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

[CuppaT]

FPE = Foot Pound Energy

[snock]

FPE = Foot Pound Energy

It's understood that the unit of measure is a measurement in energy. To state as much is like saying KmD where the D means distance.

[GoodWILLHunting]

Sub 12

[rabbitwrecker]

Why did I just read through all of this thread...

p.s. ft/lbs.....

[GPConway]

Why did I just read through all of this thread...

p.s. ft/lbs.....

Go on then, I'll bite.
Show me how you derive those units and I'll show you where you're going wrong.

George

[Waisted]

It's 16 joule coz it sounds bigger init.

[snock]

It's 16 joule coz it sounds bigger init.

Go FAC and have no limits at all.

[Loki_79]

If we are going down the pedantic route, then it should be either: ft⋅lbf, ft⋅lb_f or ft⋅lb (note the dot in the middle of the line, not a full stop). lbf or lb_f are pound-force, whereas lb could also be pound-mass, but lb is acceptable for both. Because there is no '⋅' key on the keyboard, I usually type 'ft.lb' instead, but at least I know it is wrong. As stated previously, 'ft/lb' is always incorrect for energy.

[CuppaT]

It's understood that the unit of measure is a measurement in energy. To state as much is like saying KmD where the D means distance.

If it was that obvious to everyone this thread would not exist.

[angrybear]

A ftlb can also be a measure of torque .
Can't say I've ever seen it used in a technical document with either a dot or dash so either ftlb or fpe for me, depending on the context.

[Turnup]

A ftlb can also be a measure of torque .
Can't say I've ever seen it used in a technical document with either a dot or dash so either ftlb or fpe for me, depending on the context.

I think that the accepted convention is to use the term lb-ft when referring to torque. Mathematically ft-lb is the same as lb-ft (whether torque or energy) so the distinction is only a matter of convention.

Anyway the best measurement for airgun energy is electron volts.

12 ft-lbf = 101 548,211,235,480,000,000 eV

For context, the CERN Large Hadron Collider produces a mere 13,000,000,000,000 eV which means that my Tx200 is a little less than eight million times more powerful than the most powerful particle collider on earth (and physically much more compact).

[Gareth W-B]

Thank you Turnup et al, as notwithstanding the light hearted banter bit in the middle (a MUST have interlude for the survival of any such weighty and thoughtful thread ), the science and maths that has been offered throughout, here, has been both fascinating and compelling, and all greatly appreciated, too.

[Gareth W-B]

Thank you Turnup et al, as notwithstanding the light hearted banter bit in the middle (a MUST have interlude for the survival of any such weighty and thoughtful thread ), the science and maths that has been offered throughout, here, has been both fascinating and compelling, and all greatly appreciated, too.

And again, thanks to all. This thread has proved to be one of the most contemplative and informative, via reasoned intelligent debate (with a little humour along the way) that I have seen on here in many a year. It may now be time to let this thread drift, however, yes? God I love this, our BBS, and long may it continue to be the wibblywobblyinterweb air gun number one. Atvb: G.

.

[robinghewitt]

Kinetic energy is measured as force times distance, so I would go for ft.lbf

Of course the metric equivalent is Newton meters Nm better known as Joules.

The Imperial measure, you might think would be foot poundals, ft.pdl that being the Imperial measure of force.

But, shootists don't like what you might expect, the weigh things in grains ffs. So they measure force as lbf.

Working out a value for the lbf is tricky because it requires a gravity well to convert mass to force. You have to drop weights and use Newton's wonderful f=ma equation.

To get the magic 450240 divisor you need a gravitational acceleration of 32.16 ft/s/s so it is not Greenwich

[GPConway]

A ftlb can also be a measure of torque .

True. That's because torque is a measure of energy and (unsurprisingly) has the same dimensions.
For clarification, energy is written as Ft・Lbf and torque as Lbf-Ft but the units are still the same (although I've always considered the different formatting more confusing than clarifying).
E.g., energy is simply 'work done' and 'Power' is 'work done per unit time' = Ft・Lbf/s and the rotational equivalent is Power = 2𝜋.n.t where n = revs/unit time and t = torque. Since '2', '𝜋' and 'revs' are dimensionless quantities, we're left with Ft・Lbf/s again.

Clear as mud.

To get the magic 450240 divisor you need a gravitational acceleration of 32.16 ft/s/s so it is not Greenwich

The value for 'Standard Gravity' is 32.174 Ft/s² which makes the magic number 32.174 * 2 * 7000 = 450436.
Definitely not Greenwich. Paris maybe?

George