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Archive for July, 2016

Staghorn Beetle Salvage Operation

This resembles nothing so much as a “developing country” shipbreaking operation:

Stag Beetle vs Ants - rear

Stag Beetle vs Ants – rear

For all I know, the ants haul the carcass into position, blow the scuttling charges to loosen the armor, and sink it in a convenient spot on the driveway:

Stag Beetle vs Ants - side

Stag Beetle vs Ants – side

The hulk vanished later in the day.

This is the season for staghorn beetles; the one we spotted a few years ago was in much better condition.

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SRAM Shift Indicator: Repair FAIL

The little red shift indicator tab in the SRAM X.9 rear shifter on Mary’s bike snapped:

SRAM Shift Indicator - broken tab

SRAM Shift Indicator – broken tab

In a triumph of hope over experience, I tried gluing the pieces with a bit of fixturing and a dab of IPS #3 solvent:

SRAM Shift Indicator - gluing

SRAM Shift Indicator – gluing

Didn’t work any better than the last time, of course. Every gear shift snap must apply 1000 G to that poor little tab…

What’s new & different: one can now obtain Official Repair Kits consisting of the indicator tab, the plastic cover, and the two screws for $6.47 delivered from eBay.

Done!

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Dust Collection: Vacuum Fittings

The Micro-Mark bandsaw’s vacuum port forced me to finish up a long-stalled project: adding a bit of plumbing to simplify connecting the small shop vacuum I use for dust collection.

It turns out that a 45° 3/4 inch Schedule 40 PVC elbow fits snugly into the bandsaw’s rubbery vacuum port and angles the hose in the right general direction:

Vacuum Adapters - 3-4 PVC to vac nozzle

Vacuum Adapters – 3-4 PVC to vac nozzle

The elbow OD fits into an adapter with a tapered socket for the vacuum cleaner’s snout:

Vacuum Hose Fittings - 3-4 PVC fitting to vac nozzle

Vacuum Hose Fittings – 3-4 PVC fitting to vac nozzle

That solid model doesn’t resemble the picture, because that gracefully thin tapered cylinder around the snout will definitely test PETG’s strength under normal shop usage; fat is where it’s at when it breaks. The interior has a tapered section between the elbow’s OD (at the bottom) and the nozzle taper (at the top) to eliminate the need for a tedious support structure.

The elbow’s OD pretty much matches the nozzle’s ID and leaves the air flow unrestricted. The aperture in the bandsaw frame might be half the pipe’s area, so I’m surely being too fussy.

With that in hand, I built more adapters to mate 1 inch PVC fittings with the two vacuum ports on the belt / disk sander to keep the canister out of my way and make the dust just vanish. A tee plugged into the belt sander side accepts the vacuum nozzle (bottom) and inhales dust from the disk sander (top):

Vacuum Adapters - belt sander - tee

Vacuum Adapters – belt sander – tee

A U made from two 90° elbows aims the disk sander dust into the hose going across the back side of the belt:

Vacuum Adapters - disk sander - double elbow

Vacuum Adapters – disk sander – double elbow

Those elbows have a 40 mm length of 1 inch PVC pipe between them; no need to print that!

The hose has a left-hand thread rib which, of course, required throwing the first adapter away into the Show-n-Tell box:

Vacuum Hose Fittings - hose to 1 inch PVC fitting

Vacuum Hose Fittings – hose to 1 inch PVC fitting

That’s a descendant of the broom handle thread, turned inside-out and backwards.

Building two hose adapters with the proper chirality worked fine:

Vacuum Hose Fittings - hose to 1 inch PVC fitting - Slic3r pair

Vacuum Hose Fittings – hose to 1 inch PVC fitting – Slic3r pair

Although you could lathe-turn adapters that plug PVC fittings into the sander’s vacuum ports starting with a chunk of 1 inch PVC pipe, it’s easier to just print the damn things and get the taper right without any hassle:

Vacuum Adapters - vac port to 1 PVC

Vacuum Adapters – vac port to 1 PVC

The straight bore matches the ID of 1 inch PVC pipe for EZ air flow:

Vacuum Hose Fittings - vac port to 1 inch PVC pipe

Vacuum Hose Fittings – vac port to 1 inch PVC pipe

The sleeve barely visible on the bottom leg of the tee looks like 1 inch PVC pipe on the outside and a vacuum port on the inside:

Vacuum Hose Fittings - 1 inch PVC to vac nozzle

Vacuum Hose Fittings – 1 inch PVC to vac nozzle

The source code includes a few other doodads that I built, tried out while deciding how to make all this work, and eventually didn’t need.

All the dimensions are completely ad-hoc and probably won’t work with PVC fittings from your local big-box retailer, as the fitting ODs aren’t controlled like the IDs that must fit the pipe. I cleaned things up a bit by putting the ID, OD, and length of the pipe / fittings / adapters into arrays, but each module gets its own copy because, for example, 1 inch 45° elbows have different ODs than 1 inch 90° elbows and you might want one special fitting for that. Ptui!

The OpenSCAD source code for all those adapters as a GitHub Gist:

Sketches of dimensions and ideas, not all of which worked out:

Vacuum Fitting Doodles - hose thread - 3-4 pipe - nozzle

Vacuum Fitting Doodles – hose thread – 3-4 pipe – nozzle

Vacuum Fitting Doodles - hose thread forms - 3-4 elbow

Vacuum Fitting Doodles – hose thread forms – 3-4 elbow

Vacuum Fitting Doodles - port - male port - 45 deg 3-4 elbow

Vacuum Fitting Doodles – port – male port – 45 deg 3-4 elbow

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Fairchild and Stoddard RF Current Probes / EMC Field Sniffers

I’ve always wondered how noisy those Arduino + fake Neopixel lamps might be and these RF sniffers might come in handy:

Fairchild MFC-25 and Stoddart 91550-1 Current Probes

Fairchild MFC-25 and Stoddart 91550-1 Current Probes

Even though they’re long obsolete, RF fields haven’t changed much in the intervening decades.

