Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
When the second hinge on my father-in-law’s scanner broke, he asked if I could fix it:
HP3970 Scanjet Lid – broken hinge
It’s a flatbed scanner, so the lid is nearly 18 inches long and weighs 2.2 pounds with the slide / negative backlight illuminator. The stress raiser notches, located exactly where the cracks started, look like a perfect example of how not to do these things.
I solvent-glued the hinges back together, with a square brass tube applying clamping force to the joint overnight, but this certainly won’t last for long:
HP3970 Scanjet Lid – crude repair
HP used to have some really smart engineers, but this looks like it was done by a Newkid (I was one, once, so I know the type) after a solid modeling and simulation session convinced him that those two thin plastic webs had enough strength for the job.
No. They. Do. Not.
Of course, HP provides no Official Way to repair that failure, as the hinges emerge seamlessly from the injection-molded plastic lid frame: you must scrap the scanner and buy a new one, because the lid would cost more than a new scanner. Equally of course, the fact that they don’t have a Windows driver beyond XP makes replacement a foregone conclusion.
It runs under Xubuntu 12.04, mostly, which is what I set him up with after the XP PC got compromised.
For reasons best left to the imagination, we needed some large signs for the front yard. I must look this up every time I do it, so here’s the process…
Create document in LibreOffice (or whatever), save as PDF
Convert PDF to EPS = Encapsulated Postscript
Apply poster to enlarge & paginate
Convert PS to PDF for ease of printing
Bash does the heavy lifting, after you install whatever packages your Linux distro may not have included:
A Master Combination Lock emerged in locked condition from a box o’ stuff I handled during Mad Phil’s Great Cleanout. It’s not the highest security lock you’ll ever meet; about 15 minutes of fiddling produces the desired result:
Master Combo Padlock – opened
A bit of searching suggests it’s similar to the Master No. 1523D Combination Padlock, although this one came in pink. The doc describes how to change the combination:
Unlock (or crack) the lock
Pull off the spring-loaded endcap (I had to pry with a screwdriver)
Slide off the combination wheels
Reinstall in desired orientation
After removing the cap and wheels, it looks like this:
Master Combo Padlock – wheels off
Each wheel fits onto a rotating metal disk and engages three teeth, one of which has a notch. Align all four notches with the Master logo / index line and the lock opens:
Master Combo Padlock – dial alignment marks
Given just that picture, I think you can figure out how to get past one of these in a hurry. Right?
Driven by forces beyond my control, I had to rent a carpet cleaner from a local Big Box home repair store. The rugged line cord plug had an unusual (to me, anyway) strain relief fitting on the back, consisting of a circumferential clamp around the cord and a large diameter, deeply recessed opening on the nut to prevent the cord from flexing sharply:
AC Line Cord Plug – clamp nut
But something seemed odd, so I unscrewed the finger-tight clamping nut:
AC Line Cord Plug – clamp fingers
Whoever installed the cord cut the insulation back far too much, as those fingers should close on the insulation jacket, not the conductors.
I fought down my instinctive response, took a deep breath, clicked my heels together three times, repeated “This is not my problem”, and suddenly it wasn’t my problem any more. I tried reporting it to the harried clerk at the Big Box Store, but she instantly fluttered off to help somebody else after noting my return in the Big Book of Rental Contracts.
The hard-floor brush for our old Samsung VAC-9048R vacuum cleaner began scratching the hardwood floor, which called for some investigation & repair. The Fine Manual doesn’t even mention the hard floor brush, so it’s obvious I’m on my own (as is usually the case). Believe it or not, we actually discussed buying a vacuum cleaner, but the new ones have poor reviews, bulky & awkward plastic widgets on the handle, or suffer from other glaringly obvious faults; although this one is aging poorly, it’s at least workable. Plus, I bought a lifetime supply of bags when it was new and it’s not dead yet.
