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Coin Shaving?

08/12/2009 2:33 PM

A reply for JohnDG

Rumor has the Royal family is a bit tight for money nowadays (something about investing in Scottish banks) and they decided to pick up a little extra by minting a seven sided coin, the 50p. Here it is

Now, it has the property of having a constant width (let's call that w), so it works in slot machines, pay phones, and so on. The surface area A would normally be πd if it were round. How much did they save by going to this little bugger?

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#1

Re: Coin Shaving?

08/12/2009 2:47 PM

By my calculations, they are using approx 87% of the material (this does not take into account the slight radius on the "Flat" sides, as my calculation is based upon a mathematically perfect 7 sided coin). Soo... i suppose after you factor in the non-flatness (for lack of better words) of the coin you might be looking at 90-93% of the material needed to make the 7 sided coin VS. The round coin. A 10% savings when factored into the vast quantity of coins produced could wind up to be quite a bit of savings...... But why a 7 sided coin???

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#2

Re: Coin Shaving?

08/12/2009 2:49 PM

Hello TVP45:

Not enough, I wonder what's going to happen in the few years when those sharp edges ware flat, and they start jamming coin mechanisms. Governments are the same all over the world, they try and reinvent the wheel. But hey that's just my two cents worth.

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#7
In reply to #2

Re: Coin Shaving?

08/12/2009 7:42 PM

"what's going to happen in the few years when those sharp edges wear flat ..."

50p coins have been around (but not round) for 40 years now.

http://www.royalmint.com/Corporate/MintageFigures/circulating_coins.aspx

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#17
In reply to #7

Re: Coin Shaving?

08/13/2009 7:14 AM

Hello John:

Now I'm confused, but I'm generally that way. Looking at the link it seems like they were only released last year for general circulation. Your vending machines must not be as picky as the ones here in the US.

Of course nowadays they're generally taking bills which is more practical sense our largest coin in general circulation is $.25 (larger denominations but you hardly ever see them) and you can't get much for a quarter nowadays.

Off this topic I thought about you the other day when I upgraded to a N router, saw some really nice high gain antennas/adapter down at the computer supply that would probably solve your range problem, for your second office.

You know the one Across the street.

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#19
In reply to #17

Re: Coin Shaving?

08/13/2009 7:32 AM

From the link, they were first issued in 1969 (188,400,000 coins, with Britannia on the reverse as per the pic in TVP45's OP).

Re the wi-fi link, I've been working away from home (and not just across the road !) most of the time for the past 10 months or so, so the need for the "2nd office" has been less pressing.

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#3

Re: Coin Shaving?

08/12/2009 2:57 PM

It seems the best way to find the exact material savings of this coin is by water displacement rather than rough mathematical interpretation. I suppose they may save money in the long run, maybe this is a smart long-term investment?

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#4
In reply to #3

Re: Coin Shaving?

08/12/2009 3:01 PM

My mathematical calculation is based on a largely scaled up version of both coins in Solidworks. Solidworks has calculated the volumes of both coins, and the only math I did (i took it back to elementary school for this one) was dividing the small number into the big number to come up with .87133.

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#11
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Re: Coin Shaving?

08/13/2009 4:53 AM

Surely you divided the big number into the small number to get 0.87133 ???

Dividing the small number into the big number would have resulted in a number larger than unity (approximately 1.14767).

I'm shocked that no other CR4er picked you up on this....

did you fail elementary school ? <ducks>

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#27
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Re: Coin Shaving?

08/13/2009 11:13 AM

Ohhhh my... Perhaps i did fail elementary school... or i should have!

Well... my poor attempt at humor has once again backfired in my face.

Thanks for catching that one.

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#28
In reply to #3

Re: Coin Shaving?

08/16/2009 5:50 AM

Hang on - if you have the two coins to compare, then isn't water displacement a slightly medieval way to go about it... wouldn't it be better to just stick them on a set of good quality scales? Presumably they're made of the same material, and we just want to know the amount of material in each coin - and the ratio of masses will be the ratio of costs-per-coin.

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#30
In reply to #28

Re: Coin Shaving?

08/16/2009 10:55 AM

Just because it is an old method doesn't mean that it isn't just as accurate as other methods.

Everyone was doing calculations, so I presented an alternative to mathematical calculations.

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#31
In reply to #30

Re: Coin Shaving?

08/16/2009 11:26 AM

Don't get me wrong - I thought it was a great idea (I should have put a after medieval!). I just had a giggle at the concept of the Queen setting up some tiny bowls of water and dropping coins in to see how much she'd save - seemed a bit like alchemy when you think how they would do things at the mint.

