Clinging to the Past

[John HaineParticipant @johnhaine32865]

Posted by Vic on 20/08/2021 12:50:43:

The influence of imperial measurements is still very much evident today. For some youngsters sheet goods must seem to come in weird sizes like 1220 x 2440, until you look at a tape measure. Also look at socket drives – 1/4”, 3/8”, 1/2” etc. I’m sure it must upset the French. You would have thought the EU would have replaced them with metric sizes by now. 😂

They have. 6.35, 9.5, 12.7 mm.

[not done it yetParticipant @notdoneityet]

1200 x 2400mm is now a common size – buyer beware, if the sheet is required to mend/restore one of the multitude of housing stock built before metric sizing was adopted. Several roof trusses with two-foot centres can soon get out of kelter with metric sheets. A 20mm gap between 1200mm sheets does not leave much left for fixings into ever-thinner section frameworks. 2400mm could drop off the supporting structure at 8’ centres.

Softwood was sold in metric sizes for about ten years while any hardwoods were always sold in imperial units. Don’t know if it is the same now, mind – not bought any hardwood stock for many a year.

[JasonBModerator @jasonb]

I've only really come across 1200 x 2400 on plasterboard and rigid insulation where it suits joists and roof trusses and studs at 400 & 600 cts. You do get a problem if the joists are for a flat roof as then they don't suit the ply decking sheets which like most timber panel products are still 1220 x 2440. or 1220 x 3060. Melamine boards do also come in a much larger format but I try to avoid using them if I can as I can't really manage to handle them but OK for the carcase trade, these are 2070 x 2800 or 2650.

hardwood still mostly comes in imperial nominal sizes but sold measured and sold in metric

Even 1200x 2400 is not in the true sense metric 1000×2000 or 1250 x 2500 would be more in the spirit of things.

[Phil WhitleyParticipant @philwhitley94135]

In my field of electrical engineering, the RCD and MCB and its variants have almost completely ousted the fuse as protection for final sub circuits. Strangely, neither of these devices fails safe and both are electro mechanical devices, containing many electronic components of dubious quality and lifespan, which, the old IEE regulations used to clearly say must never be used as a SOLE means of protection for a final sub circuit.

Today, the old regulations, made by experienced engineers, have been superceded by the new IET regulations, made by equipment manufacturers, and university graduates with no experience whatever. The consumer unit fire, which in my 40 odd years in the trade was completely unheard of, is now becoming so commonplace that the IET has reintroduced metalclad consumer units, and insisted that all incoming cables be sealed with intumescent mastic in order to contain the flames, as they seem to have decided that it is easier than correcting the root cause, which is partly to do with the use of the MCB/RCD as sole means of protection, and partly to do with the poorly made clamp style terminations in the MCB's and consumer units.

The Electrical industry has been going backwards since we started "harmonisation" with Europe, which at the time had atrocious electrical safety standards , and now we are out, it would be a good time to go back to sensible wire colours, and back up the MCB/RCD with an appropriatey rated fuse, and scrap the IET regs as not fit for purpose! Fuses ALWAYS fail safe!

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by Vic on 20/08/2021 12:50:43:

The influence of imperial measurements is still very much evident today. For some youngsters sheet goods must seem to come in weird sizes like 1220 x 2440, until you look at a tape measure. Also look at socket drives – 1/4”, 3/8”, 1/2” etc. I’m sure it must upset the French. You would have thought the EU would have replaced them with metric sizes by now. 😂

I don't see why it should upset the French. For many years they used the pouce (thumb) which was 1/12 of the pied (foot) and very close to the British equivalents. Indeed they still use BSP threads for domestic plumbing fittings, although named according to their approximate thread OD in mm.

Russell

[Brian GParticipant @briang]

Posted by Phil Whitley on 20/08/2021 15:15:18:

… Fuses ALWAYS fail safe!

MCBs have one advantage, it isn't easy for somebody to accidentally (or deliberately) uprate them when resetting after a trip. I can't be the only person to have seen the wrong size fusewire in a box and I know of one box that contained brass bar instead of a cartridge.

Rather than go backward, would it be possible to put a non-replaceable but slower blowing fuse inside each MCB/RCBO so that if they fail to trip, the fuse cuts the power and disables the faulty device?

