Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Mary dropped a pair of her sunglasses that disintegrated on impact: both earpieces broke off. She has trouble finding sunglasses that fit, so this is not to be taken lightly…
The sunglasses had interchangeable lenses, a feature which she’d never used, and the lower of the two tabs that snapped into the earpieces had broken off — on both sides, simultaneously. These weren’t high-snoot items, but they were name-brand: Rudy Project from, IIRC, nashbar.com.
Peering through the microscope, it turns out that the lens material may have been pretty good optically, but wasn’t up to the mechanical task: the two remaining tabs had deep stress cracks. The right-side picture shows the lens upside-down, as that was the easiest way to set up the shot.
Notice the many, many cracks that penetrate nearly all the way through the tabs. The tabs didn’t break because she dropped the glasses on the floor, they broke because there was barely anything left holding the tabs in place.
Mind you, she’d never removed the lenses from the earpieces, so this isn’t a case of failure-from-overuse, either. They’re about a year old, more or less, and have been used in stressful tasks like gardening and the occasional bike ride.
Urethane adhesive foam-in-place
I slobbered urethane glue into the ends of the earpieces to mechanically lock the remaining tabs in place and fill all the voids. It looks rather ugly here, but the excess adhesive simply snaps off because it doesn’t chemically bond with either of the other two plastics.
Rudy sunglasses stress cracking – center
After screwing everything back together again, I noticed that there’s another stress crack growing in the middle of the lens, just over the nosepiece. These sunglasses are not long for this world: that failure will be an end-of-life event.
The frames claim “Designed in Italy” which doesn’t win any points with me; the design is fundamentally flawed.
Yo, Rudy, how about designing some sunglasses with a high-tech feature like durability… rather than style?
Oh, yeah, I suppose this repair voids the Warranty. Perhaps buying from Nashbar on sale triggers this clause: “Buying Rudy Project sunglasses, goggles or helmets from an online retailer at a price below the suggested retail price (MSRP) voids your warranty.” The expense of sending them in negates any possible benefit, which I’m sure they realize, too.
Our daughter has been helping a friend learn to ride a bike (at age 15: it’s never too late!) and we’ve been rehabilitating a new-to-her bike in the process. It’s an inexpensive Ross bike, perfect for the task at hand, and is providing a good introduction to machine-shop work.
The fact that it’s much older than she is makes not a whit of difference. Nay, verily, I rode a bike pretty much like this one for hundreds & hundreds of miles back in the day. I got better ones when I could afford them and she will, too; maybe we’ll tempt her into a recumbent bike some day…
Anyhow, the seat tended to spin around even with the clamp cranked dangerously tight. Taking a look down the tube showed that they used welded-seam tubing (it really was an inexpensive bike) and didn’t bother to clean up the internal seam. As a result, the chromed steel seat post rested on maybe three small patches of metal that didn’t provide much friction at all.
I wrapped a neodymium magnet in a rag and stuffed it down the tube to catch the filings, then applied a coarse cylindrical file (a rat-tail would work as well) to the seam. When it was nearly flush, I switched to a finer file to smooth it and the other high spots. The picture shows the improved seam, ready for the seat post. Ugly, but rough is actually a Good Thing in this situation.
Seat Clamp Swaging
The seat tube has a nominal 1-inch OD, so I clamped a random round from the heap in the vise, tapped the clamp around it, and massaged it lightly with a hammer to persuade it into a more cylindrical shape. It’s still not perfect, but at least the bolt lugs engage the seat tube around the slit somewhat better.
With all that in hand, the seat post is now perfectly secure.
On her first “I can ride!” parking-lot outing, she experimentally determined that a bicycle wheel’s lowest-energy state resembles the edge of a potato chip. Fortunately, it was the front wheel and, after a bit more shop derring-do than one might wish, we swapped in another wheel that’s been hanging on the garage wall for a decade, ready for just such an occasion.
Remember how independent your first bike made you feel? It’s working that way for those two, just like it did for us. Life is full of bumps and they’ll get hurt every now and then, but there’s no other way to get through it; they’re just about ready to ride over the horizon.
Happy Independence Day for those of us in the USA!
