Garden hose

Don’t buy garden hoses with aluminum fittings — generally silver colored instead of brass.  These fittings will corrode and seize to your hose nozzles, sprinklers, and faucets.  They then have to be cut off and generally ruin the mating part.  Existing hoses can be salvaged by cutting off the aluminum fittings and installing brass fittings available from any hardware store.

Also, try to avoid aluminum in electrical fittings and switches.  The aluminum eventually forms a surface oxide layer that causes open and/or intermittent circuits and, in some cases, fires.  Years ago there was a brief effort to use aluminum wire in residential wiring before the fire hazard was recognized.  It is hard to avoid aluminum in cheap lamp sockets but the effort will be worth it.  As a couple of personal examples: our son kept fighting an intermittent ceiling light — replacing bulbs, switch, and breaker — until I swapped out the old aluminum lamp socket.  At another time, my garage door manual button stopped working — the remotes worked fine.  This was eventually traced to the use by the manufacturer of an aluminum washer under a terminal riveted to a circuit board.  There was no visible corrosion, just an invisible oxide layer that formed under the rivet head.  A bit of solder bridging over the washer from the terminal to the board cured the problem.

Aluminum is great for cookware and airplanes.  Not so much for water fittings or electrical connections.

Fungus and mildew and mold, oh my!

Each time you take a shower or a hot bath, the air in your bathroom warms up several degrees and its humidity approaches 100% — excellent conditions for growing things.  You can see the effect of  humidity in the fogged mirrors and the damp feel in the room.   To help with this, run your bathroom vent fan for 30 to 45 minutes after bathing with the bathroom door pulled almost closed to keep the damp air in the bathroom until it is exhausted by the vent fan but not completely shut to provide a path for cool dry air drawn from the rest of the house.  This will help clear the mirror too.  You can get an inexpensive humidity gauge from the hardware store to track the change from high back to normal humidity to know how long to run your fan.  If you have screw base vanity lights, going back to incandescents in the bathroom will help too — leave them on with the fan.  If you’ve been fighting mold in the bathroom, this will improve the situation.

Integrating Sampler

The standard point or impulse sampler that converts a continuous signal to a discrete data sequence has been well understood since 1924 thanks to Harry Nyquist.   It is often assumed that the impulse sampler is the only way to create a discrete sequence.  There are other sampling strategies that may have advantages in some applications.  Here is an example of one.

Blind Spots

The blind spot mirrors on cars are becoming irrelevant tech.  Many people now believe the side mirrors are rear view mirrors and mistakenly adjust them to look at the car directly behind, giving three views of the same vehicle.  If you pull up behind such a car, you will see the driver’s face in the side mirrors.

Automobile side mirrors are not rear view mirrors.  The rear view mirror is the one in the center of the windshield.  The side mirrors are safety additions to cover “blind spots”.  These are the areas behind and to each side where a car in the next lane is invisible when it pulls forward out of the rear view mirror’s field and isn’t yet far enough forward to see with peripheral vision or a glance to the side.  Properly adjusted side mirrors allow you to see a car in the blind spots and avoid a potentially disastrous lane change or turn resulting in a collision that will be your fault.

The blind spot mirrors can be roughly adjusted while parked.  Put the driver’s seat in its normal position and adjust the mirrors up or down until the horizon is in the middle of the mirror.  Lean to the left until your head touches the window and adjust the left mirror until you can just see the side of your car at the right edge of the mirror.  Lean the same distance to the right and adjust the right mirror until you can just see the side of your car at the left edge of the mirror.  This procedure produces a good approximation and will cover most blind spots.  The adjustment can be fine tuned in traffic as you observe whether you pick up passing cars in the next lane in the side mirrors before they leave the rear view field and whether you can see them with peripheral vision before they leave the side mirror fields.  Even with properly adjusted mirrors there are still blind spots for cars two lanes away and also for cars on a highway when you are merging at an angle.  But properly adjusted side mirrors will allow you to scan for converging traffic in these cases by moving your head and avoid an accident.

The really bad effect of this is that some current car engineers either do not know what the side mirrors are for, or kowtow to their marketing wonks who decided that customers do not know and shouldn’t be informed.  As a result, the blind spot mirrors on some new cars cannot be adjusted to cover the blind spots and can only be used to give a duplicate rear view.  Check this when you shop for a new car by trying the above procedure.  If the mirrors can’t be correctly adjusted, register your dissatisfaction, go somewhere else, and save yourself from a potential accident.

