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.

Tag: Improvements

Making the world a better place, one piece at a time

  • Third Eye Hardshell Mirror Repair

    Alas, the mirror I installed this spring didn’t survive our bicycling vacation; it succumbed to the second of three stuff-all-the-bikes-in-a-truck schleps arranged by the tour organizers. Being that sort of bear, I had a spare mirror, duct-taped it in place, lashed it down with some cable ties, and we completed the mission.

    So.

    Back to the Basement Laboratory Plastic Repair Wing.

    The strut broke just behind the ball at the mirror, which implies the mirror plate got stuffed against something, rather bending the strut. The ball joint still worked, so I maneuvered the stub perpendicular to the mirror.

    Drilling the strut
    Drilling the strut

    Normally I’d try to re-glue the joint as-is to get the best fit, but past experience shows that if it breaks once, it’ll break there again. I wanted to put some reinforcement into the strut, not just depend on a solvent glue joint. Some rummaging in the brass tubing stock produced a 1/16-inch diameter aluminum (!) tube about 18 mm long: just what’s needed.

    So I filed the deformed plastic flat & perpendicular to the stubs, mounted the strut in the 3-jaw chuck on the Sherline’s table, lined the spindle up with the axis, and poked a 1/16-inch hole into the strut. The alignment looks decidedly off in the picture, but it’s actually spot on: what you’re seeing is some swarf clinging to the far edge. Honest!

    Then I grabbed the mirror plate in the 3-jaw, lined up on the stub, and drilled maybe 4 mm down, which was roughly to the middle of the ball. The tubing was a firm push-fit in the hole and I hope it won’t over-stress the plastic into cracking.

    Gluing the mirror strut
    Gluing the mirror strut

    Run the spindle up, remove the drill, grab the strut in the chuck (actually, I had to swap in the larger chuck first), dab some Plastruct solvent glue on both ends, align the strut with the stub (they’re actually square in that section), run the spindle down to ram the tubing into the strut, then a bit more to apply pressure to the joint. I made the total hole depth about 2 mm longer than the tubing, so as to avoid the embarrassment of having the ends not quite meet in the middle.

    No CNC; pure manual Joggy Thing action.

    Let it cure overnight.

    It’s now back on Mary’s helmet, with a pair of black cable ties ensuring that it won’t pop off, and seems to be working fine. I’m sure the ball joint will fail later this year, although that won’t be due to this repair.

    Mirror on helmet again
    Mirror on helmet again

  • Improved Tour Easy Chain Tensioner

    A discussion on that post reminded me of this old project: replacing the chain pulleys in the midships chain tensioner on my Tour Easy recumbent.

    The problem is that the original pulleys used steel bearings in a plastic race, for reasons that I cannot fathom. They last for a few thousand miles, then get very wobbly and noisy. The solution, as nearly as I can tell, is to replace them with pulleys using cartridge bearings.

    This is what one looks like after four years slung below my bike. Surprisingly, the bearings still feel just fine, even though they’re not really sealed against the weather.

    Tour Easy - Cartridge Bearing Chain Tensioner
    Tour Easy – Cartridge Bearing Chain Tensioner

    Gotcha: the OEM pulleys are not the same OD / number of teeth as pulleys found in rear derailleurs.

    Soooo, after a bit of Quality Shop Time, I had these…

    Tour Easy Replacement Idler Pulley
    Tour Easy Replacement Idler Pulley

    This is where you really want an additive machining process, as I turned most of a big slab of aluminum into swarf while extracting each pulley.

    The first step is to drill holes around the perimeter where the chain rollers will fit, plus drill out as much of the center bore as possible. Then mill down to the finished thickness across the roller holes and helix-mill the bore to size.

    Side 1
    Side 1

    Flip it over and mill the other side to the proper thickness.

    Run it through the bandsaw to chop off all the material beyond the outer diameter.