I managed to jam the 3-jaw chuck on my lathe by turning the lathe on without the formality of snugging the chuck against the spindle first; IIRC, there was maybe 1/8″ clearance. The resounding thunk when the irresistible force hit the immovable object was the prelude to about a year of increasingly desperate attempts to remove the chuck, punctuated by long periods of despair.
The absurd derring-do with clamping the 4-jaw Sherline chuck in the 3-jaw lathe chuck described there finally prompted me to ask my buddy Eks for advice, which is what I should have done in the first place. He suggested removing the chuck body from its backplate, building a lever that bolted to the backplate with the same six bolts as the chuck, blocking the spindle with wedges under the belt pulley, and wailing on the lever with a lead hammer.
We wondered if a hard hammer would be better than the lead hammer, perhaps because the impact would be less squishy, but that was in the nature of fine tuning.
The key idea is that removing the chuck body also removes a tremendous amount of rotational inertia, so that wailing on the lever arm actually transfers force / impact directly to the backplate, rather than trying to spin the body. The somewhat risky part is that there’s a pin connecting the spindle with the drive pulley (it’s disengaged when using the back gears), so that it’s entirely possible to break the pin rather than unstick the chuck. But it was still a better idea than any I’d had so far.
Stuck backplate
Making note of the witness marks on the backplate and chuck body, I removed the body. Fortunately, there was just enough clearance between the front bearing journal and the backplate that I could get the bolts out without dismantling anything else.
That left me with the rather grody and still firmly stuck backplate. The bolt disk was brazed onto the threaded cylinder with a keyway. Although the chuck body had a key slot, it looks like the matching key had been machined off of the cylinder, so the bolts were taking all the cutting torque. Worked OK for both the previous owner and for me, so I suspect it’ll continue to work just fine for the next owner, too.
Bicycle handlebar stem in spindle
Peering through the spindle reminded me of some recent bike repairs and it occurred to me that maybe, just maybe, a old-skool split-wedge handlebar stem would get enough traction inside the spindle to hold it in place. Some rummaging in the Bike Junk box produced just such a stem and it fit exactly into the spindle bore. Now the spindle is fixed in place by its ID and there’s no risk of breaking the locking pin or (shudder) the back gear.
Even better, the lumber pile emitted a chunk of 1×4 (actual dimensions!) wood that was precisely the correct length to reach from the floor to the stem. I like it when projects work like that; finding exactly the right stuff in the pile is sort of an omen that things are going well.
Fundamental rule: always start with a hunk of something that looks a lot like what you want to end up with.
Corollary: ya gotta have stuff!
Coordinate-drilling the lever arm
Some rummaging in the parts heap turned up several feet of nice “angle iron”, so I bandsawed off a hunk. I should have realized something was wrong when a foot of teeth stripped right off the saw blade, but I ascribed that to, oh, maybe weakening a few teeth when I soldered up the blade.
I had our daughter run the trig to generate coordinates for the six holes, then lay out the center bore and bolt holes on the plate for practice. Drilling the first hole prompted me to resharpen the drill, but poking the remaining five holes into that plate produced vast clouds of wood smoke from the sacrificial plate underneath, despite boiling copious quantities of cutting fluid off the top.
I finally admitted defeat when the “angle iron” rubbed the teeth right off a 2-inch hole saw.
As nearly as I can tell, that plate is un-machinable stainless steel, hand-forged by the Devil himself specifically to taunt me, and is good for nothing. Obviously, I hadn’t used it for anything in the years it had been in my pile and, perhaps as an omen, it didn’t have any other holes in it from anybody else’s efforts. I’ll keep the pieces around just to sneer at them; won’t get fooled again.
So, at this point, I am out a bandsaw blade, a drill bit, and a hole saw. We won’t discuss the circle cutter or my abortive attempt to lash the damn thing down to the Sherline and perform helix-milling upon it.
Unstuck backplate with beating bolt
While licking my wounds, I wondered if the bolt circle on the backplate would provide enough lever arm to make any difference. I tightened a sacrificial bolt & nut with one face of the bolt aligned along a radius from the spindle center, then deployed a big drift punch and the two-pound ball-peen hammer (a.k.a., The BFH).
