Tag: Improvements

Making the world a better place, one piece at a time

HON Lateral File: Shelf Rebuild

After sliding the HON Lateral File Cabinet shelf into place and installing the bumpers, it seemed rather loose and floppy. Comparing the situation with the other file cabinet showed it had a missing glide button in the rear and two missing slides at the front.

A replacement button emerged from the end of a Delrin rod:

The original buttons had an expanding stem, which is easy to do with an injection-molded part. I opted for simple adhesive, with enough of a blob underneath the shelf to (presumably) lock it in place forevermore:

The slides required an iterative design technique (pronounced “fumbling around”), because nothing on either side remained square / plumb / true / unbent. I hacked the first version from scrap acrylic, broke off anything that didn’t fit, and got better measurements from what remained:

HON Lateral File - shelf front guide - size test — HON Lateral File – shelf front guide – size test

With those measurements in hand, the second version used a pair of weird flat-head shoulder screws (probably from a hard drive) to anchor 3D printed angle brackets into the frame:

HON Lateral File - shelf slides - version 2 — HON Lateral File – shelf slides – version 2

Those worked reasonably well, but PETG doesn’t produce a nice sliding surface, so the final version has flat-head Delrin studs in slightly tweaked brackets:

HON Lateral File - shelf slides - version 3 — HON Lateral File – shelf slides – version 3

As with the buttons in the back, the original slides had expanding studs holding them in place, but glue works fine here, too:

HON Lateral File - shelf slides - version 3 - installed — HON Lateral File – shelf slides – version 3 – installed

The button isn’t quite square to the surface and the slide isn’t quite flush with the bent metal in the frame, but it’s Good Enough™ for a shelf that won’t get lots of mileage.

For reference, the brackets should print vertically to wrap the plastic threads around the upright for better strength:

HON Lateral File Shelf Slide - Slic3r — HON Lateral File Shelf Slide – Slic3r

If you did it the obvious way, the upright side would break right off at the first insult from the hulking shelf, although they’re basically a solid chip of plastic, with a little infill inside the bottom slab.

While I was at it, I pulled the springs to make them a bit longer, so they touch the back of the frame when the shelf is half an inch behind the front face of the drawers. A firm push and those Delrin contact points let the shelf pop out an inch or so, with plenty of room for fingers underneath the front edge.

Some drawer slide stops near the back needed attention, too:

HON Lateral File - slide stop bumper - bent — HON Lateral File – slide stop bumper – bent

I cannot imagine how hard somebody slammed the drawers, because bending the stops back to a right angle required a Vise-Grip and some muttering:

HON Lateral File - slide stop bumper — HON Lateral File – slide stop bumper

Oddly, the cushiony hollow side faces away from the drawer, toward the back of the frame, because putting it forward holds the drawer front proud of the front frame face. Maybe HON cost-reduced the steel slides by making them just slightly shorter and using the same bumpers?

The drawers have begun filling up from boxes scattered around the house:

HON Lateral File - fabric stash — HON Lateral File – fabric stash

That’s the “orange” part of Mary’s collection, now with plenty of room to grow!

The OpenSCAD source code as a GitHub Gist:

	// HON Lateral File Cabinet
	// Shelf slides
	// Ed Nisley KE4ZNU 2020-02-25

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

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

	HoleWindage = 0.2;

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

	Protrusion = 0.1; // make holes end cleanly

	inch = 25.4;

	ID = 0;
	OD = 1;
	LENGTH = 2;


	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);
	}

	//———————-
	// Dimensions

	SlideBlock = [18.0,25.0,12.0]; // across, along, height of left shelf bracket

	SlideWalls = [1.0,-SlideBlock.y/2,2.0]; // wall thicknesses, dummy Y

	HoleOffset = [8.4,7.0,0]; // hole center from left, front, dummy Z
	HoleOD = 4.0;

	Screw = [4.0,10,0.8]; // weird flat-head shoulder screw

	ScrewRecess = Screw.z + 2*ThreadThick; // depth to keep head below slide surface

	echo(str("Head base: ",SlideWalls.z – ScrewRecess));

	$fn = 12*4;

	//——————-
	// Single slide

	module Slide() {

	difference() {
	cube(SlideBlock,center=false);

	translate(SlideWalls)
	cube(SlideBlock * 2,center=false);

	translate(HoleOffset – [0,0,SlideBlock.z/2])
	rotate(180/8)
	PolyCyl(HoleOD,2*SlideBlock.z,8);

	translate(HoleOffset + [0,0,SlideWalls.z] – [0,0,ScrewRecess])
	rotate(180/12)
	PolyCyl(Screw[OD],3*Screw[LENGTH],12);
	}

	}



	//——————-
	// Build them

	Gap = 5.0/2;

	translate([0,-Gap,0])
	rotate([90,0,0])
	Slide();

	translate([0,Gap,0])
	rotate([-90,0,0])
	mirror([0,1,0])
	Slide();

view raw HON Lateral File Shelf Slides.scad hosted with ❤ by GitHub

2020-03-02

Monthly Science: Maria Mitchell Astronomy Notebooks

Back in 2016, the Special Collection Library at Vassar put on Seeing the Sun: Maria Mitchell’s Observations, 1868-1888, an exhibit featuring materials from her tenure as Vassar’s astronomer, including several notebooks of observations and calculations. Being that type of guy, I spent quite a while pondering the effort required to do science.

