Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
My high hopes for the UHMW bushing supporting the impeller lasted the better part of a day, because direct contact between the impeller and the motor bearing produced an absurdly loud and slowly pulsating rumble:
Bath Vent Fan – bushing installed
My hope that the UHMW would wear into a quieter configuration lasted a week …
Back in the Basement Shop, some free-air tinkering showed the impeller produced enough suction to pull itself downward along the shaft and jam itself firmly against the motor frame. My initial thought of putting a lock ring around the shaft to support the impeller turned out to be absolutely right.
So, make a small ring:
Bath Vent Fan – small lock ring – c-drill
With a 4-40 setscrew in its side, perched atop the impeller for scale:
Bath Vent Fan – small lock ring – size
It just barely fits between the impeller and the motor frame:
Bath Vent Fan – small lock ring – installed
This reduced the noise, but the hole in the impeller has worn enough to let it rotate on the shaft and the rumble continued unabated. The correct way to fix this evidently requires a mount clamped to both the shaft and the impeller.
Fast-forward a day …
A careful look at the impeller shows seven radial ribs, probably to reduce the likelihood of harmonic vibrations. After a bit of dithering, I decided not to worry about an off-balance layout, so the screws sit on a 9 mm radius at ±102.9° = 2 × 360°/7 from a screw directly across from the setscrew in another slice from the 1 inch aluminum rod:
Bath Vent Fan – mount ring – tapping
Centered on the disk and using LinuxCNC’s polar notation, the hole positions are:
As usual, I jogged the drill downward while slobbering cutting fluid. I loves me some good manual CNC action.
Put the mount on a 1/4 inch tube, stick it into the impeller, and transfer-punch the screw holes:
Bath Vent Fan – mount ring – impeller marking
Apparently, some years ago I’d cut three screws to just about exactly the correct length:
Bath Vent Fan – mount ring – test fit – bottom
I knew I kept them around for some good reason!
The 9 mm radius just barely fits the screw heads between the ribs:
Bath Vent Fan – mount ring – test fit – top
Some Dremel cutoff wheel action extended the motor shaft flat to let the setscrew rest on the bottom end:
Bath Vent Fan – mount ring – shaft flat
Then it all fit together:
Bath Vent Fan – mount ring – installed
The fan now emits a constant whoosh, rather than a pulsating rumble, minus all the annoying overtones. It could be quieter, but it never was, so we can declare victory and move on.
Dropping fifty bucks on a replacement fan + impeller unit would might also solve the problem, but it just seems wrong to throw all that hardware in the trash.
And, despite making two passes at the problem before coming up with a workable solution, I think that’s the only way (for me, anyhow) to get from “not working” to “good as it ever was”, given that I didn’t quite understand the whole problem or believe the solution at the start.
But it should be painfully obvious why I don’t do Repair Cafe gigs …
My collection of old USB cameras emitted a Logitech Quickcam for Notebooks Deluxe, with a tag giving a cryptic M/N of V-UGB35. Given Logitech’s penchant for overlapping names, its USB identifiers may be more useful for positive ID:
ID 046d:08d8 Logitech, Inc. QuickCam for Notebook Deluxe
It works fine as a simple V4L camera and its 640×480 optical resolution may suffice for simple purposes, even if it’s not up to contemporary community standards.
The key disassembly step turned out to be simply pulling the pivoting base off, then recovering an errant spring clip from the Laboratory Floor:
Logitech V-UGB35 USB Camera – mount removed
The clips have a beveled side and fit into their recesses in only one orientation; there’s no need for brute force.
Removing the two obvious case screws reveals the innards:
Logitech V-UGB35 USB Camera – PCB rear
Three more screws secure the PCB:
Logitech V-UGB35 USB Camera – PCB front
The ribbed focus knob around the lens makes it more useful than a nominally fixed-focus camera.
While packing the vacuum tube LEDs for the HV Open Mad Science Fair, I noticed the knockoff Arduino Nano inside one had come unstuck from the base. It seems the double-stick foam tape I’d used had lost its sticky:
Vacuum Tube LEDs – unstuck foam tape
Replacing it with my now-standard black 3M outdoor rated tape ought to solve the problem forever more.
For whatever it’s worth, the SK6812 RGBW LEDs have had exactly zero failures in the last two years or so; I finally turned off the test fixture.
Before reassembling the light, I plugged the USB cable into the bench supply and watched the Nano reset erratically. Careful poking showed the USB cable was intermittent, so I carved it up:
Failed USB cable – autopsy
As far as I can tell, the black wire (supply common) was cut mostly all the way through, with just a few strands remaining, before I peeled the insulation back.
A closer look at the solder joints doesn’t inspire much confidence in their QC:
Failed USB cable – solder joints
If those pads tarnished along with their solder blobs, the overmolded plastic isn’t the right stuff for the job. If they started life like that … ick.
I must up my cable spend, although I have no confidence doing so will improve the quality.
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
Which meant the impeller was now resting on the steel frame:
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
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
It’s hard to see between the impeller blades, but there’s actually a bit of clearance underneath:
Bath Vent Fan – bushing installed
Which left just barely enough room on the top for the retaining clip:
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.
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
The OD required touching up the edge of a brass tube punch I’d made a while ago:
Astable – Radome adhesive – punch sharpening
It worked exactly as expected:
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
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.
The Smell of Molten Projects in the Morning 