A half-dozen good shots later, the backplate spun free. Notice the very small gap between spindle and backplate… that’s all it takes!
I added a closed-cell foam washer to fill the gap between the backplate nose and the butt end of the chuck; there was a remarkable amount of crud built up in there.
I am so happy that it even makes up for the death toll among the tools…
It’s worth noting that the headstock has two honkin’ big bronze spindle bearings, no delicate balls, and a few mighty thwacks didn’t do them a bit of harm.
While replacing the rear derailleur on Mary’s Tour Easy, I rediscovered that I have two different cable sizes in my stash: large brake cables and small derailleur cables.
The large ferrules are 0.235 inches in diameter, the smaller 0.187 inches. The brazed-on cable-stop sockets are obviously sized for the larger ferrules, which makes perfect sense.
If you put a small ferrule in a large stop, it tends to cant whichever way the cable pulls it. That results in the cable sawing into the edge of the ferrule… and that results in excess friction and sometimes a broken cable.
In the past I’ve snipped out little brass shimstock rectangles, wrapped them around mandrels, and generally spent a lot of time fiddling around. This time I remembered to rummage in my collection of brass tubing cutoffs, which yielded a pair of very-nearly-perfect slip fit pieces that neatly adapted the small ferrules to the large stops.
Rear shift cable with modified ferrules
Life is good…
I have no idea what the cables look like on weight-weenie exotic-frame bikes. For sure, this isn’t a trick for hydraulic disk brakes.
Incidentally, the cable housing length worked out to 130 mm. Neither of the charts in the SRAM X.7 instructions matched the TE’s butt end; the seat stay angle is halfway between what’s normal for diamond-frame bikes. So we picked a reasonable length and it seems to be OK.
As I mentioned there, I originally connected my bicycle-mobile amateur radio gadget to the ICOM IC-Z1A radio using separate mic and speaker plugs. That seemed like a good idea, but bicycles vibrate a lot and the plugs apply enough leverage to the jacks inside the radio to pry them right off the PCB. That requires a protracted repair session that I never wanted to do again.
The solution is to mount both plugs rigidly on the radio so that they simply can’t move. I dithered for a while and finally decided that function trumps good looks on this project, particularly given that our radios spend their entire lives inside a bag behind the bike seats.
The top picture shows the small aluminum plates I made to align the plugs to the HT jacks, along with a plastic gluing fixture to hold the plugs parallel while the epoxy cures. If you just jam the plugs into the radio without an alignment fixture, you will glue the plugs together in such a way that they cannot be removed: the radio does not hold the shafts exactly parallel!
Plug stabilization – What Not To Do
How do I know? Well, I tried doing exactly that by simply epoxying the existing plugs into place, applying enough epoxy putty to stabilize the plugs against the radio. Looks reasonable, but when it came time to take them out (and you will want to take them out, trust me) they are firmly and permanently embedded. I had to carve them apart to get them out.
The mic, speaker, and coaxial power jacks are 10 mm on center. The 2.5 mm mic plug has a small shoulder that required a matching recess in the plate, while the 3.5 mm speaker plug is basically a cylinder. I don’t use the coaxial power jack, having hacked an alkaline battery pack with Anderson Powerpoles. The plate’s external contour matches the flat area atop the radio around the jacks.
You could lay out and drill close-enough holes by hand, use a step drill to make the shoulder recess, and then let the epoxy do the final alignment. However, you want the center-to-center distance exactly spot-on correct, as the plugs won’t mate properly otherwise. I turned it into a CNC project for my Sherline mill, of course, but that’s just because I have one.
HT Plugs in gluing fixture
This picture shows two plugs epoxied into the plate. While the epoxy cures, the plate rests atop the fixture with the two plugs vertical and their shell flanges flush against it. I applied the epoxy with a toothpick and worked it into the gap between the threads and the plate.
The end result will be a pair of plugs that exactly match the radio’s jacks in a plate that sits firmly atop the radio’s case. You should find that the plugs snap firmly into place and the entire assembly is absolutely rigid.
