Archive for July, 2019

NuTone 8663RP Bathroom Vent Fan Bushing

The NuTone 8663RP (for future reference) vent fan in the Black Bathroom began making horrible grinding sounds and, after a day or two, stopped turning. Pulling it out showed the impeller had slipped downward on the motor shaft:

Bath Vent Fan - impeller shift
Bath Vent Fan – impeller shift

Which meant the impeller was now resting on the steel frame:

Bath Vent Fan - impeller interference
Bath Vent Fan – impeller interference

Curiously, there’s no retainer under the impeller preventing it from sliding downward, other than good intentions and a friction fit. Nothing lasts, although it’s been working for the last two decades, so I guess it doesn’t owe me much.

My first thought was to build a steel or aluminum collar with a setscrew to hold the thing up, but I decided to try a simple bushing made of UHMW polyethylene between the motor and the impeller.

Turning it to the proper length required a test fit, then another session on a mandrel made from some aluminum tubing:

Bath Vent Fan - bushing trim
Bath Vent Fan – bushing trim

The snout came out just long enough to clear the motor frame, resting the impeller’s weight atop the bearing around the shaft:

Bath Vent Fan - bushing installation
Bath Vent Fan – bushing installation

It’s hard to see between the impeller blades, but there’s actually a bit of clearance underneath:

Bath Vent Fan - bushing installed
Bath Vent Fan – bushing installed

Which left just barely enough room on the top for the retaining clip:

Bath Vent Fan - shaft clip - detail
Bath Vent Fan – shaft clip – detail

I had high hopes for the UHMW, but it seems any contact between the rotating impeller and the stationary bearing transmits enough sound to be annoying.

So I must break down and build a collar, although it’s off the critical path right now.

As far as I can tell from the pictures, dropping $50 on a new fan unit will get me exactly the same problem. Whether it would last for two decades before failing is an open question, but my experience with freezer fans suggests what we have is as good as it gets and making a bushing is the least-awful way to proceed.

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Exhibit Hand-Out Cards: QR Version

I’ve finally had it beaten into my head: any public exhibition requires paper handouts, if only for younger folks who are too shy to ask questions. Paper may seem obsolete, but it serves as a physical reminder long after the sensory overload of a busy event fades away.

Hence, I made up cards describing my exhibits at the HV Open Mad Science Fair, each sporting a QR code aimed at far more background information than anybody should care about:

Mad Science Fair - handout cards
Mad Science Fair – handout cards

The QR codes come from one-liners:

qrencode https://softsolder.com/?s=dso150 -s 5 -d 300 -o dso150.png

So, go ahead, shoot ’em with your phone:

  • Blog search QR code: astable
  • Blog search QR code: bowl-of-fire
  • Blog search QR code: dso150
  • Blog search QR code: halogen
  • Blog search QR code: hp7475a
  • Blog search QR code: tubes

Memo to Self: put the cards in the Big Box o’ Stuff the night before.

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Astable Multivibrator Blinkies: Radome Attachment

Ping-Pong ball radomes tend to fall off their perches at the slightest touch:

RGB LED - radome test
RGB LED – radome test

Because I planned to take my collection along to HV Open’s Mad Science Fair, I finally used a Round Tuit for some adhesive action.

The general plan was to punch a ring from double-sided tape, thusly:

Astable - Radome adhesive - poor surface
Astable – Radome adhesive – poor surface

The OD required touching up the edge of a brass tube punch I’d made a while ago:

Astable - Radome adhesive - punch sharpening
Astable – Radome adhesive – punch sharpening

It worked exactly as expected:

Astable - Radome adhesive - punching
Astable – Radome adhesive – punching

Unfortunately, the 3D printed spider’s “spherical” socket has such a rough surface that the adhesive had too few contact points to hold the ball in place.

My fallback has become 3M outdoor-rated double-stick foam tape, so:

Astable - Radome adhesive - 3M foam tape
Astable – Radome adhesive – 3M foam tape

This leaves a small black ring visible between ball and socket. Recessing the foam tape by half its thickness should improve its ahem optics, although it’s probably not worth the effort with black PETG.

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Walmart Wiper Selector: FAIL

After five years, I figured it’d be a Good Idea™ to replace the Forester’s wiper blades. Being in the Walmart at the time, I tried to use their helpful Wiper Selector gadget:

Walmart Wiper Selector
Walmart Wiper Selector

You’d think whoever is responsible for updating / replacing such things would have done so several times during the last eight years.

