Archive for April, 2012

Monthly Subconscious: Thick Gravity

Perhaps this explains why quantum physics doesn’t cover all the bases:

Our thick gravity

Our thick gravity

In text:

Our thick gravity echos frantic insect thoughts

Sometimes you must roll with the spelling; the subconsicous has its own rules.

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Sears Kenmore Dryer Rattle: Quieter

Our re-sealed Kenmore clothes dryer developed a horrible rattle that Went Away with slight pressure here & there on various surfaces. I eventually located the most sensitive spot: inside the lint filter duct, on its upper surface. That suggested something lying atop the duct.

Remove the two screws securing the duct to the top surface, push forward on the back of the control panel, and the front of the top panel pops up. Tilt upward against the springy hinges, peer in above the duct, and what do we find?

Kenmore dryer - wire routing

Kenmore dryer - wire routing

Yup, wires resting on the duct!

There are no obvious wire guides to be found, so I’m pretty sure those wires were in pretty much that same position when I dismantled the dryer to install the new seal. In any event, they are where they are.

This not being a particularly hot area, I slipped a sheet of closed-cell foam between the wires and the duct, snapped the top down, and screwed the duct in place.

The lower catches on the front panel seem to be loose, too, so a pair of cardboard shims jammed discreetly into the lower edge of the joint on either side soaked up some spare motion with excellent noisemaking potential.

Unfortunately, fixing that rattle exposed another buzz that seems to be a loose plate buried somewhere in the back of the cabinet. Getting in there requires tearing the whole thing apart, which I’m not looking forward to in the least.

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Whirlpool Refrigerator Fan Noise: Final Fix Redux

Well, using a PC case fan as a freezer blower seemed like a good idea at the time: it worked, moved an adequate amount of air, and was pretty nearly silent. Until, that is, frost built up on the blades, water froze inside the frame, and the thing began sounding like a stick running along a picket fence:

Frosted PC case fan in freezer

Frosted PC case fan in freezer

I replaced the first fan with another having slightly more clearance between the blade tips and the frame, but to no avail.

So I dug the OEM fan (a.k.a., the Freezer Dog) from the heap, dismantled it, and discovered why it was howling. Turns out that the shaft nearest the fan blades was scored inside that bearing:

Freezer motor - scored shaft

Freezer motor - scored shaft

A closer look:

Freezer motor - scored shaft detail

Freezer motor - scored shaft detail

The rest of the shaft looked fine to me, so I put some green Loctite on rotor at the shaft and shoved the long end of the shaft (using the drill press as an arbor press) to put the scored section inside the rotor:

Freezer motor - relocated rotor

Freezer motor - relocated rotor

Yes, that’s the same Loctite ridge you saw there

The shaft has several small grooves that probably held lubricant or acted as alignment guides or something useful, but I’m hoping none of that matters. The rotor is turning backwards now, too, which shouldn’t make much difference: it’s pretty much symmetrical.

While I had the motor apart, I whacked the bearings with a rod to shrink them a bit:

Freezer fan bearings

Freezer fan bearings

Slobbered more STP on the bronze bearings, reassembled everything again, and it’s been quiet for nearly a week.

Perhaps the combination of new shaft surfaces and tweaked bearings will run for a few more years. I still have the “new” replacement fan in a box…

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Soaker Hose Splicing

We deployed several granulated-rubber soaker hoses last year and, while they certainly weep enough water, they’re exceedingly brittle: they kink and break with what seems to be ordinary handling.

The hose ID is much smaller than ordinary “half inch” hose, so I turned some grooves on a chunk of copper tube that’s a snug fit inside:

Grooving copper tubing

Grooving copper tubing

Slitting a piece of scrap hose (ya gotta have stuff) and clamping it around the hose and tubing holds the splice together against the 90 psi water in the Vassar Farms irrigation system and provides a bit of strain relief beyond the ends of the tubing:

Spliced soaker hose

Spliced soaker hose

While I was at it I made three more copper splices, because I know they’ll come in handy…

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Ouch!

