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.

Category: Machine Shop

Mechanical widgetry

Repurposing Tomato Cages

Bending tomato cage wires

Mary wanted to convert some old tomato cages into flower supports and deer protectors (until the flowers get big enough), by the simple expedient of flipping the cages over with the large end down. She figured we could chop off the wire ends that normally anchor the cages to the ground, then bend them into hooks for secure ground anchors.

I deployed the linesman’s pliers, which only showed that my wire size estimation is grossly underdeveloped. The high-carbon steel wires required bolt cutters… but a few minutes of twang effort scattered two dozen really stiff wires across the patio.

I ran a marker across the pile at the bend point, grabbed two random steel rods in the vise and, in short order, bent up a stack of ground anchors.

Not every job requires G-Code …

2010-07-02
Zire 71 Button Protector

Zire 71 button protector

I carry around an ancient Zire 71, from the time before PDAs merged with phones and PCs to become fashionable objects of desire.

Anyway, it turns out that the buttons on the front are remarkably easy to squash in your pocket: the poor thing spends a lot of time turning itself on and off. I machined a plate with two holes for the four buttons and a lengthwise recess with two notches for the joystick selector. The whole affair slides into the pouch Mary made for it and works fine.

I tweaked the thing a bit when I got a replacement Zire a few months ago; the grippy tape I put on the sides seemed to be just large enough to force the joystick against the protector while sliding it into the pouch. Now that’s not a problem.

Zire 71 protector in place

This is in the nature of documentation, just in case I need something like this ever again. I found these pix while looking for something else …

2010-06-28
HT GPS + Audio: Case Dimensions

Having obtained eyeballometric measurements from the case, the next step was to doodle some shapes on graph paper and pencil in the dimensions. My motivation for not using CAD is simple: it’s easier (for me, at least) to doodle using a pencil.

The outside of the case had pretty much the same features.

Pack Layout – External

The inside, of course, bore no resemblance to the battery pack; the shoulder and whatnot will support the circuit board.

Pack Layout – Internal

The original battle plan was to build the case in at least two layers, simply because it had to be so deep the Sherline couldn’t reach to the bottom with any rational end mill. It would probably make more sense to glue up four sides on a machined bottom, but that requires actual skill.

This became the Front layer, with Front and Rear faces. The Rear layer attaches to the back of this one. In this picture, the Front layer is on the bottom, taped to the radio.

ICOM IC-Z1A with GPS+Audio Interface

The two layers peeled apart, with the Front layer to the right. You can barely see the internal shoulder and external tabs.

Interface – top and bottom surfaces

2010-06-27
ICOM IC-Z1A and W-32A: BP-171 Battery Pack Dimensions

Early on, I decided that the whole APRS + voice interface for our bikes had to fit on the back of the radio, which meant it had to look a lot like a BP-171 battery pack. The first step was to get all the relevant dimensions from an existing pack.

I laid a (rebuilt) pack on the scanner and took its picture. There’s a lip on the bottom (top in the image), so I held it level with the end of the calipers you can see near the bottom. That puts it slightly above the scanner’s focal plane, but it’s close enough.

Then I scanned some graph paper (remember that?) with 10 lines per inch, overlaid that on the pack image, rotated to line it up with the pack, scaled the grid so that the major lines were 1 cm apart on the pack in both directions, and that gave me a nice 1 mm grid to eyeball the measurements.

Printed the image out at about twice real size and there you have it:

Battery Pack Dimensions

The doodles around the bottom give the Z-axis dimensions for tabs & contact slots & suchlike.

The notes near the top were a first pass at how to mill the thing; two years later, the actual G-Code bears little resemblance to that.

I put the origin at the lower-left corner of the part that fits into the radio body, 2.4 mm inside the left edge that mates with the outside of the body. That was probably a mistake, as it meant I had to touch off the final part at X=-2.4 rather than just 0.0.

We live & learn.

