Now, as most of you know, I seem to have somewhat of an obsession with English technical units. This is because I see it as crucial that the English system be taken seriously as a scientific and technical, or prospective scientific and technical, system, in order to survive. In fact, these posts of mine go largely ignored now, I fear. The thing is, I keep going on about the technical units because I view it as self-evident that English is just as good as (in fact, mostly better than) metric as a system for "everyday" things (DIY, cooking, shopping etc).

Thus, I am concerned with the technical units of English. And with the technical units, I see two main problems:


1. The lack of any coherent (not in the strict metrological sense) technical system.

2. The lack of electrical units.


Point 1 refers to the jumble we seem to have:

*kips for energy (kilo-inch-poundforce-- also the name for 1000 pounds of mass)

Yet, no names for foot-poundal units, which are, or ought to be, the more common. Not having a name for the primary units of energy and power is a real inconvenience.
Also, if you are to use the foot and pound, you really ought to use the poundal (sometimes slug and pound-force, of course).
However, we prefer to use the pounds of mass and force, and this leads to various problems, as the English system is complex and effectively ends up:

Length: inch or pound
Mass: Pound
Time: second
Force: Pound-force
Energy: Kips, horsepower hours
Power: Horsepower

Yet, this does not form a rational system, which is what is needed. Furthermore, to say that to use pound, pound-force and slugs willy-nilly is an acceptable solution is something I do not except. Of course, sometimes units might need to mix like this, but generally we have gravitational and non-gravitational absolute systems, and should use them properly.. and in a full and complete form.

Full and complete? Yes, to refer to however many foot-poundal/second squareds, is not exactly useful or practical. And, in fact, this makes a system of electrical units impossible in English (in any practical way).

Thus, surely we need to define the systems, which seem to be:

Non-Gravitational Absolute
Foot, Pound, Second, Poundal, <foot-poundal>, <ft-pl/s/s>

Gravitational Absolute:
Foot, Slug, Second, Pound-force, <foot-pound>, <ft-lb/s/s>

Plus the Rankine and Poundmole.


Now, before anyone says that no system of measurement can cater to all disciplines and needs, I concur. The fact is, though, that presently English needs a bit of sanity added to it.
Now, I understand the arguments about English is the way it is because that is what is practical, but the fact of the matter remains: English (technical) is definitely harder to quantify and justify, if you were to teach it to young students (or others). Furthermore, it seems that this whole poundal, pound-force, slug, slinch, pound mess (similar problem exists in metric) exists due to the lack of a simple conversion factor between the basic units ie THE ACCELRATION DUE TO GRAVITY, still massively important, and how we come by the dimensions of our units of force, energy, power etc, IS NOT VERY USEFUL IN EITHER METRIC OR ENGLISH, AND RESULTS IN CONSTANT SWITCHING BETWEEN KILOGRAMME-FORCE, KILOGRAMMES, TMES & SLUGS, POUNDS, POUND-FORCE etc.
*******Hence my solution of a 0.25second time unit, resulting in a g value = to 2.0 ft, and a simpler and more practical relationship between the force and mass units.




In short, English needs alternative names for:

foot-poundforce & corresponding power unit
foot-poundal & corresponding power unit
(I suggest foot-poundforce to be referred to as "fop", and the fop/second to be referred to as "worth" [from FOot-Pound & Worthington, who named the slug]; foot-poundal to be the "thom" [from Thomson, poundals inventor], and "pu" [Power Unit]

Electrical units are far more complicated and deserve serious discussion.

Bryan,

I think this is a little out of hand. The only lack of units I see in the customary units are the electrical ones. Let us not forget that the units you think have no coherent scientific system put man on the moon. So, what I suggest is that you see how NASA handled units before their great (but befuddled) crossover to metric.

You have obviously misinterpreted what I wrote. Perhaps my tone was off- not sure. I DID write it very early in the morning.

