Metrication of models

When I was at secondary school we were taught using both systems. Applied mathematics was a nightmare with foot pounds, Briish Themal Units etc. Loved Physics where it was all grams and centimeters. That's all changed, as it is now the MKS system which does produce some stupidly large or small standard units which don't relate to every day useage. Pascals spring to mind.

I am happy using Imperial or metric, although imperial is used mainly for woodwork (sheet material still 8ft x4ft) while metric gets used for metal. I still need to mentally convert large mm measurements to feet in order to visualise sizes.

Edited By Anthony Knights on 06/10/2019 09:23:21

Bandersnatch, I do know better, put it down to tiredness error,

but,

I now know you read it!

Seriously, what a hideous system of value measurement. I think it was because so many everyday items had such a low price, e.g., loaf of bread one old penny. Blame inflation for making system look so outdated. Remember one of my secondary school teachers saying that this age would go down in history as the age of change just for the sake of it. He did appear to be nearing the end of his career. I find it amazing how quickly I adapted to the then new decimal currency but still see, say 1.5mm and automatically try to convert it to 60 thou as an approximate equivalent to be able to visualise that size. Soooo annoying.

Anthony,

This is the stupidity, 8ft long board easily visualised but if "they" go and "metricate" that to 2,400mm or even worse, 2,440 or 2,450, that would be awful. Just like the 19ft new car quoted as being 57,912mm long! I would like to see my restricted to less than 1m, then go on to use say 1.4m or 2.9m or whatever, applicable to all industries, "no ifs, no buts."

This topic never ceases to amaze me at the amount of discussion it generates.

I think I have mentioned before, that having previously taught EDF Energy apprentices in the age range of 16 to 22 we have had to spend some time teaching imperial measurement, mainly due to the fact that the majority of nuclear reactors currently operating in the UK ar indeed imperial, and will continue to be so for the future as the decomissioning life still has to be addressed with repairs and replacements of the non-metric variety.

In addition the majority of older and still in comission American ships and aircraft,,still require a knowledge of the imperial system.

I refuse point blank to 'metricate' a set of drawings as the possibility of error is high and believe whole heartedly that for steam in particular, everything should be imperial. - just my point of view.

Incidntally, when introducing the EDF apprentices to Imperial measurement ( and all of the little engines they made in our workshops were on imperial drawings) , it only took them about half a day to grasp the concepts and by the end of the day working happily with supplied imperial drawings.

Regards.

Would be great if they metricated it to 2400mm, then the plasterboard on the underside of your flat roof would match the ply on top and the standard 400cts of joists.

The need for exact standard sections becomes less of an issue if the design process is thought through. Where size is not needed to be exact many designers appear to have said 'chuck a piece of 5/32" bronze bar etc when what they needed was a piece of metal large enough to finish to the desired size, more or less. Also with older designs I suspect designers did not want to inflict unnecessary machining down to size on hobbyists with limited machining facilities. To the end of his life LBSC wrote about 'those lucky enough to have a milling machine' when today far more people either possess one or have access to one through a club.

What I am trying to envisage is the designer thinking of 1.2" but making it 1 1/8" for simplicity and today needing to use 30mm for convenience. Neither of the two alternatives are accurate to the original idea, but both work and if you want accurate - today you can mill it!.

One interesting thought about measurements is regarding copper sheet. It used to be thought that 10g, for example, was a replacement for 1/8" being a few thou thicker. 3mm is about 10 thou thinner than 10swg But US 10g (B&S) is thinner again. If we are buying copper sheet or tube with our import streams focused more across the Atlantic than into Europe which will we be getting in the future??

All will probably be within any reasonable safety factor, but several published boilers with 'grandfather rights' as established designs have been questioned in today's world and I don't think this will help.

Maybe if you are building an old Loco but what about someone wanting to build say a flash steam boiler and high speed engine or a turbine, can't see any reason why they would have to be imperial, just my view.

Or what about a steam engine like this which I know a couple of people are currently building, Originally designed in metric and built in metric so why should it only be modelled in imperial? Or is steam only a British thing.

Edited By JasonB on 06/10/2019 15:04:33

Which ten years ago caused serious delays when Boeing was developing the 787 airliner. Not funny when you design an airliner in the US while relying on keeping the price competitive by having much of it made more economically abroad and it turns out the rest of the world doesn't understand US Customary units! A lot of expensive mistakes were made...

I wonder how many British engineering firms bit the dust due to upsetting export customers by failing to metricate? Unfortunately, most customers interested in buying British machines care absolutely nothing about heritage units like inches or Whitworth's genius (Sir Joseph died in 1887). What they do want is affordable equipment that's easy to maintain. Like it or not metric equipment has the edge in metric countries.

