Of Wheels, Grooves and Flanges
"A flange is an external or internal ridge, or rim.... flanged wheels are wheels with a flange on one side to keep the wheels from running off the rails" - Wiki
"A pulley may ... have a groove between two flanges around its circumference." - Wiki
A bit from the Stephen Jay Gould essay "Lucy on the Earth in Stasis":
Alfred, Lord Tennyson, wrote in 'Locksley Hall, the most famous of all Victorian lines about the inevitability of change: " Let the great world spin forever down the ringing grooves of change!"... Tennyson himself later wrote that his striking, though peculiar metaphor for change (both visual and aural) rose from a misperception during his own first journey by rail: "When I went by the first train from Liverpool to Manchester (1830), I thought that the wheels ran in a groove. It was a black night and there was such a vast crowd round the train at the station that we could not see the wheels. Then I made this line."
Let me add: Although it wouldn't be much of a consolation to his spirit, Tennyson has never been - and never will be - short of company. Admittedly, there won't be many who think train wheels run in a groove like he did but another misconception, one that merely turns his on its head, is very widely held. Indeed, billions of train travelers (more precisely, the overwhelming majority of those who ever knew trains and cared to think of such matters) have thought and still think that a train's wheel is shaped like a pulley that grips the rail with its own groove (and that it is the rail that runs thru the grooves around the train's wheels). I myself, a keen train traveler for half a life, belonged in this group till just a few months back.
Since I got disabused of this howler of a notion(*) (I won't get into how it happened), I seldom miss a chance to ask people to draw the vertical section thru both the wheel-centers of a train wheel-and-axle set as it sits on a pair of rails'. To this day, only two among those I challenged did it okay without any prompting - Pop (he continues to stump me; and to really rub it in, he claims to have figured this thing out while at school!) and a lone college student from a batch of nearly 100.
On something else: Y'day (Feb 27th) night, I saw a big flash in the south-western sky and thought it was some routine fireworks display at some local fest. Today's papers have gone to town about a fireball that streaked across the sky around that very time and was seen pretty over a wide swathe of central Kerala. Many claimed to have heard a loud rumble and seen windows trembling. I just looked up the short note 'The false explosion of a Bolide' in my old copy of 'Physics for Entertainment'. Yakov Perelman's explanation of this strange supersonic phenomenon (written long before supersonic aircraft were made) perfectly fits the description of yesterday's celestial show as given by most eyewitnesses. Aside: I now have a sneaking doubt - whether the flash that I saw was just an 'amittu' going off!
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(*) it verily looks nothing less than a howler to me - for it is so obvious that if each train wheel had two flanges that together gripped the rail, the train simply can't move from one track to the other at a join.
"A pulley may ... have a groove between two flanges around its circumference." - Wiki
A bit from the Stephen Jay Gould essay "Lucy on the Earth in Stasis":
Alfred, Lord Tennyson, wrote in 'Locksley Hall, the most famous of all Victorian lines about the inevitability of change: " Let the great world spin forever down the ringing grooves of change!"... Tennyson himself later wrote that his striking, though peculiar metaphor for change (both visual and aural) rose from a misperception during his own first journey by rail: "When I went by the first train from Liverpool to Manchester (1830), I thought that the wheels ran in a groove. It was a black night and there was such a vast crowd round the train at the station that we could not see the wheels. Then I made this line."
Let me add: Although it wouldn't be much of a consolation to his spirit, Tennyson has never been - and never will be - short of company. Admittedly, there won't be many who think train wheels run in a groove like he did but another misconception, one that merely turns his on its head, is very widely held. Indeed, billions of train travelers (more precisely, the overwhelming majority of those who ever knew trains and cared to think of such matters) have thought and still think that a train's wheel is shaped like a pulley that grips the rail with its own groove (and that it is the rail that runs thru the grooves around the train's wheels). I myself, a keen train traveler for half a life, belonged in this group till just a few months back.
Since I got disabused of this howler of a notion(*) (I won't get into how it happened), I seldom miss a chance to ask people to draw the vertical section thru both the wheel-centers of a train wheel-and-axle set as it sits on a pair of rails'. To this day, only two among those I challenged did it okay without any prompting - Pop (he continues to stump me; and to really rub it in, he claims to have figured this thing out while at school!) and a lone college student from a batch of nearly 100.
On something else: Y'day (Feb 27th) night, I saw a big flash in the south-western sky and thought it was some routine fireworks display at some local fest. Today's papers have gone to town about a fireball that streaked across the sky around that very time and was seen pretty over a wide swathe of central Kerala. Many claimed to have heard a loud rumble and seen windows trembling. I just looked up the short note 'The false explosion of a Bolide' in my old copy of 'Physics for Entertainment'. Yakov Perelman's explanation of this strange supersonic phenomenon (written long before supersonic aircraft were made) perfectly fits the description of yesterday's celestial show as given by most eyewitnesses. Aside: I now have a sneaking doubt - whether the flash that I saw was just an 'amittu' going off!
-----------------
(*) it verily looks nothing less than a howler to me - for it is so obvious that if each train wheel had two flanges that together gripped the rail, the train simply can't move from one track to the other at a join.
posted by R.Nandakumar @ 11:12 PM
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