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.

Author: Ed

Easy Reacher Pack: New Elastic Cord

The elastic cord behind the left-side under-seat Easy Reacher pack on my Tour Easy snapped some time ago, probably due to wear against the brace I installed to keep it from flopping around. Quite contrary to what I expected, the repair turned out to be almost trivially easy.

The cord terminates in a pair of plastic lugs, each with a ferrule that slipped off under moderate persuasion to reveal a pair of wedges that engaged the cord:

Easy Reacher pack – elastic cord clamp

I expected the ferrule to have a positive lock engaging those wedges, but, nope, there’s (at most) a small ridge. Pry the wedges out and the cord slides out of the lug without a protest; the wedges don’t quite meet in the middle with the ferrule in place and there’s plenty of retention force on that flexy cord.

One of the shorter bungie cords in my collection turned out to be exactly the right diameter and length, with ends secured in its hooks using a simple crimped wire. Bending the ends of the wire at right angles freed the cord from its embrace:

Easy Reacher pack – unclamping new elastic cord

The original stainless steel hook lies by the edge of the road along my usual bicycling route, but a slightly reshaped S hook (made, alas, of ordinary steel) fits around the cord well enough. When this one rusts away, I have plenty more.

Insert cord into lugs, push ferrules over locking wedges, remove one ferrule and lug, install reshaped S hook, reinstall lug and ferrule, install new cord on pack:

Easy Reacher pack – new elastic cord

Install pack on bike: done!

I have no explanation for how well this worked out; I fear the Universe is saving up spit for something truly awful.

2014-08-07
Tour Easy Kickstand Adapter Plate

The venerable Greenfield kickstand on my Tour Easy doesn’t quite match the mounting plate under the frame, with the result that it can pivot just enough to make the bike tippy with a moderate load in the rear panniers. I’ve carried a small block to compensate for sloping ground, but I finally got around to fixing the real problem.

The solution turned out to be a spacer plate that fills the gap between the back of the kickstand casting and the transverse block brazed to the mounting plate:

Tour Easy kickstand adapter plate

That little lip is 2 mm wide, so it’s not off by much.

The aluminum came from a Z-shaped post that contributed its legs to a previous project. I flycut the stub of one leg flush with the surface, then flycut a slot 2 mm from the edge:

Tour Easy kickstand adapter – flycutting recess

For no reason whatsoever, the width of that slot turned out exactly right.

Bandsaw along the left edge of the slot, bandsaw the plate to length, square the sides, break the edges, mark the actual location of the mounting plate hole, drill, and it’s done!

An identical Greenfield kickstand on Mary’s identical (albeit smaller) Tour Easy (the bikes have consecutive serial numbers) fits perfectly, so I think this is a classic case of tolerance mismatch.

2014-08-06
Kenmore 158: ET227 Transistor Drive Gain

A closer look at the collector voltage and current for the brute-force ET227 NPN transistor motor drive:

Model 158 – 77 mA base VCE 200 mA div

The motor current (200 mA/div) never goes to zero, but the ET227 collector voltage hits zero as the transistor saturates: the motor winding soaks up all the available line voltage and the transistor dissipation drops close to zero. The datasheet suggests V_CE(sat) < 0.1 V for I_C < 5 A, albeit with I_B = 30 A (!).

The ET227 base drive was 77 mA, measured on a better meter than the low-resolution one in the power supply, and the transistor gain works out to 8 = 620 mA / 77 mA along those flat tops.

Eyeballometrically speaking, the dissipation averages 50 W = 90 V x 620 mA during those spiky sections where the transistor must absorb the difference between the line voltage and the motor voltage. The cursors say that takes 5 ms of the 8.3 ms period of the 120 Hz full wave rectified power, so the duty cycle is 42% and the average average dissipation works out to 20 W. That’s still enough to warm up that big heatsink; the motor driver will need a thermal sensor and a quiet fan.

That commutation noise looks pretty scary, doesn’t it?

The test setup:

Kenmore 158 – AC motor FW ET227 drive – test setup

The bridge rectifier doesn’t really need a heatsink, but it looked better for a Circuit Cellar picture…

2014-08-05

Image File Recovery Redux

Took a picture of the sewing machine setup with the Sony DSC-F717, transferred it into DigiKam, got the “done transferring, you can disconnect the camera” message, believed it, disconnected the camera, deleted the image file, and then discovered that DigiKam mislaid the image file.

