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.
This Comet HT-224 antenna fits on my Kenwood TH-F6A radio, but the connector fitting is just slightly too long / short / something: it moves just a little bit, even with the nut firmly tightened.
This isn’t a real fix, but it pretty much eliminates the rattle: a rubber O-ring between the nut and the antenna…
The ring lasts for a few years, then cracks and falls off. My O-ring stash has what could possibly be a lifetime supply.
There’s a wrap of tape around the label, just for neatness.
The killer discount coupon that brought a new cutting board into the house also produced a new santoku knife from Cusinart (not that that makes much difference), seen here with my favorite knife:
Pursuant to that discussion, I’ve been looking for a Teflon-coated Santoku blade, but nobody in the area seems to have one.
This one claims that the row of dimples on each side make cheese slices slide right off, but that’s not what happens. Maybe it’s not quite so sticky as my knives, but I’d call it a tie.
Likes:
Dislikes:
On the other paw, maybe you can see how the blade near the heel on the old knife is getting ever so slightly hollowed out from my use of the steel. The new flat cutting board makes that embarrassingly obvious; it’s getting to be time for a trip to the slow stone.
All in all, pretty good. I use it, but not as much as the Good Old Knives.
We have an old floor lamp that’s always been a bit tippy and I finally got around to wondering what’s going on.
The cord exits through the center of the base, where it passes through a plastic nut that keeps it off the raw metal edge of the central rod holding the lamp together.
The ruler has 1/16 inch divisions, so the cord requires a bit over half an inch of clearance.
Here’s what one of the five molded-in feet look like, with a white rubber bumper that I just added to improve the ground clearance…
Notice that the foot is barely 1/4 inch tall, so the lamp has always been resting on the cord and two other randomly chosen feet. No wonder the thing was tippy.
The new rubber feet make it a lot less tippy, but there’s not a lot of clearance under there. When one of those things falls off, I’ll think of something better.
The lamp was nominally UL approved, of course…
So I stuck a CD-RW drive into the Foxconn Atom box and discovered that the pushbutton on the front panel doesn’t move quite far enough to actually hit the corresponding button on the drive.
Popped another drive off the heap and tried it out, just for grins, with the same result. Evidently the cute little ribbed back on the silvered panel button (near the bottom of the picture) isn’t quite long enough.
Solution: a bit of rubberized high-traction tape stuck to the drive button (near the top of the picture).
This is a black-on-black situation, so I pushed the contrast enough that you can actually see it.
According to the date code on the back, we’ve had this kitchen scale for nigh onto a decade, so I suppose I shouldn’t be surprised that the molded plastic sheet over the buttons has cracked. Mary & I were in the midst of a tag-team baking session when the middle (Power) button cover went crunch and gave out.
Although it’s not obvious, all three buttons are about halfway disconnected from the surface. The rightmost button has a crack nearly all the way around the perimeter.
A quick encounter with a razor knife removed the entire block of cracked plastic, revealing the surprisingly off-centered button recesses. No wonder the plastic cracked!
The junkpile disgorged a thin sheet of laminated cardboard that peeled neatly down the middle. Cut it to fit the rectangle, apply a strip of Kapton tape, and it was back in action in about ten minutes… the bread dough never missed me.
This was a quick-and-dirty fix to get the thing back in operation; when the Kapton tape fails, I’ll do something more permanent and less hideous. I promise…
Another pass at my Logitech Dual-Action Gamepad used as an EMC2 control pendant, but this time using an Eagle ULP (User Language Program) that converts a schematic into EMC2 HAL code.
I tweaked Martin Schöneck’s original ULP a bit, added (some of the) new devices found in EMC2.4, added the corresponding Eagle symbols & devices to the library, then drew up a schematic based on my hand-hewn HAL code with some improvements. Ran the script and shazam the HAL code worked just fine (after a bit of debugging the infrastructure, of course).
