Trip Report : Jewel-cutting in Idar-Oberstein

Stone-cutting and polishing town Idar-Oberstein is famous throughout the world, not merely Germany. South-Africans and even Amsterdam Jews send diamonds here to be cut and polished, big mining companies in Alaska and Canada ship semi-precious stones by the ton here and then ship the finished stones back for sale in their countries. We took a look at one of the semi-precious stone-cutter's places. Obviously I am not allowed to photograph the work-process nor the safes etc. But I preferred seeing the semi-precious stones etc. in their natural states, and wanted to share these photos with you. You can click on each individual slide to see an enlargement, as usual. To give you a sense of scale, the smallest stone (top centre) shown here is the size of a PC-keyboard and the obsidian and larger ammonite block are each the size of a small table and weigh over 100 kilos!

"No, dear, we are NOT going to ask about prices!"

Copyright ^© Stu Savory on 27th February 2007 at 06:27 CET permalink Email

Jon Jeffryes & his 2002 "Longest Day" Ride

Search Engines bring like-minded people together :-) Jon Jeffryes (UK) wrote
"I've just stumbled across your website/blog after Googling 'The Longest Day'! It seems we have a few things in common. I too am the wrong side of 45 and have been recommended to the producers of Grumpy Old Men by my ever suffering wife. I also share a love of motorcycling and prefer long distances."

A 'longest-day' ride is a decentralised motorcycle tour, with just five formal rules.

• Don't start before sunrise.
• Be home by sunset.
• Go at least 1000 kilometers.
• Document the ride.
• Do notuse the autobahn (=motorway).

Jon Jeffryes and 'The Longest Day'

"I've finally fulfilled a 25 year ambition to complete the Longest Day run,
all 708 miles of it. Mind you, it was on the FJ1200A, not a CBX, but still
worthy of a mention.

In October 1977, (UK) Motorcycle Mechanics Magazine carried 'THE LONGEST
DAY' article. Four seasoned hacks, John Thorpe, Geoff Carless, Charles
Deane and Derek Pickard choose four different bikes; the cream of the
superbikes of 1977; and spent midsummer's day covering their personal best
mileage. Each were free to choose their own route and the choice of bike
was down to the rider.

They all finished, none broke the law, all covered more than six hundred
miles and I, at the tender age of 19 was hooked. Every year since, I've
planned to go, but life always got in the way. Then 2002 came around, the
25th anniversary of the original run... so I just had to do it :-)

The basics were, leave at sun up ca. 4.45am, fit the highest mileage trip in
the hours of daylight, return to the point of departure by sundown, circa
9.31 p.m. The only rules were start and finish on the same bike and apply
the spirit of the law (no major speeding allowed).

So where did I go? Well, to be true to the original riders of 25 years
ago, I followed the southern route covered by John Thorpe who was then the
editor of Motorcycling Monthly Magazine. He covered the original trip on a
(new) Goldwing K2 and it was his route I followed to the letter.

Out from Crawley (Sussex), picking up the M23, onto the M25 and the M4, 
first stop at Leigh services for breakfast and a refuel. Then on to 
Lands End, arriving at 11.40 a.m.,  21 minutes ahead of schedule.

I allowed myself the luxury of 40 minutes for lunch and a walk about.
Gotta say I was mighty disappointed with the place. Not only was it
blowing a gale and pissing down with rain, the place is like Disneyland 
by the sea. It is so commercialised and spoilt, what a shame.

For the return journey, I allowed myself less than 50 miles of motorway,
following the A30 up through Oakhampton and on to Exeter, joining the M27
through to Honiton and switching to the A31/A27 through to Poole and then
Bournmouth.

I stopped for tea and carried on through to Chichester, picking up the
A259 through Bognor Regis, Littlehampton, Worthing, Brighton and then
changing to the A26 at Newhaven. On towards East Grinstead, picking up the
fast and swoopy A275, finally arriving home after sunset at 9.43 p.m. 
(delayed by road works on the outskirts of Crawley!) after 708 miles.

