12ft.lb ... or ... 12 fpe ?

[Gareth W-B]

Morning all. Since a similar thread on here many many moons ago (which I simply can not now find) which pre-dated my BBS Mod life iirc (so that makes it at least pre 2008), from which I learned twelve feet per pound should be written 12ft.lb, I have always written it that way.

Of late, however, both on here and another forum I visit, I've started to notice people writing twelve feet per pound as 12 fpe, so is this also a correct notation, is it the new accepted notation that dinosaurs like me should now adopt and replace the former with, or is the former still the one and only correct notation, or, err, should I get a grip as it doesn't really matter?

[LESS THAN FORTUITOUS KENNETH]

fpe is ft lb energy int it? Eggzackerly same as 12 ft/lb.

[cooper_dan]

get a grip

[tinbum]

I've started using fpe a lot of the time as it's easier to type.

[VALE BOY]

I think it may be due to the prevalence of tautology that pervades everyday speech nowadays...people overstating the same thing, twice or more, perhaps for emphasis. Such as, 'reverse back into that space'..."Tables can be pre-booked in advance". In fact this "pre-booking" expression really bugs me, as the correct terminology is simply 'Booking'!
The top one of the lot is probably the typical Politician's statement which commences..."Currently at this present moment in time"!

[Rich]

12 ft/lb is wrong, always.

[snock]

I've heard of 12psi, 12 lb of pressure and 12lb - it's amazing that so many air gunners don't know, or don't understand, the limits placed upon them.

[deejayuu]

Pedantic but to answer the OP. Imperial measurements for "work done" give Force (lbs.) moved through Distance (ft.) to give a multiple ie
Force X Distance so algebraic convention ft.lb.
"Feet per pound" is a division so ft./lb will give a much smaller, incorrect for our purpose, result using the same values.
I assume fpe to be abbreviation of "ft.lbs of energy" but probably wrong.

[lensman57]

12 ft/lb is wrong, always.

Yes it should be ft.lbs to express energy. One foot of distance divided by one pound of weight is rather meaningless.

A.G

[lensman57]

They are both correct and ' wrong ' at the same time as the they are not SI units. To be strictly correct the muzzle energy of a gun should really be expressed in joules, one J being when a force of one newton acts over one meter of distance in the direction of motion of the object/projectile.

A.G

[Shedder]

They are both correct and ' wrong ' at the same time as the they are not SI units. To be strictly correct the muzzle energy of a gun should really be expressed in joules, one J being when a force of one newton acts over one meter of distance in the direction of motion of the object/projectile.

A.G

Why is the use of Joules any more correct than foot pounds force just because it is an SI unit? Is a metre any more correct or strictly correct than a yard?

[ChrisC]

All i know is that if you open an airgun all the airgun pixies and fairies escape and can be buggers to catch and get back in again. I've found sandwiches an effective bait to lure them back, in fact that's what FPS stands for.

Fairies+Pixies+Sandwiches

[Gareth W-B]

All i know is that if you open an airgun all the airgun pixies and fairies escape and can be buggers to catch and get back in again ...

Simples. Get our Jim Tyler to lure them back in by using the gubbins tube they live in, as a Pan Pipe: job done (coz fairies can't resist our JT ) ...

[lensman57]

Why is the use of Joules any more correct than foot pounds force just because it is an SI unit? Is a metre any more correct or strictly correct than a yard?

It is not the point of being ' correct ' or not. SI units were devised so engineers all over the world would be able to understand each other. Prior to SI units every nation had their own set of nonmenculture/units for denoting weights, energy, , force, length etc. So when we were in uni even as far back as the 1970s SI units were used for engineering terms. I remember that I had an old A Level physics book that I had inherited from my cousin who sat his A levels in the late early 70s. Some of the Imperial units units such as BTU were a real pain to convert into SI.
Although a person outside of the US/Uk would understand ft.lbs to be a unit of energy they may not know exactly how much energy one ft.lbs represents. As with joules the definition is clear, energy/work of one newton of force acting upon an object over a distance of one meter in the direction of its motion.

A.G

[Rich]

But the BTU was quite simple; the amount of heat required to raise the temperature of one pound of water by one Fahrenheit degree.

In transition to metrication we had CHUs, Centigrade Heat Units, still using pounds of water but Centigrade degrees.

3,412 BTU/hr made one kilowatt. 16 ounces made a pound but if they were fluid ounces you needed 20 to make a pint. A pint of water is a pound and a quarter. But not in America. Their gallons were smaller than ours, in the ratio 5/6. Odd, that something in the US was actually smaller than in the UK, but I think it is because the same volume of water works out a bigger number in the states so it sounds larger.

Sorry for the digression.