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.

Tag: Improvements

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

Camera LCD Sunshade & Magnifier: Part 2
Lens end of viewer

With the bottle formed & trimmed to shape, it’s time to mount the lens. This view shows the final result, with the camera body angled upward.

The general idea is that the bottle cap already attaches securely to the bottle, so I can just cut a rectangular hole in the lid, make it just slightly smaller than the lens, and affix the lens inside with the planar surface facing outward.

Two motivations for making the hole slightly smaller than the lens:
- The lens has rounded corners, as it was cut from a 38 mm diameter round lens
- It won’t stick out, get bumped, and fall off
Lens opening cut in bottle cap

The first step was, of course, to make a fixture: a sacrificial wood block with a raised section that fits snugly inside the cap. I found a nice maple disk in the scrap bin, chucked it in the lathe, and turned a section to fit. I don’t have a dust extraction system, so I did this one-handed with another on the shop vac to suck up the swarf. Yuch, wood is dusty!

That simplified clamping the rather slippery lid in place. It’s probably polyethylene that would slide away under heavy cutting loads, but with a 2 mm end mill that wasn’t a problem. The origin is at the center of the cap, directly atop the convenient injection-molding sprue button.

The lens is 34.4×22.1 mm, so I cut a 32×20 mm opening using manual CNC. Given a 1 mm cutter radius, the G-Code looked something like this:
```
#1=[20/2-1]
#2=[32/2-1]
g0 x[0-#1] y[0-#2]
g1 z-2 f100
x#1
y#2
x[0-#1]
y[0-#2]
g0 z30
```
That’s from memory, so it might not work quite right. Basically, store the key variables in parameters and use those instead of mistyping a digit somewhere.

The opening even has nicely rounded 1-mm radius corners from the 2 mm cutter…

Cutting acrylic lens holder

I added a sheet of acrylic inside the lid to hold the lens in position and provide a more glue-attractive surface. The lens opening here was a slip-fit for the lens: 34.5×22.2 mm. The G-Code looks pretty much the same:
```
#1=[22.2/2-1]
#2=[34.5/2-1]
g0 x[0-#1] y[0-#2]
g1 z-2 f100
x#1
y#2
x[0-#1]
y[0-#2]
g0 z10
```
Trimming outside of acrylic lens holder

The wood disk even had a convenient hole in the middle, making it easy to re-clamp the acrylic from the center with a stack of washers. The laser aligner made alignment easy: make the nut finger-tight, put the spot on the left edge near the front, jog to the rear, twist to split the difference, iterate a few times, then snug down the nut.

Then the origin is halfway between the edges. Knowing the opening size, find one edge and touch off by half that amount.

The cardboard lid liner was 43 mm in diameter, so I figured that would work for the acrylic sheet. Circular interpolation makes getting a precise diameter trivially easy, after you remember that this is outside milling so you must add the cutter radius:
```
#1=[43/2+1]
g0 x[0-#1] y0
g1 z-2 f100
g2 i#1
g1 z30
```
Finished cap with lens

What’s not shown there is the blob of acrylic that welded itself to the cutter because I was taking picures rather than dribbling water on the workpiece to keep it cool. I hate it when that happens.

But everything pretty much worked out. The holder was a snap fit inside the cap, just like it was supposed to be.

I glue the lens to the acrylic holder with silicone snot (aka “adhesive” or “caulk”), let it cure overnight, snapped the cap on the bottle, and iterated once to get the lens properly aligned with the opening (the acrylic sheet rotates freely inside the cap).

Viewer attached to camera

The end result is, admittedly, ugly on a stick, but the first reports from the user community are encouraging!

We may add a dark cloth ruffle around the bottle cap as an eye shade and eyeglass protector, but that’s in the nature of fine tuning.
2009-05-14
Camera LCD Sunshade & Magnifier: Part 1

Viewer attached to camera

Mary take her gardening pictures with our Sony DSC-F505V camera, which has one compelling advantage for the job: the lens and body pivot, so you can take pix at odd angles without groveling in the dirt or hovering over the camera staring downward. Alas, it lacks an optical viewfinder, which means she does a lot of outdoor close-up photography peering into a washed-out LCD panel in full sun. Worse, she’s far-sighted and can’t see fine details without her reading glasses or bifocals, so it’s really hard to get proper focus.

Something must be done!