Brian G

[Phil WhitleyParticipant @philwhitley94135]

Posted by Brian G on 20/08/2021 16:10:20:

Posted by Phil Whitley on 20/08/2021 15:15:18:

… Fuses ALWAYS fail safe!

MCBs have one advantage, it isn't easy for somebody to accidentally (or deliberately) uprate them when resetting after a trip. I can't be the only person to have seen the wrong size fusewire in a box and I know of one box that contained brass bar instead of a cartridge.

Rather than go backward, would it be possible to put a non-replaceable but slower blowing fuse inside each MCB/RCBO so that if they fail to trip, the fuse cuts the power and disables the faulty device?

Brian G

Yes! that is exactly what I am suggesting, keep the MCB/RCD, but have a fuse as well protecting each circuit. Use different sized cartridge fuses so the wrong rating physically will not fit! If a fault occurs now, and an mcb/rcd fails to trip , the next in line protection is the cutout fuse, usually 100amp, which is partially why they catch fire! That and the fact that some bright spark decided it would be ok to make them for ordinary inflammable plastic instead of non flammable phenolic like the older Wylex/Tamlex type of Consumer unit. It is not rocket science, but it seems to be too complex a problem for the IET to solve!

Phil

[Tim StevensParticipant @timstevens64731]

NDIY claims 'It is undoubtedly easier to add and multiply with base 10 numbers'

This is only true if you insist on working only with base 10 numbers. What is true is that working with the system you are used to is easier than any other system. Had evolution blessed us with more, or fewer, digits, we would wonder what on earth was the point of all these decimals. If only we could talk to octopuses.

An example – Shepherds in the old days (in England at least) used to count sheep on their fingers, or on a set of stones swapped from one pocket to another, but their system was based on 20 rather than 10. Go to the market today and you can still hear animals numbered by the score – because for them, it is undoubtedly easier.

Cheers, Tim

[not done it yetParticipant @notdoneityet]

Sorry I was meaning 12 d to the bob and 20 bob to the pound alng with tanners, florins, half crowns, crowns and ten bob notes. Then again, grains, ounces, pounds, stones, cwts, and tons – except that grains are 500/Troy ounce, not avoirdupois that was a weight sytem from France? Messed about since, of course.

Now we have kilobytes with 1024 bytes because octopuses in electronics count in 8,16, etc bits of data.🙂

Hopefully it will all eventually end in decimal metrics – apart from the age-old problem of time – seconds minutes hours, etc.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, I think you'll find that steel sheet and plate still have the same aspect ratio as the old 8 x 4 but now they are 2 x1, 2.5 x 1.25, 3 x 1.5 etc. in all the common metric thicknesses Steel Stock.

Regards Nick.

Edited By Nicholas Farr on 20/08/2021 18:52:44

[oilcanParticipant @oilcan]

isn't the number system in the french language base 20? I wonder if counting sheep is the reason. I believe in England medieval shepherds would have said 'a pimp plus a dick made a bumfit' – no sniggering at the back, it just means 5 + 10 = 15. they had different names for numbers between 1 and 20.

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by oilcan on 20/08/2021 18:54:08:

isn't the number system in the french language base 20?

It's a horrible mixture of tens and twenties, tens up to fifty and twenties up to 100. I still find it difficult after 18 years in France, especially with telephone numbers which are always spoken as pairs of digits from 00 to 99!

Russell

[Michael GilliganParticipant @michaelgilligan61133]

This is not an argument, Tim … just an honest question to which I have never seen a convincing answer.

How did we make the imaginative leap from ‘counting to ten’ on the digits of two hands, to a ‘base 10’ system ?

Counting to ten involves assigning a number to each of the individual digits, and making a binary choice as to whether that digit is OFF or ON … So far so good

But in the base 10 system we use Zero [closed fist] and nine numbers … so what is the tenth digit used for ?

… is it flashed-up as a carry flag ? … or what ?

Grateful if you, or anyone else, could explain.

MichaelG.

Edited By Michael Gilligan on 20/08/2021 19:29:34

[MeunierParticipant @meunier]

Posted by oilcan on 20/08/2021 18:54:08:

isn't the number system in the french language base 20? I wonder if counting sheep is the reason. I believe in England medieval shepherds would have said 'a pimp plus a dick made a bumfit' – no sniggering at the back, it just means 5 + 10 = 15. they had different names for numbers between 1 and 20.

