Posts Tagged M2
A flashlight used as a daytime running light must point generally forward and an actual bike headlight must light up the road, so it must sit on an az-el mount. My old bike helmet mirror mount had actual vertical and horizontal joints:
Every doodle along those lines seemed too big, too fragile, too fiddly, or all at once.
Living here in the future, though, we can produce (crude) ball joints to order:
That’s an early version of the outer mount using threaded brass inserts.
The ball around the flashlight separates along the obvious plane of symmetry, with a 2 mm socket-head cap screw and brass insert on each side. I tried printing the hemispheres convex-side-up with hand-hewn support structures inside:
The huge overhanging sections parallel to the axis didn’t bond to the supports, curled upward, and began nudging the dangling Z-axis homing switch actuator. This wasn’t a completely wasted effort, though, as similar support structures came in handy for the outer clamp ring.
Flipping the hemispheres over so they printed U-channel upward didn’t work much better, even sitting on a flat section to eliminate the absurd part of the overhang. This view shows one hemisphere with the missing cap:
Flipped over, the flat surface bonded perfectly to the platform, but the overhang still warped as the upper layers cooled and pulled the perimeter upward:
Because normal support structures don’t contact the outer surface, I added fins to the model to hold the perimeter (almost) flat until the outer walls became sufficiently vertical to stop warping:
They’re fearsome hedgehogs in person:
The grip diameter determines the sphere diameter, as the sphere must have enough meat next to the grip to hold the screws and inserts. Rather than have the diameter different for every flashlight, I set it to the maximum of 45 mm or the actual diameter, which means all the flashlights in my collection have a common ball size. The hemispheres on the right have flattened ends to accommodate flashlight grips shorter than the sphere’s final diameter, achieved with a pair of
intersection() operations lopping off the protruding bits:
Because the fins extend from resolutely convex surfaces, I snipped them off with flush-cutting pliers, reamed out the holes, epoxied the inserts in place, assembled the ball, and introduced it to Mr Belt Sander.
Protip: don’t hold the ball with your finger through the hole. It will eventually fly off under the workbench and it’s better if it doesn’t break your finger in the process.
A somewhat rough outer surface turns out to be an advantage, not a liability, as the clamp ring around the ball must hold it against the normal (and unusually severe) vibrations found on a bike.
The inner cylindrical section is smooth enough to require a wrap of tape around the flashlight grip to anchor it in position. The tape adheres to the flashlight and squishes into the ball’s layer lines, even under mild pressure from the 2 mm screws. The outer clamp ring applies compression to the ball, so the tiny screws need not withstand much force at all, which is a good thing.
For reasons obvious to any cyclist, we must improve the forward conspicuity of our Tour Easy recumbents with a white daytime running light; a near-miss boosted this to the front of the project queue. While you can outfit a standard bike with a handlebar-mounted headlight (*), at any price from the sublime to the ridiculous, the smooth snout of a fully faired recumbent covers all the usual attachment points.
A small LED flashlight tacked onto the fairing support bracket seems workable enough to make up for a significant case of ugly:
That’s a J5 Tactical V2 flashlight on my bike.
Mary’s bike has a tidier Anker LC40 in an earlier mount version:
The Anker required an adapter to hold an 18650 cell in its 3xAAA-size body. The J5 V2 is resolutely 18650-only, which is fine with me.
The intent here is to find out whether this works, figure out the proper aiming point(s), then de-bulk the mount.
The next few posts will cover various bits & pieces of the design, because I must remember why I did things the way they turned out: sometimes the obvious choices didn’t work.
The Zzipper fairing originally mounted to the strut across the handlebars with a single 1/4-20 nylon screw on each side. Even with a nylon washer on the outside, the stress concentration cracked the polycarbonate sheet around the screws and brackets, so I designed & printed flat ABS plates to spread the stress over a larger area:
The tapered edges were supposed to be flexible, but the foam sheets sandwiched on both sides of the fairing actually provided most of the compliance. There’s another screw in the open hole binding the inner & outer plates together.
The mounts worked perfectly, even as they faded over the years. The fairings became quite scuffed during the course of our near-daily rides, but, heck, we’re also a bit scuffed and it’s still all good.
The new PETG inner plates seat on the bracket to nearly its full thickness:
The flashlight on the outer plate applies torque around the bolt which (I hope) the sides of the recess can resist. This is the absolutely key part of the design and, I’m somewhat ashamed to admit, took me far too long to figure out. What you don’t want: weird & fragile gimcrackery clamped onto the strut extending under the fairing’s edge, with the flashlight hanging far off to the side.
I modeled the fairing strut’s aluminum bracket as a 2D rectangle, plus a pair of chords, embiggened by a thread around the outside edge, minus the hole, then extruded to the proper height:
The hole isn’t strictly necessary, as I punch out both screw holes as part of the plate assemblies.
