The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

Author: Ed

  • Another Circumferential Seat-Frame Clamp

    This is another step along the way to getting our daughter’s radio firmly mounted to her Tour Easy, not tucked into one of the panniers. The general idea is to use a water bottle holder for the radio, with a seat wedge pack from an upright bike cushioning the radio. The secret ingredient is a circumferential clamp that mounts the holder to the lower rail of the bike’s seat frame.

    This clamp is basically the same as the ones on our bikes, but I doodled up a sketch with some illegible dimensions that almost matches the actual clamp; we may both find it useful the next time.

    Clamp layout sketch
    Clamp layout sketch

    Machining the clamp is straightforward: bandsaw a block of about the right size, square it up in the mill, helix-mill the clamp hole …

    Helix-milling the clamp hole
    Helix-milling the clamp hole

    Drill the clearance and tapping holes for the screw, bandsaw it in half, clean up the cut edges …

    Finished clamp parts
    Finished clamp parts

    Obviously, I didn’t put those nice bevels on the front side.

    Both previous water bottle holders required a spreader plate between the clamp screws and the holder’s screws, but this time the holder had a nice aluminum plate all by itself. It just fit on the Sherline and a bit of manual CNC center-drilled the curved plate and poked a jobber-length drill through the holes …

    Drilling holder for clamp screws
    Drilling holder for clamp screws

    And then it fit perfectly on the bike …

    Mounted holder
    Mounted holder

    A side view …

    Mounted holder - side view
    Mounted holder – side view

    Now, to find a wedge pack big enough for the HT and small enough to fit in the holder!

  • Casting Machinable Wax: Oops!

    Remelted machinable wax
    Remelted machinable wax

    I put a new bag in the vacuum cleaner while machining the prototype case for the bike radio adapters, which was a Good Thing: the swarf from those two halves filled the entire bag!

    I gutted the bag and dumped the swarf in a pot to melt down for another use. It started as a brick, but I figured having some rounds might come in handy. A bit of rummaging turned up some pill bottles of just about the right size.

    Unfortunately, I didn’t think quite far enough ahead: notice the shoulder around the right-hand end of the shorter cylinder? Yeah, the bottom of the bottle was bigger than the top…

    Fortunately, I don’t have a deep emotional attachment to the bottles, so carving it off the wax wasn’t a traumatic experience. Things would be different if I’d made a nice custom mold…

    Of course, the vacuum cleaner also sucked up the odd screw, paper snippet, older swarf left in nooks and crannies, and some of this and a bit of that. Most of the junk either floats to the top or sinks to the bottom, leaving the rest of the wax in good shape. I suppose I could filter the melt, but it’s pretty thick & gooey, even at 300 °F, and I doubt my cheesecloth is up to the task.

    Memo to Self: Do a better job of cleaning up before machining the wax, OK?

  • Adapting an Earbud for Bicycle Use

    I favor a small cylindrical earbud with a good seal inside my ear for use with the amateur radio on my bike. These things come with back vents that allegedly improve their bass response; that’s not a concern for communications-grade audio and, worse, the vent produces a tremendous amount of wind noise.

    Earbud with back vent
    Earbud with back vent

    The solution is straightforward: put some tape over the vent!

    Kapton tape over vent
    Kapton tape over vent

    I used Kapton tape, because I have it, but in point of fact the snippet of duct tape I applied on the first ride (having forgotten to do it on the bench) worked just fine. A drop of epoxy would be fine, too, if you were a bit careful about not letting it ooze down inside the case while it cured.

    Despite the fancy appearance, this is a random pick from the assortment of earbuds I’ve bought at $10 or less over the last few years. According to my golden-eared assistant, the audio quality varies dramatically among the assortment, but they all work reasonably well between 300-3000 Hz. I suspect the insanely cheap ones on eBay are essentially the same things, although IMO they’re intended to collect large quantities of high positive ratings: caveat emptor.

    Speaking of caveats, insert the usual safety caveats here.

    Note that we’re using one earbud for tactical comm, not boppin’ to the music, and the audio level is low enough we (well, I) can’t hear diddly at speeds over 15 mph. Your jurisdiction may prohibit “headphones” or “earphones” or some such, so behave accordingly.