Throughout the trip I used nearly 18 gallons of fuel and averaged c.42mpg.
The only problem was the instrument cluster bolts that had loosened
slightly. Not even the chain needed adjusting, testament to the benefits
of the Electronic autolube system fitted when I first purchased the bike.
No oil was used.

The satisfaction of achieving the ambition that's bubbled away for 25
years is enormous. Apart from the appalling weather (the rain finally
stopped less than a hundred miles from home,) this was one of the most
enjoyable journeys I have ever undertaken. Using a big capacity bike for
the purpose it was designed, eating miles in total comfort and safety,
there's nothing like it.

Next year, I'll take one of the other routes, maybe dinner in Edinburgh
and tea in Wales is on the cards. Anyone care to join me?"

Reproduced here with the express(sic!) permission of the non-blogging original author, Jon Jeffryes.
Well done, Jon. Meanwhile, on the iPod, Canned Heat are playing "On the Road again" :-)

Copyright ^© Stu Savory on 25th February 2007 at 06:25 CET permalink Email

Hotter'n Hell !

Some of my regular blogreaders are Xians (chacun à son goût). Some pleasant and low key about it (e.g. Vic and Liz, both UK) and others more stridently fundamentalist (e.g. Jeb, USA). When I post something patently atheist, Jeb & Co get upset. He has even sent me a hate-filled postcard. So much for forgiveness ;-) Recently he told me that I am surely going to Hell whereas he is going to Heaven, which he seems to think is a better place and quite cool, even without 72 virgins in his case ;-)

Conventional Xian wisdom(sic!) has it that Heaven is a cool place, where you sit about asexually on airy clouds wearing long ( gay?) nightgowns and singing eternal happy hosannas, whereas Hell is a place filled with bodies(sic!) burning in molten sulphur.

Well, Jeb, I have news for you (& the 143,999 others). Heaven is Hotter than Hell, it says so in your bible! And if you don't believe me, here is the proof thereof :-

Revelations 21:8 tells us that Hell is a lake of fire and brimstone (molten sulphur), as mentioned in the conventional Xian wisdom above. Sulphur melts at 115.2° Celsius and boils at 444.6° C and is molten (liquid) between these two temperatures. Now since Damnation is eternal, so is Hell, and hence the molten sulphur is unlikely to be anywhere near its boiling point, lest it evaporate off over time. So we can take a temperature just above the melting point as being being more realistic(sic!) and having less evaporation. Hell is probably about 116° C hot. Could you follow that?

Isiah 30:26 tells us that in Heaven the light of the moon is as the light of the sun; and the light of the sun is seven times the light of seven days on earth. Thus the bible tells us that the brightness in Heaven is 49½ times that on the Earth. Note the factor ½ is to take account of the phases of the moon in a heliocentric model of the solar system. If you still believe in a geocentric model then the number will be 50, not 49½. Since Heaven is eternal too, we know that the temperature of Heaven remains constant, as suggested by the conventional Xian wisdom stated above. Therefore Heaven loses 49½ times as much heat as does the earth. We (physicists) know of the Stefan-Boltzmann fourth-power radiation law, which you can confirm by experiment if you like. God made the universe so that energy is radiated proportionally to the 4th power of the temperature of the radiating body. So the temperature of Heaven must be the temperature of the Earth multiplied by the fourth root of 49½ . OK so far?

The international standard atmosphere has the mean annual temperature at sea level as averaging 15° Celsius. Before we can multiply temperatures we need to calculate the absolute temperature. Since absolute zero is at -273° C, we add the 273 to the 15 getting 288° Kelvin as the mean temperature of the Earth. Truncating the 4th root of 49½ to 2 places we get a multiplication factor of 2.65, and thus the temperature of Heaven is 2.65 * 288 = 763° Kelvin. Now we just subtract 273 to get back into Celsius, and our result is 490° C , which as you can see means that
Heaven is 374° C HOTTER than Hell! So I'm waaaayyy cooler than you, Jeb ;-)

Q.E.D

Based on Ronald DeLorenzo's 1993 article in "Problem Solving for General Chemistry", op. cit.