Rather than re-set-up and re-take the shot, I followed my own directions and recovered the image from the Memory Stick:

dmesg | tail
[43176.079853] usb 2-1.6.3: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[43176.079855] usb 2-1.6.3: Product: Sony PTP
[43176.079856] usb 2-1.6.3: Manufacturer: Sony
[43198.073652] usb 2-1.6.3: USB disconnect, device number 22
[43333.788533] sd 9:0:0:0: [sdc] 1947648 512-byte logical blocks: (997 MB/951 MiB)
[43333.803292] sd 9:0:0:0: [sdc] No Caching mode page found
[43333.803299] sd 9:0:0:0: [sdc] Assuming drive cache: write through
[43333.824681] sd 9:0:0:0: [sdc] No Caching mode page found
[43333.824688] sd 9:0:0:0: [sdc] Assuming drive cache: write through
[43333.825491]  sdc: sdc1
sudo dd if=/dev/sdc of=/tmp/pix.bin bs=1M
^C615+0 records in
614+0 records out
643825664 bytes (644 MB) copied, 38.5841 s, 16.7 MB/s
strings -t x pix.bin | grep Exif | head
  68006 Exif
 208006 Exif
 3f8005 _Exif
 7b8006 Exif
13d8006 Exif
15b0005 wExif
1798005 CExif
19c0006 Exif
1b90006 Exif
1f98005 %Exif
dd if=pix.bin of=image03.jpg bs=$((16#1000)) count=1K skip=$((16#3f8))
1024+0 records in
1024+0 records out
4194304 bytes (4.2 MB) copied, 0.0121431 s, 345 MB/s
display image03.jpg
convert image03.jpg dsc00656.jpg

Obviously, there was a bit more flailing around than you see here, but that’s the gist of the adventure. For what it’s worth, image01 was a random blurred shot and image02 is the ID picture I keep on all my cameras.

The convert step discards all the junk after the end of the image, so the dsc00656.jpg file doesn’t include anything unexpected.

The picture isn’t all that much to look at, even after cropping out the background, but …

Kenmore 158 - stepper drive test — Kenmore 158 – stepper drive test

The advantage of the manual method: renewing one’s acquaintance with tools that come in handy for other tasks.

2014-08-04

Flashlight Switch: Poor Solder Joints
My desk flashlight has three “functions”:
- 5 UV LEDs
- 10 white LEDs
- laser pointer
A four-click rotary pushbutton switch actuates the three functions (plus “off”) in sequence:

Flashlight switch – internal wiring

All three lights became intermittent, which suggested a poor return connection at the far end of the battery. The case is, of course, aluminum, with coarse-cut threads that grate as you tighten the parts. I cleaned the crud out of the threads, anointed them with Ox-Gard compound, and discovered that the laser and UV LEDs were still flaky.

Taking the thing apart and unsoldering the switch connections revealed the problem:

Flashlight switch – bad solder joints

Yup, two lousy solder joints. They’re not exactly cold solder joints, because there’s not really a joint there to begin with; the switch tabs never got hot enough to bond with the molten solder before it cooled.

A dab of flux and touch from a hot soldering iron solved that problem.

Assemble in reverse order and it works better than it ever did before!
2014-08-03
Turtle Tragedy: Raymond Avenue

Verily, ’tis the season for turtles on the move. This one clunked over the curb on Raymond Avenue at Vassar Lake, couldn’t find an escape route, and got smashed:

Smashed turtle – Raymond Ave at Vassar Lake – 2014-07-06

Turtle armor works pretty well against their usual predators, but can’t handle automobile tire impacts.

That’s a tight crop from the helmet camera, with terrible compression artifacts smearing the spalled concrete sidewalk.

For whatever reason, NYSDOT can’t do concrete sidewalks; the entire length of Raymond Avenue has lousy concrete. The fact that Vassar College B&G uses the sidewalks as their private golf-cart highway may have something to do with it, but that’s not the primary problem, because the concrete on DOT’s showcase Rt 55 between Burnett Blvd and Titusville Rd looks the same way.

2014-08-02
Monthly Science: Bicycling

Faired Tour Easy on crowned road

Mary signed up for the National Bike Challenge and is currently ranked 4201 out of 32 k riders, by simply getting on the damn bike and riding. About 3/4 of her miles count as “transport”: grocery / gardening / shopping / suchlike. We’re no longer biking to work, but when we did, riding ten miles a day, every day, added up pretty quickly; we chose houses in locations that made bicycle commuting possible.

Her father, at age 84, also signed up and ranked neck-and-neck with her until cataract surgery cut into his riding schedule; their standings flip-flopped depending on who updated most recently. He’s our role model for getting old without slowing down.

I’m not participating, being far more quantified than anyone really should be.

Makes you wonder what the bottom 28 k (*) riders are doing, doesn’t it? I mean, sheesh, my esteemed wife spots most participants an entire lifetime or two; her father spots them three or four. They’re not star athletes, that’s for sure, but they’re doing just fine.

I commend to your attention:

Less Exercise, Not More Calories, Responsible for Expanding Waistlines

Takeway: half of adult Americans report no physical activity at all.

May I suggest a health(y) plan?

(*) The Challenge had over 40 k riders at one point. We think they’ve tossed folks who haven’t done any riding at all, which might serve to improve the overall averages.

2014-08-01