Perhaps this notebook appeared in the exhibit:

Mitchell 8.6 – Longitude computations of occultations 1872-1875

Here’s what “calculations” looked like in 1872:

Mitchell 8.6 p9 – Occultation of 1253 BAC at 11 hrs – calculation

Yeah, grinding out trigonometry by hand using seven-place logarithms:

Mitchell 8.6 p9 – Occultation of 1253 BAC at 11 hrs – calculation detail 1

Not just by hand, but by hand with pen and ink:

Mitchell 8.6 p9 – Occultation of 1253 BAC at 11 hrs – calculation detail 2

Although you’ll find an occasional ink blot, she was probably using a fountain pen, rather than a dip pen, and made very few mistakes along the way. She often recorded direct instrument observations in pencil.

The next time you start pissing & moaning about how hard solid modeling is, suck it up.

Bonus: a Ginger Snap recipe suggesting it wasn’t all toil & trouble in the observatory:

Mitchell 7.5 – Ginger Snap recipe

The mystery ingredient is saleratus, “aerated salt”, now known as baking soda; they used potassium bicarbonate before today’s sodium bicarbonate.

I spent several pleasant hours browsing through selected notebooks in search of computations, taking pictures of pages under field conditions in ambient light. All images from Maria Mitchell Papers, Archives and Special Collections, Vassar College Libraries.

2020-03-01
HON Lateral File Cabinet Shelf Bumper Replacement

Somewhat to our surprise, our “new” HON Lateral File Cabinets include a pop-out shelf:

HON Lateral File – shelf – closed

The trick: push the bar inward against fairly stiff spring pressure, release it suddenly, watch it pop out maybe half an inch, get some fingers under the front edge, then pull it outward:

HON Lateral File – shelf – extended

Obviously, opening the drawer above the shelf will sweep whatever you put there onto the floor and opening the drawer below seems futile. I suppose it produced a bullet item on the features list.

Note that the topmost “drawer” is also called a “shelf”, because the front cover slides up-and-inward to reveal the contents. Should you stand eight feet tall, you might be able to look down on that shelf, but we mere mortals barely see its contents at eye level.

Dismantling the cabinets preparatory to deep cleaning revealed a pair of rubber bumpers along the rear edge of the shelf:

HON Lateral File – shelf bumper – installed

The slightly angled front side of the bumper (on the right) collides with a crossbar below the drawer just above it, preventing you from pulling the shelf entirely out of the cabinet.

Remove the bumper by pressing down and rearward (to the left), shoving the protruding lip into the slot with a thumb / screwdriver, then pull it upward through the slot:

HON Lateral File – shelf bumper – removed

The second cabinet had only one bumper, so I traced it twice onto a rubber sheet half as thick as the OEM bumper, bandsawed the shapes, and introduced them to Mr Belt Sander for cleanup:

HON Lateral File – replacement shelf bumper

Jammed side-by-side into the slot, they’ll serve the purpose:

HON Lateral File – replacement shelf bumper – installed

As with the replacement foot on the first cabinet, they’re not the prettiest things you’ve ever seen, but Mary doesn’t expect to use the shelf and they’ll never actually bump into anything.

Even the Pixel phone’s HDR image processing has trouble dealing with dark gray objects on a black background in dim light …

2020-02-26
Refrigerator Coil Wand Adapter Rebuild
After five years, the adapter between the Kenmore Progressive vacuum cleaner and the long wand required to reach inside the refrigerator evaporator coils broke at the latch opening:

$Kenmore Vacuum - refrigerator coil adapter - fracture$
Kenmore Vacuum – refrigerator coil adapter – fracture

A quick fix let me continue the mission:

Kenmore Vacuum – refrigerator coil adapter – temporary fix

A better fix required a few minutes of OpenSCAD tweakage and a few hours of hands-off build time:

Refrigerator Coil Wand Adapter – Slic3r preview

The fitting ID is now 2 mm smaller, the 3D honeycomb infill is 25%, and (contrary to the picture) it now has 4 perimeter threads. It’s a two-line change from the last time:
```
OEMTube = [35.0 - 2.0,35.0,41.7,40.5,30.0];           // main fitting tube
… then, inside MaleFitting() …
cylinder(d1=OEMTube[ID2],d2=OEMTube[ID1],h=2*OEMTube[LENGTH] + 2*Protrusion);
```
Those will propagate to anything I build from now on, although this is the first latch fracture.

Gotta love it when 3D printing lives up to the hype!
2020-02-25
The Return of High-Reliability / High-Availability Trash Cans

Five years ago, robotic trash cans were a thing on Vassar’s campus, including this duo in front of Vassar’s library:

Vassar Library – Trash and recycling containers

That was then, this is now:

Vassar Library trash cans

I infer the robotics did not work out as anticipated.

