Ultimate digital caliper for modelers.

My grumbles at the imperial length system come from three factors;

- very strange numbers of each division in the next one up. eg 5280 feet per mile, 66 feet per chain etc.

- nearly unworkable fractions of each inch, plus thou's.

- assorteg "gauges" of wire, screws and the like which differ between countries.

Regards, Greg.P.

Scale modelling would be almost impossible using roman numeral fractions!

Imagine converting a XXXI' IX +VIII/XII" long wagon/car to XXIII/M scale! Just converting the result to barleycorns would take a day's calculations.

Regards, Greg.P.

You do conversions whenever the need arises. For anyone who needs to do conversions a lot, the American system is a major hassle. That is why most American scientists and engineers use the metric system.

The American public is just too dense to change. That's okay for the older generation, but they should mandate the metric system in schools so the next generation doesn't keep looking like a bunch of hicks to the rest of the world.

It's just an example.

Greg Procter wrote: [...]

Standards are a whole 'nother can of wigglies. At least we now have the ISO, which is sl-o-o-o-owly bringing some order into the mess. But please note that the measurement system used to specify the standard is irrelevant, so long as the standard is accepted by everyone. Look at containers - specified in feet, not metres, and for a very good reason: they have to fit on US RR cars... :-)

I was an engineering student for two years, and found that besides the slipstick, the most important tool was the conversion factors booklet given by The Dominion Steel and Coal Corporation of Canada to all us impecunious seekers after technical wisdom. I still have that booklet - I still have two slipsticks, in fact -- and it's a goldmine of useless information. :-)

Here's a few conversions that the decimal system supposedly simplifies:

1 km/h == 0.2778 m/sec 1 KWh == 3.671x10^5 kg-m 1 mm mercury == 0.001315 atmosphere == 13.595 km/m^2

And so it goes. Many of the more important conversions are not simply movements of the decimal point, because Nature isn't decimal.

IOW, the metric system is really a decimal system, and any group of base unit whatsoever would have served - so why is the meter what it is? Because the French Republic decided that a "natural" measure of length would be 1/10,000 of the quarter circumference of the Earth, as measured along the meridian passing through Paris. Unfortunately, the guy who was given the job of surveying that line made a few minor errors, so that the metre is pout by about 1 part in -- wait for it -- 10,000....

Hah!

Footnote: they're called "gauges" of wire (and sheet metal, etc) because it's easier to measure those things with gauges than with calipers. Which brings us back where we started from.

Hoohah!

It's been an entertaining ride. Thanks, guys!

HTH

Errr, the ISO container standard was based on a British design, so for that reason the original dimensions were Imperial. The ISO quotes the standards in bothe feet/inches and millimeters.

Problem #1 is which of my selection of gauges should I use to decide which wire or screw to use or purchase.

A real life example: I want to mount my newly built wagon (flatcar) on proprietry bogies (trucks) The bogies have a kingpin hole of 6mm diameter. I need a styrene plastic tube kingpin of 6mm diameter and a screw to thread into said tube. Find the tube comes in inch fraction increments externally and internally. I can figure 1/4" = 6.35mm (unless of course it's 6mm tube labelled

1/4") The internal diameter isn't stated, but one can infer that it nearly matches tube two sizes down. Add tube two sizes down to shopping list to get sufficient wall thickness - internal diameter will equal tube outer diameter two sizes down. The screws in the hardware shop come in gauges, whose particular gauges unstated. Screws and taps at home all metric sizes. Attempt to convert 1/4" - 4/32" to metric in head, add thread depth (opps, two thread depths) and the visualize that in terms of unknown screws in semi-clear containers in hardware shop. Go home - create king-pins and rat small tin of random size PK screws for "something suitable". ;-)

Regards, Greg.P.

Greg Procter wrote: [...]

Interesting. A nice example of why one needs standards, so that one doesn't have to do all this furshlugginer converting back and forth. I use NMRA standard trucks: they all come with kingpin holes that take a #2 (American) screw of bolt. Piece of cake. I just don't buy trucks that don't conform to NMRA standards. Since after-market replacement trucks are bought by "serious" modellers (like me??? ROTFL), the manufacturers make sure their trucks conform.

Ah well, there's always a work-around. :-)

HTH&HF

Hmmm, there isn't any NMRA standard for 'NZR G24 scale', I make it up as I go along. How should I know if screws in the hardware shop are US #2 or Brritishish #2 gauge?

How does 1/4" factor in?

