Posts Tagged M2

Tour Easy Front Derailleur Cable Clamp

In addition to sawing through the side of the cable ferrule, the front derailleur cable began breaking at the edge of the derailleur arm:

Tour Easy Front Derailleur Cable - frayed

Tour Easy Front Derailleur Cable – frayed

It wouldn’t have survived another ride!

Dan pointed out CNC machined aluminum cable clamps are a thing, but those are sized for larger frame tubes than the 1.0 inch steel used on our Tour Easy ‘bents and, although I’ve shimmed everything else on the frame, I wanted to tweak the cable angle to match the arm on the derailleur.

A bit of OpenSCAD wrangling produces a likely candidate:

Front Derailleur Cable Clamp - Slic3r

Front Derailleur Cable Clamp – Slic3r

That’s a bulked-up revision of the prototype:

Tour Easy Front Derailleur Cable Clamp - installed

Tour Easy Front Derailleur Cable Clamp – installed

Done up in orange PETG, it demonstrated the idea worked, but two perimeter threads wrapped around 15% infill isn’t quite up to the task. Note the split along the screw on the far half and various irregularities around the ferrule.

The cable angle isn’t quite right, either, as the proper compound angle would, alas, aim the cable into the pedal crank. The bulky bushings get in the way of putting the ferrule where it should be with the screws aligned in a tidy manner, so I must get used to the jaunty angle.

The bulkier version, done with 50% infill and four perimeter threads, has the same tilt angle, but the ferrule sits further from the screws:

Tour Easy Front Derailleur Cable Clamp V2 - rear quarter view

Tour Easy Front Derailleur Cable Clamp V2 – rear quarter view

The view from the left side shows the cable angles slightly to the rear, but the smaller angle should make it happier:

Tour Easy Front Derailleur Cable Clamp V2 - side view

Tour Easy Front Derailleur Cable Clamp V2 – side view

Probably should have used black PETG. Next time, for sure!

The OpenSCAD source code as a GitHub Gist:


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Propane Tank QD Fitting Adapter, PETG Edition

Smoking bacon during the winter months brought the third tank into play, requiring the POL-to-QD adapter I’d had in the drawer for just such an occasion. Not much to my surprise, the old PLA fitting adapter snapped along the layers near the outside end of the triangular snout:



So I ran off the two orange ones in PETG with six perimeter layers and 50% infill density:

Propane QD Adapter Tool - Slic3r

Propane QD Adapter Tool – Slic3r

Those should last roughly forever …

The OpenSCAD source code as a GitHub Gist:


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MPCNC: Linear Bearing Pen Holder

The simplest way to push a pen (or similar thing) downward with constant force may be to hold it in a linear bearing with a weight on it, so I gimmicked up a proof-of-concept. The general idea is to mount the pen so its axis coincides with the DW660 spindle, so as to have the nib trace the same path:

DW660 Pen Holder - unweighted

DW660 Pen Holder – unweighted

The puck mimics the shape of the DW660 snout closely enough to satisfy the MPCNC’s tool holder:

DW660 Pen Holder - Slic3r

DW660 Pen Holder – Slic3r

The pen holder suffers from thin walls constrained by the 10 mm (-ish) pen OD and the 12 mm linear bearing ID, to the extent the slight infill variations produced by the tapered pen outline change the OD. A flock of 16 mm bearings, en route around the planet even as I type, should provide more meat.

In any event, 3D printing isn’t noted for its perfect surface finish, so I applied an epoxy layer and rotated the holder as it cured:

DW660 Pen Holder - epoxy coating

DW660 Pen Holder – epoxy coating

After letting it cure overnight, I ran a lathe tool along the length to knock down the high spots and set the OD to 11.9+ mm. Although the result turns out to be a surprisingly nice fit in the bearing, there’s no way epoxy can sustain the surface load required for the usual precision steel-on-steel fit.

A plastic pen in a plastic holder weighs 8.3 g, which isn’t quite enough to put any force on the paper. Copper weighs 9 g/cm³ = 9 mg/mm³ and 10 AWG wire is 2.54 mm OD = 5 mm², so it’s 45 mg/mm: to get 20 g, chop off 450 mm of wire.

