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: Repairs

If it used to work, it can work again

  • Tour Easy Rack: Front Mount Screw

    Long ago, I conjured a front rack mount from an aluminum bar across the seat struts on our Tour Easy recumbents, with a spherical washer soaking up the angular misalignment. The rack on Mary’s bike developed a serious wobble due to a missing screw, which was easy enough to replace:

    Rack mount screw - rear
    Rack mount screw – rear

    From the side:

    Rack mount screw - side
    Rack mount screw – side

    It’s a 2 inch screw sawed down to 1.5 inch, ground to shape, then run through a die to clean up the threads.

    The nylon lock nut over on the left should keep the screw from working its way out of the tapped aluminum bar. On the other paw, a dab of Loctite survived nearly a decade of heavy loads and vibration.

  • Bypass Lopper

    Some surreptitious brush clearing called for a tool larger than our wonderful Fiskars PowerGear pruner, so I unearthed a long-disused bypass lopper in the garage (it may have Come With The House). Alas, the pivot bolt lost its jam nut long ago:

    Bypass loppers - OEM 10 mm bolt
    Bypass loppers – OEM 10 mm bolt

    That’s an M10x1.5 bolt, for which I lack a corresponding nut.

    But 3/8-16 is approximately M10x1.5, for small values of thread engagement, and I do have an assortment of inch-sized stainless steel fasteners:

    Bypass loppers - 0.375 inch bolt
    Bypass loppers – 0.375 inch bolt

    The nylon lock nut jams the bolt against the left blade, with the split washer applying pressure to the tapered blade. Slobbering oil in the sliding joints restored it to perfect working order.

    The weird round dingus on the far side of the pivot, up against the handles, is a bumper cushioning the fully closed position. It’s a nice touch and might work better if its rubber pad hadn’t aged out over the decades spent in the garage waiting for this very day.

    It’s my kind of yard work: “What do you need killed next?”

  • Bike Brake Pad Wear

    The rear brake on my bike wasn’t stopping nearly as well as it should, even after cleaning the rim and pads with brake cleaner, so I pulled the shoes and replaced the pads:

    Bike brake pad wear
    Bike brake pad wear

    It’s down a bit beyond the --WEAR--LINE-- indicator, of course.

    New brake shoes on clean rims work exactly like they should!

  • Xubuntu 18.04 vs. VNC

    For unknown reasons, the Gnome-ish vino-server package for Xubuntu 18.04 no longer installs vino-preferences, so it’s not obvious how to configure the server.

    After considerable flailing, I installed good old x11vnc, set up a password, then started it in .xprofile:

    x11vnc -forever -find -no6 -avahi -usepw

    I don’t mind having programs change, but it’d be nice if features like, say, configuration wouldn’t just vanish.

  • Digital Tattoo Power Supply: Polarity Doesn’t Matter

    When I rewired the guts of the digital tattoo power supply to eliminate the series foot switch, I kept the original wiring polarity, with the black wire to the sleeve and the red wire to the tip:

    Tattoo Digital Power Supply - internal view
    Tattoo Digital Power Supply – internal view

    It’s the same color code I (strongly) recommend in the Squidwrench Electronics Workshops: use any color for the ground / common wire as long as it’s black, then, if you have a red wire, use it for the positive supply. You can use yellow for the higher supply voltage, but stop being clever.

    I put suitably colored Powerpoles on the far end of the cable to replace the standard tattoo machine spring clip connector, so I can attach clip leads, battery test fixtures, and so forth and so on.

    We wired the supply into a clip-leaded diode measurement setup with a current limiting resistor and a pair of multimeters to measure the diode current and forward voltage, whereupon we noticed all the meters displayed negative voltages and currents.

    After a frenzy of wire-checking verified their setup was all good, I forced the simplest possible test, herein recreated on my bench:

    Tattoo Digital Power Supply - polarity test
    Tattoo Digital Power Supply – polarity test

    Which produced this display:

    Tattoo Digital Supply - reverse polarity
    Tattoo Digital Supply – reverse polarity

    Huh.

    After a brief exploration of “Trust, but verify” territory, we swapped the clip leads from the power supply and continued the mission.

    Back on my bench, I pulled the supply apart and measured the voltage at the jack terminals:

    Tattoo Digital Power Supply - jack wiring
    Tattoo Digital Power Supply – jack wiring

    Still negative. Huh.

