Why is the world of model engineering still imperial?

ALL drawings can be "Metricated" but it's too expensive to change every design, just in case the one YOU want is available. As stated in post # - (OH, we STILL have the inability to refer to post numbers, despite THAT subject re occurring with the same monotonous regularity) the inability of some to determine which dimensions NEED to be direct conversions to metric, don't try to throw it over to today's "Universal" draughtsmen who prepare offerings via a graphics programme for magazine publication.. Even back in Percival Marshall's day when the Draughties KNEW what steam engineering was all about, could get sizes wrong.

Simple question for the CAD brigade who think pressing the 'Convert' button on a loaded Imperial drawing is the easy answer, 1/8" - 0.312" converts to 7.9248mm and before you jump in and state "That's 8mm," NOT if it's tied to part of a chain dimension - Cylinder position etc. on a steam loco. Should we change to 88.9mm gauge?

Regards Ian.

[ deleted ]

Edited By Michael Gilligan on 08/03/2023 10:36:50

As one of the CAD brigade I can assure Circlip that all my conversions are full metric conversions not just mathmatical ones as I have said a few times in this thread already.

Oh and in my book and on my screen 1/8" is not 0.312" or 7.9248 neither is 1/8" minus 0.312" depending on what you intended to write

As to the comment a bit earlier about the base of an engine not needing to be anything critical yes that is quite OK provided care is taken as to where subsequent dimensions are taken from, a lot of drawings will use all 4 sides as well as ctr lines to place various features.

Now what about published drawings, I think the last ones Myhobbystore made available were the Nemett Lynx (metric) about 12years ago, last loco or stationary engine qite some time before that and I doubt we will see any more being sold as they once were. At best you will get whatever is submitted to ME or EiM and have to get back issues to see the newer designs and apart from any errors picked up during the series unlikely to ever be revised.

I don't see much merit in metricating existing plans unless there's solid advantage in doing so. Such as selling them to newcomers with metric workshops, nothing but metric stock sizes, who have no background knowledge of Imperial or English measure. The amount of unnecessary conversion baked into Imperial is one of it's chief evils, and converting again just to be in metric is evil too. Metrication's advantages apply mostly to new design, not slavishly redimensioning old plans.

This thread's title is 'Why is the world of model engineering still imperial?' That's debatable! True modelling is popular in the UK, but surely unjustified to assume there are more British modellers than the rest of the world combined? Dare I cause further upset by suggesting it's likely more model engineers work in metric than Imperial? Not in your local club maybe, but remember that's a tiny sample. Be interesting to know how many mini-lathes are sold worldwide each year, and what proportion of them are Imperial rather than Metric. Even though I expect Imperial machines predominate in the US, is anyone prepared to bet the farm on Imperial being the winner?

Looking to the future, has it occurred to anyone else that loyally sticking to traditional British measure is a good way of ensuring that British model-engineering will die abroad, and probably here too in the long run? Very few countries know much about Imperial, and the little English boys next door to me aren't taught it at school either. My generation was probably one of the last to cover imperial in depth, and I had to learn Metric too. Being taught both in parallel gave me a very clear understanding into which of the two performed best in the large.

Strange that so many enthuse about Imperial measure without insisting we go back to £sd, a monetary system with many of the same advantages; 240d = £1, 12d = 1s, 20s = £1, 2/6 = £⅛ etc. I think £sd passed relatively painlessly into history because most people had been hurt by the way it makes sums unnecessarily hard, whilst the simple advantages of 100p = £1 were instantly obvious. Doubly so when everyone could own a calculator!

Dave

After five days we have returned to the question and probably the same answers.

Model engineering will truely go metric when there is the demand. The majority of us are boring old farts (excuse me) who can handle Imperial and SI units and even worse argue about their merits. The younger generation have, in general, little knowledge of Imperial units and don't want to know. The change will come during their time and it will be slow since the hobby is, at present, moribund (and not just because it is snowing). How the change takes place and managed is outside our influence, fortunately.

JA

Not sure why being a BOF should stop people designing in metric, take the likes of Anthony Mount most of his later designs were all metric, earlier ones dual and he is getting on, the grasshopper currently in ME is also metric and from his photo I would not say Martin is in the flush of youth.

