View Single Post
Old 3rd October 2013, 06:16 AM
Brian.Samson's Avatar
Brian.Samson Brian.Samson is offline
Allowed in Sales
Join Date: Jun 2009
Member of: Pontefract, Doncaster Airgun Range
Location: Doncaster
Posts: 2,332

Originally Posted by rich View Post
The maths can't be wrong but the model can be, and probably is.

Progress comes from challenging the status quo.

I'm unhappy with the notion that the broadside profile of the pellet has nothing to do with its wind drift, and drift only follows from the forward direction drag factor. In my day in class, force = mass times acceleration, and work done = force times distance moved. I can hear my physics master's voice today chanting the mantra, and the last time I saw him was 1961. If the pellet was frozen in time, and just hung there in mid flight, the wind would apply a force related to the dynamic pressure and the angle of incidence of the wind, and the projected area of the profile. That force, however tiny, doesn't go away just because the pellet is moving. But that isn't included in the modelling.
Now I'm not an expert on this, but the way I understand it is that you need to adjust your thinking about what's actually happening.

When a pellet leaves the barrel, it becomes part of the atmosphere and as such it's not being blown by the wind, it's being taken by the wind.
So the only motion the pellet has relative to the wind is forward motion.
The pellet is moving forwards through a substance that just happens to be moving sideways (relative to the ground)

To describe it in another way... You're standing on a bridge over a river that's flowing at 3mph and you drop two sticks off the bridge so they hit the water at the same time. One stick is big, the other is small, but you find that despite the big stick presenting a greater surface area to the flow of water, both sticks travel under the bridge at 3mph.

That's how it was described to me. But like I say, I'm no expert and yes I also think there's something missing from the wind calculation - I just don't know what it is
Reply With Quote