Sunday, March 31, 2013

A Weed Digger Restoration

This old weed digger spent the winter outside, and it's looking the worse for it.

The shank and ferrule are rusty, and the handle's paint is peeling in spots -- shameful. I'll have to set this right.

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My wire wheel machine took care of the rust in fairly short order. I've sanded the handle. (By rights, I ought to strip the old paint off entirely, but I'll just repaint over the old paint and hope for the best.)

There are a few little details about the ferrule that could stand attention. One is this needless void at the shank end of the ferrule.

I'll fill that with five-minute epoxy and create a sealed fillet that won't admit water.

And here we are.

Much better.

There's a deep dimple in the side of the ferrule.

I imagine that was done for retention of the ferrule, but it's beyond being just a dimple -- it's a puncture. I'll fill that with with five-minute epoxy to seal and level it. I'll apply CA adhesive around the ferrule/handle interface to seal that.

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Here's the dimple filled and ready for painting.

What I did there was I overfilled the dimple with epoxy. Once it hardened, it was easy to file and sand it level. Epoxy is a superb filler -- that's mostly what I use it for.

Now I can mask the handle, and paint the ferrule and shank gloss black. Once that paint has thoroughly hardened, I'll mask the ferrule and repaint the handle yellow.

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All Done -- SUNDAY, APRIL 21, 2013

Here it is fully painted.

Much better.

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Saturday, March 30, 2013

A Broken Patio Light Repair

I think a swung snow shovel is what did in this little solar-powered patio light earlier this year.

It really got whacked. It's a nasty, ragged, pulled-out break, but I was able to coax it to fit back together, like so.

That went well; all the edges of the break are mated with one another. Now I have a favourable situation for a good repair.

I'll apply fresh, runny[1] CA adhesive along all the break lines so it can wick in and adhere the pieces together. That should produce an effective, durable repair. (And when the adhesive I apply from the outside has cured, I'll reapply it from the inside to make certain that all the break lines are filled with adhesive.)

- - -

While the adhesive is curing, I can check the condition of the lamp's energy cell contacts. Those tend to be a weak point in these lamps -- the contacts oxidize and foul. Here's a view of this lamp's positive contact.

That's fairly typical. The negative terminal is bright and clean, except for a wad of spider fluff lodged in it. I'll scrape away that oxidation from the positive terminal and put the cell back in with WD-40 applied to its contacts, and this light should be back in business.

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Not Quite

The cell was completely discharged, and it refuses to accept charge. Fortunately, I have a spare on hand. I put that in and it appears to be accepting charge.

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One More Thing

At one point, the light quit working. I think the little on/off slide switch may have been responsible for that. I opened up the light's innards to inspect them, and lubricate the switch with WD-40. If you've ever wondered what's inside these things, the answer is "not much". Here's a view of this light opened up.

The heart of it is a tiny four-terminal integrated circuit (IC), a 'JD1803'. I tried to find a datasheet for it and couldn't.

Anyway, it's working. I've put it out in the sunlight to charge. I'll try to get a decent photo of it doing its job when the sun goes down today.

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Update -- SUNDAY, MARCH 31, 2013

The light worked fine last night, but I couldn't get a good photograph -- all I could get was a splotch of brilliance in the midst of darkness. I'll have to learn how to photograph such things properly.

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[1] Fresh CA adhesive is extremely runny, which is exactly what's needed for a repair like this. Adhesive that's thickened might still work, but it wouldn't be nearly as effective.

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Thursday, March 14, 2013

Flaky LED Flashlights

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[Update -- WEDNESDAY, OCTOBER 16, 2013

Since I wrote this post, I've seen evidence to suggest that there may be more to LED flashlight flakiness than meets the eye, and that I may have been mistaken in my diagnosis of the cause of it. I'll leave the post in place below as I originally wrote it, but be aware that it may be fallacious.]

* * *

I'm a big fan of LED flashlights; I have a bunch of them that my son got me for Christmas two years ago. I think they're the neatest thing since the Ford 8N tractor.

However, as with all electro-mechanical devices, LED flashlights can exhibit misbehaviours. Two of my small flashlights had the annoying habit of dimming, or going out altogether now and then. A rap against a hard surface would get them back to full brightness, at least until they'd randomly dim or go out again. As it turns out, there's an explanation for why they were doing that, and there's a fix.

Here's a view of the two troublesome flashlights.

