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.

Category: Machine Shop

Mechanical widgetry

EMC2 Logitech GamePad: Triggger Button Name Change

I just updated EMC2 on the Sherline CNC mill from 2.4.6 to 2.4.7 (which mis-identifies itself as 2.4.6 on the splash screen) and the Axis UI failed to start. A bit of digging shows that the name of Button 1 (the left button in the right-hand quad, clearly labeled 1) has inexplicably changed from btn-trigger to btn-joystick.

Most likely the change has nothing to do with EMC2, because (I think) those names bubble up from the HID driver that actually talks to the hardware and that stuff has also been updated; this is all on Ubuntu 10.04 LTS. But in any event, the name is now different.

That requires a tweak to the Eagle schematics, which will regenerate Logitech_Gamepad.hal, but you can just edit the latter file and change btn-trigger to btn-joystick.

As nearly as I can tell, changing the pin name in the Logitech library component, saving the library, then updating the library in the schematic doesn’t do squat. Evidently, Eagle keeps track of which components you’ve used and won’t update them unless you do some manual gymnatistics, which makes a certain amount of sense.

That means one must:

Delete both “gates” of the old component (INPUT.0.BUTTONS first, then INPUT.0)
Make sure you’re on Page 2 where the basic gate will go
Add the revised LOGITECH_DUAL_ACTION_GAMEPAD to get the INPUT.1 “gate”
Rename it to INPUT.0
Use Move to jiggle it around a bit to ensure its pins get hitched up to the existing nets
Switch to Page 1 where the button nets lie in wait
Type invoke input.0 into the Eagle command line
Pick -BUTTONS from the list to select that “gate”
Position that gate appropriately
Use Move to jiggle the gate
Save everything
Run the Eagle2Hal ULP to get a new HAL output file
Put that file where it’ll do the most good

There, now, wasn’t that obvious?

The modified Logitech_Gamepad.hal file:

# HAL config file automatically generated by Eagle-CAD ULP:
# [/mnt/bulkdata/Project Files/eagle/ulp/hal-write-2.4.ulp]
# (C) Martin Schoeneck.de 2008
# Mods Ed Nisley 2010
# Path        [/mnt/bulkdata/Project Files/eagle/projects/EMC2 HAL Configuration/]
# ProjectName [Logitech Gamepad - 2.4.7]
# File name   [/mnt/bulkdata/Project Files/eagle/projects/EMC2 HAL Configuration/Logitech Gamepad - 2.4.7.hal]
# Created     [10:40:31 11-Nov-2011]

####################################################
# Load realtime and userspace modules
loadrt constant		count=16
loadrt and2		count=17
loadrt flipflop		count=4
loadrt mux2		count=5
loadrt mux4		count=1
loadrt not		count=8
loadrt or2		count=10
loadrt scale		count=7
loadrt timedelay		count=1
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
addf timedelay.0		servo-thread
addf constant.14		servo-thread
addf constant.15		servo-thread
addf and2.16		servo-thread
addf and2.15		servo-thread
addf and2.14		servo-thread
addf and2.13		servo-thread
addf and2.12		servo-thread
addf and2.11		servo-thread
addf and2.10		servo-thread
addf and2.9		servo-thread
addf or2.9		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
setp constant.14.value	0.020
setp constant.15.value	0.000

