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: Repairs

If it used to work, it can work again

Cheap Rechargeable Kitchen Scale: FAIL

While pondering what to do with the shattered kitchen scale, I got a bottom-dollar replacement touting its rechargeable lithium battery. After giving it the obligatory charge-before-using, I put it in service. Five days later, its battery was dead flat discharged.

So I gutted it to extract the battery:

Cheap digital scale – lithium cell

It’s a cute little thing, isn’t it?

Much to my surprise, the obligatory battery rundown test showed it matches its 0.74 W·hr label:

Kitchen Scale – Charge1

We all know where this is going, right?

Crunche a connector on the battery, another on the scale, and make up a suitable current tap for a meter:

Cheap digital scale – current measurement setup

Which looked like this:

Cheap digital scale – active current

That’s about what I found for the craptastic scale running from a pair of CR2032 primary cells, so it’s not out of line.

Turn off the scale and measure the idle current:

Cheap digital scale – inactive current

Do you think I got a dud?

For all I know, the little microcontroller under the epoxy blob is running a continuous attack on my WiFi network, with the intent of siphoning off all my sensitive bits. Ya never know.

Dividing the battery’s 200 mA·hr rating by 4 mA says it really should be dead in 50 hours, which is close enough to five days: diagnosis confirmed!

Rather than fight, I switched to a battery with more capacity:

Cheap digital scale – NP-BX1 replacement

It’s long past its prime, but ought to last for a month, which is about as long as the shattered scale survived on a similar battery.

Sheesh & similar remarks.

2023-09-27
Tour Easy: Rewheeling

After 22 years and well over 30 k miles, I finally replaced the rear wheel rim on my Tour Easy, which went as smoothly as one could want.

The tire showed considerable wear and damage, with this gash dating back three years:

Schwalbe Marathon Plus – W5W gash

The pebble caught in this crater has worn flat on the outside and started cutting through the tire carcass into the tube:

Schwalbe Marathon Plus – Stone gash

Gotta love those Marathon Plus tires!

So my bike now has a new tire, tube, and rim on the back.

The old spokes looked OK and tightened up without incident. For the record, the Park TM-1 tension meter puts the drive-side spokes at 25 and the other side just under 20, with the total runout & wobble under a millimeter.

Having now replaced all four rims on our bikes over the course of two years, I sawed the three rims still awaiting recycling into samples:

Tour Easy – 30 k mile rim wear

Unlike contemporary bikes, our Tour Easy recumbents have rim brakes and those original rims are pretty well worn out; they’re not supposed to be concave like that.

All in all, more Quality Shop Time™.

2023-09-21
Solar-Flattening Fiskars Cutting Mats

Fiskars cutting mats must lie flat on the table to be of any use, but they’re remarkably sensitive to warping due to localized temperature variations; a hot cup of tea can wreak a remarkable amount of damage. Suggestions from the InterWebs generally involve a clothes iron, temperature tweaks, overnight cooling, and unpredictable results.

Given that the mats are large polypropylene sheets, I figured applying moderate heat to the entire mat while it’s compressed between two flat plates would work better:

Fiskars cutting mat – solar flattening

That’s one of Mary’s 36×24 mats atop an MDF sheet (with pictures of wood laminated to both sides), under a 7/32 inch = 5.6 mm sheet of non-tempered glass, with a maple shelf supporting the last two inches of the unwarped edge, all sitting on the driveway in full sun.

The first attempt started too late in the afternoon for good heating and, after a few hours, had only slightly reduced the warp. Laying it out the next morning got the mat up to about 110 °F = 43 °C around noon and the warp was completely gone by evening.

I don’t trust the IR thermometer’s temperature measurements on glass, but the surrounding MDF and driveway were plenty hot.

The next sunny day flattened the warp out of 24×18 inch mat on my desk, so success wasn’t a fluke.

We noticed that the larger mat is now uniformly smaller by about 3/16 inch along the 36 inch width and 1/4 inch over the 24 inch height. It was a tag sale find with unknown provenance and, due to the warp, Mary had been using her other large mat for layout, so we don’t know if this one arrived a little short or if my technique both flattened and shrank it.

