Clinging to the Past

Hi, I guessed it was to do with the PCD of the holes, but didn't have time to work it out as I had to go and do my shopping earlier because I've got a courier coming any time between now and later this afternoon. I also think that it was probably an imperial measurement on the original design, so the metric measurements make any replacements interchangeable. Used to get a lot of that sort of thing in my maintenance days.

Regards Nick.

I do model engineering because I want to keep the old methods used in the past as part of today. I suppose something like a museum. If I can interest my grandchildresn in keeping the old ways alive, then I shall be happy.

I am a physicist with an interest in quantum foundations and cosmology, so hardly your typical stick in the mud oldie.

Andrew.

MichaelG I was only quick on that , as where I work, a lot of parts are designed using the PCD for the hole spacing. Particularly when a sheet metal part was needed to be made by marking out. Sadly that designer has since passed away, but a lot of his drawings crop up from time to time along with the old tools to be repaired. Most modern stuff is just XY coordinates these days, if you are lucky, otherwise it is all left on the 3d model of the part. Using basic hand marking out tools the PCD or the PCR method is very easy and effective with quite remarkable results being achievable. I find it interesting to being able to turn finished pistons on my old Myford lathe, that most need to lap or do some other method. I only have the digital depth on the tailstock, otherwise, everything else is all old school of winding handles or dials at the right amount to a clock ticking.

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.

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.

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 1000x2000 or 1250 x 2500 would be more in the spirit of things.

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!

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

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

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

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.

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

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.

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

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

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

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

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