####################################################
# Connect Modules with nets
net a-button-minus or2.2.in0 input.0.btn-joystick and2.15.in0
net a-button-plus or2.2.in1 input.0.btn-thumb2 and2.16.in0
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 or2.4.in0 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 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 or2.9.in0
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 or2.0.in0 input.0.btn-base5
net n_12 or2.0.in1 input.0.btn-base6
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 n_29 timedelay.0.out and2.9.in1 and2.10.in1 and2.12.in1 and2.11.in1 and2.13.in1 and2.14.in1 and2.16.in1 and2.15.in1
net n_30 and2.9.out halui.jog.0.minus
net n_31 or2.9.out timedelay.0.in
net n_32 constant.14.out timedelay.0.on-delay
net n_33 constant.15.out timedelay.0.off-delay
net n_34 and2.10.out halui.jog.0.plus
net n_35 and2.11.out halui.jog.1.minus
net n_36 halui.jog.1.plus and2.12.out
net n_37 and2.13.out halui.jog.2.minus
net n_38 and2.14.out halui.jog.2.plus
net n_39 and2.15.out halui.jog.3.minus
net n_40 and2.16.out halui.jog.3.plus
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 and2.9.in0
net x-hat-plus or2.5.in0 wcomp.4.over and2.10.in0
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 or2.9.in1
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 wcomp.5.in input.0.abs-hat0y-position
net y-hat-minus wcomp.5.under or2.6.in1 and2.12.in0
net y-hat-plus or2.6.in0 wcomp.5.over and2.11.in0
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 or2.1.in0 input.0.btn-thumb and2.13.in0
net z-button-plus or2.1.in1 input.0.btn-top and2.14.in0
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

2011-11-13

Canon SX230HS Lens Cap
The SX230HS camera lives in my pants pocket, where it gets pressed between my leg and anything I lean against. Turns out that the lens turret end cap isn’t quite thick enough to not bend inward against the leaves that cover the lens, which causes them to hang up. The solution boils down to a hideous external lens cap:

Canon SX230HS with lens cap

It’s built from forget-me-not yellow filament for an obvious reason…

The sheet-metal plate bears against the non-moving rim around the turret. I marked the plate’s diameter with a compass, extracted it from the sheet with left-cutting tin snips, filed off the slivers, rounded the edge, and it snapped right into the recess where a touch of acrylic caulk holds it firmly in place.

A thin plastic cover would be too flexible and a thicker plastic cover would be too thick; this must fit into an already-snug cloth pouch where a few additional millimeters of girth actually matter. My previous camera taught me that pocket fuzz gets into everything, so a pouch isn’t optional.

The interior isn’t too inspiring, but you can see what two layers of plastic look like across the bottom:

SX230HS lens cap – interior

The front has the shallow recess that captures the metal plate. Because the front builds against the aluminum build platform, I added a support structure inside the recess:

SX230HS lens cap – support in place

The solid model gives a better view:

Lens cap – solid model – bottom view

It’s basically a ring with tabs under the recess. The ring OD matches the lens caps’s ID, with a height equal to the recess depth, so only the tabs contact the cap. I removed them by twisting each tab with a needle-nose pliers until the whole thing popped loose:

SX230HS lens cap – support structure

A bit of scraper and scalpel cleanup and it’s all good. The detail pix show the first trial of the lens cap, which lacks the nice bevel around the front rim.

The camera is smart enough to notice when something blocks the lens: it immediately shuts down and displays a lens failure error message. That’s probably not a Good Thing on a regular basis, but it doesn’t seem to do any harm.

FWIW, my previous pocket camera, a Casio EX-Z850 , sported a recessed and somewhat thicker turret end cap that didn’t have this problem. Mary says she’ll make a case for this camera, too, but until then I’m using a pouch from a dinky VOIP phone that just barely holds the camera.