No, French is base ten but constructs are used as in English, e.g the age of man is three-score years and ten
four and twenty blackbirds baked in a pie and from memory, not certain of source – maybe Kipling(Rudyard, not Mr ),Rhodes or Baden_Powell – there are six-and-ninety ways of setting land boundaries.

Tim – was mentioned in Welsh lessons some forty years ago – hugain=twenty (pronounced 'eegine ) as the shepherd counting system of old. (fingers and toes, a built-in abacus )

DaveD

Edited By Meunier on 20/08/2021 19:38:12

[Howard LewisParticipant @howardlewis46836]

Someone said that those who ignore history are condemned to repeat the mistakes.

Because basic arithmetic seems to have been omitted from the syllabus, folk now have difficulty working out pulley sizes to give a required speed, from a motor of known speed. Similarly calculating the gear ratio between Mandrel and a Leadscrew of known pitch. Cutting a screw thread of the required pitch seems to be difficult, (Except, perhaps for the geriatrics among us, who had such things drummed into our heads at an early age )..

Remember "Times Tables"? Meccano taught me multiples of 19, as well as calculating simple and compound pulley and sprocket ratios.

So fractions are still necessary to find the gears to reduce a speed to says 5/6 of its value, A 35T gear driving a 42T (if one is available ) is one possibility, or a 75T driving a 90T?. Reversed, any of those should allow a 2.5 mm pitch to be produced on a lathe with a 3 mm pitch Leadscrew.. Compounded with a 3:1 reduction the original reduction would allow a 8 tpi Leadscrew to produce a 20 tpi thread.

Just fractions really.

Ask Brian Wood!

An understanding of the basics makes the complicated more understandable.

Understanding the principles makes anything more comprehensible.

Despite spending lots of time with fuel injection equipment, to me, microns are less easy to visualise than thous.

An average human hair is more easily visualised as being 0.005" than 127 microns.

Again, using whatever system / measurement is most easily applicable. Who wants to measure their car's fuel consumption in dimensions of 1.6 Km per 277 cubic inches?

Again, horses for courses

Howard

[Tim StevensParticipant @timstevens64731]

Michael G asks about the invention of numbering systems. I don't think I have the answer for the exact question he asks, but I do know that it took a long time for the benefits of having a character for zero were realised. Neither the ancient Greeks nor the Romans, nor the pyramid builders, or the Sumerian accountants, all of whom had various goes at improvements. I think zero was first an idea from India or thereabouts, and it came to Europe along with their use of dedicated squiggles rather than using existing letters. These were brought to us by the Arabs, and so in our helpful way we call them Arabic numbers. But we played about with them for about 200 years before they were recognisable to modern eyes.

And while the Ministry advises that car number plates must use Arabic numbers and Roman letters, if you take them literally (ho ho) you will attract the attention of plod.

Hope that helps – my tea is ready.

Cheers, Tim

[pgk pgkParticipant @pgkpgk17461]

Early math didn't require a zero for the obvious reason that the math wasn't needed to any base. Addition using Roman numerals is hard enough and multiplication or division would have to be by repeat addition or subtraction. The reality is that sums were carried out on an Abacus where you can use any practical number of beads on each rail that suits you so long as you're consistent. The way numbers are written was just to document the result.
Babylonial base 60 would be easy enough on an abacus so long as coloured beads subdivided that number.
It's known that there were look-up tables for some of the commonly needed proportions (fractions)

pgk

[Frances IoMParticipant @francesiom58905]

I know I have recommended this before but Seb Falk in “The Light Ages” shows how a counting board or abacus made even division of Roman Numeral relatively easy (see pp 39-41) but obviously not a easy as Hindu-Arabic notation

[Tim StevensParticipant @timstevens64731]

But – pgk pgk – the Romans clearly used a system with a base – notably they counted in fives (a handful) and tens (two ditto). D stands for Decem = 10, and V is the outstretched fingers of one hand = 5.. So, they had a base but no zero – neither a word nor a symbol for it until well into the middle ages.