The key to this is the manner in which the head-end of the flashlights is assembled; the clear 'lens' is a 'snap-fit' part that retains the little LED array circuit board assembly inside, and establishes its electrical connection to the metal shell of the flashlight. Using a 3" length of 3/4" copper pipe as a 'punch', the whole business can be dismantled with a tap from a light mallet, like so:

Note two things -- the three spots of solder at the periphery of the circuit board, and the un-anodized (bright, uncoloured) ledge inside the flashlight's red shell. That's where the battery current circuit is made between the LED array and the shell of the flashlight. If the circuit board is not pressed tightly against the naked metal ledge, the flashlight will be flaky.

Anyway, so much for 'show-and-tell'. The upshot of all that is that there's no need to dismantle one of these little flashlights in order to fix it. All it takes is to punch the LED array down tighter, like so.

Strike the periphery of the lens lightly and evenly all around to firmly seat the LED array's circuit board against the naked metal ledge inside, and the flashlight will work reliably.

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Update -- SUNDAY, APRIL 21, 2013

The trouble recurred on the red flashlight. These things have a design flaw -- the battery contact at each end of the battery is a coil spring, applying its force in exactly the direction likely to unseat the LED circuit board from its contact ledge. I punched the lens down again, and that got the flashlight working again, but I'll have to give some thought to a way to correct the flaw permanently.

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Sunday, March 10, 2013

Aids to Layout and Centre Punching

My near vision is not what it used to be. I'm in no hurry to get reading glasses, though, because I can still read ok, and because getting reading glasses involves business and commerce, and I loathe business and commerce. However, moderately precise work with centre punches and the like can be a bit challenging. Here are a few things I've found helpful.

Masking Tape

Masking tape is a great layout medium for metalworking, and even woodworking at times. Here's an example of its use for spotting a hole location on a small piece of steel flat.

Note the two centre punches. The smaller one I keep finely pointed and sharp. The larger one is relatively a bit blunt.

Illuminated Magnifier and Black Marker

What I do with the black marker is I blacken the tip of the fine centre punch. That has a remarkably good effect on my ability to see the tip of the punch clearly. Here's how I proceed:

a) Hammer ready next to the back of the vise.

b) Viewing through the magnifier, I get the point of the punch positioned at the intersection of the lines, and press the point lightly down on the tape. That gives me a non-skid dimple in the tape that will retain the punch point's position, while I carefully move the work and the punch together to the back of the vise.

c) My left hand takes over holding the punch. I pick up the hammer with my right hand and strike the punch. Here's the outcome.

Maybe not perfect to within 0.0005", but not bad at all -- probably far better than I would have done without the aid of the tape and the blackened punch point.

I follow up with the bigger, blunter centre punch, and I've got a punch mark that will get a pilot hole started truly.

The fine centre punch's tip must be re-blackened for each use. On large work, have the work well lit, and use a hand-held magnifier to achieve the same effect.

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Saturday, March 2, 2013

Household Dashboard Instrumentation

[Every so often, I like to tackle some little project that really, truly needn't be tackled. This post sheds some light on why that is.]

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The other day, it came to mind that I have this gorgeous old Smiths oil temperature gauge that's been sitting idle in a box for decades. Here's a view of it.

It's an item I acquired in my adolescence that I never got around to installing in a vehicle. (As for why I ever thought I needed an oil temperature gauge, let's just say that it seemed like a good idea at the time, and leave it at that.)

The gauge is a proper Bourdon tube type with a sensing bulb and capillary tube. I could try to sell it -- it seems these classic gauges are worth a few bucks -- but I'd rather enjoy the use of the thing. I could install it in my truck, but I really don't feel like doing that. So, what to do with it? How about installing it as a furnace hot air plenum temperature gauge? I think that would be a fine thing for a house to have.

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Things I'll Need

  • A mounting panel for the gauge.
  • A flange to fit the sensing bulb to the sheet metal wall of the plenum.
  • A power source for the gauge's light bulb.
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The Mounting Panel

I have a piece of brushed aluminum salvaged from an old impact printer that will serve nicely for panel material. Let's see what I can do with this.

This part is a pretty straightforward thing to fabricate. I should point out something about the use of a fly cutter, though. Here's a view of the setup I used for cutting the 2 1/32" diameter gauge hole.

Whatever it takes, the work must be absolutely, positively secured. Your hands are not to go anywhere near the work while the fly cutter is in operation. Use your machine's lowest spindle speed. Slow and easy feed of the cutter gets the job done.

Here's the panel off the drill press and trial-fitted to the gauge.

Fly cutters are a devil of a thing to adjust for an exact hole size, and right off the drill press the hole was 1/64" undersize. I had to enlarge it with a 1 1/2" diameter sanding drum with a coarse sleeve on it. For a critical job that has to come out exactly right, one would be wise to do a trial cut on scrap material.

