speed things up, with mixed results.

The lathe has a quick-change tool post and the ability to remember tool offsets. But that doesn't help if you move the post or rotate the cross-slide. So the first trick was to clamp my cutter at a slight angle, meaning I can leave the tool post aligned for parting off and not have to change that.

The next trick was to leave the cross-slide at 15 degrees instead of 45. That meant I didn't have to rotate between cutting the chamfer (and doing the knurl) and the rest of the cuts. It does make it slightly harder to align some of the other cuts, though, and it means I'm bringing the knurling tool in at right angles to the work instead of along the normal of the resulting knurl.

Unfortunately, that put the cutter to where the work was rubbing along the relief. I figured out what was going on soon enough to rescue the piece, though. But I didn't get so lucky with the next one. Cut the first groove at .174 instead of .274, realized the mistake, parted off. Then realized I could chop the front off and re-use it for the other style of grenade. Except I'd parted already. I cut down the rim, and was just able (with a lot of gauge work) chuck it in over the rim and make the cuts. But I was cutting backwards now to make the final cuts. I cleaned up a battered left-handed cutter from the bin, but it still made a poor finish. And I'd slipped up in a couple other places trying to take the measurements backwards from my usual references.

So two hours of clever improvisations and I had a ruined piece of metal anyhow. Well, at least I learned a little. Didn't help me, by the way, that all the way through this another TechShop member was plowing through some really pretty lightsabre hilts. With the cleanest knurling I've seen done in that shop, too.

Well, it helped in one place. Seeing him hog on 4" billets made me rethink my first cuts. The book value for Aluminium with HSS bits is 250-350 surface feet per minute. I'm starting with a 1" billet and coming down to .790, and that means the machine RPM should be in the 9600 range. However; carbide tools can be run at twice the speed of high-speed steel.

Well, I'd been running at 9100. I bumped up to 1250 RPM and it felt pretty good. And I reduced it down to two roughing passes instead of four, taking over a tenth of an inch of metal off with each pass. This does stress the metal a little, but I'm leaving .004" consistently (and adding it to the other cuts), for a single finishing pass. Since these don't have to be fitted into other machinery, only the nominal finished dimension, and having a smooth finish, actually matter.

Unfortunately I've still got several tool changes, and because I can't chuck around the rim, I can't remove the main body until I've made that finishing pass. And the solid-body ones require a flawless cap, so I can't drill those out and hold between centers. But, still, there's probably some way I can make this a little more efficient. Oh, yes, and the tool holders seem to be going astray; there's not even enough to leave all my tools in holders as I work (which kind of negates the usefulness of the quick-change turret).



I got into a conversation with a volunteer at one of my theaters (the one where I'm trying to fix up the sound system), and realized I don't have any of the music I've created for plays on my current laptop. So I spent an afternoon or two fixing that. And listening to a lot of old work. And might post some of that here some day. Yeesh. I've got that new keyboard, and the new library, and I really should hook that up some day...