The new ULP and library are not quite ready for prime time, but this is a stick in the ground to mark some progress. You can certainly use the HAL code directly, without fiddling around in the schematic: stuff the whole program (at the end of the post) in your existing (but likely empty) custom_postgui.hal file.
The schematic is, of course, much fluffier than the corresponding code, particularly because I chopped it into five easily printed pages. Here’s the Big Picture overview of what’s going on in each page; click the pix for bigger images.
The servo thread interface device in the lower left provides the halui timing. The big block in the upper left has all the Logitech gamepad buttons, including the four big ones used for Z and A axis jogging. I changed the two left-rear buttons to activate the Abort signal rather than Estop, not that I use them all that much anyway.
The two joystick knobs have pushbuttons, which I combine and use to toggle a flipflop that will select the jogging speed: fast or crawl.
I also cut the jog deadband from 0.2 to 0.1, which makes the joysticks much more responsive.
The big block on the left has all the gamepad’s analog axes. The HAT0X and HAT0Y axes correspond to the top-hat pushbuttons; they’re not really analog at all, although they take on -1.0 / 0.0 / + 1.0 floating point values. The window comparators determine which joystick axes are active, which comes in handy later on.
The HAL jogging control has a single input that sets the default speed, but the proper value is vastly different depending on whether you’re jogging with linear or angular motion. This page picks out which ini file MAX_VELOCITY value to use, converts from units/sec to units/min, then does Cool Thing #1: scales the speed so that the fast/crawl speeds work out nicely.
I use the buttons to jog rapidly from here to there, then creep up on the alignment point using the joysticks. Pressing the joysticks downward switches from Fast to Crawl speeds, which provides sort of a gearshift that’s useful for coarse / fine adjustments.
The buttons run at two speeds:
The joysticks have a lower top speed:
All those values go into the mux4 block and thence to the HAL jog speed control.
This page does Cool Thing #2: prioritize the joystick axes and lock out the one that started moving last. The general idea is that it’s painfully easy to move the joysticks diagonally, which is great for gaming and terrible for milling machine control. A pair of flipflops for each joystick remember which axis started moving first.
If you want to move diagonally, just press the buttons; they’re not locked out, so you can do what you want.
The motion comes together on the last page, where scale blocks flip the direction of the Y and Z joystick axes so positive motion is upward. The multiplexers allow only the active axis of each joystick to reach the HAL analog jog inputs; you can vary the speed of that axis up to the maximum as you’d expect. The buttons drive the digital inputs that jog at that maximum speed; the Y and Z button directions get sorted out appropriately.
Those five pages boil down into the following code, which I manually insert into my custom_postgui.hal file, along with the tool length probe pin definition.