But you're right, with some good volumetric equipment you could measure extrmely accurately and get a figure for the metal's density into the bargain as well. More power to Archimedes I say!

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#37
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Re: Coin Shaving?

08/16/2009 10:04 PM

Well, you know that the queen had someone ELSE do the dropping of the coin in water

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#5

Re: Coin Shaving?

08/12/2009 3:20 PM

How much would they save by punching / drilling a hole into it?

and it can also be used as a washer.

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#6
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Re: Coin Shaving?

08/12/2009 4:02 PM

like these?

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#8

Re: Coin Shaving?

08/12/2009 11:21 PM

How much did they save? Ask the royal leprachaun. Who has clearly been deprived of his normal clippings...

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#9

Re: Coin Shaving?

08/13/2009 12:17 AM

RVZ717's calculation compares the area of a regular heptagon (flat sides) to that of its circumscribed circle. The coin shares the same vertices as the heptagon, but its bulges give it 93.4 percent of the area of the circumscribing circle. Still, those shavings add up! (All of these objects can be drawn as CAD polylines and listed for comparing their areas.)

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#10

Re: Coin Shaving?

08/13/2009 3:55 AM

The 20p is the same shape, though smaller. It is also exactly 2/5 the weight of the 50p coin.

The relationship between value and weight goes back a long time. In the "silver" coinage, today's 10p is twice the weight of the 5p. The size of both those coins was reduced of late so as to disconnect them from the earlier pre-decimalisation florin (2/-) and shilling (1/-) that were the same size, weight and value as the post-decimalised 10p and 5p. And in the decimalised bronze coinage, the 2p is twice the weight of the 1p, which itself is twice the weight of the now-withdrawn 1/2p

Prior to decimalisation on 14th February 1971, the "silver" half crown (2/6d) was 5/4 the weight of the florin (2/-), which was twice the weight of the shilling (1/-), which was twice the weight of the sixpence (6d). There was also a "silver" 3d piece, referred to by the elders in the population as the "silver joey", which was half the weight of the sixpence. Folklore has it that US nationals were easily confused at that time by the non-decimal relationship between the penny, the shilling and the pound, and astounded by the weight of them, being rather more than their equivalent value in US dollars and cents coinage.

The old 3d coin, the "thruppeny bit" in everyday parlance, was the odd one out, being a twelve-sided coin somewhat thicker than the others.

Then back to the old penny (1d), ha'penny (1/2d) and farthing (1/4d) which were all weight-related in direct proportion to their face value.

The reason for the weight relationship is so that banks, post offices and other coin-handling operations could value large quantities of similar coin by its weight, rather than having to count it.

Pre-decimal withdrawn coinage is today a curiosity, valued by coin collectors rather greater than its intrinsic face value, and is another one of those British hobbies that attracts varying degrees of enthusiasm through to fanaticism. There are a number of monthly magazines dedicated to this topic and to philately, with many specialised shops covering both areas.

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#12
In reply to #10

Re: Coin Shaving?

08/13/2009 4:57 AM

Can you lend me a tanner, mate? My suspenders have broken.

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#14
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Re: Coin Shaving?

08/13/2009 6:21 AM

WooooOOOoowwoooo I think that's going to be very lost on our US friends.

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#15
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Re: Coin Shaving?

08/13/2009 6:38 AM

And anyone who wasn't aged over 15 in 1971 ! (Or like me, who heard the tales at her mother's knee - I found new 5p pieces work rather well....)

Our US friends will have to get their UK English - US English dictionaries out first...then worry about the timing.

Tanners were prefered over farthings since they (the tanners) were silver and so didn't mark the skin. Anyone know where the name "tanner" came from?

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#21
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Re: Coin Shaving?

08/13/2009 9:25 AM

Go on do tell....... LOL

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#23
In reply to #21

Re: Coin Shaving?

08/13/2009 10:27 AM

But I don't know why they're called tanners - I was hoping some of you who'd used them could tell me...

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#29
In reply to #21

Re: Coin Shaving?

08/16/2009 9:47 AM

I've still got a handful of them that I kept as momentos.

But I must admit to being old enough to have used them as well as the farthings - remember farthing chews? sweets like fruit salad, blackjacks etc... 4 for a penny.

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#32
In reply to #29

Re: Coin Shaving?

08/16/2009 12:20 PM

Ah, yes, I remember it well ....

.... blackjacks on the way to school .... pressing button B in phone boxes .... those were the days.

