Category: Recumbent Bicycling

Cruisin’ the streets

Machine Shop, Recumbent Bicycling

Bafang DPC-18 Button Mollyguard

I got the Bafang DPC-18 display for my Tour Easy specifically to put the control buttons on the handgrip, rather than the buttons on the left of the 500C display on Mary’s bike:

Tour Easy Bafang - display 26 mi
Tour Easy Bafang – display 26 mi

The first pass put them on the left handgrip, just behind the thumb throttle:

Bafang DPC-18 control buttons - initial mount
Bafang DPC-18 control buttons – initial mount

This turned out to be a catastrophically bad position, because the “buttons” extend all the way to the edge of the mount and trigger when pressed a fraction of a millimeter: the dark line visible under the light gray top is the entire range of motion.

My resting hand position on the grip put the edge of my gloved index finger along the buttons, where it would inexorably nudge the + button until I was riding in assist level 9 (“Rocket Sled“) mode.

One ride was enough to convince me those buttons needed a Mollyguard:

PXL_20230321_233854755 - Bafang DPC-18 button Mollyguard - rear view
PXL_20230321_233854755 – Bafang DPC-18 button Mollyguard – rear view

It is, of course, a laser-cut piece of 1.5 mil black acrylic, held in place with hot-melt glue. Because the button housing isn’t mounted symmetrically on the handlebar, I cut a few paper templates before getting the position and size right.

A view from the front shows the lip sticking up over the buttons:

Bafang DPC-18 button Mollyguard - front view
Bafang DPC-18 button Mollyguard – front view

FWIW, the asymmetric mount put the buttons on the rider’s side of the flat handlebars found on contemporary upright city-rider style bikes. It makes perfect sense in that context, but didn’t help me in the least.

With the Mollyguard in place, I rotated the whole button assembly around the handgrip to allow pushing the buttons with my thumb in its natural position.

Now the assist level changes only when I want it to!

Electronics Workbench, Machine Shop, Recumbent Bicycling

Bafang Motor Connector Gasket Replacement

Reasonable people disagree as to the cause of the failure, but a replacement controller for the (new) Bafang motor I’m installing on my bike just arrived in the mail.

Disassembling the motor is straightforward, except for the part where you must excavate an internal plug from the silicone snot gluing it into place, eventually revealing its socket:

Bafang motor - interior gasket - connector
Bafang motor – interior gasket – connector

Regrettably, there seems no way to do that without destroying the dense closed-cell gasket around the connector:

Bafang motor - interior gasket - damaged original
Bafang motor – interior gasket – damaged original

Equally regrettable: a replacement gasket wasn’t included with the replacement controller. Although I don’t have any of the specific foam, some marginally less dense foam from the Big Box o’ Padding seemed suitable for laser cuttery:

Bafang motor - interior gasket - iterations
Bafang motor – interior gasket – iterations

The upper left prototype suggested a slightly larger rear bar that produced the gasket in front, which fit snugly:

Bafang motor - interior gasket - test fit
Bafang motor – interior gasket – test fit

It lacks the latch cutout, but the foam is squishy and I expect to never touch it again.

A generous glob of hot melt glue holds everything in place:

Bafang motor - interior gasket - replacement glued
Bafang motor – interior gasket – replacement glued

Although the usual Youtube videos show folks slathering RTV silicone caulk on these connectors, that’s a Very Bad Idea™, because RTV caulk releases acetic acid as it cures. That’s not a problem in the open-air siding-and-lumber environment the caulk was intended for, but sealing a glob of the stuff inside an enclosure will eventually corrode all of the electronics therein.

Cutting intricate doodads has become trivially easy: if you can draw it, you can pretty much cut it, just like that:

Bafang motor connector gasket - LB layout
Bafang motor connector gasket – LB layout

That was the easy part, anyway.

Machine Shop, Recumbent Bicycling

Bafang Triangle Plate Rework

The time has come to add a Bafang mid-drive motor to my Tour Easy recumbent, much like the one Mary has been using for the last two years. When I got to the point of installing the motor in the bottom bracket shell, this happened:

Bafang Triangle Plate - jammed screw
Bafang Triangle Plate – jammed screw

It turns out the triangle plate has slightly misplaced bolt holes:

Bafang Triangle Plate - misplaced bolt holes
Bafang Triangle Plate – misplaced bolt holes

If you look very carefully, you’ll see the holes sit just slightly above the midline of those ears. The additional fractional millimeter below the holes touches the motor end bell and prevents them from lining up with the tapped holes.

Normally, you’d just hit the plate with a file and be done with it, but it’s ferociously hardened steel: a file bounces right off.

I deployed a Dremel sanding drum above the ShopVac’s snout to catch the abrasive dust, eroded just enough steel to line up the holes, and everything now fits the way it should.

Done!

Oddities, Recumbent Bicycling

The Stone

Yeah, this is enough to knock your bike completely off course:

The Stone - A
The Stone – A

The black smudge matches a scuff on the right sidewall of the front tire. I think I hit it in that orientation and it pivoted clockwise while lifting the bike and shoving the tire to the left.

Another look from what was likely the right side of the shoulder:

The Stone - B
The Stone – B

I’ll give it a decent burial out back … and be glad our roles aren’t reversed!

