Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
For reasons I won’t go into, I just installed another water heater. This one, nominally a GE that’s made by Rheem, has a perfectly aligned anode rod access port. This view shows the insulation filling the port, after removing the plastic cap:
GE Water Heater Anode Rod – as shipped
A bit of excavation reveals the top of the rod:
GE Water Heater Anode Rod – excavated
And the 1-1/16 six-point socket fits exactly through the port and mates perfectly with the rod:
Evidently, it’s impossible to make a spring both good and noncorrosive:
Garden sprayer – corroded spring
I found a suitable (i.e., good, but rust-prone) spring in the Big Box o’ Medium Springs:
Garden sprayer – spring replaced
Unlike the repair for that sprayer, this spring turned out to be long enough to work perfectly. I have no idea how long I can keep this up, but … at least I’m now keeping pace with the failures.
One of my fundamental rules is that you should never, ever look inside the water lines serving your faucets. Having recently replaced a water heater, I had to violate that rule and discovered this growth inside the flex tube at the hot water outlet:
This is a classic case of investing more time and effort creating the fixture than machining the parts.
Start by squaring up the block, which came from the end of a random chunk of smoke gray polycarbonate, with two 10-32 holes matching the tooling plate hole spacing:
Corner Clip Fixture – squaring
Then drill-and-tap four holes:
Corner Clip Fixture – tapping
The left station will be for drilling the blanks clamped under a sacrificial sheet, so those screw holes aren’t used for anything other than clearance; the top millimeter will get chewed up pretty quickly. The screws in the right station will clamp a stack of drilled blanks under a cover plate. If I went into production, I could see using both stations for both functions, but …
There’s a locating pip in the front left corner that works perfectly with laser alignment:
Corner Clip Fixture – aligning
The blank sheets show where they’d be located for drilling, minus the sacrificial sheet and its clamps that you’ll see below.
The G54 coordinate system origin sits at the locating pip. The G-Code then slaps a G55 origin at each of the two stations in turn to simplify their coordinates, with offsets from M54:
Drilling = (+5,+5)
Milling = (+40,+5)
With all that in hand: stack, clamp, and drill some blanks:
Corner Clip Fixture – drilling
I tried milling a single drilled blank with a sacrificial plastic top plate:
Corner Clip Fixture – first milling setup
But that didn’t work well. I don’t know if this was due to an inept combination of climb milling, using the wrong speed / feed / material / cutter, and just poor style, but the edges of the blank mashed against the clamp plate and curled, instead of cutting cleanly:
Corner Clip Fixture – rounded-over milled edges
So I made a pair of aluminum plates to clamp both sides of the blanks, then milled another stack:
That worked quite well, although the top and bottom clips needed some slight attention from a riffler file and I did break the edges on all the clips. This shows four new clips along with a hand-cut prototype:
Corner Clip Fixture – end result
So I made a dozen more clips, picked the best eight for two sets, sent one set to Dan, installed the other, and … now I have a bunch of spares.
I suppose I should sell clip sets on Etsy / eBay to all the other M2 owners, but I have no idea how to price ’em. If you want some fancy corner clips, send whatever you think they’re worth … [grin]
The lawn mower began emitting horrible crashes, which turned out to be coming from a flange at the rear of the mower housing that was formerly spot-welded to the main chassis. Those welds broke and the flange occasionally vibrated into contact with the blade, causing heartache and confusion for both parties.
Re-spot-welding the flange wasn’t in the cards, but the elaborately formed piece of steel did have a flat section in contact with another part of the chassis with just enough meat for a bolt. I grabbed the two with a Vise-grip, whacked the flange until it was more-or-less lined up where it should be, drilled a hole, and popped in a 1/4-20 bolt:
Mower flange – side view
The curved section of the flange faces the blade, with the vertical end pointed anti-spinward: the blade nicks that edge.
A dab of red Loctite and a nylock nut topped it off:
Having recently kibitzed on a project using de-icing cables (with some success) to soften PVC pipe for bending, herewith the useful numbers.
Data printed on the original cable:
100 ft length
120 VAC
800 W
Derived values:
6.7 A = 800 W / 120 V
8 W/ft = 800 W / 100 ft
1.2 V/ft = 120 V / 100 ft
18 Ω = (120 V)2 / 800 W
180 mΩ/ft = 18 Ω / 100 ft
The starting point was a 62 ft length of the cable, as I’d long ago converted the end into a heated bed for starting plants early in the spring. That presented a resistance of 11 Ω, drew a current of 11 A, and dissipated 1.3 kW at 21 W/ft. A kilowatt-class dimmer handled the load, but adjoining sections of the cable got hot enough to melt the insulation and terminate the experiment.
A shorter length of cable might be suitable for a cheap laptop brick power supply. To keep the dissipation under, say, 10 W/ft, we have:
7.5 A = sqrt( 10 W/ft / 180 mΩ/ft )
1.3 V/ft = 7.5 A * 180 mΩ/ft
The Dell D220P-01 brick on the M2 provides 12 V at 18 A (!) and costs under $20 on eBay:
9 ft = 12 V / 1.3 V/ft
90 W = 12 V * 7.5 A
1.6 Ω = 9 ft * 180 mΩ/ft
You could run two 9 ft lengths cables in parallel from the same hulking brick. Whether that’s enough to soften a length of PVC pipe from the inside, without having the insulation get all melty, that’s another question…
This message may be useful, in the sense that it reports something about the internal state of the cash register:
Walmart cash register – buffer full message
But the fact that it appears on the customer-facing display means that the cashier won’t see it and can’t do anything about it. I’m not sure if the floor personnel know anything about buffers, either.
The cashier-facing display says: “Welcome to Walmart!”
The Smell of Molten Projects in the Morning 