The overall plate shape comes from the top half of a
hull() wrapped around four squashed spheres:
Then the inner plate is just a plate blank stamped with the bracket:
You’ll need a set for the side of the fairing without the running light:
The outer plate looks reasonably sleek in real life, although that’s not the primary consideration:
You could replace the squared-off ends with simple half-circles, maybe stretched into stylin’ ellipse shapes, without too much effort.
I got out the screws, set up to cut them with a pull saw and miter box, then realized they are plastic. Put away the saw, got out the utility knife, and cut them to length with one firm push. No distorted threads, no dust, no muss, no fuss.
(*) Opinion: any headlight with non-replaceable, USB-chargeable cells is a toy. I can replace a discharged (or failed) 18650 cell in the middle of a ride, where a dead battery inside a spendy headlight would leave me in the dark. Might not matter for a DRL, but seems absolutely critical on night rides. ‘Nuff said.
This worked surprisingly well to lay out black foam gaskets for new fairing mounting plates:
Mary uses the Fons & Porter Mechanical Pencil to mark quilting patterns on fabric. It has, they say, a “strong ceramic 0.9MM white lead” with “water-soluble dyes” capable of both laying down a durable mark and washing out without leaving a trace. I don’t care about the latter, of course, but it did brush off reasonably well.
The next step involved running an X-Acto knife around the perimeter of the plate and punching the holes.
You can get colored ceramic leads (for small values of color) for use on other backgrounds.
Anker LC40 flashlights can use either one lithium 18650 cell or an adapter holding three AAA cells. I now prefer 18650 cells, but they’re nigh onto 4 mm smaller than the flashlight ID and rattle around something awful.
I can fix that:
Three new entries appear in the cell dimension table of my OpenSCAD inter-series battery adapter program:
NAME = 0; ID = 0; // for non-cell cylinders OD = 1; LENGTH = 2; Cells = [ ["AAAA",8.3,42.5], ["AAA",10.5,44.5], ["AA",14.5,50.5], ["C",26.2,50], ["D",34.2,61.5], ["A23",10.3,28.5], ["CR123A",17.0,34.5], ["18650",18.8,65.2], ["3xAAA",21.2,56.0], ["AnkerLC40",23.0,55.0] // Flashlight tube loose-fit for 3xAAA adapter ];
I took the opportunity of adding OpenSCAD Customizer comments, which means this now works:
The model looks about the same as before, although with a few more sides just for pretty:
That was easy …
The mailing tube arrived with contents intact, although the USPS inlet scanning didn’t work and the tube pretty much teleported across several states without leaving any tracking data behind. The recipient suggested several modifications to the caps:
Review of user experience of tube end:
The ribs on the endcap are very good at holding the cap on, so much so that I had to use a prying implement to remove it, which cracked the flange.
Would consider less depth on the cap, and possibly another layer on the flange.
Some continuous process improvement (a.k.a OpenSCAD hackage) produced a swoopy threaded cap with thumb-and-finger grips:
The finger grips are what’s left after stepping a sphere out of the cap while rotating it around the middle:
That worked out surprisingly well, with the deep end providing enough of a vertical-ish surface to push against.
The two hex holes fit a pin wrench, because the grips twist only one way: outward. The wrench eliminates the need for a flange, as you can now adjust the cap insertion before slathering packing tape over the ends. Man, I loves me some good late binding action!
A three-start thread seemed like overkill, but was quick & easy. The “thread form” consists of square rods sunk into the cap perimeter, with one edge sticking out:
They’re 1.05 times longer than the cap perimeter facets to make their ends overlap, although they’re not tapered like the ones in the broom handle dingus, because it didn’t (seem to) make any difference to the model’s manifoldhood.
Not needing any endcaps right now, I built one for show-n-tell:
The OpenSCAD source code as a GitHub Gist:
Faced with a need to send documents rolled up in a tube, rather than folded flat, I sawed off a suitable length of cardboard tube from the heap, then discovered a distinct lack of end caps.
Well, once again, it’s 3D printing to the rescue:
The small ribs probably don’t actually do anything, but seemed like a nice touch.
They’re somewhat less boring from the bottom:
The fancy spider supports that big flat top and provides some crush resistance. The flat flange should collect the edge of the packing tape wrapped around the ends.
A firm shove installs them, so the size worked out perfectly:
Add a wrap of tape to each end, affix the USPS label, and they went out with the next day’s mail, PETG hair and all.
The OpenSCAD source code as a GitHub Gist:
Improving the crystal tester’s (nonexistent) grounding requires a band of copper tape around the inside of the proto board holder. Rather than cut the tape lengthwise to fit the holder, a new one will be just tall enough:
While I was at it, I deleted the washer recesses, because those didn’t work out well, and fiddled the screw holes to put the inserts in from the bottom:
Although the overhang inside the holes will be ugly, I’ll epoxy the inserts flush with the bottom and nobody will ever know.
The copper tape now makes a tidy ground strap:
With a gap in the front to eliminate the obvious loop:
The OpenSCAD source code as a GitHub Gist: