Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
The front tire (a Primo Comet blackwall) on Mary’s Tour Easy was flat when we rolled out of the garage a few days ago. While a flat isn’t pleasant at any time, it’s much nicer to find one at home, before the ride, rather than out on the road!
I figured the tire ate something sharp that managed to work its way through the tire liner and into the tube; that’s rare, but it sometimes happens. These two pix of the tread show why we use tire liners: sidewall-to-sidewall nicks, cuts, gouges, and gashes, despite the fact that the herringbone tread has plenty of life left in it. Click the pix to enlarge, if you dare…
Tire cuts 1
And another section; it’s like this all the way around the tire. I think this one is the better part of a year old, so it has maybe 2000 miles on it. It handled 200+ miles along the Pine Creek Gorge rail-trail this past summer, which was sharp crushed gravel, but most of the cuts came from roadside debris on our ordinary utility rides around home.
Tire cuts 2
As it turned out, the tire liner had prevented all those punctures from reaching the tube, while killing the tube all by itself. The sharp edge where the the two ends of the liner overlap had worried its way through the tube.
Abrasion from tire liner
The tire liner wasn’t a genuine fluorescent green Slime strip, but some translucent brown thing. The difference: Slime liners are thinner and don’t have nearly this much abrasive power.
Alas, I didn’t have a Slime liner in my stash (remedied with the most recent bike parts order), so I put the brown liner back in with a few layers of genuine Scotch electrical tape to build the end up a bit. There’s really no good way to feather the end without making it into a ragged knife edge.
New tire and tube, of course. I’m not that crazy!
With any luck, the liner and tape will behave for another few years, until the tire wears out, and then I’ll replace everything. Other than this event, flats aren’t a big part of our riding experience.
The 6 mm stainless steel shaft I installed in late June, for reasons described there, has been working just fine.
Although the shaft has some discoloration, the idler bearing slides freely this way and that. No complaints about noises or bad shifting.
I spritzed some silicone lube on the shaft and it’s way slippery again. That’s better than petroleum lubes that tend to turn road dust into grinding compound.
A few days ago I rode off to an eye doctor appointment and my ladies rode off later to meet me at the grocery store after they stopped in the garden to harvest root crops. This sort of thing is easy enough to synchronize with amateur radio, but this morning I didn’t hear a thing until they rolled up beside me in the store parking lot.
It seemed they could hear each other and me, but I couldn’t hear either of them. We’re all on 144.39 MHz, the APRS data frequency, with 100 Hz tone squelch to keep the robots out of our ears. Our daughter has the GPS APRS tracker feeding data into the mic input, which is why we’re using a data channel for tactical comm.
This has happened once or twice before, but it’s very intermittent. I now had sufficient motivation to disconnect the radio, an ancient ICOM IC-Z1A, from the bike and pith it on the Electronics Workbench for examination. The UT-93 Tone Squelch board is unplugged & flipped over, resting on the front half of the radio body at the lower-left of the photo.
Turns out that there’s nothing visibly wrong in there. I suspect it’s a molecule or two of oxidation on the (gold-plated!) connector between the UT-93 and the main board, because the UT-93’s held firmly in position by the black foam square you can see in the lower-left of the photo. The small white plug near the top of the UT-93 mates with the equally small socket on the main board, just to the left of the lithium secondary cell in the middle.
It’s all CMOS logic, of course, and there’s no actual load current involved. That’s the worst condition for contacts, as a dry connection simply doesn’t produce enough energy to burn through the least hint of oxidation. That’s why they use gold plating on connectors, but it’s been a long time since that board has moved at all; the foam square is deeply indented.
So I wiggled & jiggled all the ribbon-cable connectors while I was in there, buttoned everything back up, and the tone decoding works again. I hope this will continue…
Memo to Self: remove only the four black corner screws on the upper case, plus the two silver screws near the very bottom inside the battery compartment, and the two halves pop apart. No need to remove the mic and earphone plugs, whew!
There’s now There was a webcam[Update: dead link] watching the recently opened Walkway Over the Hudson, put on by the Dutchess County Tourism folks.
I couldn’t quite figure out where it was, though, because there aren’t any tall buildings or towers near the Walkway. The area used to be hard industrial, with plenty of smokestacks, but those days and those structures are long gone.
On a recent trip I parked the bike at the end of the chain-link fence on the north side of the bridge, eyeballed back five-and-a-half sections of fence on the south side, and spotted what I’d been missing.
The camera is a bit more than half a mile away, atop the Interfaith Towers building at 66 Washington St, on the northwest corner at Mansion Street. The Google overhead view isn’t up to date; the Walkway’s concrete decking is done and they’re tweaking some of the electrical work even as I type.
The camera’s gooseneck mount lets that loooong telephoto lens vibrate in high winds. When the webcam image looks broken up, new weather is on its way!
The picture is a crop from a larger image, with a bit of color correction and gamma tweakage.
This Philips LumiLED app note gives some specs on automotive lighting. The one we bikies all tend to ignore is the surface area: greater than 37.5 square centimeters for rear combination stop-turn fixtures. Call it a scant 4 inches in diameter. You’ve never seen a bike light that large, have you?
LED combo tail stop light
Maybe the right thing to do is start with a street-legal truck light and build some electronics around it. This is a 4 inch diameter, 44 LED rear light with both taillight and brake light terminals. At 12 V, the taillight draws 10 mA and the brake light is 250 mA. Got it from Gemplers with a recent order, but they’re certainly not the optimum supplier if that’s all you’re buying.
Obviously, it’s unreasonable to run a 3 watt taillight on a bike, as the most recent crop of single-LED killer headlights are merely a watt or three. Battery life remains a problem.
At 10% duty cycle the brake LEDs would average 300 mW. That might be roughly comparable to the running lights on some cars these days.
With the taillight constantly energized and the brake flashing at 4 Hz, it’d be 120 + 0.5 * 300 = 270 mW.
That’s more reasonable. With a 50% efficient upconverter to 12 V, that’s half a watt. Start with 4 AA cells, triple the voltage, draw 100 mA, runtime is 1500 / 100 = 15 hours. Good enough.
And it ought to be attention-getting enough for anybody! The only trouble will be fitting the damn thing on the back of the bike; fortunately, ‘bents have plenty of room behind the seat, so maybe attaching it below the top seat rail will work.
Memo to Self: The rear reflector must be something like 3 inches in diameter, too. We ignore that spec, too.
Let’s quote that text so you can read it (or click the picture for a bigger one):
Yeah… we’re talking down there. With lots of supporting data that says prolonged riding while your boys are numb is a no-no, we decided to build a saddle you can fine-tune to fit… you.
Speaking of prolonged riding, the current hour records:
Upright bike: 30.882 miles
Recumbent: 56.2948 miles
Sam Whittingham (who also holds that recumbent hour record) recently set the new human-powered land speed record at Battle Mountain: 82.43 miles per hour. Yup, pedaling a bicycle, on level ground, in minimal wind.
Admittedly, he was riding a recumbent that bears as much relation to the Tour Easy I ride as a Formula One car bears to yours. On the other paw, those Tour de France bikes aren’t exactly factory stock, either.
If you want to go as fast as you can on a bike, you want a recumbent. Unless, of course, you’re doing UCI races, in which case you may go as fast as they’ll allow you and wreck your body in the process.
When you get back from a ride on a recumbent bike, no matter how long you rode the bike, not only do all your parts still work, but nothing hurts. What’s not to like?
My earlier musing on bike performance is there. Clicking on the “Recumbent Bicycling” category summons forth more posts…
I need an LED taillight (and maybe headlight) with a metal case and far more LEDs than seems reasonable. This is a doodle to sort out some ideas… not all of which will work out properly.
The general notion is that one can put today’s crop of ultrasuperbright 5 mm LEDs to good use. While the Luxeon & Cree multi-watt LEDs are good for lighting up the roadway, they’re really too bright and power-hungry for rear-facing lights. Mostly, you want bright lights facing aft, but the beam pattern & optical niceness really aren’t too critical as long as you’re not wasting too many photons by lighting up the bushes.
I think, anyway. Must build one and see how it works. I know that a narrow beam is not a Good Thing, as cars do not approach from directly behind and it make aiming the light rather too finicky.
The problem with commercial bike taillights is that they use piddly little LEDs and not enough of them. If you’ve ever actually overtaken a bicyclist at night with a blinky LED taillight, you’ve seen the problem: they’re too damn small. Automobile taillights must have a very large surface area for well and good reason.
So the diagram in the pic explores the notion of arranging a bunch of red & amber LEDs in a fairly compact array. The shaded ones are red, the open ones are amber (with two more side-facing ambers to meet legal requirements), and there are eight of each. The OD is about 40 mm. Figure 5 mm LEDs with 2.5 mm of aluminum shell between them. If the center four LEDs were spaced right, an axial (socket-head cap?) screw could hold the entire affair together.
Turns out both the red & amber LEDs in the bags of 100 I just got from Hong Kong run at 2 V forward drop @ 30-ish mA, so that’s 16 V total for eight in series.
Four AA NiMH cells fit neatly behind the array, so the supply will be 4 – 5 V, more or less. The outer casing could be plastic pipe.
What to do for a battery charging port? Must be mostly weatherproof. Ugh.
Rather than a regulated supply and a current sink / resistor, use an inductor: build up the desired forward current by shorting the inductor to ground, then snap the juice into the LEDs. The voltage ratio is about 4:1, so the discharge will happen 4x faster than the charge for a duty cycle around 20%. At that ratio, you can kick maybe 50 mA into the poor things.
Governing equation: V = L (ΔI/ΔT)
If they’re running continuously, 2 V x 50 mA x 0.2 = 20 mW. The full array of red or amber is 160 mW, 320 mW for both. If you’re powering them at 10% duty cycle, then the average power dissipation is pretty low. Not much need for an external heatsink in any event.
A 1 kHz overall cycle means a 200 µs inductor charging period. With low batteries at 4 V and 50 mA peak current, the inductor is 16 mH. That’s a lot of inductor. I have a Coilcraft SMD design kit that goes up to 1 mH: 12 µs charge and 16 kHz overall. Well, I wouldn’t be able to hear that.
No need for current sensing if the microcontroller can monitor battery voltage and adjust the charge duration to suit; three or four durations would suffice. Needs an ADC input or an analog window comparator.
Automotive LED taillights seem to run at about 10% duty cycle just above my flicker fusion frequency; say between 50 – 100 Hz. If that’s true, red & amber could be “on” simultaneously, but actually occupy different time slots within a 100 Hz repeat and keep the overall duty cycle very low.
I’d like red on continuously (10% of every 10 ms) with amber blinking at 4 Hz with a 50% duty cycle. When they’re both on the total would be 60% duty.
The legal status of blinking taillights is ambiguous, as is their color; more there. Motorcycles may have headlight modulators. Bikes, not so much.
Battery life: assume crappy 1500 mAh cells to 1 V/cell. Red = 50 mA x 0.2 x 0.1 = 1 mA. Amber = 50 mA x 0.2 x 0.5 = 5 mA. Thus 1500 / 6 = 250 hours. Figure half of that due to crappy efficiency, it’s still a week or two of riding.
Rather than a power switch, use a vibration sensor: if the bike’s parked, shut off the light after maybe 5 minutes. It wouldn’t go off when you’re on the bike, even stopped at a light, because you’re always wobbling around a little.
Memo to Self: put the side LEDs on the case split line?
The Smell of Molten Projects in the Morning 