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#33
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Re: Coin Shaving?

08/16/2009 5:18 PM

pressing button B in phone boxes

Oh you guys are showing your age !

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#34
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Re: Coin Shaving?

08/16/2009 6:38 PM

I wuz always told "if you've got it - flaunt it"

Or somethin' like that - mumble - bugger! them young'uns 'as gone joyridin' me Zimmer again.

Memo:

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#35
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Re: Coin Shaving?

08/16/2009 6:46 PM

OK, here's the tell ; what is your lots favourite coin of memory ? Mine's the thrupenny bit. That damn thing make me salivate when I see them now. It's the quintisential coin of recent Brit times. I could wax lyrical ( OK, just 'wax' with my literary skills !), about that coin, but what do ye all think ? Name your fave coin !

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#36
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Re: Coin Shaving?

08/16/2009 7:10 PM

I'm swayed by the thrupenny bit:

... but I think the portcullis has turned me off - reminiscent of a prison? .

I'll stick with the farthing.

[Silver thrupenny bits were nice, but AFAIK not legal tender in my time - so I'm not counting them].

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#38
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Re: Coin Shaving?

08/17/2009 3:16 AM

reminiscent of a prison?

You may not be far wrong - bring back a Portcullis at Westminster, it wouldn't be at all out of place !!

I'll stick with the farthing.

Had to read that twice !

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#40
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Re: Coin Shaving?

08/17/2009 6:41 AM

The New Two Pence Piece (you'll still not get my age right ) because it's the same size as the old 1d coin, so it could be used to get a platform ticket at BTM (that one's for PWS).

OR

The coins issued by Esso about the Space Race and Moon Landings...my collection is one short .

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#41
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Re: Coin Shaving?

08/17/2009 7:04 AM

???

BTM Bottom
BTM Betäubungsmittel (German: drugs)
BTM Break The Matrix
BTM Business Technology Management
BTM Best Tuning Memory (Sony)
BTM Behind the Music (VH1)
BTM Bank of Tokyo-Mitsubishi, Ltd.
BTM Bluetooth Module (wireless technology)
BTM Beneath the Massacre (band)
BTM Butte, MT, USA (Airport Code)
BTM Big Thunder Mountain (Disney Theme Parks)
BTM Boys to Men
BTM Benchmark Timing Methodology
BTM Bromotrifluoromethane
BTM Boarding Team
BTM Ballet Theatre of Maryland (Annapolis, MD)
BTM Boarding Team Member
BTM Betäubungsmittelmißbrauch (German: Drug Abuse, used in the police records)
BTM Blame the Media
BTM Basic Transfer Mode
BTM Blood Temperature Monitoring
BTM Baggage Transfer Message
BTM Biotech Monthly (independent research firm)
BTM Baltimore Tattoo Museum
BTM Big Trellis Model
BTM Boat Tail Match (ammunition)
BTM Base TEMPEST Manager
BTM Blast Test Missile
BTM Bout That Money (band)
BTM Burst Transmission Mode
BTM Bell Telephone Number (sic)
BTM Branch Terminal Manager (banking)
BTM Backward Transformation Method
BTM Bearer Transport Node (sic)
BTM Black Top Maintenance
BTM Big Time Mafia (video game; graffiti gang)

Those are from http://acronyms.thefreedictionary.com/BTM

Also found Bradworthy Transport Museum and Bury Transport Museum, which look more promising in this context.

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#42
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Re: Coin Shaving?

08/17/2009 8:09 AM

<sigh>

I said you needed a platform ticket....do you want one more go?

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#43
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Re: Coin Shaving?

08/17/2009 8:11 AM

Ah! Brisole!

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#46
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Re: Coin Shaving?

08/17/2009 8:25 AM

<slap>

Bris-tOLLLLLL I'll 'ave ee know. It'd be a good ideal if ee knew what ee was talkin' abou' wi' pronouncin' my 'ome city & county's name. Up the Robins!!!

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#59
In reply to #46

Re: Coin Shaving?

08/17/2009 12:08 PM

John might have been having a Bisto momment

I've only just noticed, but somewhere along the line that added an 'a';

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#60
In reply to #59

Re: Coin Shaving?

08/17/2009 6:49 PM

I was prob'ly just having a Bistro moment - 'til I got expurgated.

But then I nivar cood spel.

[BTW, Kris - thanks for giving me a get-out, saving my BTM from the Wrath of ER]

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#61
In reply to #60

Re: Coin Shaving?

