Month: July 2017

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.

 

The Sound and the Fury

I just read The Sound and the Fury after putting it off for more than 50 years.  It is definitely art.  It may be great art.  Contrary to some critiques, it is not hard to follow for a modern reader accustomed to sound bites and kaleidoscopic perspective shifts.  It is entertainment in the sense that Tobacco Road, World Enough and Time, and Long Day’s Journey Into Night are entertainment.

The novel ends abruptly.  I was relieved when it was finally over, for both my sake and the characters’.

If you are plagued by overwhelming happiness, inexhaustible joie de vivre, and unbounded bliss to be living in a world of infinite possibility, this will cure you.

Magic Rub

If you want to erase pencil marks, get a MAGIC RUB® eraser — nothing else compares.  The soft composition doesn’t damage paper fibers, and its adsorbent porosity just vacuums graphite off the surface with a light rub.  MAGIC RUB® does a good job of removing pencil marks from other surfaces as well.  This non-hardening eraser wears with use, leaving a constantly clean, fresh surface.  If you’ve only experienced the standard kind of abrasive red eraser, either block or pencil tip, which leaves a rough reddish smear, you will be surprised by the the results.  There are other white erasers — vinyl, plastic, polymer — which are not the same.  MAGIC RUB® is better than gum, kneaded, white or pink pearl®, and the long cylindrical white erasers used in stick type or powered drafting erasers.  The only close equivalent I’ve ever come across is the eraser on the end of Pentel® mechanical pencils, which may be identical for all I know.

Try it, you’ll like it.

The Cost of Speed

Traveling over 15 miles per hour takes a pair of cross trainers for $50.

Traveling over 150 miles per hour takes a Corvette for $50,000.

Traveling over 1500 miles per hour takes an F15 Eagle for $50,000,000.

Traveling over 15,000 miles per hour takes a space shuttle program at $150 billion for three operating shuttles or $50,000,000,000 each.

To go 10 times faster you have to spend 1000 times as much money.

Microgravity Induced Bone Loss

The two critical problems faced by manned deep space exploration are radiation (discussed in a later post) and microgravity induced bone loss.  NASA has been studying bone loss in astronauts for 50 years and has learned enough about the biological mechanism to develop the successful ARED exercise device and nutrition protocols for the ISS.  These work well for motivated, fit astronauts, but compliance might be problematic for the larger and varied crew of a very long duration deep space mission.  The traditional hard science fiction solution is to use spin to generate centrifugal gravity.  One question is how much spin?  When (hopefully) we have Lunar, 1/6 G, and Martian, 3/8 G, permanent bases we will be able to do comparative bone loss studies.  A rat centrifuge on the ISS could produce additional data.  It is inconvenient to spin an entire spacecraft because of issues with navigation, antenna orientation, maneuvering, and frame stress.  Spinning part of a craft creates problems with seal integrity between the sections.  The internal wheel of the 2001: A Space Odyssey spacecraft was a rather elegant solution to these problems but still represents an unlikely level of technology for the foreseeable future.  It is likely any long duration manned space mission in the next 50 years will need to deal with the problem of microgravity.

The research that resulted in the ARED and also related rat research have shown that it is the lack of resistance to movement or lack of force supporting body weight stressing the long skeletal bones, rather than lack of the internal force of gravity on the bone matrix, that causes bone density loss.

Fully aquatic mammals such as whales, dolphins, and manatees spend their entire lives in a neutral buoyancy environment, effectively weightless.  While the deep dives of whales and the hunting acrobatics of dolphins may or may not give their skeletons astronaut levels of stress, manatees are the original couch potatoes.  In any case, all are fully adapted to their environment.  While none of these animals are remotely suitable for research, it is almost certain that we have DNA samples for all of them which could be sequenced.  We also have DNA for their land based relatives – hippopotami, elephants, and hyraxes – for comparison.

As NASA’s and others’ research into microgravity induced bone loss proceeds, the signaling and metabolic pathways involved along with their associated proteins will be identified.  It would be useful to compare these proteins to the aquatic equivalents to try to identify any adaptive changes.  This might suggest new paths for the pharmaceutical research already underway in rat studies.

Looking homeward

For 13 years the Cassini spacecraft has been orbiting Saturn and its moons, sending back thousands of spectacular pictures.  Now nearing the end of its mission, it will be exploring the ring system and ultimately entering Saturn’s atmosphere on September 15th, 2017.  Once in a while when the geometry is suitable, Cassini pauses to take a picture of the Earth while moving between science targets.  These homeward looks from 900 million miles away evoke a haunting loneliness.