    Grab what’s left in the three-jaw chuck and mill around the perimeter to get a nice clean edge.

    Side 2
    Side 2

    And then it Just Works. I made another for Mary’s bike, but she said it was too noisy (which is why they used plastic rather than aluminum) and I swapped it for a Terracycle idler.

    This is from back in the Bad Old Days before EMC2’s version of G-Code supported loops. You don’t need to see that code, trust me on this.

  • Stopping Bike Helmet Strap Creepage

    My bike helmet sports a mirror, microphone boom, and earbud, so I generally hang it from the top of the seat on my Tour Easy. There’s a convenient peg seemingly made for capturing the triangle of strap that normally goes over my ear and, up to the point where I set up this helmet, everything was good.

    Helmet hanging on Tour Easy seat
    Helmet hanging on Tour Easy seat

    After about a week, I noticed that the buckle was grossly off-center under my chin: the straps had shifted to one side.

    Come to find out that the front strap on this helmet passes through an opening across the central member, below the plastic covering. Judging from the teardown of an older helmet, Bell used double-stick tape to hold the strap in place. Applying a constant force in one direction (I’m a creature of habit, the helmet always hangs from its right-side triangle) gently pulls the strap through the passage.

    Front strap passing through helmet
    Front strap passing through helmet

    So I cut two slabs of closed-cell foam and jammed them into the opening atop the strap, one from each side, with a screwdriver. That forced the strap against the adhesive and mechanically wedged it in place.

    Problem solved!

  • APRS SmartBeaconing Parameters for Bicycling

    Setting relatively prime beacon times for the GPS-to-APRS trackers on our three bikes worked quite well, but I wondered how much better SmartBeaconing would be. The trick is getting the numbers right for typical bicycling speeds.

    Here’s some settings (from the TinyTrack3+ config program display) that seem to work reasonably well…

    SmartBeaconing Parameters
    SmartBeaconing Parameters

    The general idea is to beacon every 10 minutes at rest and about three / mile in motion.

    The only time I hit 3 MPH is up a really nasty hill, the likes of which I avoid with all due diligence. On the other end, 24 MPH is pretty much as fast as I can go for any length of time; faster, certainly, on downhills, but those are rare & precious commodities on most rides around here. The Slow and Fast parameters control both ends of that range. The beacon rate increases linearly below the Fast speed: 180 seconds at 12 MPH, which is roughly what I used for the constant-time setting.

    Note that the Rate parameters are actually periods. Rate is thing/time, period is time/thing. The period varies as 1/speed, while the rate varies directly with speed. See the SmartBeaconing writeup or the TinyTrak3+ doc for the algorithm.

    The Turn Slope parameter is the most confusing. It has units of degrees/MPH degree·MPH and serves to modify the Min Turn Angle so that you must turn more sharply at lower speeds to generate a beacon. This works better for vehicles with a wider dynamic range: our bikes tend to stay within 5-20 mph and a factor-of-four doesn’t affect the basic angle very much at all.

    My track through a residential area shows pretty good “Corner Pegging” for those settings and, in any event, it’s much better than the simple every-three-minutes beaconing I’d been using before. On the other hand, this is in a low-RF-traffic area with a digipeater about a mile away across the Northway, so very few packets get clobbered.

    APRS Track with SmartBeaconing
    APRS Track with SmartBeaconing

    Perhaps setting Turn Slope to 240 degrees/MPH degree·MPH with a Fast Speed of 24 MPH and a Turn Angle of 10 degrees would be slightly better. At top speed the minimum turn angle would be 10 + 240/24 = 20 degrees and nose-pickin’ speed relaxes the angle to 10 + 240/6 = 50 degrees. On the other hand, that track looks pretty good as-is!

    One problem with three bikes in close proximity (the track above is just me) is that we’ll all be turning at about the same time and, thus, sending beacons almost simultaneously. This will take a while to sort out, given that many beacons never make it to a receiver…

    [Update: A correction shows why the units aren’t what I expected.]

