Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
I’ve carried all my stuff in a belt pack since long before such things were fashionable and, quite some years ago, a friend made me a custom-sized one that’s been in constant use ever since. Of late, one of the zippers got cranky and finally failed completely.
An autopsy showed the middle of the cross bar on the tab had worn completely through, the stubs had bent outward, and the remains no longer engage the zipper tooth lock.
Worn-through zipper tab
I replaced the tab with a short length of chain and a jump ring, but I fear the pack fabric is also reaching end of life.
The Wouxun KG-UV3D has three holes along the base that capture three tabs in the battery case, with tapered edges to align the case with the contacts. After a few passes to get the dimensions right, the plate matching those features came out like this:
Base plate with tabs
The solid model shows the edge tapering down to a single layer:
Case Tab Base – Solid Model
The compound taper on the corners must match both the base and the sides of the radio. The bottom plate and shell have corresponding tapers that extend across the glued joints:
Radio interface tapers
That worked out surprisingly well, given the small dimensions and odd angles. The tabs, in particular, bumped right up against the 0.66 mm extrusion width; they’re 2.0 mm thick, so there’s barely one thread width inside the perimeter for fill. A bit of filing & slicing removed the usual enlargement at the end / start of each perimeter thread on the tabs, which is entirely acceptable for something this finicky.
The OpenSCAD source code with dimensions is all part of that post, but here’s the radio base shape that gets subtracted from the plate to make those tabs:
Radio Base Polygon – solid model
This seemed easier than adding a bunch of tiny pegs & triangles, but it’s certainly tedious working around a polygon:
Unlike my old ICOM IC-Z1A, the Wouxun KG-UV3D radio has mic and speaker jacks recessed into the case, so that a custom plug plate can absorb all the stress from forces applied to the cables without wiggling the plugs. Even better, there’s a removable cover with a mounting screw that can hold the new plate in place!
Wouxun plug mounting plate – overview
The first pass at the mount required a bit of filing, as the deepest part of the recess turns out to be not exactly rectangular. That’s (probably) fixed in the source code:
Wouxun plug plate – detail
The solid model looks about like you’d expect, with terribly thin side walls between the plugs and the not-quite-rectangular section. The whole affair is asymmetrical around the long axis; the not-quite-rectangular block and hole really are offset:
Plug Mount Plate – Solid Model
When printed, the thin sections come out one 0.66 mm plastic thread wide:
Wouxun plug mounting plate – build
I spent quite some time iterating through OpenSCAD, RepG, and SkeinLayer to make sure that came out right. This is from a later version with larger recesses around the plugs:
Plug Mount Plate – skeinlayer
Some epoxy eased down along the plugs will lock them into the plastic, with an epoxy putty turd over the top to stabilize the cables and terminal connections. That’s a T6 Torx bit to mate with the 2 mm screw (with a captive washer!) pulled from the Small Drawer o’ Salvaged Metric Screws:
Wouxun plug plate – trial fit
The OpenSCAD source code is part of the huge block of code at the bottom of that post, but here’s the relevant section:
The keyboard on my trusty HP 48GX calculator finally deteriorated to the point of unusability, so I tore the thing apart following the useful instructions there. The warning about applying force to the rivets that hold the case halves together gives you not the faintest concept of how much force is actually required to pry the mumble thing apart at the battery compartment; I finally invoked force majeure with a chisel scraper…
HP-48GX case rivets
I expected the calculator would not survive this operation and I wasn’t disappointed.
An HP 50g is now in hand. Here in late 2011 I’d expect HP’s top-of-the-line RPN calculator to sport a crisp high-resolution display, but noooo the low-contrast 131×80 LCD seems teleported directly from the latter part of the last millennium. The manuals are PDFs, which is OK, but their content is far inferior to the HP 48GX manuals. In particular, the editing / proofreading is terrible. I infer that the HP calculator division can barely fog a mirror and is on advanced life support; HP’s diverting all their money to, uh, executive buyouts or some other non-productive purpose.
The fact that HP sells new-manufacture HP 15C calculators doesn’t crank my tractor, even though I lived and died by one for many years. A one-line 7-segment display doesn’t cut it any more, even if the new machinery inside allegedly runs like a bat out of hell.
My HP 16C, now, that one you’ll pry out of my cold, dead hands. At one point in the dim past, I’d programmed the Mandelbrot iteration into it to provide bit-for-bit verification of the 8051 firmware for the Mandelbrot Engine array processor I did for Circuit Cellar: slow, but perfect. That calculator has a low duty cycle these days, but when I need it, I need it bad.
ABS plastic shrinks as it cools and large objects with thin sections tend to delaminate, as seen in the Barbie Pistol and a few other objects. The box for the GPS+voice interface is four threads thick and 35 mm tall, which provided enough energy to rip the side apart:
Box wall delamination
Solvent glue and a clamp shoved it back together again:
Clamping delamination
This one was extruded at 190 °C, which works fine for small objects and isn’t quite enough to fuse something like this. I’ll crank it up to 210 °C for the next iteration to see if that improves the result.
The first pass at the box that will eventually hold the GPS+voice interface for the KG-UV3D radio looks like this, from the end that engages the alignment tabs on the bottom of the radio:
Case Solid Model – Tab End View – Fit
The other end has the opening for the TT3’s serial connector to the GPS receiver, a probably too-small hole for the external battery pack cable / helmet cable / PTT cable, and a hole on the side for the radio mic/speaker cables.
Case Solid Model – Connector End View – Fit
The serial connector opening has a built-in support plate that’s the shape shrunken by 5% so it’s easy to punch out. That worked surprisingly well; the line just above the right edge isn’t a break, it’s a stack of Reversal Zits. This version is rectangular; the solid model shows the proper D shape.
KG-UV3D box – connector hole support removal
The bottom has battery contact recesses and counterbores (if that’s the right term for a molded feature) for the PCB mounting screws. In retrospect, those holes should be tapping diameter and the screws inserted from the top, through the PCB.
Case Solid Model – Battery Contact View – Fit
The colors mark individual pieces that get glued together. I can probably reduce the wall thickness on the top & bottom by three threads, which is in the nature of fine tuning. The latch mechanism that holds this affair to the radio is conspicuous by its absence…
The Smell of Molten Projects in the Morning 