# HAL config file automatically generated by Eagle-CAD hal-write.ulp # (C) Martin Schoeneck.de 2008 # Mods Ed Nisley 2010 # Path: [/mnt/bulkdata/Project Files/eagle/projects/EMC2 HAL Configuration/] # ProjectName: [Logitech Gamepad] # File name: [/mnt/bulkdata/Project Files/eagle/projects/EMC2 HAL Configuration/Logitech Gamepad.hal] #################################################### # Load realtime and userspace modules loadrt constant count=14 loadrt and2 count=9 loadrt flipflop count=4 loadrt mux2 count=5 loadrt mux4 count=1 loadrt not count=8 loadrt or2 count=9 loadrt scale count=7 loadrt toggle count=1 loadrt wcomp count=6 #################################################### # Hook functions into threads addf toggle.0 servo-thread addf wcomp.1 servo-thread addf wcomp.2 servo-thread addf wcomp.3 servo-thread addf and2.0 servo-thread addf and2.4 servo-thread addf and2.3 servo-thread addf and2.2 servo-thread addf and2.1 servo-thread addf constant.6 servo-thread addf constant.5 servo-thread addf constant.4 servo-thread addf constant.3 servo-thread addf constant.2 servo-thread addf constant.1 servo-thread addf constant.0 servo-thread addf constant.7 servo-thread addf constant.8 servo-thread addf scale.1 servo-thread addf scale.2 servo-thread addf scale.3 servo-thread addf mux4.0 servo-thread addf mux2.0 servo-thread addf scale.4 servo-thread addf scale.0 servo-thread addf wcomp.5 servo-thread addf wcomp.4 servo-thread addf wcomp.0 servo-thread addf flipflop.1 servo-thread addf flipflop.0 servo-thread addf and2.5 servo-thread addf and2.6 servo-thread addf and2.7 servo-thread addf and2.8 servo-thread addf flipflop.2 servo-thread addf flipflop.3 servo-thread addf or2.4 servo-thread addf or2.8 servo-thread addf or2.7 servo-thread addf or2.6 servo-thread addf or2.5 servo-thread addf or2.3 servo-thread addf or2.2 servo-thread addf or2.1 servo-thread addf or2.0 servo-thread addf not.1 servo-thread addf not.2 servo-thread addf not.3 servo-thread addf not.4 servo-thread addf not.5 servo-thread addf not.6 servo-thread addf not.7 servo-thread addf not.0 servo-thread addf constant.9 servo-thread addf mux2.1 servo-thread addf mux2.2 servo-thread addf mux2.3 servo-thread addf mux2.4 servo-thread addf constant.10 servo-thread addf constant.11 servo-thread addf scale.5 servo-thread addf scale.6 servo-thread addf constant.12 servo-thread addf constant.13 servo-thread #################################################### # Set parameters #################################################### # Set constants setp constant.0.value +0.02 setp constant.1.value -0.02 setp constant.2.value 60 setp constant.3.value 1.00 setp constant.4.value 0.10 setp constant.5.value 0.50 setp constant.6.value 0.10 setp constant.7.value +0.5 setp constant.8.value -0.5 setp constant.9.value 0.0 setp constant.10.value [TRAJ]MAX_LINEAR_VELOCITY setp constant.11.value [TRAJ]MAX_ANGULAR_VELOCITY setp constant.12.value -1.0 setp constant.13.value 0.1 #################################################### # Connect Modules with nets net a-button-minus input.0.btn-trigger or2.2.in0 halui.jog.3.minus net a-button-plus input.0.btn-thumb2 or2.2.in1 halui.jog.3.plus net a-buttons-active or2.2.out or2.3.in0 or2.4.in1 net a-disable not.7.out and2.5.in1 net a-enable flipflop.3.out not.7.in mux2.4.sel net a-jog wcomp.2.in input.0.abs-z-position mux2.4.in1 net a-knob-active not.2.out or2.4.in0 and2.7.in1 net a-knob-inactive wcomp.2.out not.2.in and2.6.in1 net a-select and2.8.in0 and2.7.out net a-set flipflop.3.set and2.8.out net angular_motion or2.4.out mux2.0.sel net any-buttons-active mux4.0.sel0 or2.8.out net az-buttons-active or2.3.out or2.8.in1 net az-reset flipflop.2.reset and2.6.out flipflop.3.reset net button-crawl scale.4.out mux4.0.in3 net