I don't know how the counting system worked in Babylon – but I'm sure that they didn't count sheep (or camels) in sixties. My guess is that they had worked out that 60 was a very useful number you could divide by 2, 3, 4, 5, 6, 10, 12 … which solved one problem – dividing up an inheritance – and became the basis for dividing the heavens and the hours – and probably lots of other stuff, now taken over, along with barleycorns and pennyweights, following the French, scientific, industrial, (etc) revolutions.

And while the abacus was used in Europe, we had our own system based on a sort of draughts or chequers board. Not for nothing is the chap who looks after our money called the Chancellor of the Exchequer.

And why 21 shillings in a Guinea – this will be next weeks lesson. Perhaps, too, why IV is four except on clocks.

Cheers, Tim

[SillyOldDufferModerator @sillyoldduffer]

Imperial measure popping up in new kit shows technologies are rarely replaced outright, because there are always edge cases where old ways remain competitive. A few examples of Losers and their nemesis:

• Canals versus Railways (except Suez and Panama are both doing well)
• Railways versus Roads (except heavy goods moved long distance overland and mass commuter traffic)
• Steam versus Internal combustion (except for Nuclear Power Plant)
• Long distance Railways versus Aircraft (except for heavy goods)
• Sail versus steam, (except for recreational use)
• Wrought Iron versus Steel (apart from decorative blacksmithing)
• Steam versus Diesel Locomotives (except for heritage railways)
• Diesel Locomotives versus Electric (except where traffic is too low to pay for the infrastructure.)
• Pencil and paper versus CAD (except for small or amateur work)
• Cast-iron versus plastic (except where mass is an advantage)
• Electronic Valves versus transistors (except for repairing old radios and pleasing HiFi aficionados )
• Computers versus mechanical mechanisms (except where physical strength is essential)
• Imperial and English measure versus metric (except for back compatibility and the USA)

Many other examples! I don't suggest these are 'good' or 'bad', it's just how it is. Technology is driven by user needs, which vary by time and place. If your country happens to sit on a large coal-field, makes sense to get rich by exploiting it. When coal runs short, the old reliable of making money breaks. Time to forget coal and move on to something else.

I'm all for celebrating our technical heritage, but not if doing so cripples what needs to happen next. Engineering is about solving problems, not defending time expired methods because they worked well when I was young. The manual machining I do for fun in my workshop has very little relationship to modern manufacturing, which is driven brutally by economics, not by craftsmanship, nationalism or a glorious past. I hate change, but pretending it wasn't happening didn't save me!

Dave

[pgk pgkParticipant @pgkpgk17461]

Tim,

Babylonian numbers were prefixed so essentially they were in groups of ten but without a zero.
Subitizing is the ability to recognise numeric groups of objects. You and I would know the number nine if grouped in the pattern on a playing card without counting. I'm sure that in past times folk would have learned how to spot and accumulate such groups – say a flock of sheep spread in a field totted by 5's (or another arbitrary number) groups. The shepherd wouldn't necessarily need to move stones from one pocket to another because not being able to read or write leads demands keeping one's memory trained.

[Howard LewisParticipant @howardlewis46836]

In"The Old Workshop" at The WaterWorks Museum is a treadle lathe.

So when the electrical power supply fails, it will still be possible to do some turning by the the light of an Aladdin or hurricane lamp, measuring with Micrometers or Vernier callipers!

Not much hope for me with my VFD, though!

Howard

[Michael GilliganParticipant @michaelgilligan61133]

Returning to my unanswered question …

This is the sort of ‘belief’ that worries me:

”Many people think that we use base 10 because we have 10 fingers on which we can count.”

It doesn’t make sense [for the reason I stated] … but it was the simplistic ‘fob-off’ that we got as children.

Ref. __ **LINK** https://www.advanced-ict.info/mathematics/bases.html

MichaelG.

.

Note: __ thankfully, a quick look on the web suggests that primary education has improved since my day.

.

P.S. __ the punch-line on the linked page is good

[Nicholas FarrParticipant @nicholasfarr14254]

Hi MichaelG, I've not had much to do with binary bases or numbers really, but having a little study of your link I think the answer to the punch-line is; 31-16+(8+2)=25, that is you would have 2 in the 64 column and 5 in the 8 column. I've probably got it completely wrong and I won't be offended if you tell me so.

Regards Nick.

[Michael GilliganParticipant @michaelgilligan61133]

Good work, Nick

31 OCTal = 25 DECimal

MichaelG.

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