This blog-entry is best read at 451°F ; meanwhile - on the iPod - AC/DC are playing "Highway to Hell" ;-)

Copyright ^© Stu Savory on 23rd February 2007 at 01:23 CET permalink Email

News from XXXX

I n the Discworld® series of novels by the inimitable Terry Pratchett, XXXX is the name of a faraway continent on the other side of the ...er, hub. XXXX is named after the taste of their bier beer ;-) And it is from XXXX that I got the following eMail from my faithful blogreader Anna Pashen :-

" My partner and I toddled off on Valentine's Day to hear Terry Pratchett speak. It was fantastic but had had virtually no publicity. An old converted chapel entitled 'The Great Hall' with around 50 people in it for Terry to address. He seemed very relaxed and happy to be there and I have to say it was the best Valentine's Day I have had in a good long while :-)

My partner and I both did run downs on it on our respective blogs along with a few pics we snapped. Here are the permalinks to his photoalbum, and to my blog.

Terry did a signing at the end of it and I 'just happened' to have my copy of "Wintersmith" on hand should the occasion arise. He gave it a lovely inscription that will give me the warm fuzzies for years to come.... "

H owever, my uncertainty above about describing the position of XXXX on the Discworld® did remind me of the joke told in the next paragraph. If you take a long strip of paper and give it half a twist before glueing the ends together, you will get a Moebius strip as shown on the left. A Moebius strip has only one side and only one edge! Follow 'em!

Q : Why did the chicken cross the road (e.g. the Las Vegas strip) ?
A : To get to the other side!
Q : And why did the chicken cross the Moebius strip?
A : To get to the other . . . oh, shit, no, what?, oh, wait a minute, buggrit, buggrit...

Copyright ^© Stu Savory on 19th February 2007 at 06:19 CET permalink Email

Six of the Best (and Six of the Worst)

J acqueline (Kansas) wrote: "Judging by your mighty organ piece(sic!), Stu, you seem to have an eclectic taste in music. So to continue punishing us with your schoolboy reminiscences(sp?) why don't you give us Six of the Best? Pieces of 21st century music that is; and preferably as links to YouTube so we can judge them for ourselves. Tell us too what music you just can't take (if any)."

OK, Jacqueline, here are my 6 best links, clicking them opens a separate window.

And here is the kind of vinyl you'd never catch me listening to (my 6 of the worst):-

And for the sake of a meme, let's open this up to other bloggers : so I'm tagging my blogreaders to do this for Jacqueline too and send me your permalinks so that I can list them here :-)

Copyright ^© Stu Savory on 17th February 2007 at 06:17 CET permalink Email

School library duty in the 1950s

Back on January 13th I blogged about the book bus (German: Kreisfahrbücherei, or Bücherbus) which is a mobile library serving the local villages. Young Hamish from Scotland asked me how libraries worked before they had computers (such as the laptops I showed on the January 13th photos). Well, Hamish, I've been racking my remaining brains to remember how I did library duty at school when I was about 11 or 12 (which would date it in the mid 1950's). I think I've remembered it correctly, but I know that there are several librarians who read this blog (Hi Karen, Hi Helen, Hi Carolin), so I'd like to hear their anecdotes if they differ from my memories :-)

Back in the 1950's we junior boys (that's me on the lower right of this picture) were appointed to library duty for the school library. Library users were other pupils and teachers. Each was issued with three library tickets. These were small stiff brown manila pockets (about C7 in size) on the back of which we librarians typed the new users name, class and year. So even at age 11/12 we got to use advanced office technology (a typewriter) :-) I've been hunting and pecking ever since, because we were not taught 10-fingered typing, which I've regretted all my life :-(

A borrower could come into the library (only open at lunchtimes) and borrow up to three books. Reference books bore a red stripe of sticky tape and could only be read there, not borrowed. The borrower would bring the book(s) of his choice to the duty librarian. Each book also had a stiff brown manila pocket stuck on the inside cover. This pocket contained a snug-fitting card (A7?) onto which was type-written (when the book was acquired) the names of the authors, the title, a copy number (if there was more than one copy in the library) and the date acquired by the school. There were sometimes also usage counters handwritten on the card, more about this later.