The OpenSCAD source code:
```
// Lens cap for Canon SX230HS
// Ed Nisley KE4ZNU - Nov 2011

//-------
//- Extrusion parameters must match reality!
//  Print with +1 shells, 3 solid layers, 0.2 infill

ThreadThick = 0.33;
ThreadWidth = 2.0 * ThreadThick;

HoleFinagle = 0.20;
HoleFudge = 1.00;

function HoleAdjust(Diameter) = HoleFudge*Diameter + HoleFinagle;

Protrusion = 0.1;			// make holes end cleanly

function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);

//-------
// Dimensions

LensDia = 53.0;
LensRad = LensDia/2;
LensLength = 8.0;

PlateThick = IntegerMultiple(0.75,ThreadThick);
PlateDia = 48.0;

Shell = 2*ThreadWidth;
Spacer = 2*ThreadThick;

CapOD = LensDia + 2*Shell;
CapLength = LensLength + Spacer + PlateThick;
CapSides = 48;

CenterHoleDia = 44.0;

BevelWidth = PlateThick;

NumStruts = 16;
SupportStrutLen = (PlateDia - ThreadWidth)/2;		// small gap to cap

//-------

module PolyCyl(Dia,Height,ForceSides=0) {			// based on nophead's polyholes

  Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2);

  FixDia = Dia / cos(180/Sides);

  cylinder(r=HoleAdjust(FixDia)/2,h=Height,$fn=Sides);
}

module ShowPegGrid(Space = 10.0,Size = 1.0) {

  Range = floor(50 / Space);

	for (x=[-Range:Range])
	  for (y=[-Range:Range])
		translate([x*Space,y*Space,Size/2])
		  %cube(Size,center=true);

}

//-------

ShowPegGrid();

difference() {
  PolyCyl(CapOD,CapLength,CapSides);

  translate([0,0,(Spacer + PlateThick)])					// lens shell
	PolyCyl(LensDia,(LensLength + Protrusion),CapSides);

  translate([0,0,-Protrusion])								// center hole
	PolyCyl(CenterHoleDia,(CapLength + Protrusion));

  translate([0,0,-Protrusion])								// bevel
	difference() {
	  cylinder(r=(CapOD/2 + 2*(BevelWidth + Protrusion)),
			   h=(2*BevelWidth + Protrusion),
			   $fn=CapSides);
	  cylinder(r1=(CapOD/2 - BevelWidth - Protrusion),
			   r2=(CapOD/2 + BevelWidth),
			   h=(2*BevelWidth + Protrusion),
			   $fn=CapSides);
	}

  difference() {
	translate([0,0,-Protrusion])							// cover plate recess
	  PolyCyl(PlateDia,(PlateThick + Protrusion));
	for (Index=[0:(NumStruts - 1)])							// support struts
	  rotate(Index*360/NumStruts)
		translate([-ThreadWidth,-SupportStrutLen,0])
		  cube([2*ThreadWidth,SupportStrutLen,PlateThick]);
  }
}

difference() {									// support ring
  PolyCyl(CenterHoleDia,PlateThick);
  translate([0,0,-Protrusion])
	PolyCyl((CenterHoleDia - 4*ThreadWidth),(PlateThick + 2*Protrusion));
}
```
2011-11-12
Magic Magnetic Protection

If this is true, I can scrap out my roll of mu metal shielding:

Magnetic card protection sleeve

I think they mean the sleeve protects the magnetic stripe from mechanical damage, but wedging those two sentences together certainly suggests the envelope has serious anti-magnetic mojo…

2011-11-10
Auto Escape Hammer LED Flashlight Hackage

A cheap auto escape hammer (IIRC, free in the bottom of a tag-sale box filled with stuff I could actually use) has been kicking around the back of the bench for far too long; it had a feeble single-cell incandescent bulb flashlight with the cheapest possible non-switch. I ripped all that out, carved out enough plastic to fit a CR123 lithium cell, hot-melt-glued a real pushbutton switch and 10 mm white LED in place, and soldered it up:

Lithium cell hacked into auto escape tool

The CR123 puts out enough juice to light up the LED, but it’d be happier with a bit more current. There’s no limiting resistor, so the LED gets what it gets.

Augment the screws with a few snippets of Kapton tape, use some real 3M Velcro tape, and it’s all good (albeit ugly on a stick):

Hacked auto escape hammer

Now, there’s no way to test the hammer part of it (perhaps I could visit a junkyard and whack out a few windows for practice?), but at least now we have a disposable flashlight in the van…

2011-11-08

OpenSCAD: Useful Sizes file

My Useful Sizes.scad file has been accumulating the dimensions of nuts & bolts & a motor that don’t (seem to) appear elsewhere in the OpenSCAD universe:

//-- Useful sizes

Tap2_56 = 0.070 * inch;
Clear2_56 = 0.082 * inch;
Head2_56 = 0.156 * inch;
Head2_56Thick = 0.055 * inch;
Nut2_56Dia = 0.204 * inch;
Nut2_56Thick = 0.065 * inch;