Got one of those painful, bloodless slices:

Split thumbprint

Split thumbprint

From, believe it or not, the razor-sharp edge of a fillet of cured green Loctite:

Freezer motor shaft - Loctite fillet

Freezer motor shaft - Loctite fillet

Of course, it didn’t stay bloodless for long: every time I put pressure on the ball of my thumb, the split gets longer.

I hate it when there’s blood all over the workpiece…

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Brita Pitcher Lid: Second Hinge Pin Failure

Although that fix continues to work, the second pin failed pretty much as expected:

Brita pitcher lid - second broken pin

Brita pitcher lid - second broken pin

I glued the pin to rebuild the base, sheared the pin off, extracted the matching screw from the Tiny Vial of Teensy Screws, drilled a hole, and forced it in. This shot of the underside of the pitcher lid clearly shows that drilling the hole perpendicular to the edge doesn’t produce the proper alignment, but it works well enough:

Brita pitcher lid - pin angle

Brita pitcher lid - pin angle

The “Smart Pitcher” LCD panel in the lid that counts down six weeks until filter replacement didn’t survive its most recent trip through the dishwasher, so we’re reduced to marking the calendar. How 20th century…

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Quilting Pin Caps

Mary has been quilting up a storm lately and is growing dissatisfied with the special safety pins she’s been using to hold the layers together. Long straight pins are ideal, except that maneuvering a large quilt through her sewing machine resembles stuffing a porcupine into a keyhole. A commercial solution costs nearly half a buck per pin, which seems unreasonably spendy for something you need by the hundreds.

We kicked around some finger- and quilt-friendly dimensions and I cobbled up a solid model:

Quilting Pin Cap

Quilting Pin Cap

Which turned into an array of small octagons that won’t roll off the table:

Pin cap array on build platform

Pin cap array on build platform

We figured 25 would be enough to decide if this is workable and whether the dimensions fit fingers, pins, and quilts.

Filling them with silicone rubber required one squirt each:

Filling pin caps with silicone

Filling pin caps with silicone

The trick with the silicone rubber is to cut the snout so it fits flat on the cylinder top. Put the cylinders on a piece of non-stick paper (I used the back of the carrier for some double-sided tape, but wax paper would be better), hold one with tweezers, squirt in enough rubber to fill the cylinder solidly from bottom to top, then slide the snout sideways to smooth the surface.

Wait for a day, pop them off, and remove any drool:

Silicone-filled pin caps

Silicone-filled pin caps

It’s garden planting time right now, so it’ll take a while before I tweak the design and run off the next batch.

I don’t know how to compute an actual cost for each of those things. I regard the entire Thing-O-Matic as fully depreciated and pretty much a sunk cost, which means the expense boils down to the incremental cost of plastic and silicone. All the Quality Shop Time is, of course, free… and maybe even therapeutic.

The (trivially simple) OpenSCAD source code:

// Quilting pin caps
// Ed Nisley KE4ZNU April 2012

//- Extrusion parameters must match reality!
//  Print with +1 shells and 3 solid layers

ThreadThick = 0.25;
ThreadWidth = 2.0 * ThreadThick;

HoleWindage = 0.2;

function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);

Protrusion = 0.1;			// make holes end cleanly

//----------------------
// Dimensions

ID = 5.0;
OD = ID + 2*ThreadWidth;
Length = 5.0;
Sides = 8;

//----------------------
// Useful routines

module PolyCyl(Dia,Height,ForceSides=0) {			// based on nophead's polyholes

  Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2);

  FixDia = Dia / cos(180/Sides);

  cylinder(r=(FixDia + HoleWindage)/2,
           h=Height,
	   $fn=Sides);
}

module ShowPegGrid(Space = 10.0,Size = 1.0) {

  Range = floor(50 / Space);

	for (x=[-Range:Range])
	  for (y=[-Range:Range])
		translate([x*Space,y*Space,Size/2])
		  %cube(Size,center=true);

}

//----------------------
// Build them!

ShowPegGrid();

  rotate(180/Sides) {
	difference() {
	  PolyCyl(OD,Length,8);
	  translate([0,0,-Protrusion])
		PolyCyl(ID,(Length + 2*Protrusion),8);
	}
  }

,

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