Why no ISBN number you ask? ISBN numbers were not invented (by W.H.Smiths in the UK) until 1966. Each publisher had their own numbering scheme, or none at all.

The borrower's library card envelope, containing the book-card was stacked back to front into a wooden 'shoe-box' made to size in the school's woodworking class, and sorted by the borrower's name. Why back-to-front? That way we could search by borrower by looking at the backs and search by books by looking at the cards in the front of the cut-off pocket library cards. So much for borrowing books.

When a borrower returned a book, we looked in the name-sorted shoe-box for his library-ticket and extracted the book-card. We checked the book for damage (e.g. scribblings, torn pages etc just by flipping through it. If it was OK, we put the card back in the book's envelope and gave the borrower his card back. If the book was damaged, we put it in a special 'damaged' drawer, confiscated the borrower's library ticket, put the card in it so we could identify later who had damaged what, and informed the borrower he would be held liable for the damage :-(

There were actually three shoe boxes painted different colours, one for this week, one for next week and one for a fortnight hence. At the end of each week we would move these boxes around one position; if there were any envelopes left in the 'new' box, then these were by definition overdue books. So at the school assembly on the following monday, we had to get up next to the headmaster and publicly denounce those boys whose books were overdue. Oh the shame! And when they brought the delayed book back, that particular library card of their three was confiscated and they were fined ( one penny per week, I seem to recollect). The system was thus self-regulatory, three-lates-and-you're-out!

New books were bought by the English teacher who had the budget. Replacements for damaged books too, with a contributory damage-fine from the sinner (who didn't get his library card back, so this system was self-regulatory too). When a new book came in, we typed up two cards. One went in the book for use as described above and the other went onto the stock-list which was a card-index sorted by author.

The reservation system was not as well thought out, it was obviously a later add-on. If the book you wanted was not on the shelves (sorted alphabetically by author) you could reserve it for when it came back. We librarians would then put a pencilmark on the card in the card-index. When a book was returned, we could check if it had been requested and if so put it in a special 'requested' drawer. It was up to the borrower to ask on a weekly basis if the book had come back. If so, it would be issued as usual and the pencil-mark rubbed out of the card-index.

The disadvantage of this reservation system happened when several people wanted to reserve the same book. Then whoever re-asked for it first after it was returned got it. Certainly not first-come first-served :-( The system was later refined so that boy's names were pencilled on the index-card to ensure first-come first-served. Also the maximum length of the queue was recorded there so that we could tell the English teacher when we thought it advisable to buy an additional copy :-)

Our duty-librarian's desk was at the sole door, as a measure against books being 'stolen' by boys who had run out of library tickets. At the end of each term there was an inventory made (with as many boys as possible participating). They counted the number of date stamps on the 'return-by' sheets and wrote this count in the card index. Then a report was produced, and even also sorted manually by usage frequency, so that the teachers (and school governors and even interested parents) could get an idea of what was being read and what was not.

The catalogue cards were also edge-notch coded, to tag them by subject matter. So here we were using tagging in the mid-1950's. Get that, you Web 2.0 fans! We could use several long knitting needles to select logical subsets of the books for special reports (e.g. all geography books, or all biology books, or books covering both geography AND biology).

Of course we duty-librarians cheated :) When a new book came in which interested us there was a short delay until it appeared on the shelves, we were keeping ahead of the class ;-) This was especially interesting for the 'censored' books. The English teacher would put a blue(sic!) sticker inside these books and write an age below which it was NOT to be read. So you couldn't read e.g. Somerset Maugham's Cakes and Ale until you were 15 (the porno/censorship trials about Lady Chatterley's Lover did not take place until 1960).

All in all the system worked well within the closed environment of a school. And it trained some of us to become burocrats (=bureaucrats for you, Doug). It certainly gave ME a feeling for business processes and systems design later in life. Carpe diem!