08/18/2009 2:02 AM

Bristols a word that send my typing completely off track

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#62
In reply to #61

Re: Coin Shaving?

08/18/2009 3:03 AM

DON'T GO THERE !

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#66
In reply to #61

Re: Coin Shaving?

08/20/2009 6:34 AM

Of course with my heritage, I'm a Bristol City fan...up the Robins !!!! (haven't I said that before ???)

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#65
In reply to #60

Re: Coin Shaving?

08/20/2009 6:31 AM

It's the thorns that cause the most damage

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#67
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Re: Coin Shaving?

08/20/2009 6:51 AM

<Ouch!>

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#45
In reply to #42

Re: Coin Shaving?

08/17/2009 8:17 AM

The Sims ? Pulwhari Sharif railway station ??

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#48
In reply to #41

Re: Coin Shaving?

08/17/2009 9:50 AM

Bristol Temple Meads - the terminus of one Isambard Kingdom Brunel's 7ft gauge railway that still runs in 1432mm form from London Paddington. "Brunel's billiard table" - at least the bit east of Swindon was.

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#44
In reply to #40

Re: Coin Shaving?

08/17/2009 8:14 AM

hehehe.....the jigsaw is forming....

I've still got some cool coin collections (a little tatty) from filling stations; vintage cars, animals, and historic figure. Oops, the last one is cards, and without going to the cupboard I'm not sure who issued them.

Which coin are you short of ? There's still a few weeks of car boot sale season left....

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#47
In reply to #44

Re: Coin Shaving?

08/17/2009 8:34 AM

From memory one towards the bottom right of the mounting card. Being more exact would entail a trip into the loft and knowing which box it's in...if it's not still at my parents' house

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#49
In reply to #40

Re: Coin Shaving?

08/17/2009 9:52 AM

Nonononononono!

The 2p is the same size as the old 1/2d. Honest!

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#51
In reply to #49

Re: Coin Shaving?

08/17/2009 9:57 AM

Have you found my marbles over there? I seem to have misplaced them.

Now you've said that, I think we had to buy a 1d piece (for 2p?) to operate the machines. The station recirculated the 1d pieces - cheaper that installing new machines, and a delight for small children....it's all so long ago....

The conversion would seem about right, since £1 = 240d = 100p

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#54
In reply to #51

Re: Coin Shaving?

08/17/2009 10:39 AM

Once upon a time, in a galaxy far, far away, there was a coin sorting centre for a major high street bank that employed layabouts students inbetween terms. Much of their work involved shooting coins out of coin bags onto a table, and throwing out the foreigners and the bent ones prior to loading the rest by the bucket-full into coin sorting and counting machines.

Although the 2p and the old ha'penny were the same size and shape, UK coinage has a distinctive "ring" that is not shared by the coinage of any other nation. One knew instantly whether an odd-bod was in the heap because of the sound. Even ha'pennies and 2ps, although they are the same size and weight, ring differently. So one could carry on with a chat and a leg-pull around the table without looking at what was there and still get it right. Indeed, if one looked too long, all one saw was circles for weeks afterwards....

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#57
In reply to #54

Re: Coin Shaving?

08/17/2009 11:09 AM

That is soooo true....

Reminds me of when I worked at a place with a coffee machine, I was talking to the guy as he emptied the coins out and one fell on the floor and DEFINITELY did not sound right....

We both stopped and picked it up took it into quality control and put it under a microscope.... It was a one shilling bit made from two halfs glued together!!!

A definite forgery....

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#58
In reply to #51

Re: Coin Shaving?

08/17/2009 11:21 AM

.....which is the derivation of the colloquialism "spend a penny".

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#64
In reply to #58

Re: Coin Shaving?

08/20/2009 6:29 AM

I used to be a dab hand at getting into those for free....and then handing the cubicle over to my little sister....people used to get so upset.

I did it as a student at Birmingham New Street...and the attendant came and hammered on the door and yelled abuse. I took a little longer than usual and scuttled out! I always regarded it as a game...

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#52
In reply to #35

Re: Coin Shaving?

08/17/2009 10:01 AM

My favourite is the crown as it was worth a lot of money when I was young.... 5/- or five bob to you young 'uns....

Failing that my favourite would have to be the half-crown.... 2/6d or two and a tanner to the younger ones....

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#53
In reply to #52

Re: Coin Shaving?

08/17/2009 10:18 AM

<...half-crown.... 2/6d or two and a tanner to the younger ones....>

One could get double-egg-and-chips and a cup of tea for 2/6d at one time. <Sigh>

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#55
In reply to #53

Re: Coin Shaving?

