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

[Gareth W-B]

Clearly an in joke I'm not party to.

Lol. Google the Family Guy S&M Bondage Feitish Bedroom scene and listen for the pre-activity code word they agree on to shout, to stop proceedings, if things go too far.

[ChrisC]

Clearly an in joke I'm not party to.

Apologies Pete, i was assuming a man of your calibre would have had the Family Guy Boxset.......

[snock]

Apologies Pete, i was assuming a man of your calibre would have had the Family Guy Boxset.......

I don't have any box sets, mate. Not even of the blessed Star Wars


Any decent fan would know the script off the top of their head, and not need a box set

[RichardH]

pssst....what's your safe word pete?

harder!!

:d

[Rich]

Lol.. listen for the pre-activity code word they agree on to shout, to stop proceedings, if things go too far.

Would Mornington Crescent suffice?

[MartynB]

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

That was my thought

[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.

[Shed tuner]

Why do you see runners and athletes eating bananas then?

This is true, I've never seen them eating daffodils... Or penguins... That closes the matter then

A ftlb can also be a measure of torque .

Way too much tork on this thread...


seriously though, Tinners is correct, for the reason given:

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

[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.

[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

[Turnup]

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 = 2��.n.t where n = revs/unit time and t = torque. Since '2', '��' and 'revs' are dimensionless quantities, we're left with Ft・Lbf/s again.

Clear as mud.

George

Torque is a measure of energy - this has troubled me for a long time. I get your explanation above and this is fine for a moving system (rotational energy), however torque can be static:

Imagine a spanner on a nut and a weight on the spanner tending to either do it up or undo it (it makes no difference) but insufficient to turn the nut. There is a continuously applied and measurable torque on the nut but nothing is moving - where now is the energy?

[Shed tuner]

where now is the energy?

Potential energy in the weight. Or the penguin.