Preferred Numbers and the “Preferred Measurement System”

Charles Renard (1847-1905)

By The Metric Maven

Bulldog Edition

In 1877 the French Engineer Charles Renard was instructed to look into improving captive balloons. These stationary, moored balloons were then in use by the French military, and of great importance. What Renard discovered was that 425 different sizes of cable were being used to moor these balloons. Clearly this large number of cables was not required from the outcome of any Engineering analysis, and were a nightmare to inventory and procure.

Renard determined that for mooring balloons, the most important inherent property of these cables, is their mass per unit length. He was able to develop a mathematical relationship which allowed him to replace the 425 sizes of cable with 17, which covered the same engineering range of requirements.

Renard’s geometric series was a perfect fit for a base 10 decimalized system, as it starts with 10 and ends with 100. The system he had in mind was of course, the metric system. This series produces what are proverbially known in engineering circles as preferred numbers (also called preferred values). Renard’s system was adopted as an international standard, ISO 3, in 1952, and are appropriately referred to as a Renard Series, or R Series. A similar series, the E series, is used to determine the values of electronic resistors, capacitors, inductors and zener diodes.

When metric was introduced into the building industry, a choice of dimensions which could easily be manipulated in one’s head was thought best. Grid lines on drawings are multiples of 100 mm. This is the basic “module” and the center to center of major dimensions are to be multiples of this value denoted as M. Therefore 3M = 300 mm, 6M = 600 mm and 12M = 1200 mm or 1.2 meters. According to Wikipedia:

For example, a multiple of 600 mm (6 M) can always be divided into 2, 3, 4, 5, 6, 8, 10, 12, 15, 20, 24, 25, 30, etc. parts, each of which is again an integral number of millimetres.

No decimals! Preferred numbers rock! Why don’t we use metric construction like the Australians again?

But not everyone is so enamored with preferred numbers and the metric system. When I was a youthful Engineer working in Aerospace, I was involved in a number of proposals for large projects. I asked, what to my fellow workers, was an incredibly naive question: “Why aren’t we bidding this in metric?” A copy of the provisional bid “boilerplate” was then shown to me. On one of the first few pages of the proposal, was a small section about metric, it read something like: “The dimensions and system of units will be of the inch-pound system. This is necessitated because of the difficulty of procuring metric fasteners in this country, and because many, many more fasteners and hardware exist and are available in inches than in metric.” I began to realize that this “boilerplate” form had been used from time immemorial as a magical talisman to vanquish any thought of using metric in Aerospace. With each new bid, it was copied like junk DNA. I’m certain a similar document is in use in Aerospace to this day, to keep metric at bay.

At that young age I was definitely naive, because I swallowed the assertion, hook, line and imperial sinker. It seemed that limiting fasteners and other hardware might keep one from creating an essential Engineering design. OMG! for want of a nail, the spacecraft might be lost!  Later I would learn from a salesman what this ploy actually was. It was FUD. In case you haven’t heard of it, this is a salesman’s term for what to do if your companies products are clearly inferior to your competitors. You must instill your customer with Fear, Uncertainty and Doubt (FUD) about the alternative product. If you use a competitors electricity, it will burn all your toast! Your soft water will come out hard! X-rays will come out of your light bulbs! The electrons will spill on the floor, and act like tiny ball bearings and you’ll slip! I hope you have health insurance! You better use Brand X electricity, or suffer the consequences!

The other option often employed to keep customers from choosing a competitor, is to create a proliferation of products who’s only purpose is to be non-interchangeable with any other competitors. I have seen this with RF/Microwave connectors. There are hundreds of them and I used to jokingly refer to each new offering as “connector of the week.” Many of them have Olde English screw threads and metric dimensions—but that is another blog. When a product is chosen by a market place “food fight” there is no guarantee that an optimal solution will be the survivor.  If one chooses a product that is not satisfactory, and is incompatible with competitors, a temptation arises to rationalize its use. “It would cost too much to switch over now, this works good enough.”  The person making the purchase does not want the bad choice to reflect on them, and will do their best to make do. Like the non-adoption of metric in the US, inculcated intellectual inertia to continue using a bad design will often prevail over reform.