Eclipse 2017

My first total eclipse.  The moon relentlessly sweeping across the  dazzling surface and eating sunspots, heading towards a destiny that you know will come but can’t quite believe.  A hot August day cooling as the sun turns into a thin bright crescent. Baily’s beads and the diamond ring just before totality.  Suddenly the world turns strange as if you are in a Gothic movie.  The comforting brightness in the sky you’ve lived with all your life has become a photographic negative. The sky at midday is dark enough to see stars and planets.  Prominences  (9 o’clock and 11 o’clock upper left) and the spectacular corona burst into view.  There is sunset color on the horizon for 360 degrees around you.  Cheers and tears, everyone seems to have an emotional response.  Words cannot do it justice.  Pictures cannot do it justice.  There is no way to convey what the experience is like, standing out under the open sky, with that incredible event happening overhead.  Don’t miss the next one.

Reever Knot

I first ran across this charming knot as a bit of decorative graphics on the Contents page of “What Knot?” by Budworth and Hopkins.


The working and standing ends ran off the page so it was not obvious which was which.  Unidentified on the page and appearing nowhere else in the book, it piqued my curiosity.  It was an interesting looking bend and I spent some time playing with it.  It appeared to be very secure, had no tendency to “tumble”, and unlike most secure bends, e.g. zeppelin, Hunter, Ashley, which bring the ends out the sides, this brought the working ends out in parallel alongside the standing ends.  With symmetric standing ends it snugs up to a nice slender compact knot.  This would be a good bend for passing through an eye.  Eventually I discovered that this topology was called a Vice Versa with the top B-A pair (or bottom A-B pair) as the standing ends.  I had already discovered that this caused the knot to cramp into a bow and lose its tidy cross-section.  Wikipedia came through with the information that this knot with A-A for the standing ends was a Reever Knot.  In either version it is reportedly excellent for slippery cordage.  The Reever version maintains the compact shape with a slight skew.  A nameless version with B-B for the standing ends that applied force close to the center axis and resulted in a neater square shape was my sentimental favorite.  I developed a good way to tie it.

Enter the heartless wind of science.  I used some 30 lb test monofilament line and tied a bunch (technical term) of these.  The Reever Knot locked up tightly and held all the way to the point where the line broke without any slipping.  The Vice Versa slipped some and then broke at a similar load.  The B-B version consistently slipped completely at a lower load.  I used monofilament to discriminate.  None of these are suitable for wet fishing line.  Abstract:

Reever                   Great     (Now I have to practice tying this.)

Vice Versa              OK, not as neat, nor as good for really slick line.

Anonymous B-B    Back to the irrelevant tech pile for you.

Dual Clutch Transmission

Elements of irrelevant tech are much like animals in a zoo, interesting to look at but, for the most part, not very good pets if you have to live with them.  Every once in a while one of the animals escapes into the general population.  A case in point is the dual clutch transmission.  These started appearing in production cars about 15 years ago although they have a longer history in various prototypes, specialty sports cars, and Porsche Le Mans cars.  Prior to that, the two standard choices for consumer car transmissions were manual (stick shift) or conventional automatic.  Manual transmissions are simple, rugged, and efficient but not for everyone.  Modern conventional automatic transmissions are the result of 90 years of refinement.  They routinely provide reliable, quiet performance far in excess of 100,000 miles.

The dual clutch “automatic” transmission is very complex with a large number of moving parts, many more than a conventional transmission.  It is effectively two manual transmissions, one (as an example) for 1st, 3rd, 5th, and 7th gear and the other for reverse, 2nd, 4th, and 6th gear.  It has two clutches to switch the engine torque between the two gear trains, two counter shafts, and two sets of synchronizers.  It contains multiple electric motors, reduction gears, and actuators to activate the two clutches and the shift forks for the various gears on each side and a computer to run the whole thing.  This tends to make them fairly expensive.

