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Tex · New Member

Anybody ever suspend one of those little one pound barbells and pop the end to see what movement your pellet produces? Would give a pretty good indication of pounds per sq. inch at target distance. At least it'd remove most doubt. (let's see if this idea ends up on other forums. lol)

Rogerflat · Silver Status Member

It'd be interesting to see what it does, but how would you measure it other than just eyeing it?

jonathan · Member

You are forgetting about gravity and friction.......

broommaster2000 · Moderator

We more often refer to power(or Energy) as Ft/Lbs or Joule. For a guy like me, most other things don't make much sense, but I do know that PSI is something that can be used to measure pressure. In this case, we could also use BAR, which is used on most pre-charged pneumatics.

This doesn't necessarily show the amount of power, as there are rifles that use a 300 bar reservoir, but only deliver 12 Ft/Lbs ([i]or Fpe = Foot Pounds of Energy) when actually shot. This has to do with the chosen spring and hammer, but that's a whole other story.

So, in the airgun world, you'll want to use the term Fpe or Joule, as everything can be calculated from that with either the weight or the velocity of the pellet.

fritz · Silver Status Member

Tex, there are a lot more complexities to what you want to do that that.

Let's say you hung it from a rope or string, and you shot the end closest to the ground. (this is all occuring in a fraction of a second possibly) It will first jump back because of Newton's first law, and then the bottom will go back more as the force was more applied to it. The barbell will then begin to swing back and forth converting the new kinetic energy back to potential. This will happen faster if there is more friction on the rope and if gravity has a stronger pull in that area.

That test also proves nothing. A more accurate test would be to put that barbell flat on a (frictionless) plane. Then shoot the end of it. Should you take FOOT POUNDS literally, then however many feet the barbell moves, would be your footpounds.

I'm sure there are a plethora of inaccuracies and such and that a good physicist could explain all of this.

BUT THE EASY WAY IS TO JUST USE A SIMPLE FPE CALCULATOR!

rsterne · Moderator

except that if the plate was frictionless, the barbell would never stop moving after being struck by the pellet.... Shocked

Bob

fritz · Silver Status Member

rsterne · Moderator

Actually, if the plate curved with the surface of the Earth, gravity would NOT stop it.... however, air resistance would.... eventually.... Rolling Eyes

I'm done.... Bob

fritz · Silver Status Member

Oh, I didn't remember that the plate was completely frictionless. Yeah, you're right (haven't been wrong in a while Mr. Green

).

Even if it wasn't curved it may keep going because the farther away from the Earth's core you are the less effect it's gravity has on you.

Either way it's easier to use a FPE calc.