2020-02-23

Bird Box Entrance Reducers: Round 2

One of the bird box entrance reducers I installed nigh onto a decade ago is still on duty, although downy woodpeckers definitely want a larger hole:

Bird Box - gray PVC pipe reducer - woodpecker damage — Bird Box – gray PVC pipe reducer – woodpecker damage

Another reducer had gone missing over the years, so I made one from a length of PVC pipe:

Bird Box - PVC pipe reducer - shaping — Bird Box – PVC pipe reducer – shaping

It started as 1-½ PVC pipe, 1-⅞ inch actual OD and should fit into a 1-½ hole, so I measured 1.5 × 3.15 around the circumference, bandsawed out the excess, draped it over a 1-½ Forstner bit, toasted it with a heat gun, and squashed it so it’s just a little bit bigger than the (enlarged!) hole in the box.

Now the entrance is 1-¼ (-ish), just like it should be:

Bird Box - PVC pipe reducer - installed — Bird Box – PVC pipe reducer – installed

The bird box in the front yard has been attracting starlings, in addition to serving as a hawk perch:

New Coopers Hawks - bird box takeoff whoops — New Coopers Hawks – bird box takeoff whoops

The oblong hole required advanced manufacturing techniques:

The front face should be too slick for larger birds and the little ones will zip right into the hole:

Bird Box - 3D printed entrance reducer — Bird Box – 3D printed entrance reducer

The two starlings who’d been evaluating the box seem to have moved on; we doubt they’re now homeless.

The OpenSCAD source code as a GitHub Gist:

	// Bird Box – oval entrance reducer
	// Ed Nisley KE4ZNU 2020-02-12

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

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

	HoleWindage = 0.2;

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

	Protrusion = 0.1; // make holes end cleanly

	inch = 25.4;

	//———————-
	// Dimensions

	EntranceID = 1.25 * inch;

	BoxHole = [1.5,2.25] * inch;
	BoxWall = 0.75 * inch;

	HoleOC = BoxHole.y – BoxHole.x;

	FlangeWidth = 5.0;
	FlangeThick = 5*ThreadThick;

	$fn = 12*4;

	//——————-
	// Build it

	difference() {
	union() {
	linear_extrude(height=BoxWall + FlangeThick)
	hull()
	for (j=[-1,1])
	translate([0,j*HoleOC/2])
	circle(d=BoxHole.x);
	linear_extrude(height=FlangeThick)
	hull()
	for (j=[-1,1])
	translate([0,j*HoleOC/2])
	circle(d=BoxHole.x + 2*FlangeWidth);
	}
	translate([0,0,-Protrusion])
	cylinder(d=EntranceID,h=2*BoxWall);
	}

view raw Oval Entrance Reducer.scad hosted with ❤ by GitHub

2020-02-19

Kensington Expert Mouse Scroll Ring Fix

Apparently the newest Kensington Expert “Mouse” trackballs have a hack re-orienting the scroll ring quadrature detector. The picture from my original writeup shows the previous situation:

Scroll ring IR emitter-detector quadrature pair

The quadrature detector, the black block on the left, is oriented with its lens (and, thus, the actual detectors) pointed away from the IR emitter. I thought it might be an assembly screwup, but it’s actually worse: the PCB layout is wrong.

A note from Tristan in NZ explains the situation:

So I have a later model than yours. It has a 2nd PCB chunk between where the legs normally would be. Just a floating piece with two holes for the legs, holding the legs from the board […] to the main board.It is also pointing the correct way (with the lens towards the three leg emitter).

Kensington scroll wheel revision2

The new quad detector has only three pins and no convex lens, but the active area now faces the emitter across the gap.

Because the interposer PCB occupies the space previously devoted to the emitter & detector leads, Kensington apparently soldered the new parts directly to the top surface without any clearance:

It’s like they failed to put through-vias to the rear or didn’t route them to the bottom another way, hence the solder is under the component

Tristan managed to wreck the detector while attempting to re-solder the intermittent joints, a situation I’m painfully familiar with. He replaced it with a quad detector harvested from a mid-90s optical mouse and it’s back in operation.

So I think the correct “fix” for the old-style PCBs (without the new interposer) is to unsolder the detector, rotate it so the lens faces the emitter, then somehow rewire the pins to the original pads. This won’t be easy and definitely won’t be pretty, but as long as it’s pointed in the right general direction it should work:

mine works off axis quite a bit

Should either of my Expert Mouse trackballs fail, now I know what to do

Many thanks to Tristan for reporting his findings!

Update: A note from Alan brings more data to the discussion

2020-02-17

Tag: Improvements

HON Lateral File: Shelf Rebuild

Monthly Science: Maria Mitchell Astronomy Notebooks

HON Lateral File Cabinet Shelf Bumper Replacement

Refrigerator Coil Wand Adapter Rebuild

The Return of High-Reliability / High-Availability Trash Cans

Bird Box Entrance Reducers: Round 2

Kensington Expert Mouse Scroll Ring Fix