Machine Shop, Science

Laser Water Chiller: Heating

The previous Basement Laboratory generally stayed above 60 °F = 15 °C, so I set the LightObject water chiller’s low-temperature alarm accordingly.

Having reached the point where I can set up the laser in its new home, I connected the chiller tubes, filled the reservoir with distilled water (and a squirt of algaecide), connected the alarm wiring, turned it on, and had the cool water trigger an alarm:

LightObject Laser chiller - low temp alarm
LightObject Laser chiller – low temp alarm

Which was relayed to the controller:

KT332N Diagnostic display - water protect active
KT332N Diagnostic display – water protect active

Silencing the chiller’s alarm clears the error indicator in the controller, so it’s possible to Fire The Laser with too-cold water if necessary.

As with the previous icemaker chiller, plotting the water temperature as a function of time shows the pump adds some energy as it moves the water around the loop:

LightObject Q600 chiller - water heating
LightObject Q600 chiller – water heating

The gap in the data shows where I had a few other things to do, but the exponential rise is obvious. The chiller compressor starts at just over 21 °C and stops at just under 20 °C, so the exponential curve had gone about as far as it could go.

The numbers in the upper right of the plot give the weight of:

  • An empty water bottle
  • A full gallon bottle
  • The partially empty bottle used to top off the reservoir
  • How much water went into the chiller reservoir

The figures in the bottom mash the initial slope of that curve together with the weight of the water to find the 21 W required to heat the water at that rate, with a bank shot off British Thermal Units because why not.

A Kill-a-Watt meter shows the Q600 chiller draws 36 W with the pump running, which includes the controller and a column of blue LEDs behind the water level tube.

The pump (in the lower left) isn’t exactly water-cooled, but it’s not losing a lot of heat through that foam wrapper and maybe most of the heat really does come from the motor:

LightObject Laser chiller - right side internal view
LightObject Laser chiller – right side internal view

The basement temperature will rise as Spring becomes Summer, so the chiller will start working right away, and it’ll definitely get more exercise when the laser starts cutting again.

Home Ec

Folding Step Stool Handle Repair

It turns out that if you drop a heavy sheet of laminated cardboard in exactly the right spot, you can shear the pot metal handle right off a two-step folding step stool:

Folding step stool - exposed handle
Folding step stool – exposed handle

I mean, it’s just a perfect target:

Folding step stool - handle detail
Folding step stool – handle detail

It was a clean break leaving gritty surfaces ideal for JB Weld epoxy and a clamp:

Folding step stool - epoxy clamping
Folding step stool – epoxy clamping

In truth, using epoxy in tension isn’t a good idea, but this is light duty and the repair ought to be good for a while.

Now, as to why I was standing on a two-step ladder fiddling with a heavy sheet of laminated cardboard, that story must wait for a while …

Home Ec

Tub Re-Caulking

Every tub & shower looks like this after a decade or so:

Old tub caulk
Old tub caulk

Go look carefully at your bathroom if you don’t believe me.

Tubs have a raised lip around their perimeter, but our downstairs bathroom had a caulk crack that routed water running down the wall under the tile, over the lip, and onto the subfloor beside the tub. This had been going on unnoticed for years, but we apparently take showers differently enough to put a puddle of water on the basement floor.

Some exploratory surgery revealed a patch of rotted subfloor (which is why we know it was an ongoing problem), but no structural damage. A few hours of tedious razor knife and hook work extracted the old caulk, after which squirting new caulk took almost no time at all:

New tub caulk
New tub caulk

I screwed a small fan across the subfloor opening to pull air across the wet area:

Subfloor fan drying
Subfloor fan drying

A few days dried things out nicely, so I can proceed with a project involving the adjacent shower stall, about which more later.

They don’t install drain pipes like that any more! Judging from the many scorch marks on the joists, the plumber had considerable difficulty keeping enough heat on the fittings for good solder joints.