Aphorisms, Photography & Images, Recumbent Bicycling, Science

Stone Cold Swerve

We’re southbound on Rt 376, ticking along at about 15 mph, with fresh string-trimmer debris littering the shoulder:

T – 50 ms

Did you notice the rock? I didn’t.

The fairing ripples as my front tire hits the left side of the rock:

T = 0

I have no memory of the next two seconds.

The offset impact turns the front wheel to the left, so the bike steers out from underneath my weight:

T + 500 ms

Because the bike frame was still aimed straight ahead, the wheel is steering further to the left and putting me even more off-balance. I am somehow trying to lean left far enough to get my weight lined up with the bike:

T + 1.0 s

One second into the event, Mary has no idea what’s going on behind her.

My memory resumes with an image of the yellow midline just beyond my left foot:

T + 2.0 s

Mary heard an odd sound and asks (over the radio) “Are you all right?”

I’m approximately balanced, turning toward the shoulder, and manage to shout “NO!”:

T + 3.0 s

I’m coasting toward the shoulder with my feet off the pedals:

T + 4.0 s

Mary is stopping and I coast past her:

T + 5.0s

Landing gear out:

T + 6.0 s

Back on the shoulder, lining up with the guide rail:

T + 7 s

Dead slow:

T + 8.0 s

Docking adapter deployed:

T + 9.0 s

And stopped:

T + 10.0 s

I sat in that exact position for nearly four minutes.

A slideshow view of the same images so you can watch it unfold:

  • T – 50 ms
  • T = 0
  • T + 50 ms
  • T + 500 ms
  • T + 1.0 S
  • T + 2.0 s
  • T + 3.0 s
  • T + 4.0 s
  • T + 5.0 s
  • T + 6.0 s
  • T + 7.0 s
  • T + 8.0 s
  • T + 9.0 s
  • T + 10.0 s

Doesn’t look like much, does it?

If I could have looked over my shoulder, this is what I would have seen, starting at T = 0 with the rock impact blurring the image:

  • T = 0
  • T + 67 ms
  • T + 1.0 s
  • T + 2.0 s
  • T + 3.0 s
  • T + 4.0 s
  • T + 5.0 s
  • T + 6.0 s
  • T + 7.0 s
  • T + 8.0 s
  • T + 9.0 s

Surely scared the daylights out of that driver, perhaps confirming all the usual expectations of crazy bicyclist behavior.

Here’s what Mary would have seen over her shoulder, again starting at T = 0 with the fairing bulging from the impact:

  • T = 0
  • T + 467 ms
  • T + 833 ms
  • T + 1.0 s
  • T + 2.0 s
  • T + 3.0 s
  • T + 4.0 s
  • T + 5.0 s
  • T + 6.0 s
  • T + 7.0 s

Timing is everything.

That Benz is new enough to have automatic emergency braking, as it slowed pretty dramatically while I was busy getting out of the way, but it’s not clear whether AEB knows about small / lightweight targets like pedestrians and bicyclists.

We completed the ride as planned, although I finally realized the front fender bracket had broken a few miles later.

Every adult human male has at least one story beginning “But for that millisecond or inch, I wouldn’t be here.” Now I have one more.

I must not fear. Fear is the mind-killer. Fear is the little-death that brings total obliteration. I will face my fear. I will permit it to pass over me and through me. And when it has gone past I will turn the inner eye to see its path. Where the fear has gone there will be nothing. Only I will remain.

Frank Herbert, Dune
Machine Shop, Recumbent Bicycling

Tour Easy: Another Front Fender Bracket

The mudflap on my front fender rides low enough to snag on obstacles and the most recent incident (about which more later) was a doozy, breaking the left strut ferrule and pulling the bracket off its double-sticky foam tape attachment. Fortunately, the repair kit now has plenty of duct tape.

The replacement printed up and installed just like its predecessors:

Tour Easy - front fender bracket
Tour Easy – front fender bracket

Having the bracket be the weakest link makes perfect sense to me …

Machine Shop, Recumbent Bicycling

Tour Easy: Chain Drop Pin

Every now and again, an upshift to the large chainring on my Tour Easy would go awry and drop the chain off the outside, where it would sometimes jam between the pedal crank and the spider. In the worst case the flailing chain would also jam in the TerraCycle idler, but I fixed that a while ago.

Contemporary chainrings (i.e., anything made since the trailing decades of the last millennium) generally have a chain drop pin positioned against the crank specifically to prevent such chain jamming.

Making a chain drop pin is no big deal if you’ve got a lathe and an M4 tap:

Tour Easy - DIY Chain Drop pin
Tour Easy – DIY Chain Drop pin

A closer look:

Tour Easy - DIY Chain Drop pin - detail
Tour Easy – DIY Chain Drop pin – detail

That’s a 10 mm length of 5/16 inch brass rod drilled with a recess to fit the head of a 10 mm M4 socket-head cap screw.

The pin should be a micro-smidgen shorter, as it just touches the crank, but, if anything, moving the chainring inward by one micro-smidgen improved the upshifts and I’m inclined to go with the flow.

Should’a done it decades ago …