Copyright ^© Stu Savory on 15th February 2007 at 06:15 CET permalink Email

For the Missus, away in far Alaska today . . .

Robert Mannyng of Brunne (1269-1340) wrote this 700 years ago; it is still true :-)

NO thyng ys to man so dere 
As wommanys love in gode manere. 
A gode womman is mannys blys, 
There her love right and stedfast ys. 
There ys no solas under hevene 
Of alle that a man may nevene 
That shulde a man so moche glew 
As a gode womman that loveth true. 
Ne derer is none in Goddis hurde 
Than a chaste womman with lovely worde.

Copyright ^© Stu Savory on 14th February 2007 at 06:14 CET permalink Email

Welsh Letters

A Welsh lady who reads this blog has sent me a postcard from the village of Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch, which probably explains the non-standard aspect ratio of the postcard, more like a french letter than a welsh¹ postcard ;-) Thanks, Mary. We visited there in 2001, I really like the way the station platform sign has a pronunciation guide to help US tourists :-)

Mary has a maths² question. She knows the rules for testing for divisibility by three: "A number is divisible by 3 if the sum of its digits is too", but wants to know WHY?

Well, Mary, let's take an arbitrary-length number whose digits are ABCD in this example. The value of this number is thus 1000*A + 100*B + 10*C + D, and the sum of its digits is A+B+C+D. Now let's calculate the difference by subtraction as :- 999*A + 99*B + 9*C, and factorise this to 3*3*(111*A + 11*B + C). And so we see that the difference is divisible by three. This implies that the number ABCD has the same remainder when divided by three as does A+B+C+D. Zero when divisible by 3. And since our example ABCD was chosen arbitrarily, the divisibility rule is always valid.

Sara (from Rchyduchaf, near Laka Bala) whom I met in 2002 sent me this unusual wedding photo. OOPS! I guess the groom will have some serious explaining to do ;-)

Thanks also to Peter - who knows I am a Bulldog fan - and who gave me a bright red foam-rubber zarf to keep my coffee longer warm so that I might blog more and longer trip reports (hint! hint!). You know what, Peter ? It keeps the beer cold too;-)

No thanks however to the postal services between Swansea (Wales) and here. The pound of cake which Liz promised me still hasn't arrived. Maybe the P.O. security forces classified it as a biological terror weapon before scoffing it themselves ? :-(

Finally, Huw has asked me to update the Sudoku in the right sidebar. 'Tis done sir :)

¹ : Meanwhile, on the iPod, I am listening to the 1994 Last Night of the Proms, containing "Rule Britannia" as sung by Bryn Terfel, who surprised us all by singing the third verse in Welsh ;-)

² : "You know, I don't think Math is a science. I think it's a religion. All these equations are like miracles: you take two numbers and add them, and they magically become one new number! No one can say how it happens. You either believe it or you don't!" I thought you'd like that quote too, Liz ;-)

Copyright ^© Stu Savory on 9th February 2007 at 06:09 CET permalink Email

A bird in the hand...is worth two in the bush

This is my friend Markus with his favourite eagle, Ares, about to go hunting.

After my article last saturday about the bird-watching 'scope several of you wanted some bird photos. Dave (USA) is just taking up birdwatching and wanted to know more about photography; the best bet is to follow the digiscoping link for serious advice, I just use the scope discussed last saturday when taking the dog for a walk for casual nature observation :-) The photo above of Markus and Ares was taken close up while Ares was on the leash and on Markus's wrist. Now Ares can get moody at times and this is when you need to watch for your finger and even for your nose ;-) Usually Ares is fed every day but friday, 'cos saturdays they go hunting :-)

Mohammed (Dubai) is into falconry and asked if I had any photos of hunting falcons, sorry man, no, but this is the best alternative I have :-) Neil (UK) wants a photo of my favourite bird. With Valentine's day approaching I have to give him this photo of the missus, or were you referring to the aerobatic or the plain old feathered variety?