Machine Shop, Recumbent Bicycling

Tour Easy Coolback Seat Restringing

The Kevlar cord on Mary’s bike survived the crash without breaking, but it was badly scuffed and holding on by only a few strands. Unlike in years gone by, Kevlar cord is now cheap & readily available, so I decided to restring the thing:

Tour Easy - seat cord - restrung
Tour Easy – seat cord – restrung

The cord path isn’t at all obvious, even given the smudges on the seat struts:

Tour Easy - seat mesh removed
Tour Easy – seat mesh removed

Pictures of the original cord as installed at the Easy Racers “factory” served as guidance:

Tour Easy - seat cord - front view
Tour Easy – seat cord – front view
Tour Easy - seat cord - side view
Tour Easy – seat cord – side view
Tour Easy - seat cord - rear view
Tour Easy – seat cord – rear view
Tour Easy - seat cord - bottom detail
Tour Easy – seat cord – bottom detail

The knots joining the cord at the top, taken juuust before I pulled the right knot apart:

Tour Easy - seat cord - knots
Tour Easy – seat cord – knots

Those are in addition to my Tour Easy a few feet away, but you can never have enough pictures.

A 3.5 meter cord will be plenty long enough and marking the midpoint simplifies equalizing the two sides. The cord crosses the seat frame at the bottom from the lower guides, although I’m reasonably sure it wouldn’t matter if you ran separate lengths up the two sides with a knot in the lower guide.

The new cord claims to be 1000 pound test (200 pound working), but the vital dimension is its 2.6 mm diameter to match the OEM cord. It does not claim to be UV stabilized, which may turn out to be a problem over the course of a few years.

Tightening the cord proceeded as before and a test ride indicated the installation was all good.

Machine Shop, Oddities

3-In-One Motor Oil: Mystery Inclusions

Our new-to-us house included a heavy-duty basement dehumidifier with a blower motor calling for a few drops of SAE 20 oil twice a year. Some searching turned up a specialized flavor of 3-In-One Oil for motors.

It arrived with free inclusions:

3-in-One Motor Oil - top inclusion
3-in-One Motor Oil – top inclusion

Backlighting makes them more obvious:

3-in-One Motor Oil - top inclusion - backlit
3-in-One Motor Oil – top inclusion – backlit

There’s also a free-floating jellyfish slightly denser than the oil:

3-in-One Motor Oil - bottom inclusion - backlit
3-in-One Motor Oil – bottom inclusion – backlit

As is now the typical case with Amazon purchases, the only choices are to return / exchange the item, as the seller cannot be contacted directly. I tried sending 3-In-One a question through their website, en passant discovering they’ve been Borged by The WD-40 Company, only to be rejected by the site’s Captcha without ever seeing the test images.

AFAICT, it’s oil and the motor will just have to get used to it.

Home Ec, Machine Shop, Oddities

Mailbox Post Repair

One doorbell ding came from a guy who sheepishly admitted he had just collided with our mailbox, which sits on the outside of a gentle curve and sticks out, IMO, a bit too far into the street.

This not being my first time in this rodeo, I allowed as how if he’d replace whatever broke, I’d do the fixing and it’d be all good. As it turned out, the only broken part was the foamed-plastic post, which split neatly along its length around the crosspiece hole. After looking things over, I said I’d just epoxy it together and call it done.

That afternoon, I mixed up a generous cup of the casting epoxy I’d been using for coasters and suchlike. It is now well past its best-used-by date and somewhat cloudy, but I figured it would suffice for the purpose; nobody will notice cloudy epoxy on a mailbox post.

I have Too. Many. Clamps. and know how to use them:

Mailbox post repair
Mailbox post repair

He departed, quite literally in tears, over my not raking him through the coals. I figured anybody who’d stop and admit to property damage needed encouragement, not chastisement, and replacing the headlight on his pickup would be more than enough punishment.

That was easy.

Home Ec, Machine Shop

Drop-leaf Table Repair

An old antique drop-leaf table serves as a plant stand and time reference:

Drop leaf table - in use
Drop leaf table – in use

While adjusting the clock for Daylight Saving Time, one of the folding leaves … folded, dumping the clock on the floor.

It turns out the latches holding the leaves in place have been repaired / replaced many times since the table left the factory:

Drop leaf table - random latches
Drop leaf table – random latches

I’m certain the latch in the upper right came from my father’s hands.

Although it’s an antique, it’s not a priceless antique, so I had no compunction about drilling out the wood screw holes, installing metric threaded inserts, and converting all the screws to M4 button heads:

Drop leaf table - wood insert
Drop leaf table – wood insert

That’s a brad-point bit intended to produce clean-sided flat-bottom holes (modulo a triangular pit from the tip) exactly right for screwing an insert all the way down. The table top just barely fit on the drill press, so I could set the depth stop to make the answer come out right every time.

A dot of low-strength threadlocker keeps the screws from turning, although the table has pretty much reached a steady state these days.

That was easy …