The introduction of metric is a perfect opportunity (as Pat Naughtin has pointed out) to introduce much needed reform into the different trades. Pat Naughtin offers a number of examples of useful reform in his lectures, which I will not repeat here. The one example which does stand-out as perfectly in sync with the savings one can obtain by using preferred numbers, occurred in Australia. When metric was introduced into an Australian Ford car plant, the number of fasteners used by Ford were reduced by a factor of four after metric conversion. The implementation of metric threads reduced the hodgepodge of bolts by 88% and nuts by 72%. The number of sheet metal thicknesses in some factories were considerably reduced, which saved on inventory costs, and had no impact on Engineering design options. According to  Kevin Wilks in his book Metrication in Australia (thanks Klystron): When standardizing containers, Australia was able to reduce the number of can sizes, for packing goods sold by mass, from approximately 90 to 30. He goes on:

Another example in wholesale packaging concerned corrugated fiberboard cases for packing fruit. With the establishment of metric packing quantities the opportunity was taken to reduce the variety of shapes and sizes from many hundreds to about 50.

The use of preferred numbers with the metric system is good for business, despite protestations to the contrary. The metric system’s absence in the US requires consumers to pay an unseen externality penalty. Business can ignore metrication because the citizens of the US pick up the tab, but don’t realize it. This unseen cost to consumers exists because of an inefficient measurement system, which powerful segments of the business lobby in the US, have perennially refused to allow government to legislate out of existence, since at least 1921. The cost of extra waste and inefficiency is just passed on to the consumer.

These costs also make American industry more expensive when compared with overseas companies. We need mandatory metrication, and we need it now to reform America, and make it competitive in the 21st Century—before the 22nd arrives.

Weight Watchers and Measures

By The Metric Maven

Filmmaker Amy Young, who is making a documentary film entitled: The State of The Unit: The Kilogram, has met her goal on Kickstarter. Thanks to everyone who contributed.  $22.7 K so far and needs to raise a total of $26.8 K (i.e. $4,100 more) in the next seven days to fund her film. Please consider donating to her Kickstarter campaign here. If you have contributed already, thanks. Now the blog.

My Youngest sister has been a member of Weight Watchers (WW) for many years. It has worked well for her, and continues to do so. The WW members have discussion threads where they talk about how to compute Weight Watchers points from food labels. The use of grams and Calories (versus calories) and kilojoules is a perennial topic for discussion. Here is an entry by SCHILA which my sister shared with me concerning an Italian food label:

This causes a face-palm. I realize that it’s not her fault, it’s our lack of the exclusive use of the metric system in the US, and how the incompatible mixture of metric and non-metric units pervades our culture which is to blame. One can immediately see that the Nutritional Information (NI) is actually all metric—in a sense. The Calorie is a pre-SI unit of energy, which was replaced by the Joule in 1948. The Calorie was “metric” 65 years ago.

According to Wikipedia:

Definitions of the calorie fall into two classes:

  • The small calorie or gram calorie (symbol: cal)[2] approximates the energy needed to increase the temperature of 1 gram of water by 1 °C at standard atmospheric pressure (101.325 kPa). This is approximately 4.2 joules.
  • The large calorie, kilogram calorie, dietary calorie, nutritionist’s calorie or food calorie (symbol: Cal)[2] approximates the energy needed to increase the temperature of 1 kilogram of water by 1 °C. This is exactly 1,000 small calories or approximately 4.2 kilojoules.