I chopped off a bit more than that, straightened it, annealed it, and wound it around a random contestant from the Bucket o’ Sticks with an OD just over the pen OD:

DW660 Pen Holder - copper weight forming

DW660 Pen Holder – copper weight forming

The helix is 13.5 mm down the middle of the turns and 14 turns long (trimmed of the tail going into the chuck and fudging the tail sticking out as a partial turn), so it’s 593 mm long and should weigh 26.7 g. It actually weighs 27.6 g: close enough.

Which is enough to overcome stiction due to the holder’s surface roughness, but the mediocre epoxy-on-balls fit allows the pen point to wander a bit too much for good results.

The prospect of poking precise holes into 16 mm drill rod seems daunting, but, based on what I see here, it will produce much better results: rapid prototyping FTW!

The OpenSCAD source code as a GitHub Gist:

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MPCNC: USB Camera Mount With Lock Screw

It turned out the previous version of the USB camera mount lacked sufficient griptivity to hold the ball’s position against even moderate bumps, so the upper “half” is now tall enough to hold a lock screw directly over the ball:

MPCNC - USB Camera mount - lock screw - Slic3r

MPCNC – USB Camera mount – lock screw – Slic3r

It doesn’t look much different:

MPCNC - USB Camera Mount - lock screw

MPCNC – USB Camera Mount – lock screw

A view from the other side:

USB Camera - lock screw mount

USB Camera – lock screw mount

The previous iterations used Genuine 3M foam tape, which seemed too flexy for comfort. This one sits on a bed of hot melt glue and is absolutely rigid. We’ll see how long it survives.

Tightening the cap screw requires needle-nose pliers, because the whole affair has no room for a hex key.

The OpenSCAD source code as a GitHub Gist:

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Baofeng BL-5 Pack Rebuild

The 18650 cell protection PCBs with 8205 ICs arrived and seemed small enough to simply tuck into the gap between the rounded cells in the second Baofeng BL-5 pack:

Baofeng BL-5 - new protection PCB - wiring 1

Baofeng BL-5 – new protection PCB – wiring 1

For whatever it might be worth, you’re looking at the only Baofeng battery pack containing an actual 10 kΩ thermistor, harvested from the benchtop Tray of Doom:

Baofeng BL-5 pack - thermistor

Baofeng BL-5 pack – thermistor

Unfortunately, the components on the PCB stuck up a bit too far from the cell surface and held the lid just slightly proud of the case. Applying pressure to lithium cells being a Bad Idea, I rearranged the layout by flipping the cells over, tucking the PCB components between the cells, and connecting everything with nickel tape instead of insulated wires:

Baofeng BL-5 - new protection PCB - wiring 2

Baofeng BL-5 – new protection PCB – wiring 2

The snippets of manila paper and Kapton tape hold things apart and together, as needed. Looks ugly, fits better.

Pop it in the charger to reset the protection PCB lockout and it’s all good again.

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Baofeng BL-5 Battery Pack Base Dimensions

My original idea for the APRS + voice gadget was a snap-in battery pack replacement holding the circuit boards and connected to an external battery pack. A trio of dead Wouxun radios, plus the ready availability of 18650 lithium cells, suggested putting two cells in the backpack, along with the circuitry, and skipping the external pack.

Here’s the base of a Baofeng BL-5 pack overlaid with a 1 mm grid:

Baofeng BL-5 - Base with mm grid overlay

Baofeng BL-5 – Base with mm grid overlay

The grid is parallel to the case body and centered left-to-right, with a Y grid line set at the front face of the pack, where it’s also flush with the lid surface. You can read off the coordinates of all the points, feed them into your CAD model, and maybe, with a bit of care, get something 3D-print-able.

Haven’t used it yet, but it’s bound to come in handy at some point.


MPCNC: Raspberry Pi Screw-down Case

Directly from  0110-M-P’s Thingiverse thing, because a Raspberry Pi in a 75 mm VESA mount case will work for me:

RPi in VESA case

RPi in VESA case

The hole fits a 25 mm fan, but the thing runs cool enough it should survive without forced air; think of it as a contingency. Mounting the case on standoffs seems like a Good Idea, however, as the bottom plate includes many vent slots for Good Circulation.

The top plate builds upside-down, so I had Slic3r add teeny support plugs inside the recessed screw holes. I think button-head screws would fit neatly in the recesses, but we’re obviously not in this for the looks.

The tiny white stud is a Reset switch hot-melt glued into the slot. I plan to just turn off the AC power after shutting the RPi down, so a power-on will suffice as a reset.

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