Luckily we do have the likes of Luker who has given us some metric design locos and also bucked the "it must be copper" trend too so as said change is coming but maybe not that fast.

And yes I did get a bit done in the workshop this morning, making an engine that came out in 1924 but my fully metric design. 2" 50mm of snow won't stop me.

I'm not sure this is true, at least in Britain it's still pretty common for young people (who do anything remotely practical at all) to have good familiarity with both imperial and metric systems, and to be able to convert between the two freely.

Most of us* prefer metric, but as long as America exists we have to be conversant in both and the US influence on young people has if anything grown as a result of the internet making "the pond" a lot smaller in people's digital lives.

​

When you get to young people who are being trained in engineering occupations, unit conversions are still considered a fundamental skill they love to drop into the curriculum to catch people out at every level right up to people doing MSc/MEng... At least for people in the process industries.

Because in real life you have to work with systems that were designed anywhere from 1840 to the present day, and built all over the world.

So you may well find yourself having to modify or integrate with an assembly originally built when your grandfather was your age, which now has different components specified by long since defunct OEM's in SI, CGS, US Customary, Imperial, and drawn to three or four different standards.

​

That latter point is why I don't get why metrication of the hobby really matters... In real life the existence (and continued promulgation by Americans) of the imperial system is just something you deal with.

*Yes, I'm claiming to be a young person, but being early 30's that statement is somewhat relative.

Edited By Jelly on 08/03/2023 12:36:01

I think modelling will remain largely Imperial for some yet not just because the drawings are Imperial but because of legacy tooling that often gets passed on to newbies as well as part completed models. Since modelling is rarely profit making using what is easily and cheaply available is prudent. The more likely scenario will be the gradual introduction of metric parts such as fasteners and gears etc. One may build a model to Imperial measurements but substitute commercial of the shelf metric screws rather spend time finding a source of ME screws.

In fact someone starting out in the hobby may find the complexity of different measurement systems and component availability a serious negative and find something easier to do.

CS

A branch off this thread would be "the future of model engineering?"

Both my sons in law (in their early30's) have no idea about "practical" stuff let alone have engineering skills or the pro's and cons of metric or imperial measurement.

Houses are getting more expensive for the younger generation and those that have a garage or even a garden big enough to put a shed in suitable for a workshop are at a premium. If you live in rented accommodation then its even harder to create a workshop. Not even factoring in the cost of machine and hand tools against the cost of living and bringing up a young family for example.

I do not want to change the direction of this thread but I think there maybe a part of imperial measurements that may turn off budding model engineers (young and old).

The days of coming home from work having your tea and going out to the "shed" to bash some metal have changed dramatically.

But the world of Model Engineering is slowly, albeit very slowly turning metric thanks to new published designs (thanks to Jason and others!) - I think this makes the design more accessible and understandable to the metric only generation......and they are the future model engineers

There are bits that have moved to metric long ago. Low hanging fruit and all that. It’s fairly standard to use drills in the 1mm to 10mm range in 0.1 increments for nearly all drilling operations. Said drill being cheaper and more available.

regards Martin

Oh and clockmaking wheel cutters are Mod now rather than DP

Edited By Martin Kyte on 08/03/2023 13:50:55

No. That is a new topic and I have been resisting starting it for a few days. At present I have got my hands full with the minor disasters of life (not weather or health related).

JA

When I was teaching computing I noticed that students had a hard time adopting different number bases: Binary, Hex etc. Eventually I put this down to only having had a denary educate and not having had the experience of the different fractions used in Imperial system. There can be advantages in being exposed to more than one system.

Martin - Tracy tools (others available) Imperial drills same price as metric ie HSS 1/16" - 1/2 inch by 64ths £30 (29 in a set) and Metric 1mm - 13mm x 0.5 increments £25 (24 in a set). So ignoring any slight differences, metric same price as imperial - £1 per drill on average.

Bob

I'm getting the impression that some think the slim list of straightforward units encountered in ordinary life are the Imperial system, and may not be aware Imperial is far more extensive than that. Inches, pounds and pints are just the tip of an iceberg. It's what's below the waterline that's the problem.

I have a high opinion of young Jelly, and wonder if he would mind listing the units he thinks comprise the Imperial system. For the avoidance of doubt, it would reveal if we're talking about the same thing! I'm against Imperial as used in professional engineering, not inches measured in home workshops by chaps who only do basic engineering mathematics!