<<
Now, as most of you know, I seem to have somewhat of an obsession with English technical units.
>>

It is interesting top note that 17 engineers and scientists have been honoured by having SI units of measure named after them. Of these 17, 6 were British, more than any other country.

Ok, let me see if I can simplify this a bit.

NASA used the British Gravitational System for all their computations with their mass a derived slug. This corresponds to what I have stated before about slugs being used for dynamic computations. Thus, it's a coherent system.

Most engineers deal with forces, instead of mass; it's convenient for them to use a system that has as its base units length, time, and force, instead of length, time and mass.

There are two sets of systems then which correspond to two metric systems:

British Gravitational System (Coherent, Non-absolute)

Base Units:
Foot
Pound-force
Second
Degree Rankine

Derived slug mass unit

This corresponds to the metric meter/kilogram-force/second system.

English Engineering System (Coherent, Absolute)

Base Units:

Foot
pound-mass
second
degree Rankine

Derived pound-force force unit.

This corresponds to the SI system of units.

The poundal I believe should be completely avoided. It does not fit into an appropriate set of units at any good level.

Now as for the rest of the derived units, you can get rid of the horsepower then to keep the systems coherent.

Work: ft-lbf
Power: (ft-lbf)/s

Thus these are the base derived units of work and power. Any other units needed can be then created from these. The BTU I belive should be retained because of it's classic definition.

MattS wrote

<<
The poundal I believe should be completely avoided.
>>

When I was at University (1965-9), I was taught that the opposite - engineers using the British system worked in poundals and those using the American system the slug. Since South Africa used the British System, the slug was ignored.

Before this gets into a slanging match, may I remind Matt that Sir Winston Churchill once said "Britain and the United States are two countries divided by a common language".

That's an interesting fact Martin, one of which I was not aware. I would still hold that the poundal is a kind of anomoly unit which doesn't fit. I think a better coherency can be established with foot/pound-mass/second and foot/pound-force/second. It seems to keep everything uniform and only adds the slug to units necessary while keeping one consistant pound-force. Thus you have two related systems one "coherent-absolute" and one "coherent"

But, that's just my opinion. I will say however, that as an American I have never ever used the poundal. I have used pounds-force, pounds-mass and slugs for the applications I have noted before.

Engineers and scientists can work in any system of units they choose. There is no such thing as a system of units that is fundamentally better than any other, at least in principle.

In the end any system can be made to work. Indeed I have shown previously that electical units an be defined in non-metric if you so wish.

BUT that misses the point about SI/metric.

First, it's crazy to proliferate many different systems which all do the same job.

Second, although workable, non-metric ignores the simple fact that we count and do arithmetic base ten. Ordinary people with limited mathematical ability don't cope very well in non-decimal systems of measures beyond simple comparison.

Finally, the tools available to us in everyday life are decimal - pocket calculator, spreadsheet etc. Non-decimal can be accomodated with the necessary skills (which most ordinary people don't have) but require extra effort for no good reason.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
English Engineering System (Coherent, Absolute)

Base Units:

Foot
pound-mass
second
degree Rankine

Derived pound-force force unit.

This corresponds to the SI system of units.
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<


How is that coherent? If the pound mass is used, then the poundal MUST be used. This is NOT an equivalent to SI, as in SI the force unit's- the newton- forumla would be:

Newton = kilogram x metres/second squared.

Likewise, the poundal is:

Poundal = Pound x feet/second squared.


To use the pound-force and pound simultaneously is actually non-coherent.

Now, don't get me worng, I DO see the pracitcality of using both pounds of force and mass at the same time. I also see the drawbacks, however. Hence my suggestion for adopting a time unit equal to 1/4 seconds exactly. Now, g = almost exactly 2 feet per time unit squared, and so the units could all be used coherently, with no issue (instead of converting pound-force to poundals by dividing by 32.17, you would divide by 2.00)


The Poundal, far from ebing an anomaly, actually makes the foot-pound system coherent.