button-fast scale.2.out mux4.0.in1 scale.4.in net jog-crawl toggle.0.out mux4.0.sel1 net jog-speed halui.jog-speed mux4.0.out net knob-crawl mux4.0.in2 scale.3.out net knob-fast mux4.0.in0 scale.1.out scale.3.in net n_1 constant.10.out mux2.0.in0 net n_2 and2.0.in0 input.0.btn-top2 net n_3 and2.0.in1 input.0.btn-base net n_4 and2.0.out halui.abort net n_5 halui.mode.manual input.0.btn-base3 net n_6 wcomp.0.max wcomp.1.max wcomp.2.max wcomp.3.max constant.0.out net n_7 halui.program.resume input.0.btn-base4 net n_8 wcomp.0.min wcomp.1.min wcomp.2.min wcomp.3.min constant.1.out net n_9 mux2.0.in1 constant.11.out net n_10 constant.12.out scale.5.gain scale.6.gain net n_11 input.0.btn-base5 or2.0.in0 net n_12 input.0.btn-base6 or2.0.in1 net n_13 constant.9.out mux2.1.in0 mux2.2.in0 mux2.3.in0 mux2.4.in0 net n_14 mux2.1.out halui.jog.0.analog net n_15 toggle.0.in or2.0.out net n_16 constant.2.out scale.0.gain net n_17 constant.5.out scale.1.gain net n_18 constant.3.out scale.2.gain net n_19 constant.4.out scale.3.gain net n_20 scale.4.gain constant.6.out net n_21 halui.jog.1.analog mux2.2.out net n_22 mux2.2.in1 scale.5.out net n_23 scale.6.out mux2.3.in1 net n_24 constant.13.out halui.jog-deadband net n_25 wcomp.4.max constant.7.out wcomp.5.max net n_26 constant.8.out wcomp.4.min wcomp.5.min net n_27 mux2.3.out halui.jog.2.analog net n_28 halui.jog.3.analog mux2.4.out net vel-per-minute scale.0.out scale.1.in scale.2.in net vel-per-second mux2.0.out scale.0.in net x-buttons-active or2.7.in0 or2.5.out net x-disable not.4.out and2.4.in1 net x-enable not.4.in flipflop.0.out mux2.1.sel net x-hat-jog wcomp.4.in input.0.abs-hat0x-position net x-hat-minus wcomp.4.under or2.5.in1 halui.jog.0.minus net x-hat-plus or2.5.in0 wcomp.4.over halui.jog.0.plus net x-jog wcomp.0.in input.0.abs-x-position mux2.1.in1 net x-knob-active not.0.out and2.1.in0 net x-knob-inactive wcomp.0.out not.0.in and2.2.in0 and2.3.in0 net x-set and2.1.out flipflop.0.set net xy-buttons-active or2.7.out or2.8.in0 net xy-reset flipflop.0.reset and2.2.out flipflop.1.reset net y-buttons-active or2.6.out or2.7.in1 net y-disable not.5.out and2.1.in1 net y-enable flipflop.1.out not.5.in mux2.2.sel net y-hat-jog input.0.abs-hat0y-position wcomp.5.in net y-hat-minus wcomp.5.under or2.6.in1 halui.jog.1.plus net y-hat-plus or2.6.in0 wcomp.5.over halui.jog.1.minus net y-jog wcomp.1.in input.0.abs-y-position scale.5.in net y-knob-active not.1.out and2.3.in1 net y-knob-inactive not.1.in wcomp.1.out and2.2.in1 net y-select and2.4.in0 and2.3.out net y-set flipflop.1.set and2.4.out net z-button-minus input.0.btn-thumb or2.1.in0 halui.jog.2.minus net z-button-plus input.0.btn-top or2.1.in1 halui.jog.2.plus net z-buttons-active or2.1.out or2.3.in1 net z-disable not.6.out and2.8.in1 net z-enable not.6.in flipflop.2.out mux2.3.sel net z-jog wcomp.3.in input.0.abs-rz-position scale.6.in net z-knob-active not.3.out and2.5.in0 net z-knob-inactive not.3.in wcomp.3.out and2.7.in0 and2.6.in0 net z-set and2.5.out flipflop.2.set
The ULP script that eats the schematic and poots out the HAL code:
/******************************************************************************
* HAL-Configurator
*
* Author: Martin Schoeneck 2008
* Additional gates & tweaks: Ed Nisley KE4ZNU 2010
*****************************************************************************/
#usage "<h1>HAL-Configurator</h1>Start from a Schematic where symbols from hal-config.lbr are used!";
string output_path = "./";
string dev_loadrt = "LOADRT";
