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.

Category: Machine Shop

Mechanical widgetry

Sunglasses Repair: New Hinge Holes

Milling to remaining hinge plate

With the epoxy cured overnight, I fired up the Sherline CNC mill to poke screw holes in the brass hinge splice.

The first step was to mill a flat-bottomed hole in the lower surface of the thin brass to expose the threaded hole in the remaining hinge plate. I crunched the end of the frame in a machinist’s clamp, then grabbed that in the Sherline milling machine vise; the frame is upside-down in the picture.

The brass stock was 0.015 inches, so I milled downward 0.020 inches to get through the epoxy. I’d love to say that worked perfectly, but I had to fiddle around a bit and eventually put a slight divot in the hinge plate.

That alignment was by pure eyeballometric guesstimation, but poking a small epoxy disk out of the threaded hole revealed that the 2 mm milled hole was centered on the hinge hole. Pretty close. Kinda-sorta. Good enough for my purposes, anyway.

Laser alignment to hinge hole

I aligned the spindle to the actual hinge hole with my laser aligner, a process that turned out to be surprisingly easy: note where the red dot vanishes on each side of the hole, split the difference, repeat for the Y axis, and you’re done.

Through-drilling top hole

With the spindle centered, I ran a #60 drill through the threaded hole (which it just barely cleared) and poked a hole in the thicker top plate (which is on the bottom here, remember). The packing under the hinge is a cut-up credit card; a handy source of thin sheets of stiff plastic.

Then I flipped the frame over and drilled out the top hole with a #54 drill to clear the threads on a 00-90 machine screw. I’d like to say I did a precision alignment job, but what I actually did was chuck that little bitty drill up in my big drill press, run it on the slowest spindle speed (maybe 400 rpm), brace my arms on the table, and feed the frame onto the drill by hand. Works perfectly… if only because I’m enlarging the hole by, what, 7 thou on each side.

Finished hinge – top view

A bit of filing cleaned up the drill chaff inside the hinge so I could mount the earpiece on the frame and screw it in place. I don’t have a 00-90 tap and wouldn’t use it in a titanium frame anyway, so you can tell this isn’t going to have a happy outcome, but, by and large, the undoubtedly metric threads in the frame did a pretty good job of re-forming the 00-90 brass threads. Ugly, but serviceable.

Some Dremel-tool work with an itsy grinding wheel on the flexy shaft eroded the back side of the U-shaped brass and new hinge plate to clear the earpiece; I think it only took half a dozen trial fittings & tiny grindings before the earpiece folded properly.

A dab of low-strength purple Loctite in the threads and I’d say that screw is in there for life!

Finished hinge – side view

Finished hinge – bottom view

Then I cleaned it up with a miniature wire wheel and, hey, it’s got a certain geeky charm, doesn’t it?

I have my doubts about how well the epoxy affixes itself to the brass, so I suspect I’ll be drilling a hole or two to mechanically lock it in place with some urethane adhesive when it falls off.

If the remaining hinge plate fractures, however, then the frame is toast.

Until I get around to having the optical shop dye up another pair, these should suffice for my simple needs.

Trivia:

The plastic film on the lenses comes from a big roll of the stuff they use to protect CRT monitors in shipping. Works great for shop projects and, back in the day, I used it when I was hauling monitors around. I think it’d suck the front right off an LCD panel, so I haven’t used much of it lately.

If you’re following the pictures, you’ll notice that the dsc* numbering series resets right in the middle of the story. That’s where my Sony camera gagged while writing an image and explains why I don’t have pix of the first drilling steps.

The color balance is weird on the milling machine pix because the shop lights are much cooler than the warm compact fluorescent bulb hovering over the table.

2009-04-18
Sunglasses Repair: Half a Hinge Is Better Than None

Broken hinge and brass shim stock repair parts

Some years ago I managed to talk one of the local optical shops into stripping the anti-reflective coating off my second-oldest pair of glasses, dunking the lenses in the gray dye pot, then re-coating them. I got a fine set of variable-bifocal sunglasses for 75 bucks; that’s why it took some persuasion. The near vision lens is a bit under my current prescription, but it’s good enough for driving and biking.

All good things must come to an end: the right-side hinge broke. The bad news is that it’s a titanium frame (can’t be brazed, at least by me) and the whole affair is old enough that it’s not worth sinking a bunch of money into a new frame. This year calls for new glasses anyway, so with any luck they’ll be able to do it again.

The good news: I can fix this thing with JB Weld epoxy and a few brass bits. So off to the Basement Laboratory, Machine Shop Division, we go…

Resistance soldering brass parts

Fortunately, the unthreaded top hinge plate broke off, leaving the threaded bottom plate intact. The plan: replace the plate with a suitable bit of brass shim stock, solder it to a U-shaped sheet of brass, epoxy the thing to the temple, drill a hole through the new plate, and run a screw into the threaded plate.

