Does a RB travel with constant rotation, or accelerate?

[Griz44Mag]

Is the answer to that question important to you? How important, if so?

To me, just a curiosity...... And some fun numbers to play with when you have the range to yourself and some time to play.
I got on target at 200 yyards and was able to repeat the hits on a man sized target.
With only 3 + feet to elevate a shot aimed just over the head would land on the body.
On my Lyman with a Pedersoli ghost peep - that's 8 full turns up on the rear thread post.
On my Frontier - it's a hold over...
AND - it was a lot of fun trying.

 

[rdlowe]

Right on. Curiosity is a heck of a motivation, even if for its own sake.

 

[tenngun]

So now I have to ask the question already asked or stated here earlier.
Is any of this advanced physics going to be put to any useful purpose by any member here?
Or are we going to go out and shoot our muzzies exactly the same as we have been doing for the last 500 years?
Load - point - shoot - repeat...........adjust aim as required.

I have shot my .54 Lyman out to 500 yards using data from the ballistics calculator.
Although I did not hit the man sized silhouette at 500 yards - I did get close enough to take out the horse he could have been riding on.
.View attachment 39488
That's 42.5' elevation.

When you bake a pie you cut three holes, one to vent the steam two cause mama did it that way. I ‘spect we’ll keep on doing the old way
‘Mathematic is fine
but you left out a trifle
Like the head hands and eyes
That back up the rifle’

 

[Rich]

Forget it is a PRB. Any object traveling forward and rotating will slow down, period. Its a function of drag gravity. Unless an outside force acts upon the ball to accelerate it, it slows down in both rotation and velocity. The rate of deceleration in velocity is easy to measure. Just put a chronograph in front of the muzzle and another in front of the target. The rotation is more difficult without something like a very high speed camera. On a 50 yard shot, I imagine it is minimal, but it does slow down.

 

[hawkeye2]

Here is where the train derails. You can only think of spin rate in terms like 1 turn in 48" while the projectile is still in the barrel. From the time it starts to move till it exits the muzzle it must turn at 1 revolution in 48" (let's assume a 48" long barrel for simplification). Let's use the data in Griz44Mag's post (#78) above. at exit from the muzzle the ball has the spin on it imparted by the 1 in 48" (or 1 in 4') rifling. It is now traveling at 1610 FPS and spinning at a rate of 24,120 RPM. We have converted the data to revolutions per minute and when dealing with RPM it doesn't matter whether the ball is moving or not Your big block Chev powered 53 Studebaker is sitting in the pits, you rev the engine to 7,500 RPM, vehicle speed 0 MPH, now at 1.5 miles the engine is doing 7,500 RPM and and the vehicle is traveling 208 MPH, the speed of the vehicle or the distance traveled has no bearing on RPM. As I posted before the formulas for angular velocity and angular momentum (spin speed and rotational momentum) do not deal with the distance, if any, traveled by the body, it can be stationary or traveling at the speed of light. The formula for angular acceleration, the change in rotational speed either accelerating or decelerating, refers to the change in RPM and it doesn't matter here either if the body is moving or not. The velocity at which the projectile is traveling is not relevant (the distance and time it took to travel from point A to point B) and attempting to drag them into the calculations will only cloud the issue to the point of zero visibility.

Gyroscopic action is not a force acting on the spin but rather is a result of the spin and mass of the spinning object and it in itself cannot change the rate of spin of the object as it in itself is not a force.






Everything slows but how much. Will 24000 RPM out last 1600 fps?
[/QUOTE]

 

[nkbj]

Yall're forgetting that round ball are metallic and that considering any rotating conductor passing through a magnetic field can induce a torquing elctromagnetic effect upon a ferritic icebox handle, producing cold suds.

 

[hawkeye2]

"So now I have to ask the question already asked or stated here earlier.
Is any of this advanced physics going to be put to any useful purpose by any member here?"

Not one D@%$ bit of it! Now I'm ready for a Corona, the liquid kind and not a corona effect.

 

[hawkeye2]

Yall're forgetting that round ball are metallic and that considering any rotating conductor passing through a magnetic field can induce a torquing elctromagnetic effect upon a ferritic icebox handle, producing cold suds.

Darn, now the cats out of the bag. My flint linear magnetic field particle accelerator is still in the planing stages but won't come as a surprise.

 

[tenngun]

That sounds like an Asimov novel, ‘Hawkeye Joe and his electric flintlock’

 

[tenngun]

Here is where the train derails. You can only think of spin rate in terms like 1 turn in 48" while the projectile is still in the barrel. From the time it starts to move till it exits the muzzle it must turn at 1 revolution in 48" (let's assume a 48" long barrel for simplification). Let's use the data in Griz44Mag's post (#78) above. at exit from the muzzle the ball has the spin on it imparted by the 1 in 48" (or 1 in 4') rifling. It is now traveling at 1610 FPS and spinning at a rate of 24,120 RPM. We have converted the data to revolutions per minute and when dealing with RPM it doesn't matter whether the ball is moving or not Your big block Chev powered 53 Studebaker is sitting in the pits, you rev the engine to 7,500 RPM, vehicle speed 0 MPH, now at 1.5 miles the engine is doing 7,500 RPM and and the vehicle is traveling 208 MPH, the speed of the vehicle or the distance traveled has no bearing on RPM. As I posted before the formulas for angular velocity and angular momentum (spin speed and rotational momentum) do not deal with the distance, if any, traveled by the body, it can be stationary or traveling at the speed of light. The formula for angular acceleration, the change in rotational speed either accelerating or decelerating, refers to the change in RPM and it doesn't matter here either if the body is moving or not. The velocity at which the projectile is traveling is not relevant (the distance and time it took to travel from point A to point B) and attempting to drag them into the calculations will only cloud the issue to the point of zero visibility.