Tap3_48 = 0.079 * inch;
Clear3_48 = 0.096 * inch;
Head3_48 = 0.184 * inch;
Head3_48Thick = 0.058 * inch;
Nut3_48Dia = 0.201 * inch;
Nut3_48Thick = 0.073 * inch;

Tap4_40 = 0.089 * inch;
Clear4_40 = 0.110 * inch;
Head4_40 = 0.211 * inch;
Head4_40Thick = 0.065 * inch;
Nut4_40Dia = 0.228 * inch;
Nut4_40Thick = 0.086 * inch;

Tap10_32 = 0.159 * inch;
Clear10_32 = 0.190 * inch;
Head10_32 = 0.373 * inch;
Head10_32Thick = 0.110 * inch;
Nut10_32Dia = 0.433 * inch;
Nut10_32Thick = 0.130 * inch;

Tap025_20 = 0.201 * inch;
Clear025_20 = 0.2660 * inch;
Head025_20 = 0.492 * inch;
Head025_20Thick = 0.144 * inch;
Nut025_20Dia = 0.505 *inch;
Nut025_20Thick = 0.161 * inch;

NEMA17_ShaftDia = 5.0;
NEMA17_ShaftLength = 24.0;
NEMA17_PilotDia = 0.866 * inch;
NEMA17_PilotLength = 0.080 * inch;
NEMA17_BCD = 1.725 * inch;
NEMA17_BoltDia = 3.5;
NEMA17_BoltOC = 1.220 * inch;

It seems I’m among the few CamelCase holdouts…

2011-11-06

Logitech Ball Camera Tripod Adapter
The Logitech notebook webcam that peers into the Thing-O-Matic has terrible dynamic range compensation; turning on the LED ring light washes out the image something awful. An old Logitech ball camera seems better, but it sits atop a rubbery dingus adapted to grip huge old laptops. So I built an adapter with a standard 1/4-20 tripod screw thread in the bottom that ought to make it more useful.

The old & new mounts compared:

Logitech ball camera mounts

The color change comes from switching to yellow filament for an upcoming larger object.

The solid model shows those tiny little notches will require a bit of riffler file work:

Logitech camera tripod adapter – solid model

The bottom has a blind 1/4-20 tapped hole. Lacking a bottoming tap, not having any broken 1/4-20 taps, and being unwilling to grind the end off a perfectly good taper tap, I filed three notches along a bolt. Ran the taper tap in until it hit bottom, ran the bolt in likewise, and defined the result to be Good Enough:

Homebrew bottoming tap

On the other end, the most probable failure will leave that delicate little post jammed firmly inside the camera’s socket. There’s not enough post to allow printing a small guide hole, but there’s no real need for one; I drilled a #50 hole right down the middle, ran a 2-56 screw into it without tapping the hole, and filed the screw head flat:

Camera mount with filed screw

After cleaning up those notches, it snapped solidly into place:

Logitech ball camera with mount

And then the camera sits neatly atop a cheap Gorillapod knockoff:

Logitech ball camera on tripod

That tiny reddish dot in the middle of the imposing set of rings marks the actual lens, so it’s more of a pinhole camera than anything else. The fixed focus kicks in beyond a meter, but a bit of rummaging in the Box o’ Lenses produced a random meniscus lens that pulled the focus in to maybe 100 mm. Alas, that means the camera must float in mid-air about 15 mm inside the Thing-O-Matic’s box. If I can conjure up a mount that holds the ball inside the box, above-and-forward of the stage, that’d work great. VLC can allegedly rotate the image upside-down, so maybe I can mount it bottom-up.

Here’s everything I know about those two cameras, with the ball camera on top and the webcam on the bottom:

Logitech ball and notebook webcam data

Apparently it’s easier to put that information on a tag than provide a good old data plate on the camera body.

