The Smell of Molten Projects in the Morning
Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Making the world a better place, one piece at a time
I couldn’t resist setting this up for my next Digital Machinist column on logarithmic scales:
The caption will read “Photo 1: A replica Tektronix Circuit Computer shown with its natural enemy, an HP 50g Graphing Calculator.”
It’s my desk calculator. In the Basement Laboratory, I use the HP 48 calculator app, with a couple of $10 Sharp calculators in harm’s way.
Because the cheap batteries I use in the Sony HDR-AS30V camera provide just slightly less runtime than our longest usual ride after a year of use, I carry a spare battery in a small red felt bag. The bag also holds a USB card reader helping to make the MicroSD card somewhat less lose-able on its trips betwixt bike & desk.
Here I am, swapping batteries in Adam’s Fairacre parking lot before starting the trip home:
You can see it coming, right?
Eight minutes later, we’re turning onto the Dutchess County Rail Trail:
And then it’s gone:
Mary drove past there on her way to a distant meeting, but the little red bag was not to be found anywhere. Maybe it’ll reappear on a fence post or taped to the bulletin board; I’ve tried to return things I’ve found that way.
I expect somebody got a nice present and, if naught else, it’s good to drop happiness into the world.
There’s another reader and a quartet of batteries on their way.
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:
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:
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:
As with the buttons in the back, the original slides had expanding studs holding them in place, but glue works fine here, too:
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:
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:
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:
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:
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(); |
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:
Here’s what “calculations” looked like in 1872:
Yeah, grinding out trigonometry by hand using seven-place logarithms:
Not just by hand, but by hand with pen and ink:
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:
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.
Somewhat to our surprise, our “new” HON Lateral File Cabinets include a pop-out shelf:
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:
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:
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:
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:
Jammed side-by-side into the slot, they’ll serve the purpose:
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 …
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:
A quick fix let me continue the mission:
A better fix required a few minutes of OpenSCAD tweakage and a few hours of hands-off build time:
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!
Five years ago, robotic trash cans were a thing on Vassar’s campus, including this duo in front of Vassar’s library:
I infer the robotics did not work out as anticipated.
The Smell of Molten Projects in the Morning 