Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Back in the early 90s, I bought a Branson Ultrasonic Cleaner for small parts. It turned out to be ideal for eyeglasses, migrated to the bathroom, and has been used at least daily ever since. After nigh onto three decades, this happened:
Branson ultrasonic cleaner – failed switch cover
We tend to push the ON button and let it turn off by itself after a little over four minutes (exactly 255 seconds!), so the gray plastic sheet over the ON switch failed first. You can barely see the outline of the transparent film previously covering both switches, which probably helped waterproof the switches.
The gray plastic disk sits atop the switch actuator, so I punched a slightly larger polypropylene disk (from my stash of clamshell packages), stuck it to the disk with double-sided tape, lined it up over the hole, and covered the mess with Kapton tape:
Branson ultrasonic cleaner – expedient fix
This is in the nature of an expedient fix, as I’m not sure the polypro disk is flexible enough. The next iteration will cover the entire gray area and I’ll see about a transparent tape covering.
The flanges around the door of our giant mailbox rusted through, leaving the door to bend along the embossed (debossed? Whatever) lines across the front. Eventually, the bend got bad enough to keep the door from latching closed, but reviews of the current crop of mailboxes suggest they’re even more prone to rusting after even fewer years.
Well, I can fix that:
Mailbox door rebuild – installed
Because the bottom third of the door, basically everything around and below that horizontal ridge, had corroded, the general idea was to stiffen it with an internal plate:
Mailbox door rebuild – interior
The array of small holes suggest the plate’s rich lived experience. Some are even tapped!
External angle brackets stiffen the sides along the corroded flanges and surround the equally corroded pivot holes:
Mailbox door rebuild – exterior
The term “brick shithouse” springs unbidden to mind, doesn’t it? Those spare holes come from previous uses; I decided this application didn’t demand cosmetic perfection and, as a result, the remaining angle stock has no holes at all.
Also, the angle brackets are as long as they are because that’s the maximum throat depth for Tiny Bandsaw™. I splurged on a Proxxon 10-14 TPI blade (for future reference: PN 28172) that cuts aluminum like butter, much better than the stock 14 TPI blade.
The hinge pins used to be rivets. After careful consideration, I replaced them with 1/4-20 button-head cap screws:
Mailbox door rebuild – hinge detail
Yes, the sheet metal now pivots on screw threads, rather than a nice smooth cylinder. The nyloc nut maintains the proper amount of looseness around the battered sheet metal.
While I had the door open, I slobbered hot melt glue over the flag anchor, which should keep it from spitting the ratchet pin into the roadside debris ever again:
Mailbox door rebuild – flag anchor
A pleasant evening of Quality Shop Time, indeed!
The alert reader will note I’m securing aluminum plates with stainless steel hardware on a (nominally) galvanized steel box, thereby forming several batteries with a brine electrolyte from wintertime road salt. My engineering judgement determined this repair will last Long Enough™ and, most likely, succumb to somebody not quite making the curve while accelerating from the traffic signal.
The rear tire of my bike was flat before our morning ride and pumping it up produced a hissing sound with a spray of tube sealant:
Marathon tire puncture – tread gash
We run Schwalbe Marathon Plus tires on the rear of our Tour Easy ‘bents, because otherwise I’d be spending far too many hours repairing flats by the side of the road. Searching the blog for the obvious keywords will produce many examples of what it’s like to ride a bike in Dutchess County NY.
Schwalbe says the tires have 5 mm of “highly elastic special rubber” and claims “Even thumbtacks can’t puncture it.” They use the term “Flat-Less” in the sense of “flat less often”, rather than “not flatting”, which seems disingenuous at best.
Flatting less often may be true, but they obviously haven’t tested against Dutchess County road debris:
Marathon tire puncture – glass chip
It’s not quite 5 mm in the longest dimension, but it was embedded deep enough in the tire tread to cut through the armor belt and nick the Michelin Protek tube:
Marathon tire puncture – tube damage
Of course, the hole is dead-center between the two bumps that are supposed to compress around the puncture while the goo fills and seals the void.
Before taking everything apart, I tried gently inflating the tire and putting the puncture at the bottom to let the sealant fill the hole overnight. In the morning, the tire was once again flat, although the floor wasn’t covered in goo. Pumping the tire up produced another spray of sealant.
It’s likely the Protek tube got me home with a slow leak on the previous day’s ride, but it definitely didn’t solve the problem and, frankly, I’ve had ordinary tubes do the same thing. Given the trivial size of the puncture and the complete lack of permanent self-repair, I don’t know what kind of damage it’s supposed to cure.
I’ve already discarded two Protek tubes with slow leaks through the valve stem and no punctures, so they’re definitely not worth the hassle. Michelin no longer lists the tubes on their bike tire site, so it seems they agree.
I made up a boot by punching a 5 mm polypropylene disk, sticking it to a small tire patch, then sticking the patch over the puncture on the tire. With a bit of luck, nothing will line up with the gash and punch through the boot.
I recently replaced all four tires on the Forester, slightly ahead of schedule for reasons not relevant here, and it’s worth noting that a Marathon Plus tire costs about a third of what I paid for a car tire; they’re not to be discarded lightly.
It’s been sitting there for least five years, as witnessed by the sun-yellowed hot melt glue blob, which is pretty good service from a switch intended for indoor use. The 3D printed button never fell off and, in fact, was difficult to remove, so that worked well.
I took it apart and cleaned the contacts, but to no avail, so her bike now sports a new switch with a similar rounded dome:
Tour Easy – new PTT switch
I clipped the wires a bit beyond the terminals and soldered the new switch in place, so it’s the same cable as before.
Ordered 100 stainless steel M3 washers from a “US Seller”, received this:
M3 stainless steel washers – short count
Yeah, it looked a bit short to me, too.
The chopped and bent washers in the upper right corner suggest the seller got floor sweepings from his source, which is about what you’d expect for a bottom-dollar vendor.
The seller refunded half, which wasn’t particularly generous, but I wasn’t ready to go to the mat for two bucks.
Unfortunately, the thermal tape on one of the CPU heatsinks was sufficiently wrinkled to prevent good contact with the CPU:
RPi taped heatsinks – as received
The seller sent a replacement copper slug with tape on one side. Presumably, they glue it to the heatsink with thermal silicone:
Moster RPi Heatsink – silicone adhesive
Of which, I have none on hand.
So I did what I should have done originally, which was to drop a few bucks on a lifetime supply of thermally conductive heatsink tape, apply it to the bare side of the slug and stick the slug to the heatsink with their tape:
Moster RPi Heatsink – replacement adhesive tape
The blue stuff is the separation film, with the tape being white. It doesn’t match the black tape on the other side, but seems gooey enough to work.
Done!
Despite the heatsink hype, ball grid array chips dissipate most of their heat through their pads (and perhaps a central thermal pad) into the PCB, so sticking a heatsink atop the package is largely decorative, along the lines of hotrod ornamentation.
The epoxy packages used in previous Raspberry Pi iterations had better thermal conductivity to their top surface:
RPi 3 B – epoxy CPU
Than the more recent metal-top packages, which surely have inert-gas fill under the lid:
Yes, the heatsink does conduct some heat into the air, even if not nearly as much as you might want.
(*) I’m pretty sure “Moster” was a typo in the original eBay listing which took on a life of its own to become something of an unofficial trademark. All of the search results ship from Duluth, Georgia (USA), regardless of the nominal seller; feel free to draw your own conclusions.
The Smell of Molten Projects in the Morning 