    The bottom of the power supply PCB shows exactly what you should expect by now:

    Tattoo Digital Power Supply - reversed color code
    Tattoo Digital Power Supply – reversed color code

    The red wire near the top of the board is, indeed, soldered to the trace labeled GND and goes to the jack’s tip terminal; the adjacent black wire goes to the front-panel LED. Similarly, the black wire just below it, soldered to the same trace as the yellow wire, goes to the jack’s sleeve terminal; that trace also connects to a resistor leading to the trace labeled LED+ and the LED’s red wire.

    Although tattoo machines run from DC supplies, their motors or vibrators don’t depend on any particular polarity and will run fine with a backwards supply.

    Resoldering the red and black wires where they should go produces the expected sign at the jack:

    Tattoo Digital Supply - meter leads
    Tattoo Digital Supply – meter leads

    Although measuring and plotting diode voltages and currents may seem tedious, actually wiring stuff together and taking data reveals how difficult the real world can be.

    I trusted the supply’s internal color code and, although I’m certain I tested the Powerpoles, I obviously didn’t notice the meter’s sign.

    Memo to self: Sheesh.

  • Summer Downshift

    We have several high-intensity / long-attention-span home projects scheduled this summer, all of which will keep me away from the Basement Laboratory.

    We’re OK, all is right with our world, but painting rooms and yard maintenance always take way more time than they should, while having close to zero intellectual content.

    Like, for example, the result of a strenuous morning devoted to removing a severely overgrown holly bush:

    Mother of All Holly Bush Stumps
    Mother of All Holly Bush Stumps

    I’ll post odd & ends a few times a week until maybe mid-August, whereupon I should get back to more usual pursuits.

    Enjoy your downtime …

  • Tour Easy Front Derailleur Cable Clamp

    In addition to sawing through the side of the cable ferrule, the front derailleur cable began breaking at the edge of the derailleur arm:

    Tour Easy Front Derailleur Cable - frayed
    Tour Easy Front Derailleur Cable – frayed

    It wouldn’t have survived another ride!

    Dan pointed out CNC machined aluminum cable clamps are a thing, but those are sized for larger frame tubes than the 1.0 inch steel used on our Tour Easy ‘bents and, although I’ve shimmed everything else on the frame, I wanted to tweak the cable angle to match the arm on the derailleur.

    A bit of OpenSCAD wrangling produces a likely candidate:

    Front Derailleur Cable Clamp - Slic3r
    Front Derailleur Cable Clamp – Slic3r

    That’s a bulked-up revision of the prototype:

    Tour Easy Front Derailleur Cable Clamp - installed
    Tour Easy Front Derailleur Cable Clamp – installed

    Done up in orange PETG, it demonstrated the idea worked, but two perimeter threads wrapped around 15% infill isn’t quite up to the task. Note the split along the screw on the far half and various irregularities around the ferrule.

    The cable angle isn’t quite right, either, as the proper compound angle would, alas, aim the cable into the pedal crank. The bulky bushings get in the way of putting the ferrule where it should be with the screws aligned in a tidy manner, so I must get used to the jaunty angle.

    The bulkier version, done with 50% infill and four perimeter threads, has the same tilt angle, but the ferrule sits further from the screws:

    Tour Easy Front Derailleur Cable Clamp V2 - rear quarter view
    Tour Easy Front Derailleur Cable Clamp V2 – rear quarter view

    The view from the left side shows the cable angles slightly to the rear, but the smaller angle should make it happier:

    Tour Easy Front Derailleur Cable Clamp V2 - side view
    Tour Easy Front Derailleur Cable Clamp V2 – side view

    Probably should have used black PETG. Next time, for sure!

    The OpenSCAD source code as a GitHub Gist:

    // Tour Easy Derailleur Cable Clamp
    // Ed Nisley KE4ZNU – June 2017
    /* [Build Options] */
    Layout = "Build"; // [Build, Show]
    /* [Extrusion] */
    ThreadThick = 0.25; // [0.20, 0.25]
    ThreadWidth = 0.40; // [0.40]
    function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);
    /* [Hidden] */
    Protrusion = 0.01; // [0.01, 0.1]
    HoleWindage = 0.2;
    ID = 0;
    OD = 1;
    LENGTH = 2;
    /* [Cable Clamp] */
    FrameOD = 25.7; // Tour Easy has hard inch tubing + paint
    Ferrule = [1.5,5.1,12.0]; // cable ferrule
    EntryPoint = [0,13,60]; // cable entry to derailleur, +Y to rear of bike
    CableTilt = -20; // tilt from parallel to frame tube
    CableTheta = 0; // rotation around clamp from +X axis
    /* [Screws and Inserts] */
    ClampScrew = [3.0,5.5,35.0]; // M3 button / socket head cap screw
    ClampWasher = [3.7,7.0,0.7]; // M3 washer
    ClampNut = [3.0,6.0,4.0]; // M3 nylock nut
    /*
    ClampScrew = [4.0,7.0,25.0]; // M4 button head cap screw
    ClampWasher = [4.5,9.0,0.8]; // M4 washer
    ClampNut = [4.0,8.0,5.0]; // M4 nylock nut
    */
    NutShift = -0; // slide bushing toward nut for clearance
    //- Set clamp ring dimensions
    WallThick = 10.0;
    BushingSides = 8;
    Bushing = [ClampScrew[ID],
    // ClampWasher[OD]/cos(180/8) + 4*ThreadWidth,
    Ferrule[LENGTH]/cos(180/BushingSides),
    ClampScrew[LENGTH] – 2*ClampWasher[LENGTH] – ClampNut[LENGTH]];
    Ring = [FrameOD + HoleWindage,FrameOD + 2*WallThick,Ferrule[LENGTH]];
    ClampScrewOC = IntegerMultiple(FrameOD + ClampWasher[OD],1);
    echo(str(" screw OC: ",ClampScrewOC));
    ClampKerf = 0.75; // kerf between separated halves
    NumSides = 8*4;
    //- Adjust hole diameter to make the size come out right
    module PolyCyl(Dia,Height,ForceSides=0) { // based on nophead's polyholes
    Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2);
    FixDia = Dia / cos(180/Sides);
    cylinder(r=(FixDia + HoleWindage)/2,h=Height,$fn=Sides);
    }
    // Construct things
    module ClampRing() {
    difference() {
    union() {
    cylinder(d=Ring[OD],h=Ring[LENGTH],$fn=NumSides); // basic ring
    for (j=[-1,1]) // screw bushings
    translate([Bushing[LENGTH]/2 + NutShift,j*ClampScrewOC/2,Ring[LENGTH]/2])
    rotate([0,-90,0]) rotate(180/BushingSides)
    cylinder(d=Bushing[OD],h=Bushing[LENGTH],$fn=BushingSides);
    intersection() {
    rotate([CableTilt,0,CableTheta]) // reinforce cable ferrule
    translate([(Ring[ID] + Ring[OD])/4,0,Ferrule[LENGTH]/2])
    rotate(180/8)
    cylinder(d=3*Ferrule[OD] + 0*ThreadWidth,2*Ferrule[LENGTH],center=true,$fn=8);
    cylinder(d=2*Ring[OD],h=Ring[LENGTH],$fn=NumSides); // basic ring
    }
    }
    translate([0,0,-Protrusion]) // frame tube
    cylinder(d=Ring[ID],h=Ring[LENGTH] + 2*Protrusion,$fn=NumSides);
    rotate([CableTilt,0,CableTheta]) // cable ferrule
    translate([(Ring[ID] + Ring[OD])/4,0,-0.25*Ferrule[LENGTH]]) {
    rotate(180/8)
    PolyCyl(Ferrule[OD],Ferrule[LENGTH],8);
    rotate(-22.5)
    PolyCyl(Ferrule[ID],2*Ferrule[LENGTH],4);
    }
    for (j=[-1,1]) // screw holes
    translate([Ring[OD]/2,j*ClampScrewOC/2,Ring[LENGTH]/2])
    rotate([0,-90,0]) rotate(180/6)
    PolyCyl(Bushing[ID],Ring[OD],6);
    for (i=[-1,1], j=[-1,1]) // screw & nut seats
    translate([i*(Bushing[LENGTH]/2) + NutShift,j*ClampScrewOC/2,Ring[LENGTH]/2])
    rotate([0,i*90,0]) rotate(180/BushingSides)
    cylinder(d=Bushing[OD],h=Bushing[LENGTH],$fn=BushingSides);
    translate([0,0,Ring[LENGTH]/2]) // slice it apart
    cube([ClampKerf,2*Ring[OD],2*Ring[LENGTH]],center=true);
    }
    }
    //- Build things
    if (Layout == "Show") {
    translate(EntryPoint)
    cube(1,center=true);
    ClampRing();
    }
    if (Layout == "Build") {
    ClampRing();
    }
    view raw Derailleur Cable Clamp.scad hosted with ❤ by GitHub