The top picture shows the broken hinge and the tediously cut-and-filed brass parts. The tab on the end of the flat plate fits around the remaining part of the hinge, the upper part is flush against the frame, and most of the plate will be trimmed off.

Rough-filed hinge splice

After demonstrating that my smallest torch can satisfactorily melt tiny bits of brass shim stock, I (tediously) re-cut and re-fit another set of parts, then deployed the resistance soldering gadget I built a while back (and wrote up for Circuit Cellar, Feb / Apr / Jun 2008) and silver-soldered the bits together. I must describe that thing here one of these days; it’s built around a rewired kilowatt-class microwave oven transformer with triac pulse-duty-cycle switching to control the heat.

A bit of diagonal cutter and file work produced a U-shaped channel that exactly fit over the remaining hinge. The rounded end (in the rear) is too wide, but that’ll get trimmed to fit when it’s in place.

Aligning earpiece and frame for epoxy

Wisely is it written that you cannot have too many clamps, which is what I used to build a fixture and align the earpiece with the lens frame to epoxy the hinge splice in place. As is always the case, nothing is square, plumb, true, or parallel. Fortunately, the glasses weigh basically zilch, so after I get the pieces aligned, they won’t shift out of place.

That done, I worked some JB Weld epoxy into the hinge stub’s crevices, then slipped the splice into place. A small blue clamp applied a bit of pressure to make the friction fit marginally more secure…

Final clamping overview

The trick here is to leave the plastic lid with the rest of the mixed epoxy sit on the workbench; if the epoxy in the lid isn’t cured, then there’s no point in moving the glasses and breaking the bond.

Clamping with epoxy applied

Then I let the epoxy cure overnight… when the story continues.

2009-04-17
Anchoring Sherline Stepper Motor Wires

Anchoring stepper motor wires with cable ties

The wires coming out of Sherline CNC milling machine stepper motors, as with most small stepper motors, emerge from an epoxy-filled opening. As a result, whenever the motor or wires move, all the stress concentrates right at that epoxy surface.

Which is exactly where the wires will break…

There’s no good way to add strain relief to that point (more adhesive isn’t helpful), but you can anchor the cable to the motor frame so that the individual wires do not move relative to the motor.

Cable ties will suffice. Add one around the entire motor to hold the wires in place, then lash the spiral sheath to one of the unused mounting holes in the motor frame.

Pull those ties until they squeak! You can grab the tabs with flush-cutting diagonal cutters to get some traction, then rotate the cutters against the ratchet housing to pull another notch past the ratchet. When it’s so tight you’re stretching the tie, then it’s tight enough; clip the end off with the cutters.

To cross-check, wiggle the connector end of the cable. If the wires move at the epoxy, then you haven’t done a sufficiently good job. Repeat until satisfied.

This works for the milling machine and, as shown in the picture, the rotary table. Just do it!

2009-04-16
Tour Easy Coily Lock Holder

Coily-cable bike lock holder

Although I’m pretty sure nobody would think of stealing my Tour Easy (“How long did it take you to learn to ride that thing?”), it’d be a shame to be wrong. So I carry a coily-cord lock and lash the bike to a post or, for lack of anything better, the front wheel to the frame.

If they can figure out how to get the back wheel out in less than ten minutes without a work stand, they’re a damn sight better mechanic than I!

Anyhow, the trouble with a coily lock is that it’s far too heavy and sinks to the bottom of whatever pack you put it in, crushing the groceries on the way down.

So I built a small plate, tucked into the corner above the bottom bracket, to hold the lock out of the way and within easy reach.

Lock holder – right side

It’s a 1/16-inch aluminum plate held to the bike frame with a pair of padded clamps. I applied a hole saw to the middle to get a way to lash the lock to the plate with two more of those ubiquitous Velcro straps.

The 2.5-inch 10-32 machine screws support the cable coils; the lock already has a plastic coating, so I didn’t bother putting any padding on the screws. Nuts on both sides compress the clamps and support the plate.

The small aluminum plate sticking up prevents the lock coils from pressing the brake cable against the frame. If you forget that, your back brake won’t release completely.

Lock holder – left side

There’s nothing fancy on the left side…

Put Loctite on the threads under the nuts to ensure nothing rattles loose!

The black cable taped to the top frame tube carries the push-to-talk button back to the amateur radio behind the seat. That’s a story for another time.

2009-04-13
Recumbent Bicycle Chain Catcher

Chain catcher

You’re puffing up a serious hill, finally downshift to the smallest chainring, and the chain falls off on the inside. You’re already at stalling speed, so you stop abruptly and gracelessly. If you haven’t used up your weekly luck allotment, you neither fall over nor get rammed by the rider behind you.

Not to be endured, sez I.