string dev_loadusr = "LOADUSR";
string dev_thread = "THREAD";
string dev_parameter = "PARAMETER";
string dev_names[] = {
"CONSTANT", // must be first entry to make set_constants() work
"ABS", // 2.4
"AND2",
"BLEND", // 2.4
"CHARGE-PUMP", // 2.4
"COMP",
"CONV_S32_FLOAT", // 2.4
"DDT", // 2.4
"DEADZONE", // 2.4
"DEBOUNCE", // 2.4
"EDGE",
"ENCODER", // 2.4
"ENCODER-RATIO", // 2.4
"ESTOP-LATCH",
"FLIPFLOP",
"FREQGEN", // 2.4
"LOWPASS",
"MULT2", // 2.4
"MUX2",
"MUX4", // 2.4
"MUX8", // 2.4
"NEAR", // 2.4
"NOT",
"ONESHOT",
"OR2",
"SAMPLER", // 2.4
"SCALE", // 2.4
"SELECT8", // 2.4
"SUM2",
"TIMEDELAY", // 2.4
"TOGGLE", // 2.4
"WCOMP", // 2.4
"XOR2", // 2.4
"" // end flag
};
string init = "# HAL config file automatically generated by Eagle-CAD hal-write.ulp\n# (C) Martin Schoeneck.de 2008\n# Mods Ed Nisley 2010\n";
/*******************************************************************************
* Global Stuff
******************************************************************************/
string FileName;
string ProjectPath;
string ProjectName;
void Info(string Message) {
dlgMessageBox(";<b>Info</b><p>\n" + Message);
}
void Warn(string Message) {
dlgMessageBox("!<b>Warning</b><p>\n" + Message + "<p>see usage");
}
void Error(string Message) {
dlgMessageBox(":<hr><b>Error</b><p>\n" + Message + "<p>see usage");
exit(1);
}
string replace(string str, char a, char b) {
// in string str replace a with b
int pos = -1;
do {
// find that character
pos = strchr(str, a);
// replace if found
if(pos >= 0) {
str[pos] = b;
}
} while(pos >= 0);
return str;
}
// the part name contains an index and is written in capital letters
string get_module_name(UL_PART P) {
// check module name, syntax: INDEX:NAME
string mod_name = strlwr(P.name);
// split string at the : if exists
string a[];
int c = strsplit(a, mod_name, ':');
mod_name = a[c-1];
// if name starts with '[' we need uppercase letters
if(mod_name[0] == '[') {
mod_name = strupr(mod_name);
}
return mod_name;
}
string comment(string mess) {
string str = "\n\n####################################################\n";
if(mess != "") {
str += "# " + mess + "\n";
}
return str;
}
// if this is a device for loading a module, load it (usr/rt)
string load_module(UL_PART P) {
string str = "";
// it's a module if the device's name starts with LOADRT/LOADUSR
if((strstr(P.device.name, dev_loadrt) == 0) ||
(strstr(P.device.name, dev_loadusr) == 0)) {
// now add the string to our script
str += P.value + "\n";
}
return str;
}
// count used digital gates (and, or, etc) and load module if neccessary
string load_blocks() {
string str = "";
int index;
int dev_counters[];
string dname[];
// count the gates that are used
schematic(S) { S.parts(P) {
strsplit(dname,P.device.name,'.'); // extract first part of name
if ("" != lookup(dev_names,dname[0],0)) {
for (index = 0; (dname[0] != dev_names[index]) ; index++) {
continue;
}
dev_counters[index]++;
}
} }
// force lowercase module names...
for (index = 0; ("" != dev_names[index]) ; index++) {
if (dev_counters[index]) {
sprintf(str,"%sloadrt %s\tcount=%d\n",str,strlwr(dev_names[index]),dev_counters[index]);
}
}
return str;
}
string hook_function(UL_NET N) {
string str = "";
// is this net connected to a thread (work as functions here)?
int noclkpins = 0;
string thread_name = ""; // this net should be connected to a thread
string thread_position = "";
N.pinrefs(PR) {
// this net is connected to a clk-pin
if(PR.pin.function == PIN_FUNCTION_FLAG_CLK) {
// check the part: is it a thread-device?