2010-06-26
HT GPS + Audio: Battery Case Contacts

The case for this gadget slides into the back of the ICOM IC-Z1A HT and powers the radio through its usual battery contacts. I reshaped 5/16″ 4-40 brass machine screws into flat-top studs, then soldered 8-mil tin strips to their tops.

Grab a screw in a pin vise, brace it on the bench vise, and file off everything that doesn’t fit:

Reshaped 4-40 screws

The result should fit neatly into the flatted recess, with the top flush in the rectangular slot:

Studs in their recesses

Cut an oversized strip of 8-mil tin and solder it to the stud. I tinned both pieces to get nice solder coverage, although the notion of tinning a piece of pure tin with silver-tin solder did give me pause. It’s all in the flux, I suppose.

Anyhow, put the two tinned sides together and hit the combo with a half-second pulse at 100% duty cycle from my resistance soldering gadget. Perfect:

Tin strip soldered in place

Then snip off whatever doesn’t fit into the slot with an ordinary (albeit shop-only) scissors, making it just slightly shorter than the slot so the end doesn’t snag on anything. File the sides and corners so they’re easy on the fingers, flatten the strip so it fits neatly into the slot, buff it up a bit, and it’s all good.

Contacts in place

Takes longer to describe than to do it, at least the second time you do it…

2010-06-24
Bike Mirror Ball Clamp Doodles
The plastic-ball-in-plastic-socket joint found in bicycle mirrors seems to fail after a year or two of constant use. These are some doodles & thoughts about building a small, robust, adjustable joint.

A bike mirror needs two ball joints:
- at the helmet mount to put the mirror in the proper spot
- at the mirror to align the image
A flexy boom can replace the helmet joint, although rotation around X (pitch) is still handy.

A flexy mirror mount can replace the mirror joint, but it must also be compact.

Without heroic measures, the range of travel for a ball joint isn’t all that much.

How to make a ball? Anneal & drill a standard ball bearing for a wire shaft? Solder onto chrome steel? CNC mill the end of a bar in a rotary table?

How to make a socket? Some of that low-temperature themoplastic might be useful. Mold it around the ball, slit radially, and squash it in a circ clamp?

How to adjust? Circumferential clamp around the socket or pull the whole socket into a wedge? Radial cuts through the socket to allow compression or depend on plastic/elastic deformation?

How much friction? You want it stiff enough to hold position in a strong wind and easy enough to reposition. You definitely don’t want grub screws or fiddly knobs!

The doodles are all far too complex, some are absurd, one can’t be built (at least by me), and I’ll probably end up using some bendy wire anyway.

Something of this may be useful in another project … and now I can throw out that scrap of paper.

Mirror clamp doodles
2010-06-23
HT GPS + Audio: Modified Plug Alignment Plates

As described there, I made a fixture and a small plate to hold 2.5 mm and 3.5 mm plugs in the proper alignment for the mic & speaker jacks on our ICOM IC-Z1A HTs. Knowing I was going to rebuild the interface boxes, I made several spare plates and tucked them into a small bag against future need.

Jack Plates – Oblique

Time passes.

Come to find out that the new gratuitously gold-plated 2.5 mm plugs in my stash have a slightly thicker front plate that doesn’t quite fit into the recess I milled in the plates for the old nickel-plated plugs. So I set up a little nest in on the Sherline’s table, snuggled each plate into the corner, and poked a 9/32-inch end mill 1 mm down into the plate. The net change was a 0.5 mm deeper recess. Sheesh.

Milling the plug plate recess

I’d originally create the recess with helical milling, but I recently uncovered a stash of shiny-new end mills in a box: 9/32 is 7.31 mm, just about exactly what you want for a 7-mm dia plug front plate surrounded by a blob of fast-curing epoxy.

Plugs epoxied into plate

This epoxy just holds the plugs in the right position for wiring and initial testing. After the cable checks out, I’ll smoosh a blob of epoxy putty around the whole thing as before.

2010-06-21