Teaching students to work from imperial drawings in an afternoon glides over Imperial's secret shame. On their own inches, pounds, miles, and pints etc are familiar and even cuddly. Perhaps that's part of the problem. The trouble starts when Imperial is applied to physics and those incoherent Imperial units have to work together. The full awfulness of the Foot-Pound-Seconds system doesn't really bite until serious engineering is afoot which rarely happens in the average home workshop. Imperial measure may seem friendly to chaps skimming the surface, but it's pure treacle for anyone doing proper engineering rather than knocking stuff up from someone else's design.

No-one should be allowed to support imperial until they can explain Slugs, Biot-seconds, Candles, the various definitions of 'pound', and all those strange conversion numbers that pop up in formulae only because Imperial is internally inconsistent. Definitely not allowed to lobby in favour until the difference between FPS and Technical FPS is understood, and a working knowledge of British vs USA FPS would be an advantage. Man-in-pub and woodworkers need not apply.

Anyone who thinks Imperial does a good job has only skimmed the surface. Metre-Kilogram-Seconds is more suitable because it's simpler. Apart from backward compatibility, is there a logical reason for sticking with Imperial measure in future? I can't think of one.

Dave

Does that mean nobody should use metric unless they understand ALL the metric units that exist?

I was taught cgs at school but I can work in metric or imperial but I do not know all the units, only those I need.

Richard

Unfortunately, " the " metric system, to me, means either:

- cgs system

- mks system

- rationalised mks system

- SI system

- (and another. I think, which escapes me at the moment).

Each of which were drilled into me at one time or another.

At least the imperial system was relatively stable. Give me a slug any day of the week.

I fear that die hard Imperialists will never change their opinion, it's a bit of a religion, but if you're making a 5"g model of a standard gauge loco, using 2.25 mm to 1 inch (27 mm to the foot) is pretty good (actually 2.24779), and a lot easier than 1.0625" to the foot

What utter drivel! No one's eyes and brain are naturally calibrated in inches/feet/whatever, they're just trained to do so. 2400mm is as visualisable as 8 feet, it just takes the same amount of practice. And bumping it up to the next used measurement(there's a good reason to go straight to metres from mm) doesn't need any calculation either.

.

The real problem is that 8 feet = 2438.4mm

... but the people that sell boards don’t appear to know that.

“measure twice, cut once” is a good mantra if you are doing anything fussy.

MichaelG.

No but your thumbs and feet are.

regards Martin

Personally I just use whatever it's designed in.

"Utter drivel" What a damn insult. When car sizes are quoted in umpteen thousands of mm, that is the rubbish /abuse of metric. How the hell can that be visualised? Only fit for comparing relative sizes of diff. makes and models, nothing else, like will it fit my garage?

Maybe more sensible to quote boards as 2.4m or go up to 2.5m, but not pig- headedly use 2400mm. Since when were they quoted as 96"?

At school we were subjected to that awful chant system of learning that 10mm = 1cm, 10cm =1 decimetre and so on but it was all a waste of time. We might as well have just been told about all the other divisions and their names and leave it at that. They don't seem to be in every day use.

To get back to strictly on topic, it would seem best to leave all the published designs alone, complete with their myriad errors and start afresh with new designs only in pure metric, not a bastardised metric conversion of Imperial measurements.

I have seen, e.g., somewhere on the Internet, a list of errors with Sweat Pea design and I understand other designs have received similar treatment. Just imagine re-hashing the design into metric and rounding the results to look nicer. Think of all the new errors that could arise.

It is really just a case of what you are used to, I have clients who can't visualise feet and inches and have to stand there looking at a tape measure if I talk to them in imperial as they are of an age that has been brought up in metric.

Not a problem for me I just get to know what they are happy with and talk to them in whatever suits be it feet and inches for older clients and a couple I have from the USA, mm and meters for others depending on the job in hand and my regular French lady client and several interior designers who like centimeters.

I'd rather judge the size of my bottle of beer by eye than worry about how many millilitres it contains, or convert that to pints...

Neil

15 years ago, a workmate was building a custom car, road legal, based on a Ford Pop which had a tuned small block Chevy engine with nitrous injection (9.75 quarter mile, that thing went well) and several of the special goodies bought from the USA had metric threads and fasteners.

Edited By old mart on 07/10/2019 21:45:26

I wouldn't be without my Shetack Monument thread reckoner. It has metric coarse, BA, UNF, UNC, BSF and Whitworth threads side by side. This makes it easy to compare sizes quickly.

**LINK**