Young Hamish (Scotland) asks me to explain the numbers on telescopes and also on binoculars, plus why do I refer to one as a day-glass and another as a night-glass? Dave asked a similar question, so here goes :-

With numbers like 15x50, the number 50 is the aperture of the main lens in millimetres and 15x is the magnification. But magnification is not everything. The larger the aperture the more light gathered, so night glasses mostly have larger apertures than day glasses. Divide the aperture (eg 50mm) by the magnification (e.g. 15x) to get the exit pupil size (50/15=3.33mm). This needs to match the size of your eye pupil under the seeing conditions you (will) have. On a sunny day your pupil will be only 2mm across but at dawn/dusk it will be 7 or 8mm, which is why I talked about day and/or night glasses. Thus an 8x20 foldable mini-binocular whilst very light only gives an 20/8=2.5 mm exit pupil and so is only suitable for bright daylight. A glass of 7x56 has 56/7=8mm exit pupil and so is called a night or twilight glass. But of course, the bigger the aperture, the heavier the binoculars will be to cart around :-(

With magnification, you might think : the more, the merrier. That said, the question is really "What can you hold steady"? Well, as an archer, I can hold my bow hand (left) steady enough to hit the proverbial William Tell apple at 20 yards almost every time and hit a target the size of a man's chest at 100 yards almost as often too. So this means I can (just) hold a 15x magnification scope single-handedly steady enough to be see-able. You, dear reader, need to experiment. Nigh on everyone can hold the 7x and 8x binoculars. Go to your local optical store and try out 10x and 12x to see what YOU can hold. Most people max out at 10x. Beyond that they need a tripod ; more stuff to cart about :-( Blogreaders, I don't know whether you wear spectacles as I do, if so you need to consider eye-relief, meaning how far the eye is away from the eyepiece. Spec-wearers need more eye relief. That answer your question, Hamish?
And yes, my 15x50 monocular does have a tripod screwhole should it be needed :-)

But to get back to Ares. Let me tell you - and Markus - an urban legend about his name. Ares is the name of the Greek god of war (not many people know that) , whereas Mars is the name of the Roman god of war [more people know that, even more think it is just a bar of chocolate, best eaten deep-fried :-( ]. When Masterfoods (who also make Snickers, Bounty, M&M's and Maltesers) were looking for a name for a big brown sticky chocolate bar, it was a tossup between Mars and Ares. Mars won out when the PR man misspelled it MASR and the name-choosing committee realised that if this kind of typo happened to Ares, it might be unfortunate for their big brown sticky ... um, er, Ares ;-) Urban legend as I say :-) Actually Masterfoods are to be commended as they have recently decided as a public health contribution to stop aiming advertising at children under 12. Very good, Masterfoods, though long overdue !

Copyright ^© Stu Savory on 7th February 2007 at 06:07 CET permalink Email

Eratosthenes' tale ; a fictionalisation.

And so it came that on midsummer's morn I was at the marketplace and did talk to a merchant with a newly arrived caravan. Whence came he, I did ask, and he told me of Syrene^** whence comes nothing of interest to learned men save, he said, that at midsummer's noon the sun can be seen shining up from the wells. How 'tis here? he did ask. I knew not.

So we did hold a stone on a string to get a plumbline and placed a rod the height of a man into the sand according to the plumbline (such as are used to make wells). And at noon the shadow of the rod was as the three middle knuckles of my right hand, and so the sun would not have shone up from the wells of Alexandria :-(

Thinking that evening of the Greek geometers I did realise I now knew to deduce the height of the sun, which would surely please my lord Ptolemy! For the angle of the shadow unto the rod in the sand is like the angle of an unknown straight way to Syrene is unto the height of the sun. So I ran to the tents of his caravan and did wake the caravaner merchant and demand a count of the length of the way to Syrene. Alas, he knew not :-( And yet, it is but 50 days travel by caravan of many camels, he said.