If any Imperial supporters are interested in plumbing the depths, I'll post a few exam questions from my collection of 1930's textbooks. I've done this before, and they're usually ignored - too difficult! However, important to realise that recommending Imperial to youngsters, means the whole system is being pushed, not just the icing on top!

Anyway Jelly, what do you think the Imperial system is? Without looking anything up, please list the units you know how to use.

Ta,

Dave

Whatever about model engineering, fullsize practice seems to have almost totally Metric.

Around here, to look for Whitworth fixings would be like looking for Unicorn droppings, most supplier seem never to have heard of them, [the Whitworth stuff, not the droppings ]

I need a simple 3/8" whitworth screw/bolt a few days ago and went to my good old box full of screws, bolts, nuts ect, the type of things which "will come in handy some time " There must be two hundred or more items in there, but was there even one 3/8" whitworth ? You must be joking ! everything else, Bsf, Unf, Metric fine, others that I dont know what the hell they are.

However, the Gods took pity on me when I found one still cling to an old frame in my scrap box.

So, good as the system was, it appears to have had its day.

I rest my case, and put on my tin hat !!!

Honestly, I couldn't truly differentiate between "Imperial Imperial" and US customary at this point, other than knowing through bitter experience to ask "Which Gallons" or "Which Tons" when someone tries to use those units.

I know this won't be truly complete, but should be a fairly good cross-section, so let's have a crack...

Mass:

• Grain, [interstitial base 16 unit I can't remember the name of] Oz, Lb, Stone (people only), Cwt (I actually find hundredweights oddly intuitive to estimate the weight of big things), Tons, [avardopoidis sp? versions of the same].

Volume:

• [weird appothacaries units], flOz, Pint, Quart, Gallon, [comical brewing barrel sizes], bbl (strictly it's an oilfield unit, but it's defined in US Gal), cuYd, cuft

Pressure/Force:

• Psi, KSI,

Length:

• "mil", "tenth", "thou", Inch, Foot, Yard, Mile, Nautical Mile (still in use in metric too because it's defined conviently via something to do with arc-seconds of longtiude).

Area:

• Acre, sqft, sqin, square mile

Power:

• hp, lb*ft/s, BTU/hr

Energy/work

• lb*ft, BTU,

Force:

• lbf, poundal (might be the same as lbf, Slug (not the same exactly but the unit of mass which gives the imperial system it's equivalent of 1kg = 9.81N equivalence for gravity), kip (us customary unit used for statics calcs in steelwork)

Torque:

• lb-ft, lb-in, oz-in (not the same as lb*ft, thanks whoever decided on that convention!),

Radioactivity units:

• Curie, Rad & Rem (just URGH, because radiation protection was just soooooo simple before that I needed the unit conversions to spice it up right?).

From there you get into the compound units in imperial, many of which would be derived units with their own name in SI and CGS (in this regard imperial can be better when you're trying to ensure an analytic solution or non-dimentionalisation makes sense), like lb*s/ft² (or lbf*s/ft² because people couldn't agree) for viscosity (the reyn might be a dynamic viscosity unit in imperial actually, it's that or stokes but I'm pretty sure the stokes is CGS), which are actually what I encounter most in an engineering context.

Most of the plants I've worked on over the years have had at least some parts which were developed pre-metrication (in which case it's a CGS vs. Imperial toss-up) or during metrication (urgh, CGS), it's also really common to see upgrades to UK and European plants which have integrated equipment from American and Canadian vendors, which is designed and specified in US customary units (which isn't Imperial, but is close enough to trap you).​

I would wholeheartedly agree with your statement:

as long as we can chuck US customary units in with Imperial.

I don't mind either in a historic context, as it's a trade off for some quite cool opportunities to get up close with artefacts and living history which allows me to see the evolution of different industries (and how long some equipment lasts) first hand...

But for the love of god stop deliberately using them in new designs for sale to the international market!

Oh, forgot the "inches of [insert substance here]" pressure measurements, in-hg and in-h2o being common in different fields.

I've got some scruples if anyone still uses this unit of mass.

CS

The American gallon is smaller than the Imperial so does that mean their pints are as well.