08/17/2009 10:43 AM

... or a pint of Best and a packet of crisps ... complete with blue twist of salt ... <Sigh>

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#56
In reply to #55

Re: Coin Shaving?

08/17/2009 10:50 AM

Even nostalgia isn't what it used to be....<sigh>

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#39
In reply to #32

Re: Coin Shaving?

08/17/2009 6:06 AM

pressing button B in phone boxes

I heard about those on the reruns of Paul Temple....what were they for again ?

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#24
In reply to #15

Re: Coin Shaving?

08/13/2009 10:37 AM

Best I could find:

"tanner - sixpence (6d). The slang word 'tanner' meaning sixpence dates from the early 1800s and is derived most probably from Romany gypsy 'tawno' meaning small one, and Italian 'danaro' meaning small change. The 'tanner' slang was later reinforced (Ack L Bamford) via jocular reference to a biblical extract about St Peter lodging with Simon, a tanner (of hides). The biblical text (from Acts chapter 10 verse 6) is: "He (Peter) lodgeth with one Simon a tanner, whose house is by the sea side..", which was construed by jokers as banking transaction instead of a reference to overnight accommodation. Below in more money history Nick Ratnieks suggests the tanner was named after a Master of the Mint of that name. A further suggestion (ack S Kopec) refers to sixpence being connected with pricing in the leather trade. I have no other evidence of this and if anyone has any more detail relating to the derivation of the tanner please send it. An obscure point of nostalgic trivia about the tanner is (thanks J Veitch) a rhyme, from around the mid-1900s, sung to the tune of Rule Britannia: "Rule Brittania, two tanners make a bob, three make eighteen pence and four two bob…" I am informed also since mentioning this here (thanks to the lady from London) who recalls her father signing the rhyme in the 1950s, in which the words 'one-and-sixpence' were used instead of 'eighteen pence'."

The above is from http://www.businessballs.com/moneyslanghistory.htm

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#25
In reply to #24

Re: Coin Shaving?

08/13/2009 10:45 AM

I doff my cap to you, kind sir.

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#63
In reply to #24

Re: Coin Shaving?

08/19/2009 10:24 PM

Interesting - here is another reference from Online Etymology. The dating and the reference to its small size are common to both references.

tanner "sixpence," slang word first recorded 1811, of unknown origin. J.C. Hotten, lexicographer of Victorian slang, thinks it may be from tanner and skin, rhyming slang for "thin," presumably in reference to the smallness of the coin. (Not to be confused with tenner, slang for "ten pound note," which dates from 1861.)

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#13

Re: Coin Shaving?

08/13/2009 6:15 AM

So a saving of just under 6.6% compared to the circumcircle, BUT compared to a coin with the same diameter:-

The "shaving saving" is only just over 1.7%

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#16
In reply to #13

Re: Coin Shaving?

08/13/2009 6:54 AM

Started doing it symbolically, but gave it up (as a waste of time) after:

R = 2√(r2sin2(Θ/2)+(r(1+cos(Θ/2)))2),

... where R and r follow your notation, and Θ = 2π/7

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#18

Re: Coin Shaving?

08/13/2009 7:27 AM

Now, it occured to me last night that, if you roll one of these 50p down an incline, the center of rotation will "wander" about. But, could one make a gear set out of two of these? It would give uneven speeds I think but the shaft distances should be OK. I've just wiped out my hard drive and lost (temporarily, I hope) my CAD programs, so I can't do an accurate model.

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#20
In reply to #18

Re: Coin Shaving?

08/13/2009 7:50 AM

I'm used to men not listening to me, but they usually read what I've written !

The common diameter but wandering centre effect is demonstrated in many of the hands on museums for children (of all ages). The Bristol Exploratory had one, I'm sure the Eureka! has one.

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#22
In reply to #18

Re: Coin Shaving?

08/13/2009 10:03 AM

If you matched 2 identical shapes as gears they would work ok, check out oval gears.

http://www.youtube.com/watch?v=RqDTwP1a6bo

Much more complicated to manufacture but good leverage for special applications.

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#26
In reply to #22

Re: Coin Shaving?

08/13/2009 11:04 AM

Neat. Thanks.

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#50
In reply to #18

Re: Coin Shaving?

08/17/2009 9:55 AM

A cam interlock set, maybe? i.e. shaft B will only rotate while shaft A is stopped in one of seven positions?

BTW: defacing a coin classes as treason, though it's virtually unheard of for someone to be prosecuted for doing it.

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