Now caravan masters tell us that a caravan travels about 100 stadia^*** each day, sometimes more, sometimes less. And so Syrene must be 5000 stadia from Alexandria. Excited, I measured the count of my three-knuckles along the height of the rod appearing out of the sand. There are 50 three-knuckles to the height of a man (the visible length of my rod). And so the height of the sun must be 50 times 5000 = 250,000 stadia! Using that same rod I had measured the angle of the width of the sun scarcely a week gone by, and so, knowing the height of the sun we now did know the size of the sun also. Thus deduced, we did get mighty drunk (on the Graecian wine of a navigating merchant who sails to far Athens), to have learned two unknowns within a single week [and the sinking of the Roman fleet, 284 ships] :-)

But the navigator hearing I knew all things (well, many) asked why things get smaller as he sails away from them,even the mighty cities of Alexandria and Athens. And so I did tell him he is seeing the angles that get smaller when he is further away, for neither men nor cities do change their size when he sails away. But he tells me the cities, and other ships, do sink into the waters when he sails away from them and rise again from the waters when he returns. And yet I know that this is not so, for no-one drowns just because the navigator - or indeed any navigator - has sailed away.

A nd after more and deeper thought (and more Graecian wine) I drew a picture in the sand and mused that if the world were a circle, like the little hole made by my rod or the wall of the well, then he would not see the cities nor other ships until they were close. And then they would appear to rise from the waves and yet have always been dry!

But the navigator said that cannot be so, for the growing and the rising of the cities is ever so, whether he cometh from north or east or west.

"Then it must be that the world is a ball!, I cried drunkenly. But the navigator refuted that if that be so, then sometimes he is nearer the sun and sometimes further from it, and yet it does not change in size.

T hen the sun must be very far away indeed and the world small. Indeed I cannot now know the height of the sun, but I now know the size of the world! For by my previous deduction, surely the world is a ball with a circumference of 250,000 stades" ^**** I deduced triumphantly. For surely, the angle between the light of the far sun and my plumblined rod in the sands of Alexandria is like unto the angle at the centre of the circle drawn by the 5000 stadia between Syrene and Alexandria. And we did drink the rest of the Graecian wine for the might of our deductions and for the knowing of the size of the Earth :-)

But the Navigator was still with wonder, for he knew he had seen but a sixtieth of it.

And so, dear blogreader, when you travel this fair world, think of Eratosthenes in 255 BC, who knew that the world is round and calculated the size of the Earth. And curse the vandals who burned down the library at Alexandria, putting us back 1700 years :( Curse too the One True Church™ who gave us a millenium of Dark Ages :-(

Let there be Light!

^* : 499 AUC = 255 BC when Eratosthenes also built the first heliocentric Armillary Sphere.

^** : Syrene was where the Assuan high dam on the river Nile is (in Libya) these days .

^*** : There are about ten Greek stadia to a modern mile .

^**** : 250,000 stadia, or 25,000 miles, is a damn good estimate for the size of the Earth, given the imprecision of Eratosthenes' assumptions ;-)

Copyright ^© Stu Savory on 5th February 2007 at 06:05 CET permalink Email

Digiscoping with a 15x50 Pocket Telescope

Although I already own a couple of pairs of binoculars (a chunky 7*50 night glass and a small foldaway 8*20 daytime shirt-pocket glass) I've been looking for something with more magnification but still hand-held. So when I saw this chinese 15*50 monocular on Amazon for under €50 I snapped it up, you can't go far wrong at those prices. 15x magnification is about the most you can hold steady in your hand and the camera-style grippy jacket helps you wrap it into your hand. As it is also small (and light) enough to fit into the pocket of an anorak or parka it is ideal for birdwatching. The feathered variety too ;-)

And because I wanted to give you an impression of the surprisingly good quality, I've taken some digital photos using it. To do this I merely held the monocular in my left hand as shown above and - holding a digicam (6 megapixel Olympus FE-120) in my right hand - pointed the digicam into the eyepiece. I could then use the camera's little monitor to see that I was aiming correctly. So all the photos below are hand-held!