Gyroscopic action is not a force acting on the spin but rather is a result of the spin and mass of the spinning object and it in itself cannot change the rate of spin of the object as it in itself is not a force.






Everything slows but how much. Will 24000 RPM out last 1600 fps?

[/QUOTE]so you Rev your engine up to x, engage your drive now your car is going a hundred MPH then you turn off the fuel line. No energy is going to keep up that RPM it instantly starts to slow. Disengage your drive, ie take it out of gear and and the engine slows instantly. Keep your car in gear you slowly decrease your rpm until zero as the car slows.
Apt anolgy? I don’t know.

 

[Col. Batguano]

Let's also remember that due to the acceleration force, and the maleability of lead, that the bigger the load you put under it, the faster it accelerates, the more it will deform, and decrease the ballistic coefficient. The effect of this is in increasing the straight walled portion, (the nose of the ball will be about the same but the base will be flatter) or portion with maximum diameter. The further it is away from the axis of rotation, the more inertia it will have in wanting to maintain that rotational velocity.

Drag and rate of rotational decay will also be affected by the depth of the grooves, and whether you have round bottomed or square groove rifling.

 

[Rich]

Yes I are using that there edvand pysical formulas. I are using it to figure how far to off sat my aimin place to alot for da turing rotatle of the erth. See ifin i wer to point ant one place and the ball goes that wa it mite have missed the place I were sindin it to. My phomuler was reviews by Jethro Bodine, noted breain surgerin person.

 

[hawkeye2]

so you Rev your engine up to x, engage your drive now your car is going a hundred MPH then you turn off the fuel line. No energy is going to keep up that RPM it instantly starts to slow. Disengage your drive, ie take it out of gear and and the engine slows instantly. Keep your car in gear you slowly decrease your rpm until zero as the car slows.
Apt anolgy? I don’t know.
[/QUOTE]

That is of course true and I don't know if it works as an analogy or not either. In my post I was assuming power was kept on to keep the engine at a constant speed in this case 7,500 RPM at rest and at 208 MPH constant speed.

 

[hawkeye2]

Drag and rate of rotational decay will also be affected by the depth of the grooves, and whether you have round bottomed or square groove rifling.
[/QUOTE]

In supersonic flight each grease groove will set up a shock wave. It's possible if the rotational surface speed of the projectile was high enough it might happen there too. Yes the grooves left by the rifling will increase drag and slow rotation faster but by how much?

 

[Col. Batguano]

Think about it in terms of an airplane. Even at subsonic velocity, the turbine blade tips (or propeller) could be traveling at supersonic velocities. A 50 cal RB @ 24,000 RPM is spinning at surface velocity of 37,700 inches per minute at it's equator, or roughly 52 feet per second. So though roughly 1080 fps is the speed of sound, until velocity drops below 1028 fps, the ball will still be (at least a portion of it) traveling at supersonic speed, and be unstable during that transitional period.

 

[Griz44Mag]

When you bake a pie you cut three holes, one to vent the steam two cause mama did it that way. I ‘spect we’ll keep on doing the old way
‘Mathematic is fine
but you left out a trifle
Like the head hands and eyes
That back up the rifle’

And as we get older - and older - those factors become MUCH more pronounced.... (Good one)

 

[tenngun]

And as we get older - and older - those factors become MUCH more pronounced.... (Good one)

Not mine. Was in the ol buckskin report or black powder report late 70s or early 80s end of a long poem published one time. I recall parts but not all nor the writer.
Stared
Said the coon on the peg,
I’m a hat on his head
Cause I simply forgot about
Fine alloyed lead
With me said the deer
My insides were wrecked
By ballistic co effecicent
And corlis effect
And legions of red coats
With their muskets and gear
All shook their heads
And agreed with the deer
‘It’s not through skill or bad luck
We encountered deaths path
But simply because that boy knew his math’
It went on but I forgot the rest till the last stanza
Lost my copy years ago

 

[tedium27]

Or is it tumbling ???

Or rotating?

 

[Billy Boy]

"So now I have to ask the question already asked or stated here earlier.
Is any of this advanced physics going to be put to any useful purpose by any member here?"

Not one D@%$ bit of it! Now I'm ready for a Corona, the liquid kind and not a corona effect.

I had physics this morning. Could have been too much butter and warm syrup on my waffle or reading this post again. Why don’t we start working on solutions to some other imaginary problems?

 

[Griz44Mag]

In any case, the changes in the speed either one of them rotates is very slight and for the most part, it can be overlooked when it comes to the original post's question.

Completely agree!

With flight times in the fractions of a second - the loss of rotational speed is not going to be a factor in the flight of the ball.
Think about it this way,
A ball with 1:48 original spin (One rotation each 4') - at original velocity of 1610 FPS - degrades to 1049 FPS and takes .24 seconds to reach a 100 yard target, the ball makes approximately 75 full rotations (approximately 64,800 RPM). At 50 yards even less - 38-40 rotations.
Just how much rotational speed can be lost in that distance and in that short of an amount of time? It's going to be miniscule!
IF the rotational speed drops as fast as the velocity (65%) - that number of turns would only drop to 48.
Since only the front surface of the ball is catching the air resistance - only half that area should be considered - so the number of rotations should only drop to 62.
Either way - seems to me that rotational speed is negligible - (see Zonies statement above)