if(strstr(PR.part.device.name, dev_thread) == 0) {
// we need the name of the thread
thread_name = strlwr(PR.part.name);
// and we need the position (position _ is ignored)
thread_position = strlwr(PR.pin.name);
thread_position = replace(thread_position, '_', ' ');
}
} else {
// no clk-pin, this is no function-net
noclkpins++;
break;
}
}
// found a thread?
if(noclkpins == 0 && thread_name != "") {
// all the other pins are interesting now
N.pinrefs(PR) {
// this pin does not belong to the thread
if(strstr(PR.part.device.name, dev_thread) != 0) {
// name of the pin is name of the function
//string function_name = strlwr(PR.pin.name);
string function_name = strlwr(PR.instance.gate.name);
// if functionname starts with a '.', it will be appended to the modulename
if(function_name[0] == '.') {
// if the name is only a point, it will be ignored
if(strlen(function_name) == 1) {
function_name = "";
}
function_name = get_module_name(PR.part) + function_name;
}
str += "addf " + function_name + "\t" + thread_name + "\t" + thread_position + "\n";
}
}
}
return str;
}
string set_parameter(UL_NET N) {
string str = "";
// is this net connected to a parameter-device?
int nodotpins = 0;
string parameter_value = "";
N.pinrefs(PR) {
// this net is connected to a dot-pin
if(PR.pin.function == PIN_FUNCTION_FLAG_DOT) {
// check the part: is it a parameter-device?
// str += "** dev name [" + PR.part.device.name + "] [" + dev_parameter + "]\n";
if(strstr(PR.part.device.name, dev_parameter) == 0) {
// we need the value of that parameter
parameter_value = PR.part.value;
// str += "** value [" + PR.part.value +"]\n";
}
} else {
// no clk-pin, this is no function-net
nodotpins++;
break;
}
}
// found a parameter?
if(nodotpins == 0 && parameter_value != "") {
// all the other pins are interesting now
N.pinrefs(PR) {
// str += "** dev name [" + PR.part.device.name + "] [" + dev_parameter + "]\n";
// this pin does not belong to the parameter-device
if(strstr(PR.part.device.name, dev_parameter) != 0) {
// name of the pin is name of the function
//string parameter_name = strlwr(PR.pin.name);
string parameter_name = strlwr(PR.instance.gate.name);
// if functionname starts with a '.', it will be appended to the modulename
// str += "** param (gate) name [" + parameter_name + "]\n";
if(parameter_name[0] == '.') {
// if the name is only a point, it will be ignored
if(strlen(parameter_name) == 1) {
parameter_name = "";
}
parameter_name = get_module_name(PR.part) + parameter_name;
// str += "** param (part) name [" + parameter_name + "]\n";
}
str += "setp " + parameter_name + "\t" + parameter_value + "\n";
}
}
}
return str;
}
// if this is a 'constant'-device, set its value
// NOTE: this is hardcoded to use the first entry in the dev_names[] array!
string set_constants(UL_PART P) {
string str = "";
// 'constant'-device?
if(strstr(P.device.name, dev_names[0]) == 0) {
str += "setp " + get_module_name(P) + ".value\t" + P.value + "\n";
}
return str;
}
string connect_net(UL_NET N) {
string str = "";
// find all neccessary net-members
string pins = "";
N.pinrefs(P) {
// only non-functional pins are connected
if(P.pin.function == PIN_FUNCTION_FLAG_NONE) {
string pin_name = strlwr(P.pin.name);
string part_name = strlwr(P.part.name);
pin_name = replace(pin_name, '$', '_');
part_name = replace(part_name, '$', '_');
pins += part_name + "." + pin_name + " ";
}
}
if(pins != "") {
string net_name = strlwr(N.name);
net_name = replace(net_name, '$', '_');
str += "net " + net_name + " " + pins + "\n";
}
return str;
}
/*******************************************************************************
* Main program.