To the naked eye the birdfeed ten yards away in the back garden looks like this (photo scale 1:1 when you use the 800*600 screen resolution for which this blog is designed). With the digicam zoom set to wide-angle (i.e. a magnification of 0.7) the 1:1 view through the monocular looks like this (15*0.7 = 10x magnification) :-

So as you can see it is a good choice for bird-watching. Now let me show you some more extreme examples. The panoramically trimmed photo here is again 1:1 what the eye sees from our terrace. You might (just!) be able to see that the yellow ring contains a (man-sized!) pile of cut wood a half a mile away and that the red ring contains a tree about a mile away. Don't strain your eyes, use the pocket telescope!

With the camera's zoom set to 1:1 you get some vignetting (photo shown at 10% of real size), but each log in the woodpile in the yellow ring is clearly visible at ½ mile:

And at the absolute limit, with the camera's optical zoom maxed to 2:1 (giving a total magnification of 15*2 = 30x ) this hand-held shot of the tree shown above in the red-ring (which is a mile away) will let you (just) see finger-thick twigs at the top of the tree. Not bad quality for fifty Euros, don't you agree? Well made, China :-)

As I mentioned above, I just wanted something which would fit in a coat pocket and this is ideal. However, it seems there are people who make a hobby of doing this, it is called digiscoping. They use $1500(!) refractor telescopes of upto 75x magnification, upto 80mm aperture and use a tripod mount to keep the scope steady. There are adapters available to attach the usual digicams to the eyepieces and so they can get some magnificent photos. But I didn't want to have to carry all that gear (tripod, 30cm telescope, together weighing several Kg) so I'm happy with my €50 compromise :-)

Copyright ^© Stu Savory on 3rd February 2007 at 06:03 CET permalink Email

Around and Around : 50 years of Wankelling

The Wankel cycle is a four-stroke cycle : suck, press, bang, push. The rotor has a constant diameter. As one of its 'corners' comes past the intake pipe it acts as an opening valve, the volume above the rotor increased and the petrol/air mixture (shown in light blue in the animation) is sucked in from the intake pipe (the top one).

As the next 'corner' comes past the intake pipe the intake valve is closed for this lobe of the rotor (and opened for the next one) and the mixture (now shown in a darker blue in the animation) is pressed together by the decreasing volume as the rotor turns towards the sparking plug. The mixture is then ignited (goes bang) and expands, forcing the rotor around as the hot (red) gas expands. As the 'corner' comes past the exhaust port (opening the exhaust valve) the turning rotor pushes the exhaust (pink) out the lower port.

You can see this happening in all three sectors of the rotor, each 4-stroke cycle takes one revolution of the rotor and the three sectors fire 120° apart. The engine thus fires three times per revolution rather than once every second revolution in a single-piston engine, and so a single-rotor Wankel engine fires like an in-line six. Twin-rotor Wankel engines (eg Norton or Mazda) fire like a 12-cylinder piston engine. Smooooth!

Note that there is no valve gear, no camshaft, no cams (for the tuners to regrind), and indeed no crankshaft. The Wankel engine runs very smoothly, revs high (no fear of valve-bounce) but consumes disproportionately much fuel :-(

Initially there were also problems with the blade-shaped seals at each 'corner' of the rotor and the engine got a bad reputation for reliability and so never achieved the breakthrough which it deserved :-( Aside from NSU who used it in various cars from the Prinz to the RO80, the only other manufacturer using it regularly is Mazda, whose Renesis engine powers their RX-8 sports car.

Because a Wankel engine is very light (50% of a reciprocating engine) it was also attractive to motorcycle manufacturers. There was a Wankel motorcycle built in Germany by Herkules, in Holland one by OCR-van Veen, in Japan by Suzuki, and in England several by Norton, none were a breakthrough success. I've seen the racing F1 Wankel-Norton in the Isle of Man and the sound of it going through the Bungalow (where I was marshalling that year) had to be heard to be believed. Thanks, Felix :-)

Copyright ^© Stu Savory on 1st February 2007 at 06:01 CET permalink Email