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.

Month: April 2012

  • Failed Gyro Cube

    This slightly shrunken whosawhatsis Parametric Gyro Cube didn’t end well at all:

    Failed Gyro Cube
    Failed Gyro Cube

    The print failed when the nozzle snagged one of the tines, which instantly jammed up against the bottom of the heater block and stalled the platform motion with a horrible crunch. Surprisingly, the motors didn’t lose all that many steps, but you can see extruded thread drooling off the top layers.

    The 0.25 mm layer thickness contributes to the problem: any distortion while the plastic cools produces blobs on the top or poor adhesion, depending on whether the just-printed layer moves up or down.

    This was with infill = 60 mm/s, perimeter = 20 mm/s, and moves = 250 mm/s.

    That speed difference produces crap quality objects, because the high speed infill produces ragged edges that a single perimeter thread can’t convert into a smooth surface. Two perimeter threads work fine, but the top surface looks ragged from the mechanical wobbles induced at every direction reversal.

    The root cause: my heavily modified Thing-O-Matic  has too much moving mass and not enough rigidity, of course. Time to back off the speed for better results…

  • Schwalbe Marathon vs. Brown Glass: Flat Tire

    Having suffered flat tires due to the tire liner chafing the tube, I’ve been running the Tour Easy without a rear tire liner since last year. Worked fine, up until the steering went mushy on a recent ride:

    Brown glass chip - in tire
    Brown glass chip – in tire

    Ever notice how a rear flat means you can’t steer and a front flat means you can’t pedal? Works that way on our recumbents, too. Weird.

    The chip probably came from a beer bottle tossed out a car window, those being the canonical source of brown glass on the road. That razor edge punched right through the Kevlar belt in the Schwalbe Marathon tire and just barely penetrated the tube:

    Brown glass chip - detail
    Brown glass chip – detail

    Fortunately, I discovered all that in a nice grassy area, patched the tube, fired a pair of CO2 capsules into the thing, and rode another 20 miles around the block on a lovely day. Unfortunately, I managed to pinch the tube while installing it, producing a very slow leak that flatted the tire by the next morning.

    While repairing that flat in the comfort & convenience of the Basement Laboratory Repair Wing, I installed a tire liner with two strips of silicone tape over the ends to see if that reduces the abrasion:

    Silicone tape on tire liner
    Silicone tape on tire liner

    Silicone tape doesn’t adhere to anything other than itself, so I added two duct tape snippets to hold them in position while I buttoned up the tire. And, yes, I left the transparent plastic cover tape in place, in the hope that it can’t do any harm.

    Perhaps the inevitable slow leak will produce a flat in the garage, not on the road…