The difference between a calorie and a Calorie is a factor of 1000 in the US. Why shouldn’t SCHILA be confused. The label has Cal 122 KCAL which is a capitalized Calorie abbreviation, which then tries to make it more understandable by putting it in all caps as KCAL, which of course could be confused for Kilo-Kilo-calories. No wonder the poor woman is on a discussion thread asking for help. The logical solution to me is to be done with calories and Calories (1000 calories or a kilocalorie), switch to SI (official metric) and use kilojoules—like the rest of the world.

Here is a package of licorice from Australia (courtesy of Mike Joy). It is advertised as one meter long. The front of the package has only one mass (weight) given: 120 grams. That’s it!  You don’t need any other information.

On the back the nutritional information is:

Nutrional Label for Australian Licorice

We see that the Australian food vendors also use untidy numbers like 4.8 servings in a package. The serving size is 25 grams which is 353 kilojoules, that’s it! Every other description: protein, sugar, sodium and so on are broken out in grams or milligrams.

Ok, how many kJ’s do you get a day? Well in the US I generally see 2000 Calories on food labels as the recommended daily intake. This works out to about 8375 kilojoules. Look how many kJ’s you get! Doesn’t that sound better than 2000 Calories? Here is a short table to give you an idea of the range of kJ’s and the old way:

5000 kilojoules is 1194 Calories (1200)
5500 kilojoules is 1313 Calories (1300)
6000 kilojoules is 1433 Calories (1400)
6500 kilojoules is 1552 Calories (1500)
7000 kilojoules is 1671 Calories (1600)
8000 kilojoules is 1910 Calories (1900)
8500 kilojoules is 2030 Calories (2000)

So for many WW members somewhere between 5000 and 8500 kJ’s is the range for you to think about. The Australian Government has recently sponsored a push to get Australians to eat around 8700 kilojoules per day. Here is a page from their website:

click to enlarge image

So what does the back of a licorice label in the US look like? This is from Twizzler’s web page:

Not all that that different, other than the use of Calories (i.e. kilocalories). So what’s the big deal? Well, the big deal is that because the US is not exclusively metric like Australia, very few Americans have any idea what a gram is. (It is about the weight of a plain chocolate m&m). This lack of exclusive metric adoption in the US obscures dietary data that is readily available. Any confusion will cause many people to just not bother with the nutritional information.

Should we go back to Ye Olde English units on food packaging?—well they’re actually Olde English sizes used prior to the English reforming their units in 19th Century, but we’ll let that pass for now. Some people who believe claim they are trying to help the public say yes. These people are from the anti-metric Wall Street Journal, and like James Taranto are there to yelp—I mean “help.” Their anti-metric “Numbers Guy” seems to be more interested in running a numbers racket than actually enlightening people about numbers.

When the Wall Street Journal is on the side of the Center for Science in the Public Interest–watch out–what they have in mind is not in the public interest. They want teaspoons and tablespoons back! I’ve already written about how confusion between the two, and the lack of metric in the US kills about 98,000 persons in the US each year. It would also make our nutritional labeling completely incompatible with the rest of the world—which all use metric. They want to swap mass (grams) for volume (Tsp, Tbl)? Isn’t it bad enough we use ounces interchangeably for weight and volume already?  Do you think 8 (by weight) ounces of cheese doodles is a cup (8 oz by volume) of them? The Wall Street Journal has never found a bad Weights and Measures idea they didn’t like.

The frustration the rest of the world has with us is completely understandable and surfaces on the WW discussion thread:

All I can say is You Go Girl!

What started this WW discussion thread was a question about the nutrition label on the back of an Italian food product. If all our US packaging was in teaspoons and tablespoons, and grams became even more unfamiliar, this would further alienate us from 95% of the worlds population and their products. I guess the Wall Street Journal just can’t help themselves—they like trade barriers. Once again the inability of our legislators to pass mandatory metric only legislation for the US, with a plan, and funding, and so on, hurts the nations physical and economic health. Congress has been goofing around since 1866 thinking about metric, isn’t it time they finally got to work and dealt with the metrication issue?