The two sides take turns as the transmission is shifted between gears.  As an illustration of normal operation assume the transmission has just up shifted to 3rd with the odd side now driving.  The disengaged even side is in 2nd and will be moved to 4th to get ready for the next shift.  To make that shift, the odd side clutch is disengaged and the even side clutch is carefully engaged to supply power in 4th gear.  Note that there is no fluid coupling or torque converter as in a conventional automatic transmission so the clutch engagement must be handled as carefully and smoothly as with the clutch on a manual transmission to avoid jerks.  One problem here is that the transmission has to guess which gear you will need next.  For a straight acceleration up through the gears, or for a normal downshift pattern coming to a stop, this is not a problem.  However, if you slowed down for a turn and want to speed up again, the off side transmission will find itself in the wrong gear and will have to shift back internally before it can transfer between the two clutches to apply power in the proper gear.  On paddle shift versions this means that sometimes the dual clutch transmission shifts when you hit the paddle and sometimes it shifts later.

When a new tuned and adjusted dual clutch transmission leaves the factory it shifts as smoothly and as quietly as a conventional automatic.  As it is driven, all the electric motors, reduction gears, actuators, bearings, and clutches start to wear.  After a few thousand miles the transmission develops a slight whir with sliding noises when it shifts, especially during turns in traffic.  When you take it to the dealer they will tell you there is nothing wrong with it as they are all like that.  The reason the dealer tells you that is that they are all like that.  After a few more thousand miles the whir turns into a whine of electric motor gears and the sliding noise turns into the shift forks clanking.  Once again the dealer assures you that they are all like that.  They offer to upgrade the software in the transmission, which doesn’t appear to do anything.  After a few more thousand miles the actuators are worn enough, and there is so much slop in the linkages, that the clutches can no longer be operated smoothly, so the car jerks and shudders when pulling away from a stop.  This was not a problem for the Porsche 956 Le Mans car, but it only had to run for 24 hours.

The dual clutch transmission is irrelevant tech.


Microgravity Volume Gauge

Traditional methods of gauging fluid levels in a tank include inserting a measuring stick as is done at gasoline stations around the world, using a float mechanism, measuring the distance from the tank top to the fluid surface via ultrasonics or something similar, or sensing the pressure at the bottom of the tank due to the weight of the fluid.  These methods all have two problems.  The exact shape of the tank must be known for accurate readings.  And, since they only work in a stationary tank in a gravity field, they are completely unsuited for microgravity.  Here is an alternative in the irrelevant tech spirit.

The Great Banana Conspiracy

The Great Banana Conspiracy was triggered by a technological advance.  Around 1880 the commercial production of residential kitchen iceboxes began, bringing the promise of preserving perishable foods.  The governing board of the world banana cartel immediately recognized the threat to their bottom line.  The cartel decided upon a disinformation campaign based on a kernel of truth: in a sealed container the natural plant hormones released by bananas accelerate ripening.  This effect was already used commercially to ripen bananas for market.

The word went out: “Do not put bananas in the refrigerator.  They will turn brown and go bad.”   It was passed to the grapevine, fed into the rumor mill, gossiped over back yard fences, and inserted into the interminable Senate filibusters of the time.  It was picked up by our great-grandmothers, passed to our grandmothers, who taught it to our mothers, and now we indoctrinate our own children and grandchildren.  It has resulted in 130 years of soft, sticky, and blah bananas resting in cute little mesh slings or dangling from crescent-shaped hangers on kitchen counters.

In point of fact, when fresh bananas are put into the refrigerator, they do develop a superficial light brown dusting on the surface of their skins after a few days.  Yet when you take one out, you find that the peel underneath is still crisp and the fruit inside is fresh, firm, and sweet.  (Keep green bananas at room temperature until the bodies just turn yellow and then put them in the refrigerator.)

We were also told to not put bread in the refrigerator, effectively the same misdirection.  As a practical matter, the early iceboxes were small, and what little space they had was needed for eggs, meat, and milk.  Bread was baked at home and generally eaten on the same day.  So the habit of no refrigeration became the rule.  Modern refrigerators have eliminated the space problem and store-bought bread has replaced daily baking – however, the rule has remained while modern smaller families are taking longer to finish a loaf.

The fact is that bread keeps just fine for several days in its plastic wrap in the refrigerator.  It doesn’t get moldy, it doesn’t get soggy, it doesn’t dry out, and it doesn’t become stale.  It toasts the same way, makes perfectly good sandwiches, and stays generally indistinguishable from non-refrigerated bread.  If you need a room temperature slice or two, a mere 8 or 10 seconds in the microwave takes care of that.  And since in the refrigerator the bread does not get moldy, you won’t find yourself trying to remember how many days ago you bought it.  There may be an exotic crusty French boule that’s edible only while still warm from the oven, but if your bread came from the grocery store, throw it in the fridge.