The smaller mat seems unaffected by its similar treatment, so your mileage may vary.

In any event, a flat mat is much more useful than a warped mat, so we’ll call the operation a success.

2023-09-19
Craptastic Kitchen Scale: Shattered

So it turns out the surface of the craptastic kitchen scale really was tempered glass:

Kitchen scale – shattered glass

That’s after an inadvertent drop edgewise onto the concrete patio.

Stipulated: given what I’ve already done to / for the thing, the usual warranties do not apply.

The frame around the NP-BX1 lithium batteries held the glass fragments together surprisingly well:

Kitchen scale – shattered glass – detail

Of course, harvesting the good stuff resulted in a pile of fragments, but the carcass cleaned up nicely and, after grafting a temporary top made from scrap acrylic it still worked:

Kitchen scale – temporary surface

I expected to just cut a slab of 6 mm acrylic to match the original 5 mm glass, but for reasons probably related to dielectric constants, the touch controls do not work through that much acrylic. In fact, they don’t work through anything other than the 1.5 mm acrylic shown above, which seems a bit too flimsy for normal use.

The original glass had a design screened on the back surface and covered with paint, which I can certainly mimic, but right now I’m unsure how much effort to put into the thing.

2023-09-14
Tour Easy Broken Spoke

A rear spoke snapped on Mary’s Tour Easy while we were at the far end of a ride. Unlike most broken spokes, the flanged end that I couldn’t maneuver the stub out of the hub and deploy the FiberFix, so we rode home slowly while avoiding as much rough pavement as feasible.

Once in the shop, pulling the sprocket and extracting the stub posed no problem:

Tour Easy broken spoke

Install the new spoke, crank to 23 on the Park Spoke Tension Meter to match the rest of the wheel, check the truing, and it’s all good.

At some point in the last two decades of riding, it seem the chain fell off the high side and gouged the spokes around the hub:

Tour Easy broken spoke – damage

If another spoke snaps in the near future, I’ll replace the lot of them, but until then, well, there’s riding to be done …

2023-09-08
Onion Maggot Fly Sticky Trap Repair
One of the sticky traps absorbed a mighty blow during the season and its ski-pole mount snapped off. Rather then rebuild the whole thing, I decided to just epoxy the pieces together and stick a reinforcing plate on the bottom.

I added a pair of screw holes to the OpenSCAD model and produced a projection of the bottom layer:
```
if (Layout == "Projection") {
    projection(cut=true) {
        Attachment();
        Cap();
    }
}
```
Which looked like this:

Sticky Sheet Cage – projection

Cutting that shape from an adhesive sheet looks the same:

Onion Maggot Fly Trap – adhesive sheet

The somewhat raggedy large hole seems to come from OpenSCAD’s somewhat low-res SVG outline conversion.

Fill the broken part with epoxy:

Onion Maggot Fly Trap – epoxy ready

Clamp it together on a plate to keep the bottom aligned:

Onion Maggot Fly Trap – clamping

Cut an acrylic baseplate:

Onion Maggot Fly Trap – acrylic cut

Apply adhesive sheet to acrylic, stick it on the bottom of the cage, add a pair of stainless steel screws, and declare victory:

Onion Maggot Fly Trap – bottom view

We’ll see how long that lasts out in the garden next year …
2023-08-30
Zenni Optical Glasses: Metalbending

The new batch of glasses I just received makes me take back any nice things I previously implied about Zenni Optical’s nose pad alignment:

Zenni eyeglass pads – as received

Zenni does have a guide to reshaping the frames, but it does not include aligning the pads parallel to your nose, which definitely goes better with wire-bending pliers in hand.

They should look more like this when you’re done:

Zenni eyeglass pads – aligned

I suppose this is a consequence of being able to get two eyeglasses + two sunglasses in three different frame styles and two different prescriptions, each with progressive lenses and antireflective coating, for about $350 delivered halfway around the planet.

Makes owning a set of metal-forming pliers look downright economical.

A few years ago, Mary paid more than that for a single pair of badly fitted glasses from a local outlet. Those days are over.

2023-08-28