The OpenSCAD source code:
```
// Tripod mount for Logitech ball camera
// Ed Nisley KE4ZNU - Oct 2011

include </home/ed/Thing-O-Matic/lib/MCAD/units.scad>
include </home/ed/Thing-O-Matic/Useful Sizes.scad>
include </home/ed/Thing-O-Matic/lib/visibone_colors.scad>

//-------
//- Extrusion parameters must match reality!
//  Print with +0 shells and 3 solid layers

ThreadThick = 0.33;
ThreadWidth = 2.0 * ThreadThick;

HoleFinagle = 0.2;
HoleFudge = 1.02;

function HoleAdjust(Diameter) = HoleFudge*Diameter + HoleFinagle;

function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);

Protrusion = 0.1;			// make holes end cleanly

//-------
// Dimensions

BallDia = 60.0;				// camera ball
BallRad = BallDia/2;

BaseDia = 16.0;				// interface at tripod surface
BaseRad = BaseDia/2;

BaseLength = 10.0;			// to base of ball

BoltDia = Tap025_20;		// standard 1/4-20 thread
BoltLength = 7.0;

StemLength = 8.5;
StemDia = 4.7;
StemRad = StemDia/2;

FlangeWidth = 6.6;
FlangeThick = 2.6;

NotchSectionDia = 1.4;		// toroid cross-section diameter
NotchSectionRad = NotchSectionDia/2;
NotchOffset = 2.3;			// from top of stem

//-------

module PolyCyl(Dia,Height,ForceSides=0) {			// based on nophead's polyholes

  Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2);

  FixDia = Dia / cos(180/Sides);

  cylinder(r=HoleAdjust(FixDia)/2,h=Height,$fn=Sides);
}

module ShowPegGrid(Space = 10.0,Size = 1.0) {

  Range = floor(50 / Space);

	for (x=[-Range:Range])
	  for (y=[-Range:Range])
		translate([x*Space,y*Space,Size/2])
		  %cube(Size,center=true);

}

//-------
//

ShowPegGrid();

translate([0,0,BaseLength])
  union() {
	difference() {
	  translate([0,0,-BaseLength])
		cylinder(r=BaseRad,h=2*BaseLength);
	  translate([0,0,BallRad])
		sphere(r=BallRad);
	  translate([0,0,-(BaseLength + Protrusion)])
		PolyCyl(BoltDia,(BoltLength + Protrusion));
	}
	rotate(180/16)
	  cylinder(r=StemRad,h=StemLength,$fn=16);
	difference() {
	  translate([0,0,StemLength/2])
		cube([FlangeWidth,FlangeThick,StemLength],center=true);
	  translate([0,0,(StemLength - NotchOffset)])
		rotate_extrude(convexity=3,$fn=64)
		  translate([FlangeWidth/2,0,0])
			circle(r=NotchSectionRad,$fn=16);
	  translate([0,-FlangeWidth/2,StemLength + sqrt(FlangeWidth)])
		rotate([0,45,0])
		  cube(FlangeWidth + 2*Protrusion);
	  translate([0,FlangeWidth/2,StemLength + sqrt(FlangeWidth)])
		rotate([0,45,180])
		  cube(FlangeWidth + 2*Protrusion);
	}
  }
```
2011-11-05
Harbor Freight Bar Clamp Failure

The squeeze handle that tightens the bar clamp cracked exactly where you’d expect: directly across the pivot hole where the miracle engineering plastic thins down to a precarious ridge. The end of the handle is still inside the clamp:

Bar clamp with broken handle

Nothing bonds that plastic, so, in the nature of a quick fix, I cut a steel strap to wrap around the perimeter of the broken section and epoxied the whole mess together:

Reinforced bar clamp handle

That lasted for exactly 2.5 squeezes and then pulled apart; the epoxy doesn’t really have anything to grab.

ABS isn’t a good substitute for engineering plastic, so this will require a bit of CNC work on the Sherline. I’ll probably carve the first one from polycarbonate, just because I have a sheet of the right thickness, but it really cries out for aluminum, doesn’t it?

Why CNC? Well, I’m going to make a handful of handles and get proactive on the other clamps.

My other bar clamps have much heavier sections in that area, so perhaps the folks supplying Harbor Freight could take a hint? Yeah, but the clamp was cheap, which always conflicts with good. On the other paw, I’ve seen exactly this same clamp priced at not cheap elsewhere.

2011-11-04