The general notion is to put an opaque shield around the LCD with a lens that magnifies the viewfinder. If you happen to have perfect near vision, the lens is optional and you can probably use one of the commercial sunshades that attach with hook-and-loop strips. That isn’t going to work for us.

With inspiration from that project, I retired to the Basement Laboratory. [Update: a somewhat less intricate do-it-yourself project starting with a slide viewer. I suspect it works better for normal-looking cameras, not this one.]

Raw material: rectangular lens and opaque bottle

Rummaging in the Bottle Supply turned up a dark brown plastic bottle made from PETE, the same stuff that makes soda bottles, with a black plastic snap-cap lid. PETE has a glass transition temperature around 75C, which means you can reshape it with a heat gun (not, alas, a hair dryer). Actually, I found two bottles, so I have a backup.

A bit of soaking in water, followed by a generous application of xylene, got rid of the label & adhesive residue. You can get xylene in small quantities as Goof-Off adhesive remover or just buy a quart at your local big-box home-repair store. Do the xylene part outdoors and don’t toss the rags in the trash until they’re dry.

Further rummaging in the Lens Supply turned up a 34.4×22.1 mm plano-convex rectangular lens with perhaps a 100 mm focal length. Haven’t a clue where it came from, but perhaps from the Surplus Shed optical supply shop. Pretty nearly any lens with those general specs will work, so use what you have. You do have a box of lenses, don’t you?

Putting the flat side of the lens close to my (distance-corrected, I’m nearsighted) eyeball and looking through it at the LCD from about 75-125 mmm produces a very nicely enlarged, distortion-free image. This will work!

Bottle cutting and forming

The bottle is much thicker than a soda bottle, but easily cut with a razor knife and a bit of care. I removed the bottom and measured the ID as 68 mm. The circumference is, obviously, 214 mm, which is a key dimension: it must fit around the LCD’s perimeter with a bit to spare.

I made a wood mould block that’s sized and shaped roughly like the back of the camera around the LCD: Mr Block, meet Mr Belt Sander. This avoids the prospect of melting the camera with the heat gun, as it’s largely plastic, too.

The block is 52×57 mm, for a perimeter of 218 mm, and a totally non-critical 38 mm tall (it came from a 2×4″ chunk of lumber). The pyramidal section acts as a forcing cone to persuade the bottle to stretch around the slightly larger block and become nicely rectangular as it does.

Wood forming block

Position the bottle over the block, apply the heat gun all around, and ram the bottle downward as it softens. Eventually the bottle will eat the block, even though it’s not completely happy about doing so, at which point you can concentrate on heating each side separately. The bottle will settle down and stretch neatly around the block, giving it a rectangular base with a smooth transition from the round top. The cut edge tends to curl outward in the middle of each flat side, so don’t overheat it.

Cut the corners back so there’s about one focal length from the cap to the cut, then heat the side flaps (the shape is rectangular: get this right!) and bend them back. I flattened them against the bench to remove the curve. The top and bottom flaps will fit over the top and bottom of the camera and hold the whole affair in place.

Trim the side flaps to a few mm, as they’ll just form a light shield, and shape them to clear the controls as needed. Form the top & bottom flaps to fit snugly around the camera and trim to fit; they cover up the buttons just under the camera’s LCD, but those aren’t used in normal operation.

I used plain old electrical tape to hold the bottle in place, as anything thicker will interfere with the lens rotation. If you have a box-shaped camera, hook-and-loop may be your friend.

That was enough for one day. Tomorrow: a bit of CNC work on the lid…

2009-05-13
Homebrew V-750 Dosimeter Charger Pedestal: Overview
Although my V-750 dosimeter charger cleaned up reasonably well, I wanted to see if I could build a high-voltage supply from more-or-less contemporary parts to charge the dosimeters. The circuit is easy enough, but the charging pedestal that connects to the dosimeter turned into an interesting shop project.

V-742 dosimeter charging contact

Pencil-style electrometer radiation dosimeters, like the V-742 shown here, have a charging contact pin embedded in a transparent plastic (?) end cap recessed in the bottom. Inside the dosimeter a mighty spring (or, perhaps, the plastic cap itself) holds the pin outward so that it does not make electrical contact with the gold-coated quartz fiber in normal use.

This baffled me at first, because I did not understand why the charge didn’t just leak off the fiber through the charging pin. In order to dump charge onto the fiber, you must first press the pin inward by about 1 mm against the internal spring: no pressure, no contact, no charge.

