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.
Cruisin’ the streets
It turned out those window screen splines lasted a dozen years until this happened:
Some rummaging in the Big Box o’ String produced the spool of 1000 pound test Kevlar cord most recently applied to the seat back on Mary’s bike, so this happened:
Having re-confirmed that frayed Kevlar cannot be melted into a blob, another UV-stabilized cable tie at each end will control those tufts.
Those cords should last forever …
It turns out that keeping the garage door remote clipped to the starboard underseat pack on my Tour Easy attenuated its RF enough that even the directed receiver antenna couldn’t grab enough signal until I rolled onto the end of the driveway.
While contemplating what’s involved in making a 3D model of the remote’s curved backside, I realized the bike already had a perfect spot:
A few strips of good outdoor-rated foam tape later:
Believe it or not, the camera is looking through the year-old and unwashed fairing on my bike.
Stipulated: aligning the PCB antenna flat against a small aluminum plate atop a bunch of aluminum bars isn’t perfect. However, enough RF wriggles out to trigger our opener from four houses down the hill, giving it plenty of time to haul the door out of my way.
That was trivial …
Do you see the Cooper’s Hawk?
Neither did I!
(The last three digits in the caption tick along at 60 frame/s. Opening each iamge in a new tab will let you embiggen the details, although the images aren’t all that great.)
The second wingbeat, over on the left, is more visible as the hawk lifts off:
This was about when I figured out what was going on:
A hawk can easily outfly me!
The snake dangling from the hawk’s talons didn’t see it coming, either:
Up and away!
About 2.3 s of elapsed time: plenty for a hawk and not nearly enough for me. Or the snake, for that matter.
Mary’s zero-mph crash loosened the starboard handlebar plug enough to let it eventually decamp for parts unknown. Its replacement, a somewhat fancier aluminum plug with an expanding cone retainer using an actual M3 nut, worked fine for the last year, but Mary recently noticed the socket head screw had worked loose.
In the interim, I’d moved the Bafang thumb control from its original position on the crossbar to just above the rear shifter:
Which moved the clamp on the shortened grip off the end of the handlebar tube, so I flipped the grip around, tightened the clamp, and installed the plug.
Unfortunately, the grip ID is 4 mm larger than the tube ID, which meant the plug’s cone retainer was struggling to hold on in there. Perhaps the plastic cone has relaxed bit, but I figured giving it more traction would be a Good Idea™ before I declared victory:
It’s a little plastic sleeve with slots to let it expand against the inside of the grip:
Yes, it’s sticking out slightly; you can see the corresponding gap up inside next to the tube.
A wrap of double-sided sticky tape glues it in place as the retainer presses it against the grip ID and a dot of low-strength Loctite should keep the screw from loosening again.
The OpenSCAD source code:
// Handlebar grip sleeve
// Ed Nisley - KE4ZNU
// 2025-10-25
include <BOSL2/std.scad>
/* [Hidden] */
ID = 0;
OD = 1;
LENGTH = 2;
HoleWindage = 0.2;
Protrusion = 0.1;
NumSides = 3*2*4;
$fn=NumSides;
Sleeve = [18.5,22.0,14.0];
Kerf = 1.0;
difference() {
tube(Sleeve[LENGTH],id=Sleeve[ID],od=Sleeve[OD],anchor=BOTTOM);
for (a=[0,90])
zrot(a)
up(Sleeve[LENGTH]/4)
cuboid([2*Sleeve[OD],Kerf,Sleeve[LENGTH]],anchor=BOTTOM);
}
That was easy …
Although the 3D printed tires for our Terracycle chain idlers fit nicely, adjacent TPU threads didn’t bond well:
Based on some earlier items, I’d been printing TPU at 220 °C, but 230 °C fuses the threads together:
The filament turned out to be 1.79 mm diameter, rather than the nominal 1.75 mm, and a few iterations showed a 0.95 Extrusion Multiplier worked much better.
Those were printed at 30 mm/s with 0.25 mm layer height.
I now have a good stock of spare tires, each slightly different than all the others:
The first two slightly delaminated printed tires will remain in service until they show signs of falling apart, because I’d rather ride the bike than fiddle with it.
The Terracycle (now T-cycle, for reasons presumably involving the transfer of money) chain return idlers on our Tour Easy bikes developed hardening of their urethane tires:
Urethane shouldn’t crack like that, but after more than fifteen years, stuff wears out.
The white ring is 95A TPU printed on the Makergear M2, which is definitely more flexy than the original tire, but has the redeeming feature of being both Good Enough and trivially easy to model:
include <BOSL2/std.scad>
NumSides = 4*3*2*4;
$fn=NumSides;
Thick = 3.5;
ID = 46.4;
OD = ID + 2*Thick;
Length = 11.2;
tube(Length,id=ID,od=OD,anchor=BOTTOM);
It printed with 5 mm brims on both the ID and OD, because TPU has the barest adhesion to the M2’s glass plate + hair glue. There’s a long-unopened box now on the bench with a BuildTak PEI surface (thank you: you know who you are!) that should improve the situation.
In any event, the tires fit well:
The layer-to-layer adhesion isn’t as good as I think it should be, so I’ll likely use those tires as testcases for tweaking the new build plate & settings.
The forecast of several pleasant days will have me in the garage wrenching on bikes, doing car maintenance, and finishing home chores.
Back next week …
Obligatory cat(erpillar) picture:
The Smell of Molten Projects in the Morning 