Caveat: don’t use an aluminum plate if your radio depends on separate electrical connections for the mic and speaker plug shells. The IC-Z1A has isolated shells, but remains happy when they’re connected. My Kenwood TH-F6A HT uses the shells for entirely different functions and will not work with them shorted together.
With the epoxy cured, wire the connections as usual. I had a small cable with enough tiny wires to put the mic conductors in their own shielded pair, but that’s likely overkill.
Finished plugs with epoxy blob
You could machine a nice enclosure, but I simply molded an epoxy putty turd around the connections, shells, and cable. The trick is to wait until it’s nearly cured, plug it into the radio, then shave off whatever gets in the way of the knobs, antenna plug, and other appurtenances.
The little red pointer inside my Tour Easy’s rear SRAM Grip-Shift broke. Back in the old days, this wouldn’t be a problem, as we used friction shifters on the downtube (as we rode to school, uphill, in the snow, both ways) and knew by feel which gear was engaged. But that was then, this is now, and fixing things is what I do anyway.
The pointer turned out to be a thin plastic strip, molded into an L with a domed arch over the pointy end. It simply rests in a slot in the shifter mechanism, held in place by the transparent cover (which, mercifully, came off without dismantling the bike or even removing the cable).
I made a similar replacement from thin red-anodized aluminum, but that didn’t work out at all. The mechanism snaps from one gear to the next at roughly the speed of heat, accelerating the pointer so rapidly that the aluminum deformed. Score one for plastic!
Actually, I made two aluminum pointers. Prototype One vanished into the Sargasso heap in front of the Solvents & Lubricants Shelves at the first upshift; that’s when I discovered just how much snap that shifter applies to the pointer. Made another one, installed the cover, and then discovered it wasn’t going to work.
So I applied some Plastruct solvent adhesive to the broken plastic bits, lined the parts up on my crusty surface plate, applied a bit of gentle pressure overnight, and in the morning had a like-new pointer. It installed just fine and works like the original.
Solvent-bonded plastic is supposed to be just about as strong as the original material. We’ll see just how long this repair lasts…
Pop Quiz: Do you know the first four derivatives of position w.r.t. time?
Answer: Velocity, acceleration, jerk, and snap. You could look it up…
Update: Alas, the repair lasted only about two weeks before failing at the same spot. Some deep rummaging produced a similar (but more thoroughly dead) SRAM shifter. Turns out the pointers are similar, so I salvaged the older one. Ya gotta have stuff… and remember it, too, which is becoming something of a challenge.
Our Tour Easy recumbents have linear-pull brakes on the rear and, for some reason, the noodle on Mary’s bike didn’t quite clear the frame: the cable bent slightly around the frame when the brake was active.
That made the brake difficult to adjust, as linear-pull brakes depend on an exact balance between the restoring springs on each side. With the cable pulling to the right, the left-side pad would contact the rim first and give the brake lever a mushy pull until the right-side pad clamped down.
A quick lathe session applied to some nylon scrap turned out an extension tube that fit between the steel noodle and the (slightly broken) plastic hoodickie that engages the brake arm. I used nylon (or something slippery like that) to make sure the cable wasn’t going to bind on it.
Epoxy Potting
The noodle originally fastened into the plastic hoodickie with a small collar that snapped into a pair of holes, but I took a shortcut: JB Kwik Epoxy. The shank end of a small drill slip-fit into the hoodickie’s cable passage kept the extension aligned while the epoxy set up. The masking tape prevented the epoxy from drooling out through the two small holes: the cured epoxy plug will have a pair of retaining posts in exactly the right places. The smears on the plastic parts chipped right off, not that anybody will ever notice.
I’m depending on spring force to hold the noodle in the extension, which seems to be working just fine. This is one of those jobs where everything’s under compression all the time and the cable tension ensures good alignment.
The socket on the extension’s fat end is a snug fit to the collar swaged on the noodle; other noodle varieties seem to have other sorts of ends, so check to make sure this will work for you.
These pix show the brake assembly from below (the paint failed on the frame cross-member early on and I’ve been meaning to slather some rust converter on that spot for years. Sigh.) and the now-positive clearance between the brake cable and the frame with the brake applied.
The Smell of Molten Projects in the Morning 