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Another Garden Hose Y Valve Autopsy

An outlet thread failed on yet another garden hose Y valve:

Garden Fittings - Failed Y valve - detail
Garden Fittings – Failed Y valve – detail

Out of an abundance of curiosity, I battered the remaining parts out of the carcass:

Garden Fittings - Failed Y valve - autopsy
Garden Fittings – Failed Y valve – autopsy

One of these days, we must buy an assortment of new fittings …

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Shower Curtain Magnet Anchors

Back in the day, bathtubs had a porcelain coating over a cast-iron carcass, so embedding little magnets in shower curtains worked perfectly to keep the loose ends from billowing out of the tub. Surprisingly, even here in the future, with plastic bathtubs ruling the land, some shower curtains still have magnets. The mud-job tile walls of shower stall in the Black Bathroom have nary a trace of iron, but we though I could add ferrous targets for a new shower curtain, thusly:

Shower Curtain Anchor - installed
Shower Curtain Anchor – installed

The magnet lives inside a heat-sealed disk, so it’s (more-or-less) isolated from the water. As you’d expect, it’s a cheap ceramic magnet, not a high-performance neodymium super magnet, with no more strength than absolutely necessary to work under the most ideal of conditions.

My anchors must also be waterproof, firmly attached, non-marking, easily removable, and no more ugly than absolutely necessary. The general idea is to slice the bottom from a pill bottle, entomb a thin steel disk in epoxy, and attach to the tile with a patch of outdoor-rated foam tape.

So, we begin …

Cutting a narrow ring from a pill bottle requires a collet around the whole circumference, which started life as some sort of stout aluminum pole:

Shower Curtain Anchor - cutting tube stock
Shower Curtain Anchor – cutting tube stock

Bore out the inside, with a small step to locate the bottle:

Shower Curtain Anchor - boring fixture
Shower Curtain Anchor – boring fixture

Clean up the outside, just for pretty:

Shower Curtain Anchor - turning fixture OD
Shower Curtain Anchor – turning fixture OD

Slit the fixture to let it collapse around the bottle, then chuck up the first victim with support from a conveniently sized drill chuck in the tailstock:

Shower Curtain Anchor - cutting bottle
Shower Curtain Anchor – cutting bottle

I did a better job of cutting the second bottle to the proper length:

Shower Curtain Anchor - parting base
Shower Curtain Anchor – parting base

Nibble disks from sheet metal, half-fill the bottle bottoms with steel-filled (and, thus, magnetic!) JB Weld epoxy, insert disks, add sufficient epoxy to cover the evidence:

Shower Curtain Anchor - epoxy curing
Shower Curtain Anchor – epoxy curing

Fast-forward to the next day, punch out two disks of double-sided foam tape:

Shower Curtain Anchor - adhesive foam
Shower Curtain Anchor – adhesive foam

Affix, install, and it’s all good.

Actually, it’s not. The ceramic magnets are so weak they don’t hold the curtain nearly well enough to satisfy me. The next anchor iteration should have embedded neodymium magnets to attract the curtain’s crappy ceramic magnets, but this is Good Enough™ for now.

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HP 7475A Plotter: Ceramic-Tip Pen EOL

Ceramic-tip plotter pens draw wonderfully crisp lines:

Spirograph pattern - black ceramic pen - detail
Spirograph pattern – black ceramic pen – detail

Eventually, though, the fiber tip wears flush with the ceramic shell, becomes slightly indented, and ceases to make its mark in the world:

HP 7475A Plotter - Ceramic pen - worn tip
HP 7475A Plotter – Ceramic pen – worn tip

As the lady says, “Starting from zero, got nothing to lose”, so I applied a fine diamond file around the tip:

HP 7475A Plotter - Ceramic pen - filed tip
HP 7475A Plotter – Ceramic pen – filed tip

Well, all I can say is it seemed like a good idea at the time.

Alas, even the newly exposed fiber didn’t make much of a mark on the paper and, as you’d expect, the ragged ceramic tip dragged painfully across the paper. I assume the fiber had filled with fossilized dry ink.

A New Old Stock bag of fiber-tip pens emerged from the Big Box o’ Pens while I was flailing around:

HP 7475A Plotter - NOS Green pen package
HP 7475A Plotter – NOS Green pen package

I think the “812” in the lower right corner is a date code, most likely early in 1988, so the pens started their lifetime countdown at least three decades ago. They still work, though:

HP 7475A Plotter - NOS Green pens
HP 7475A Plotter – NOS Green pens

The plotter appeared at HV Open’s Mad Science Fair, because everybody loves a plotter!

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