So, we begin…
The rollers that used to support the front of the brush have worn down, allowing the bottom cover to erode on the floor. The right side ran through something sticky in the recent past:
Samsung 9048 – worn roller – right
The left side may not be sticky, but it’s in no better shape:
Samsung 9048 – worn roller – left
Remove the two obvious screws, pry the front edge up, and the whole cover plate pops off to reveal the two rollers. They pull straight out of the shaft support brackets molded into the top frame. Even their metal shafts show grievous wear:
Samsung 9048 – worn roller parts
The rollers consist of a hard plastic hub supporting a flexible rubbery tire, turning on a 3 mm steel shaft that’s worn on one side (which was downward, of course). The central holes in the rollers probably used to fit the shafts, but they’re now worn to 4 mm ID. The tires were probably a lot larger in diameter, too, back when they were new.
A bit of rummaging in the Basement Laboratory Warehouse Wing produced a bag of vibration isolation bushings that had about the right consistency to become tires:
Samsung 9048 – rollers and surplus vibration isolation bushings
They’re much larger than necessary, but are now, shall we say, fully depreciated and ready for a new, if somewhat downsized, lifestyle.
Unfortunately, they don’t fit onto the existing hubs, so I can’t use the hubs as a template. Fortunately, I have a lathe and some random nylon stock (with crosswise notches that didn’t pose much of a problem):
Samsun 9048 – turning roller hub
I came to my senses before converting this into a 3D printer project. If I had to make more than two hubs, it’d be a good idea to solid-model and print them, even if they’re just barely large enough to allow solid infill:
Samsun 9048 – finished roller hub
I’d go for a 3 mm ID to increase the wall width; these have a 4 mm ID to fit the brass bushings described below. There’s no significant overhang and they’d print with no problems. Maybe next time?
The isolation bushings cut easily with a sharp razor knife, so I pared them down to a bit over what I estimated to be the finished roller OD and width:
Samsung 9048 – roller tire before grinding
The 10-32 screw in that shiny new hub serves as an arbor in the lathe, where I held a Dremel tool with a sanding drum down on the compound rest, ran the lathe at its slowest back-gear speed, and sanded the bushing down to what seemed to be the right OD for the tire:
Samsung 9048 – grinding roller tire
The white snout in front leads to a shopvac that caught most of the dust. The front of the lathe chuck shows it wasn’t perfectly effective and I should have worn a dust mask; my glasses didn’t collect much dust, so maybe my lungs didn’t, either.
A trial fit in the floor brush body showed that this one was slightly too large and the sides needed tapering. The inside view:
Samsung 9048 – ground roller before side trim
The outside view, with the cover just slightly unable to snap closed:
Samsung 9048 – slightly oversize roller in place
Grinding a bit more off produced a pair of 15.5 mm OD tires which fit nicely. Some careful razor knife work smoothed and tapered the sides:
Samsung 9048 – finished rollers
Brass tubes (from the stash of cutoffs) compensate for the flat on the severely worn steel shafts; a fix that turned out to be much easier than building new shafts:
Samsung 9048 – roller shaft bushing hub
Then reassemble in reverse order and it’s all good!
I wrapped a layer of silicone tape around the large and slightly worn hard-plastic rear tires, even though I’m sure that won’t last very long at all:
Samsung 9048 – repaired hard floor brush – bottom
The shop doodle giving all the sizes:
Samsung 9048 – Roller dimension doodles
Now, if that doesn’t count as a gonzo repair, I don’t know what would… [grin]
So I finally got around to spraying some 10% bleach on an inconspicuous section of the roof (*) to see whether it would have any effect on that black fungus / mildew / crud. It’s too soon to tell, but in the process I discovered that the sprayer nozzle didn’t produce the nice, round pattern it used to. I completed the mission and took the nozzle to the basement. The problem was obvious:
Sprayer nozzle – with crud
Soaking it in vinegar didn’t have any effect; whatever made those deposits wasn’t soluble in water or mild acid. A few minutes with an awl and a (manually turned!) Dremel grinding point restored it to good condition:
Sprayer nozzle – cleaned
You’d be more careful cleaning the orifice of a fine spray nozzle, but this is for a hand-pumped garden sprayer: Good Enough.
As soon as the weather clears, we’ll see if the situation up on the roof has improved. If so, I get to spray the rest of it.
(*) The whole north slope over the garage, in case you’re in the market…
The Smell of Molten Projects in the Morning 