******************************************************************************/
// is the schematic editor running?
if (!schematic) {
Error("No Schematic!<br>This program will only work in the schematic editor.");
}
schematic(S) {
ProjectPath = filedir(S.name);
ProjectName = filesetext(filename(S.name), "");
}
// build configuration
string cs = init + "\n\n";
FileName = ProjectPath + ProjectName + ".hal";
cs += "# Path: [" + ProjectPath + "]\n";
cs += "# ProjectName: [" + ProjectName + "]\n";
//cs += "# File name: [" + FileName + "]\n\n";
// ask for a filename: where should we write the configuration?
FileName = dlgFileSave("Save Configuration", FileName, "*.hal");
if(!FileName) {
exit(0);
}
cs += "# File name: [" + FileName + "]\n\n";
schematic(S) {
// load modules
cs += comment("Load realtime and userspace modules");
S.parts(P) {
cs += load_module(P);
}
// load blocks
cs += load_blocks();
// add functions
cs += comment("Hook functions into threads");
S.nets(N) {
cs += hook_function(N);
}
// set parameters
cs += comment("Set parameters");
S.nets(N) {
cs += set_parameter(N);
}
// set constant values
cs += comment("Set constants");
S.parts(P) {
cs += set_constants(P);
}
// build nets and connect them
cs += comment("Connect Modules with nets");
S.nets(N) {
cs += connect_net(N);
}
}
// open/overwrite the target file to save the configuration
output(FileName, "wt") {
printf(cs);
}
Most of that script is Martin’s work; I just cleaned it up. You can download it by hovering over the code to make the little toolbar pop up near the upper-right corner of the text, then:
You’ll also need the Eagle library that goes along with the script, but WordPress doesn’t like .lbr files. Here’s the hal-config-2.4.lbr file with a totally bogus odt extension. Download it, rename it to remove the .odt extension, and it’s all good.
There is basically no documentation for any of this. I figured out what to do by looking at the source and Martin’s sample schematic, but now you have two sample schematics: the situation is definitely improving!
Rode around the big block on some errands, stopped at the Vassar Farm garden to haul some squash home, rode off… and the bike handled poorly. Well, with a few dozen pounds of produce in the panniers that’s not unusual, but this was worse. Yup, another flat.
This time, however, our daughter was home and could rescue me in the van. Back in the shop, I found this obvious suspect:
Once again, however, this wasn’t the problem, as the tire liner was barely scuffed. Those are glass fragments inside the gash, which might actually be the same one as before.
There weren’t any other pointy objects embedded in the tire, but the tube wouldn’t stay inflated long enough to find the leak. I took the tube upstairs, submerged it in a pan of water, and found a rash of holes. Not pinholes, not a failed tube, but a series of punctures.
Examining the tire liner revealed the cause: a strand of what my buddy DBM calls Michelin Hair poking through the tire liner. It’s a fragment of the steel belt from a car or truck tire, most likely shed from a disintegrating semitrailer recapped tire.
There is absolutely no defense against these things, because they have razor-sharp points on both ends where the wire fractured. When the tire picks one up, every rotation drives it through the rubber, the Kevlar belt, the tire liner, and the tube. The usual symptom is a slow leak, eventually followed by a row of holes in the tube as it shifts position under low pressure.
In fact, the tube had a slow leak since I installed it a few weeks ago after a tube failure. I wondered if I’d inadvertently installed a fold, but now I think I ran over this wire during the first few rides and it’s been getting worse ever since.
That tube is a goner! I installed another Schwalbe tube and we’ll see what happens; one has been working fine on Mary’s bike for the last three months.
Here’s a look at the steel wire from the side:
It was completely through the liner, with only a stub sticking out on the tire side. There’s certainly a matching hole somewhere on the tire, but it’ll be indistinguishable from all the other nicks and gashes.
The Smell of Molten Projects in the Morning 