Duh…

The dosimeter’s innards must be kept scrupulously clean and full of dry air. After you pull the pin out to admire it, the dosimeter won’t hold a charge ever again. I yanked the pin out of a dosimeter that simply didn’t work and, after a bit of fiddling, the dosimeter can now be set to zero, but the charge leaks off in a matter of hours rather than days.

Charging contact pedestal

The V-750 charging pedestal has an outer sleeve (the negative contact) and a central pin (the positive contact) that fit neatly into the end of the dosimeter. The pin stands about 2 mm proud of the plastic insulator that pipes light into the dosimeter to illuminate the scale. The sleeve, insulator, and pin move as a single unit: the dosimeter presses them down into the V-750 against two stacked springs.

A 1-lb spring holds the insulator in place by pressing the whole cylinder outward against its shoulder. The charger turns on when the dosimeter reaches that spring’s limit of travel at about 1 mm, but it’s not firm enough to press the dosimeter pin into contact with the quartz fiber. That’s the position you use to read the dosimeter: the light is on, but the fiber won’t move yet.

In order to charge the fiber, the dosimeter must move down an additional 3 mm against an 8-lb leaf spring until it seats against the pedestal’s threaded shell. Holding the dosimeter steady against that pressure while twiddling the voltage knob to adjust the dosimeter fiber to the zero point of the scale is more challenging than you might expect: grab it in your fist and hold on tight. It’s a good idea to wear glasses, as the dosimeter optics provides maybe 5 mm worth of eye relief: you can easily poke yourself in the eye with the fool thing if your grip loosens.

So, basically, a new charging pedestal must include a shell that meets the dosimeter’s body and a central shaft consisting of a sliding outer sleeve, a transparent insulator, and a central pin. The shaft must be pushed against the dosimeter by a really stiff spring to close the charging contact.

Not-quite-as-built cross section sketch

Finished charging pedestal

The overall plan looked something like this, at least before I started cutting metal…

What changed:
- a larger spring surrounds the LED
- no need for the weak spring
- no switch: the voltage-adjust knob has one
- a single slot in the side to prevent rotation
- screws, not solder, holding bolt to EMT shell
- no sleeve inside the bolt: it’s a copper bolt
But, all in all, it worked out OK.

Charging pedestal components

Here’s what the final result looked like, all spread out so you can see the innards…

The next few posts will show various bits & pieces, with notes & asides.
2009-05-07
Tour Easy: Fitting Novara Transfer Bike Panniers

Mary recently replaced her well-worn REI packs with a pair of Novara Transfer panniers, chosen because they’re just about the biggest packs available without insanely specialized world-touring features. They seem rather less rugged than the older ones, so it’s not clear how long they’ll last.

They fit her Tour Easy recumbent fairly well, but there’s always a bit of adjustment required.

Ramp on front edge of lower clamp rail

She hauls tools and clothing and veggies to & from her gardens, food from the grocery store, and the Token Windows Laptop to presentations. She brings the packs inside, rather than leave them on the bike, so they get mounted & dismounted for every ride.

The packs hang from the top bar of the rear rack, with a sliding clamp near the bottom of the pack that engages the rack’s vertical strut. I adjusted the clamp to the proper fore-and-aft position, but we found that the front end of the rail holding the clamp jammed against the seat support strut. That’s not a problem found on a diamond-frame bike.

The top picture shows the solution: Mr Pack, meet Mr Belt Sander. A ramp chewed onto the front end of the rail lets it slide neatly over the strut and all is well. The only trick was to avoid sanding through the pack fabric: the line perpendicular to the rail is sanding dust, not a gouge!

Acorn nut caps inside pack

Each top rack hanger mounts to the plastic pack frame with three bolts covered by plastic acorn nuts on the inside; the acorns cover actual metal nuts, so it’s a lot more secure than it looks. Three more bolts secure the bottom rail to the frame, with three more acorns poking into the pack, for a total of nine acorn nuts.

Most folks carry clothing and suchlike in their packs, so the 10 mm bump at each acorn presents no problem. Unfortunately, those things look like a nasty bruising hazard for soft veggies and groceries.

Top hanger pad – outside view

I sliced up some closed-cell foam packing material (everybody saves some of that stuff, right?), punched holes at the appropriate locations, and tucked the pads over the acorns. An inner fabric layer covering the frame and nuts should hold the pads in place.

Bottom pads with hole punch

It’s not clear the bottom pads will stay in position, but I wanted to try this without adhesives, mostly because I doubt any adhesive can secure polyethylene foam to whatever plastic the pack frame is made from or coated with. Perhaps double-sided foam tape will work?