Fairchild Electronics may have become Electro-Metrics before they vanished in turn; the single useful search result offers a limited spec sheet that describes it as part of a set of three “loop probes covering the frequency range 10kHz-230MHz designed to search for RF magnetic leaks, especially in cabinets and shielded enclosures”. This one, with the blue coating, has a bandwidth of 22 MHz to 230 MHz. It has a TNC connector that now sports a cheap BNC adapter; note that it has standard polarity, not the reverse polarity required by FCC regulations that don’t take Amazon Prime into consideration.

Stoddard Aircraft Radio Co, Inc passed the 91550-1 baton to ETS-Lindgren, which (as of right now, anyway) offers a datasheet for a gadget that looks remarkably similar. The 30 Hz lower limit on the data plate suggests it’s roughly equivalent to ETS-L’s contemporary 20 Hz 91550-1L probe, but I doubt that makes much practical difference for my simple needs. The adapter takes the probe’s N connector to BNC.

The Word According to Mad Phil: If you can get to BNC, you can get to anything.

 

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Vacuum Tube LEDs: Bowl of Fire Floodlight

Although I didn’t plan it like this, the shape of the first doodad on the mini-lathe reminded me that I really wanted something more presentable than the (now failed) ersatz Neopixel inside the ersatz heatsink atop that big incandescent bulb.

So, drill a hole in the side:

Ersatz aluminum heatsink - drilling

Ersatz aluminum heatsink – drilling

Epoxy a snippet of brass tubing from the Bottomless Bag o’ Cutoffs into the hole:

Ersatz aluminum heatsink - tubing trial fit

Ersatz aluminum heatsink – tubing trial fit

Recycle the old wire and PET loom, solder to another fake Neopixel, blob epoxy inside to anchor everything, and press it into place:

Ersatz aluminum heatsink - epoxying LED

Ersatz aluminum heatsink – epoxying LED

Cutting the failed LED & plastic heatsink off the wire left it a bit too short for that tall bulb, but some rummaging in the heap produced a 100 W incandescent floodlight with a nicely pebbled lens:

Reflector floodlight - overview

Reflector floodlight – overview

A thin ring of clear epoxy secures the ersatz heatsink to the floodlight:

Reflector floodlight - finned LED holder

Reflector floodlight – finned LED holder

This time, I paid more attention to centering it atop the General Electric logo ring in the middle of the lens, which you can just barely see around the perimeter of the aluminum fin. By pure raw good fortune, the cable ended up pointed in the general direction of the socket’s pull-chain ferrule; you can’t unscrew the bulb without tediously unsoldering the wires from connector atop the knockoff Pro Mini inside the base and squeezing them back out through the ferrule.

With the firmware set for a single fake Neopixel on pin A3 and a 75 ms update rate, the floodlight bowl fills with color:

Reflector floodlight - purple phase

Reflector floodlight – purple phase

It puts a colored ring on the ceiling and lights the whole room far more than you’d expect from 200 mW of RGB LEDs.

Pretty slick, even if I do say so myself …

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Mini-Lathe: First Cuts

Despite the craptastic way finishing and the cross slide DRO malfeature, the Little Machine Shop 5200 lathe works well enough for my simple needs. I really like the quick change toolpost:

LMS Mini-lathe - first cuts

LMS Mini-lathe – first cuts

The QC post and tool holders have very nice machining and surface finish; they evidently come from an entirely different production line than the lathe components. I can definitely get used to using carbide inserts, although I ordered some HSS inserts for interrupted cuts.

The HSS cutoff tool does what you’d expect:

LMS Mini-lathe - first cut - drilled and slotted

LMS Mini-lathe – first cut – drilled and slotted

The holes in the end came from short (“screw machine”) drill bits I got for the Sherline’s painfully limited Z axis travel. Even so, chucking one in the 1/2 inch capacity LMS drill chuck shows why a 16 inch bed isn’t excessive:

LMS Mini-lathe - drill chuck vs bed length

LMS Mini-lathe – drill chuck vs bed length

The 6 inch = 150 mm scale on the bed (to the right of the tailstock) extends to the limit of tailstock travel, so you could have another half foot of stock sticking out of the 3 jaw chuck. A collet in the spindle would give you another two inches, but it’s snug in there.

On the other paw, this is a little lathe intended to make little things. It’ll do fine…

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Mini-Lathe: Control Box Cover Screws

It’s easier to remove the leadscrew while dismantling the carriage and apron, which requires removing the cover from the control box containing all the switches & knobs. Come to find out the “cover” actually holds all the gadgetry onto the headstock:

LMS mini-lathe - control box interior

LMS mini-lathe – control box interior

I want to replace the Power indicator with something visible in normal shop light; judging from the connectors and overall brightness, it’s a neon bulb inside a green housing.

Anyhow, the four screws holding cover to the headstock weren’t identical:

LMS Mini-lathe - cover screws

LMS Mini-lathe – cover screws

I thought the oddball screw was deliberate, perhaps fastening that corner to a plastic frame of some sort, but it turned out to be a quick fix for a boogered tap job:

LMS Mini-lathe - mistapped cover hole

LMS Mini-lathe – mistapped cover hole

A bag of 4 mm knurled brass inserts will arrive in a while, after which I’ll drill out all four holes and epoxy inserts in their place. Might have to use stainless hardware, just for nice…

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