Cheers, John

The only suitable sized styrene plastic tube my hobby shop stocks to make a kingpin is in fractional inch measurements. (Evergreen) The LGB and Bachmann bogies have a loose 6mm pivot hole. Styrene because I need to make a rigid mounting point within the frame depth of a flat deck wagon. Using a quarter inch screw into the styrene frame as a kingpin would leave too few threads holding for the forces likely to be encountered. My lathe was and is still packed away due to a major move so the engineering was under kitchen table standards. (actually, the kitchen table was also packed)

The gages don't count, as they were not standardised, except in the particular trades that originated them.

In their context all the units of the imperial system have their place. Feet and inches are logical and usefully divided units for the things they generally get used for, as are rods, chains, and miles.

Arguing that they are not usefull, on the basis that they do not easilly convert to other less practical units for the purpose, is a mugs game, to be played by those that wish to make excuses.

So it's tough to translate rods to inches. So what!

I find it somewhat funny, that the school system in Canada is teaching imperial measures again, as someone figured out the reality, that a great deal of the world has been divy'd up into 1 mile by 2 mile squares, (take a look at the Canadian prairies on a sattelite view, eg: Google Earth), and that a guy who is expected to be able to go into a pre metric building and do repairs, renovations, or the like, must be conversant in the units that the building was built with, both lumber and hardware, if he wishes to come out with any numbers that make sense.

Cheers Trevor Jones

In Italy they buy bread (and other loose commodities) by the "etto" -

100g. "Due etto di pane Toscano" means to cut off a 200 gram wedge of bread from one of those big round loaves.

That's because of our American neighbours who dominate much of our lifestyle. Ironically, their metric conversions are more accurate than what we use.

Cheers, John

Good Morning to you to, John,

It's got less to do with the Americans, than it has to do with several hundred years of using the same measuring system that they started out with, mainly originating in Britain.

In the mid to late 1800's the American watch industry (THE high tech industry of it's day, making interchangeable parts before anyone else in the world!) was working almost entirely in metric measurements. It had far less to do with the workmen originating in Europe, than it had to do with the appropriateness of the measuring unit for the job it was being applied to.

Legacy measureing systems are a fact of life. If you want to order a part and have it fit, you will have better luck if you order it to the same measuring standard that the item was built using. A fine example of that is the French ligne, used as a unit to measure watch movements and crystal sizes. They sorta but don't exactly coincide with the two decimal place metric measurements that are usually also printed on them.

If you want Irony, the American inch is officially defined as being a unit 25.4 millimeters exactly (changed a while back to make it an even tenth of a MM)

Cheers Trevor Jones

Well yes they do when materials are sold in terms of "gauges" and I'm in the hardware shop (away from references) and faced with packages marked only in those terms.

As a scratch-builder I need to make a lot of conversions, sometimes, as in the example I've given, in situations where I don't have conversion tables or calculators handy.

Aircraft navigation has always been in imperial measurements. As I think I've already stated that most of my prototype data is imperial, original plans etc not having updated themselves during our conversion to metric thirty years ago. But I'm prepared to live with that. The problems are with dimensions of materials available to me and in particular having at least five different measuring systems involved.

Regards, Greg.P.

No that misses the point - no one is facile in the use of roman numerals. The Romans did some great things, but not in mathematics. They did not have the notion of zero for example.

And some things are just more convenient, even if they are mathematically equivalent.

I see you are using Microsoft Outlook Express. It would be much less convenient if you had to control your computer through commands that would amount to a long string of binary numbers. Mathematically this is equivalent - in terms of being fit for human use they are not. It is not by accident that user interfaces play such an important role. See the recent success of the iPhone, iPod or even windowed user interfaces on computers.

Converting units is not done by many people - there is an argument that this is precisely because it is difficult. So why make it more difficult?

I would think the British have switched with a good reason.

To sum it up: Mathematically equivalent ways of doing things may be very different in how easy it is for human beings to do them, ie the fit between the task, the notion used for it and the way the human brain works is key.

Marc

IOW, real people use units that are useful to them, regardless of what the self-styled rationalists think they're doing.

but only part switched over all the distances and speeds for road traffic is still in good old miles and we still quote MPG for fuel consumption and a pint of beer is still a pint, boats still travel in Knots,tyre pressures still in PSI and probably a lot more that refuse to go away so us Brits have not gone totally metric, and being 45 I tend to measure in both systems as old habits die hard

Actually, historically, the English (or Imperial, if you prefer

The times that I have had to scale stuff, I generally converted all the fractions to decimal, and worked entirely in decimal inches or decimal millimeters.

I would make a long list of actual measurments, work out a scaling factor, then multiply the measurement by the factor to arrive at an end result.

I suppose a guy could work out a spreadsheet program that could be linked with an SPC capable caliper, but that seems a different hobby, all told.

Cheers Trevor Jones