Top pad – with tools

So far, the early reviews are good …

2009-04-27
Anchoring Sherline Stepper Motor Wires

Anchoring stepper motor wires with cable ties

The wires coming out of Sherline CNC milling machine stepper motors, as with most small stepper motors, emerge from an epoxy-filled opening. As a result, whenever the motor or wires move, all the stress concentrates right at that epoxy surface.

Which is exactly where the wires will break…

There’s no good way to add strain relief to that point (more adhesive isn’t helpful), but you can anchor the cable to the motor frame so that the individual wires do not move relative to the motor.

Cable ties will suffice. Add one around the entire motor to hold the wires in place, then lash the spiral sheath to one of the unused mounting holes in the motor frame.

Pull those ties until they squeak! You can grab the tabs with flush-cutting diagonal cutters to get some traction, then rotate the cutters against the ratchet housing to pull another notch past the ratchet. When it’s so tight you’re stretching the tie, then it’s tight enough; clip the end off with the cutters.

To cross-check, wiggle the connector end of the cable. If the wires move at the epoxy, then you haven’t done a sufficiently good job. Repeat until satisfied.

This works for the milling machine and, as shown in the picture, the rotary table. Just do it!

2009-04-16
Recumbent Bicycle Chain Catcher

Chain catcher

You’re puffing up a serious hill, finally downshift to the smallest chainring, and the chain falls off on the inside. You’re already at stalling speed, so you stop abruptly and gracelessly. If you haven’t used up your weekly luck allotment, you neither fall over nor get rammed by the rider behind you.

Not to be endured, sez I.

The solution is the Chain Catcher from Bike Tools Etc. It normally attaches to the seat tube of diamond-frame bikes and prevents the chain from falling off inside the smallest chainring, but it works fine on ‘bents, too.

Alas, their smallest Chain Catcher, part number CC-04A, fits a 28.6 mm seat tube: it’s much too large for the 1-inch tube on a Tour Easy.

Never fear! Go to your local home-repair store with ruler in hand and examine the plumbing aisle’s plastic fittings. I used a sink drain tailpiece, but any tube with an outside diameter over 1-1/4” and 1/16” walls will work. Buy one, take it home, cut off a ring as wide as the Chain Catcher with a saw or a razor knife, and smooth the edges. Cut the ring lengthwise, slip it over the bike tube, mark the spot where the ends cross, remove it, and trim to fit neatly on the tube.

If you make a mistake, you have spares aplenty…

(This is trivially easy with a lathe, but you need not go full-on geek for this project.)

Install the Chain Catcher over your shim with its thumb pointing forward and align it with the chain’s rivets, not quite touching the chain on the smallest ring. Firmly tighten the Catcher’s mounting screw.

This won’t fix a badly adjusted front shifter, but it does eliminate those occasional glitches.

Ride on!

2009-04-12
Tour Easy Handlebar Hydration Mount

Handlebar-mounted hydration pack (fairing removed for visibility)

My esteemed wife returned from a shopping expedition with the crushed remains of a water bottle that fell out of her Tour Easy’s under-handlebar cage. Fortunately, the truck flattened the bottle, not her, but Something Had To Be Done. She also had trouble maneuvering those newfangled long-body bottles around the rear edge of the Zzipper fairing.

My TE has a hydration pack attached behind the seat with the hose passing around my arm to a Velcro (nah, it’s generic hook-and-loop) strip safety-pinned to my shirt. Mary didn’t like that arrangement, because it required some fiddling when she sat down and poked pinholes in her shirt. She wanted an arrangement that Just Worked.

Recycled pack support plate

I removed the under-the-handlebar bottle cages from her bike and bolted a salvaged aluminum plate to the four tapped ferrules. The numbered holes on the plate originally held coaxial cable connectors, but I think they give the plate that snooty, high-tech, drilled-out, weight-weenie look.

A 50-ounce hydration pack (“Styled for women!”) fits neatly atop the plate, below the cables, and between the handlebars. We wrapped a two-inch-wide Velcro bellyband around the pack, Velcroed the bag’s top loop to the handlebar’s crosspiece, and secured the valve with another Velcro strap that doubles as her parking brake. The whole affair looks quite tidy under the fairing.

Now she simply picks up the hose and takes a sip: no acrobatics, no dropped bottles, no hassle. Life is good!

2009-04-11