The solution is the Chain Catcher from Bike Tools Etc. It normally attaches to the seat tube of diamond-frame bikes and prevents the chain from falling off inside the smallest chainring, but it works fine on ‘bents, too.

Alas, their smallest Chain Catcher, part number CC-04A, fits a 28.6 mm seat tube: it’s much too large for the 1-inch tube on a Tour Easy.

Never fear! Go to your local home-repair store with ruler in hand and examine the plumbing aisle’s plastic fittings. I used a sink drain tailpiece, but any tube with an outside diameter over 1-1/4” and 1/16” walls will work. Buy one, take it home, cut off a ring as wide as the Chain Catcher with a saw or a razor knife, and smooth the edges. Cut the ring lengthwise, slip it over the bike tube, mark the spot where the ends cross, remove it, and trim to fit neatly on the tube.

If you make a mistake, you have spares aplenty…

(This is trivially easy with a lathe, but you need not go full-on geek for this project.)

Install the Chain Catcher over your shim with its thumb pointing forward and align it with the chain’s rivets, not quite touching the chain on the smallest ring. Firmly tighten the Catcher’s mounting screw.

This won’t fix a badly adjusted front shifter, but it does eliminate those occasional glitches.

Ride on!

2009-04-12
Tour Easy Handlebar Hydration Mount

Handlebar-mounted hydration pack (fairing removed for visibility)

My esteemed wife returned from a shopping expedition with the crushed remains of a water bottle that fell out of her Tour Easy’s under-handlebar cage. Fortunately, the truck flattened the bottle, not her, but Something Had To Be Done. She also had trouble maneuvering those newfangled long-body bottles around the rear edge of the Zzipper fairing.

My TE has a hydration pack attached behind the seat with the hose passing around my arm to a Velcro (nah, it’s generic hook-and-loop) strip safety-pinned to my shirt. Mary didn’t like that arrangement, because it required some fiddling when she sat down and poked pinholes in her shirt. She wanted an arrangement that Just Worked.

Recycled pack support plate

I removed the under-the-handlebar bottle cages from her bike and bolted a salvaged aluminum plate to the four tapped ferrules. The numbered holes on the plate originally held coaxial cable connectors, but I think they give the plate that snooty, high-tech, drilled-out, weight-weenie look.

A 50-ounce hydration pack (“Styled for women!”) fits neatly atop the plate, below the cables, and between the handlebars. We wrapped a two-inch-wide Velcro bellyband around the pack, Velcroed the bag’s top loop to the handlebar’s crosspiece, and secured the valve with another Velcro strap that doubles as her parking brake. The whole affair looks quite tidy under the fairing.

Now she simply picks up the hose and takes a sip: no acrobatics, no dropped bottles, no hassle. Life is good!

2009-04-11
Recumbent Bike Kickstand Ground Plate

Kickstand ground plate in action

Have you ever done this? You pull up to a rest stop, flip down the kickstand, walk off to snarf some snackage, and crash your ‘bent falls over behind your back. Not only is it tough to look cool when that happens, even a zero-mph drop can scuff up your bike.

A long recumbent leaning heavily on its kickstand will inexorably push that spike right into mowed turf, bike-tour mire, or sun-softened asphalt. The small plywood square shown in the first photo solves that problem: the kickstand fits into a shallow recess and the plate spreads the bike’s weight so it simply can’t penetrate the ground.

The plate is a 3-inch square of 1/2” plywood, painted bright forget-me-not yellow. I used a 3/4” Forstner bit to drill a flat-bottomed recess through the top veneer layer, but you can poke several shallow holes with a 1/4” drill and then carve out the rest with a knife or chisel. The recess captures the end of the kickstand so the bike can’t slide off the block.

The parking brake shown in the second photo will keep your bike firmly in place even when you park on a slope. It’s a hook-and-loop (a.k.a Velcro) strip pulling the brake lever to the handgrip. Your nearby big-box retail store’s computer department mislabels these as “cable organizers” and a single package will provide enough parking brakes for your entire fleet.

Bicycle parking brake strap

Notice that dark extension on the kickstand? Just after I got my Tour Easy, I decided that the kickstand was about an inch too short. Rather than buy a new kickstand, I jammed a few inches of 1/2” copper water pipe on the end, trimmed it to the proper length, and sealed the top with glue-filled heatshrink tubing. Aluminum plus copper equals corrosion, but that lasted for about five years before the entire kickstand failed.

The small plate on the kickstand hinge holds a switch that lights an LED on the handlebars when the kickstand is down. It’s surprising how far you can slide on your forearms along a steep downhill asphalt road when you forget to flip the kickstand up, but that’s a story for another time.

A slightly different version of this note appeared in Recumbent Cyclist News back in early 2006, more or less, but everybody keeps asking me about that little yellow plate when we’re on organized rides.

2009-04-10