  • APRS Beaconing: On Being Relatively Prime

    I ran into an amusing situation on a recent family bike ride with our GPS-to-APRS trackers running: my ladies were transmitting a few seconds apart. As a result, I had to listen to a pair of very short data bursts in quick succession throughout the whole ride.

    Under normal circumstances that doesn’t happen, because I set the TinyTrak3+ trackers to delay during and wait a second after a voice PTT that collides with an automatic beacon. Somehow they never managed to delay an APRS beacon to knock the synchronization off kilter.

    So I tweaked the automatic transmission intervals to make us relatively prime: 179, 181, and 191 seconds. That’s close enough to the original 180 seconds as to make no difference, while now ensuring that we won’t collide with each other for very long even if we should get aligned.

    An alternative is SmartBeaconing, which I’ll turn on in a while after I collect a bit more data.

    A useful table of primes is there.

    If you have some spare CPU and power, you can join the Great Internet Mersenne Prime Search and help find new primes, albeit ones much larger than I need…

  • Yaesu FT-857 Front Panel: Up-Armored Plug

    The  remote cable for the Yaesu FT-857 I have in the car terminates in an 8-pin modular plug. The connector body has a cutout for the round rubber (?) insulation around the cable; it’s not set up for a standard flat 8-wire network cable. However, the cable makes a right-angle bend immediately outside the Front Panel to fit inside the confines of the remote mounting case, which pulled the insulation out of the connector.

    Connector with displaced insulation
    Connector with displaced insulation

    The electrical connections are fine, but that can’t last. I finally got around to armoring that bend to (I hope!) prevent any problems. Contrary to what you might expect from my proclivity to blob epoxy on everything, I blobbed on hot-melt glue to hold the wires in place, as well as turn a bit of the cable into a rigid body. Even in a hot car, this ought to work fine…

    Connector with hot-melt glue
    Connector with hot-melt glue

    I put some ordinary adhesive tape on the back of the Panel, butted up against the connector body, to keep the glue out of the socket and off the (back of the) Front Panel. That prevents the connector from becoming one with the Panel.

    Pause while the glue solidifies, release the latch and pry the connector+glue off the tape with a small screwdriver, trim the excess glue, then peel the tape off the Panel. The connector snaps into place just like it should and the wires no longer have any freedom of motion.

    Here’s what the modified connector looks like in all its glory. The cable really does bend downward slightly beyond a right angle in order to fit into a recess in the Front Panel.

    Finished connector kludge
    Finished connector kludge

    This isn’t suitable for a connector getting a lot of the old in-out in-out, but the Front Panel remains in place for months at a time and this should delay the inevitable failure.

  • SPD Cleat Backing Plate: Filling the Gap

    SPD cleat backing plate gap filler
    SPD cleat backing plate gap filler

    Mary’s feet are exquisitely sensitive to irregularities in the insoles of her shoes, which poses a real problem with her bike shoes: those SPD cleat recesses are no good at all.

    This is a view down into one shoe, with the SPD cleats adjusted all the way to the rear. That leaves a large recess in the front, which was painfully obvious to her sole. The white shape is the gap filler…

    I pressed a sheet of paper across the gap to get the general shape, traced it twice onto a slab of 0.060-inch aluminum with a nice pebbly paint job, and cut the two pieces out. A few conversations with Mr Belt Sander, a few licks with a rat-tail file, and they dropped right onto place. The recess is slightly curved, but I didn’t have to bend the pieces to fit.

    I laid duct tape across the whole affair, put the insoles back in place, and it was all good.

    The backing plate is 0.072 inch thick and she was content with the difference.

    In previous shoes, with the cleat near the middle of the adjustment range, I’ve stuffed epoxy putty into the gaps. That works, but it doesn’t bond to the (miracle engineering plastic) soles and tends to crumble. This is Not A Good Thing…