    All the officers I’ve met think the radios are a great idea, if that means anything.

  • Machinable Wax: First Cuts

    This is a prototype for the case that will eventually hold a TinyTrak3 GPS-to-APRS encoder, along with a homebrew circuit board that combines the APRS data with voice from the helmet mic. The case slides into the back of our ICOM IC-Z1A and W-32A HTs, replacing the battery case.

    It’s the most complex CNC machining I’ve done so far and I figured that was the perfect reason to carve up a block of machinable wax that’s been sitting on the shelf for far too long.

    The exterior view shows why you use wax for the first pass… the ugly gash came from not retracting the end mill before the final G30, combined with trying to clamp a bendy shell in the vise. That was, of course, the final operation on that part!

    Machinable wax case - exterior
    Machinable wax case – exterior

    The inside view shows the TinyTrak serial connector cutout (left half), as well as the shoulder to support the audio interface circuit board (right half). The two holes at the upper-right are 4-40 clearance for screws that serve as contacts for the HT’s battery connection and hold the board in place.

    Machinable wax case - interior
    Machinable wax case – interior

    These survived far too many setups and takedowns as I figured out how to get all the cuts laid out and in what sequence to do everything. Now that I know a bit more about what to do, the plastic version should come out better; I’m sure I’ll also make better mistakes.

  • Bell Bicycle Helmet Teardown

    Having gotten our new helmets up & running, I decided to tear down my old helmet to see what’s inside. The thin plastic shell was already cracked (and probably brittle from years of sun), so it tore off very easily. The foam structure was in good shape, but I was surprised to see that everything’s held in place by glass filament tape!

    Peeled bike helmet
    Peeled bike helmet

    The straps pass through an H-shaped locking clip tucked into a recess in the rear apex (to the left in the picture). The front strap simply loops over the foam shell (to the right of the tape crossing on the right), where it’s held in place on double-sided adhesive foam tape by the glass filament tape.

    All in all, a low-cost, low-weight design that works just fine.

  • Visor-mounting a Third Eye Hardshell Mirror

    Tweaked Third Eye Mirror
    Tweaked Third Eye Mirror

    The Third Eye Hardshell Mirror was designed back in the day when Bell Helmets had actual hard plastic shells over a foam core, with a lip around the shell’s edge. These days, helmets consist of an elaborate foam structure with a paper-thin plastic covering. Mary’s helmet is like that, but it has a visor and I figured the mounting clamp might grab onto that.

    It almost worked, but the edge of the clamp tapered the wrong way: tightening the screw tipped the clamp away from the visor lip.

    Solution: chop off the offending part of the clamp, file off the sharp edges, and screw it in place. Works like a champ.

    I’m not convinced this mount will survive the test of time, though. We already know that the clever ball joint will eventually lose its griptivity, but that’s fixable.

  • CycleAware Mirror Repair

    Original CycleAware Attachment
    Original CycleAware Attachment

    While installing the audio gear on our bike helmets, I found a defunct CycleAware Reflex helmet mirror in the big box o’ bike stuff.

    This pic shows that the mirror attaches to the boom through a clever ball joint that allows both rotation around the mirror’s long axis and a slight amount of tilt. Unfortunately, after a few years, the ball stem breaks and at least one of the socket petals snaps. It’s a nice  plastic design that’s totally unsuited to a few years of more-or-less daily bicycle travel.

    The repair was easy enough, particularly because I think the boom has enough adjustment range to handle the job on its own (and I don’t care about how it looks). I filed off the stem stub and milled a slot for a 2-56 machine screw along the back edge.

    Milling slot for screw
    Milling slot for screw

    Then you just slide a brass tube from the cutoff box over the end of the boom around some JB Weld epoxy, shove the screw into the blob, align the mirror with the boom, and let it cure.

    Reinforced attachment
    Reinforced attachment

    Although it’s not shown here, the helmet attachment is aligned with the mirror at right angles to the helmet bracket. That puts it in roughly the proper position with the boom bent as usual.

    I don’t actually plan to use this one for anything, but if I need a somewhat scuffed mirror in a pinch, well, it’s in the box!