Stan,

For a start, English units in a technical cotnext are usually related by the number ten and its multiples (10 manpower = 1 horsepower, 1000mil = 1 inch, 1000 pounds = 1 kip, 1000 feet = 1 kilofoot etc). Secondly, problems can be avoided by knowing how the basic fractions are represented as a decimal. I know, for instance, that 5/6 = 83.333%, and that 1/16 = 0.0625, to name only two.

<<
First, it's crazy to proliferate many different systems which all do the same job.
>>
It's equally crazy to suppress a system that is doing the job just fine.

<<
Second, although workable, non-metric ignores the simple fact that we count and do arithmetic base ten.
>>
But our minds tend to think naturally in fractions. If I hand a random person a string and tell him to cut off 30% of it, he will instantly think that that is a bit less than one-third. He will never mentally divide the string into ten pieces.

<<
Ordinary people with limited mathematical ability don't cope very well in non-decimal systems of measures beyond simple comparison.
>>
Ordinary people with limited mathematical ability cope well with whatever system they are taught and grow up with.

<<
Finally, the tools available to us in everyday life are decimal - pocket calculator, spreadsheet etc. Non-decimal can be accomodated with the necessary skills (which most ordinary people don't have) but require extra effort for no good reason.
>>
That is simply a consequence of our number system. And although in theory it would be difficult to enter non-decimal combinations of units in calculators, spreadsheets, etc., in practice this does not pose a problem because you almost always use only one unit when processing data. (For example, heights in inches only.) The argument that you state above proves that metric is superior from a mathematical perspective, but in practice it simply does not work that way.

Bud wrote

<<
in practice this does not pose a problem because you almost always use only one unit when processing data
>>

That is the American work-around for the system. In the UK, dual units are often used, for example where people measure their weights in stones and pounds.

MattS wrote

<<
NASA used the British Gravitational System
>>


I find this surprising for two reasons:

1. The first director of NASA was von Braun - a German engineer who was trained in Germany.

2. The slug assumes a fixed value for "g", but rockets do not.

As I have said before, pounds-mass is used in "substance" computations when pounds-force are only needed for secondary applications. The reason I would retain the pound-force is that most dynamic computations in the US use the pound-force for the reasons I have stated before. American Engineers tend to prefer the following units:

pounds-mass
slugs
pounds-force

NASA used slugs and pounds-force. Using these two units there is no gravitational factor required. This is why NASA used it. Slug becomes a derived unit then of: The amount of mass that would be accelerated to one foot per second squared from one pound of force. The pound-force is the base unit and the slug is derived without a constant for g.

1 lbf = 1 slug-ft/s^2

To relate pounds-mass and pounds-force you need to use a gravity constant for the given place. Since the pound-mass is generally used for "substance" computations, then moving from pounds-mass to pounds-force is unecessary. If this needs to happen, the mass in pounds should be converted to slugs so that pounds-force becomes meaningful.

To further clarify, NASA also used a unit they invented called the "slinch" (a contraction of slug and inch).

The slinch was used in space where distances and velocities may be small. It's the mass accelerated by one pound-force at 1 inch per second squared.

Thus there are 12 slinches per slug.

Yes Virginia, Neil Armstrong landed on the moon with feet, pounds-force, slugs, and slinches.

Matt, I think you mean there are 12 slugs to the slinch.

Yes, thank you. Slip of the fingers on that one.

12 slugs per 1 slinch.

<<
That is the American work-around for the system. In the UK, dual units are often used, for example where people measure their weights in stones and pounds.
>>
So wouldn't switching to pounds only be much less of a hassle (and cheaper) than switching to an entirely new system?

Most likely. But then I DO generally prefer US weights and measures...

Bud wrote

<<
So wouldn't switching to pounds only be much less of a hassle (and cheaper) than switching to an entirely new system?
>>

In the case of stones and pounds it is not going to happen. Two types of "bathroom scales" are available in the UK - domestic scales which are calibrated in St/lbs and in kg and medical scales which are in kg only.

Furthermore, using a thitd type of measure will complicate matters still further.

My doctor's surgery had both