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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Bullet lift, does it exist?
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<blockquote data-quote="Brown Dog" data-source="post: 177520" data-attributes="member: 1622"><p>And to top it all, you don't even understand ironic humo(u)r.</p><p></p><p></p><p></p><p>Catshooter,</p><p></p><p>In your simple "I once saw tracer burn out" understanding of ballistics; </p><p></p><p>enlighten me as to how point detonating impact fuzes function.</p><p></p><p></p><p>Base your answer on a shell fired at a 47 degree elevation.</p><p></p><p></p><p></p><p></p><p>AJ,</p><p></p><p>What a relief that one of you does humour!</p><p></p><p>I'll extend what I wrote earlier:</p><p></p><p>"The actual mechanism by which this is achieved is as follows: when the projectile is yawed in one plane it experiences an overturning moment in that plane, the gyroscopic reaction to this moment then yaws the projectile in a plane normal to the original one and thus creates a 'negative feedback' situation which causes the yaw in the original plane to decrease (although there will be some residual yaw in the other plane)."</p><p></p><p>This mechanism operates satisfactorily whether a projectile is statically stable or unstable...but a problem arises if the projectile is neutrally stable....because then there is no aerodynamic overturning moment (the upward pressure being applied to the nose due to the nose attitude caused by the 'falling' trajectory) and gyroscopic stabilisation will not work correctly and the projectile will tend to retain its initial attitude. Thus, if the projectile is nearly neutrally stable, or the spin rate is excessive, there WILL be a tendency for the projectile to retain its firing attitude, but such a projectile would be described as 'overstable'.</p><p></p><p>Thus there is an upper and lower bound on the spin rate used for gyroscopically stabilising statically unstable projectiles. If the spin is too low then the projectile will not have enough angular momentum to counteract gyroscopically the aerodynamic overturning moment, if it has too much spin it will be overstable (and yes, it would then land at its firing attitude).</p><p></p><p>So, appropriately spun, it is the gyroscopic reaction and its 'negative feedback' loop as it responds to off axis airflow that causes the nose to follow the trajectory.</p><p></p><p></p><p></p><p></p><p>Just popped back to edit, you posted whist I was typing. The yaw of repose is usually a few fractions of a degree. Don't ask Catshooter, he doesn't believe it exists.....which, if he were correct, would rather render 6DOF ballistic modelling irrelevant!</p><p></p><p>Just popped back again, Your link actually states "Although, for the example shown in the drawing, the yaw of repose never exceeds half a degree" under the graph <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /></p></blockquote><p></p>
[QUOTE="Brown Dog, post: 177520, member: 1622"] And to top it all, you don't even understand ironic humo(u)r. Catshooter, In your simple "I once saw tracer burn out" understanding of ballistics; enlighten me as to how point detonating impact fuzes function. Base your answer on a shell fired at a 47 degree elevation. AJ, What a relief that one of you does humour! I'll extend what I wrote earlier: "The actual mechanism by which this is achieved is as follows: when the projectile is yawed in one plane it experiences an overturning moment in that plane, the gyroscopic reaction to this moment then yaws the projectile in a plane normal to the original one and thus creates a 'negative feedback' situation which causes the yaw in the original plane to decrease (although there will be some residual yaw in the other plane)." This mechanism operates satisfactorily whether a projectile is statically stable or unstable...but a problem arises if the projectile is neutrally stable....because then there is no aerodynamic overturning moment (the upward pressure being applied to the nose due to the nose attitude caused by the 'falling' trajectory) and gyroscopic stabilisation will not work correctly and the projectile will tend to retain its initial attitude. Thus, if the projectile is nearly neutrally stable, or the spin rate is excessive, there WILL be a tendency for the projectile to retain its firing attitude, but such a projectile would be described as 'overstable'. Thus there is an upper and lower bound on the spin rate used for gyroscopically stabilising statically unstable projectiles. If the spin is too low then the projectile will not have enough angular momentum to counteract gyroscopically the aerodynamic overturning moment, if it has too much spin it will be overstable (and yes, it would then land at its firing attitude). So, appropriately spun, it is the gyroscopic reaction and its 'negative feedback' loop as it responds to off axis airflow that causes the nose to follow the trajectory. Just popped back to edit, you posted whist I was typing. The yaw of repose is usually a few fractions of a degree. Don't ask Catshooter, he doesn't believe it exists.....which, if he were correct, would rather render 6DOF ballistic modelling irrelevant! Just popped back again, Your link actually states "Although, for the example shown in the drawing, the yaw of repose never exceeds half a degree" under the graph :) [/QUOTE]
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Bullet lift, does it exist?
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