Note that I did the layout marking for the panel's semicircular lower perimeter prior to cutting the hole. The centre-point for the hole is also the centre-point for the perimeter, so the complete layout had to be done prior to obliterating the centre-point. That sort of work-sequence consideration arises often. It pays to be mindful of it.

Here's the finished panel, all shaped and deburred and polished and ready for installation.

I did the shaping on the new belt sander/grinder I acquired recently. I'm quite pleased with the machine. This little shaping job was a breeze with it.

Next up is the flange for installing the sensing bulb in the furnace plenum. That will be a little more challenging than the mounting panel was.

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The Flange w/Pipe Fitting -- SUNDAY, MARCH 3, 2013

Here it is.

At the left is one if the 2" square sill-plate washers I started with. I added the four 3/16" mounting fastener holes, and bored out the 9/16" bore to 5/8" to accept the pipe fitting that accepts the gauge's sensing bulb, then soldered[1] it together. I've cut a roughly 3/4" diameter hole in the wall of the plenum with a fly cutter.[2] That'll do for this weekend.

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Installed -- SATURDAY, MARCH 9, 2013

Here's the gauge attached to the underside of the main hot air duct, in a spot where I can see it easily, but it's out of harm's way.

And here's the sensing bulb end of the capillary tube mounted in its pipe-fitting flange. (I thought the flange deserved a paint job, so I gave it one.)

All that's left is to provide power for the gauge's light bulb.

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Gauge Illumination Power -- SUNDAY, MARCH 17, 2013

12.6 volt filament transformers from vacuum tube days are a near-ideal power source for 12 volt automotive light bulbs, and I happen to have one on hand that's suitable for this. Here it is fully installed and operational.

The transformer's primary winding line cord is plugged into a switch-controlled outlet, so the transformer is only energized when I need/want it to be.

One end of the transformer's secondary winding is tied to the same air duct's sheet metal (i.e. earth ground) that the gauge's frame is attached to, so this gauge illumination installation is no different from that in a vehicle -- only one discrete electrical conductor is needed to feed the gauge's light bulb, like so.[3]

The lighting effect is adequate, but dim and unspectacular -- it doesn't photograph well.

As the furnace runs, the gauge's reading peaks at about 40 degrees Celsius (104 degrees Fahrenheit). It's not great utilization of the gauge's scale, but it's better than having the gauge sit idly taking up space in a box, and it does give me some information.

I suppose that a rising peak plenum temperature would be indicative of the filters becoming clogged and diminishing the air-stream.

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Now, where to from here?

A plenum air-velocity gauge comes to mind. A plenum air relative-humidity gauge would be nice. A plenum air particulate matter counter wouldn't hurt. (Did I mention that I really like instrumentation?)

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[1] Mild steel solders quite readily with tin/lead solder and ordinary paste flux, but the steel must be absolutely, positively free of oxides. In preparation for soldering the pipe fitting to the sill-plate washer, I sanded the washer with medium aluminum oxide paper on an orbital sander. That was the one sure way I could be certain of getting down to bright, clean steel that would accept tin/lead solder. Steel-wooling and/or wire-brushing would likely have been inadequate.

[2] The same fly cutter I used for the 2 1/32" diameter hole in the mounting panel. Using a fly cutter with a portable drill is not a good practice, but this was a case where it was a reasonably safe and sure thing to do. The work (the plenum's wall) was absolutely immobile. The material was thin. The fly cutter was sharp. As with the larger diameter hole done on the drill press, slow rotation speed and a gentle, easy rate of feed get the job done.

[3] This is the great thing about a DeVry Institute of Technology education in Electronics Engineering Technology -- you know how to wire up stuff like dashboard gauge lighting in unorthodox applications.

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What's Inside?

"What's inside?" is my favourite question. I love knowing 'what's inside'. Had I been born many centuries earlier, I might have been one of the early anatomists of the human body -- God knows what all sort of trouble such a pursuit might have gotten me into.

As things are these days, I'm content to satisfy my curiosity about 'what's inside' with inanimate objects like laser printers and gasoline engines and electric toothbrushes. It so happens that I have an electric toothbrush that's reached retirement age. Before it's consigned to the landfill, it behooves me to see what's inside. Here goes.

Here's a view of the toothbrush's handle.

Note the notches in the white base of the thing. They suggest to me the possibility that the base might 'unscrew'. Let's see.

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Nope. It turns, with accompanying crunching sounds, but it doesn't unscrew. Oh well, on with plan 'B' -- I'll saw it open. Here we are.

And here it is further dismantled.

It's quite an exquisite little piece of engineering. I look forward to seeing advertisements for courses at the DeVry Institute of Electric Toothbrush Repair.

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