To lesson the entering turn yaw, used Progressive springs, 15 w oil and slightly more preload in the front. Progressive 11 in shocks in rear. Yawing is at minimum, and actually takes curves pretty good for ancient design. It be old man styling.
spin stabilization of projectile--yes or no?
- Thread starter stagpanther
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To lesson the entering turn yaw, used Progressive springs, 15 w oil and slightly more preload in the front. Progressive 11 in shocks in rear. Yawing is at minimum, and actually takes curves pretty good for ancient design. It be old man styling.
stagpanther
New member
I got my ninja in the 1980's--lightning fast for its day. I remember once going up a highway in the wee hours of the morning (back when cops couldn't tag you on radar cause of all the plastic) at somewhat north of 120 mph and hit a small rock on the road. This set off a vibration in the front fork which quickly intensified into a bad wobble--luckily I backed off fast enough to get it under control.
I almost got T-boned a hundred times by cars that went right through stop signs without seeing me--even if they looked, and finally got clipped on the side once--that's when I went with a Harley for casual cruising. Mine was fun cruising--but it was on a perpetual mission to shake a screw loose or start an oil leak, so I got rid of it.
I almost got T-boned a hundred times by cars that went right through stop signs without seeing me--even if they looked, and finally got clipped on the side once--that's when I went with a Harley for casual cruising. Mine was fun cruising--but it was on a perpetual mission to shake a screw loose or start an oil leak, so I got rid of it.
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stagpanther
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Well, it's my thread, and i don't mind, and there are a couple of similarities.
stagpanther
New member
Hmmmm...probably illegal--makes for an interesting image though.
Yes. The mathematics (which I will not attempt to present) do allow for a point in the bullet's trajectory where the rotation of the bullet overcomes any perturbations of the trajectory caused by expelling the bullet from the muzzle.
The significance of this effect is dependent upon propellant, bullet weight, bullet configuration, velocity, number of turns per inch in the barrel, as well as wind conditions downrange.
In short, is there a point beyond 100 yards where a bullet strains greater stability; yes, possibly.
Is that stability predictable - or even achievable for the average reloader - no.
The significance of this effect is dependent upon propellant, bullet weight, bullet configuration, velocity, number of turns per inch in the barrel, as well as wind conditions downrange.
In short, is there a point beyond 100 yards where a bullet strains greater stability; yes, possibly.
Is that stability predictable - or even achievable for the average reloader - no.
stagpanther
New member
I have recently ventured back into 22lr shooting (which BTW can be very expensive if you're after accuracy beyond 50 yds) and it's really fascinating in the respect that it puts aerodynamic projectile effects on a smaller scale while exaggerating the factors that throw off the projectile's flight.
As Bart says, the bullet slows 10 or 15% by the time it travels 1000 yards. However, the velocity drops by half or more. This means the drag that attempts to overturn the bullet is maybe a quarter of what it was near the muzzle, so it is much easier to stabilize the bullet out there. The result is the stability factor goes up as the bullet goes downrange. You can see this for yourself by using a stability calculator and increasing the spin pitch by the speed loss ratio, then adding your ten or fifteen percent.
stagpanther
New member
Wouldn't this also depend on other factors such as center of gravity and air "bow-wave" dispacement of the projectile's design? (phishing for knowledge here
)What about over spinning the bullet ? Thought it’s best to spin the bullet the least amount to accomplish stability. So wouldn’t the faster the bullet is spinning the slower the velocity could actually be bad ??? As Stag just pointed out , many factors here . Blanket statement spinning fast is better just does not sound accurate.
stagpanther
New member
I took Bart's statement to mean the opposite, as spin slows along with velocity at distance, stability improves. I'm easily confused though.
That is correct. Stability factor generally goes up as the bullet goes downrange. Use this calculator and you can see the increase in gyroscopic stability factor with range in the last column of the table at the bottom of the result page.
We start with the assumption is that the bullet is fired with enough spin to be stable to begin with. Any initial yaw not so great as to cause direct tumbling will be about 80-90% damped out after a couple of hundred yards (see Litz's plots of this in his Applied Ballistics for Long Range Shooting, page 156 of the 1st Ed.). Interestingly, that distance does not change with spin rate because while it is true faster spin reduces the number of cycles of coning needed to close in on the final stable orientation of the bullet (assuming constant wind conditions), the greater gyroscopic stiffness of the faster spin makes each one of those cycles slower. The two effects cancel each other out.
As to center of gravity, that determines the location of the transverse moment of inertia, and the axis location of the axial moment of inertia, both of which are critical to calculating minimum stable spin rate at any particular velocity. You can determine both by using a vertical torsion pendulum and a stopwatch. I won't go through the procedure here because you can look at several methods published by physics teachers online. A critical point is that if the CG is not exactly centered in the bullet axis, faster spin of the bullet will introduce helical wobble. Additionally, lateral drift after exiting the muzzle that is due to spinning an off-center CG in the bore will also increase with spin rate. So, when people say, "over stabilized", they are really just saying that it is spinning faster than is strictly necessary for best accuracy, and therefore increasing the chances that a small manufacturing error in the bullet CG location, or an off-center CG caused by a few thousandths of bullet tilt in the barrel, will open the group more than you have if you stuck to a stability factor of about 1.5.
The shockwave formation does, of course, affect drag by creating the sound barrier effect, but that is just a rise in drag that exceeds what Newtons formula predicts. It is not more than you have at still higher velocities. So, again, if you are spinning fast enough to be stable at the muzzle, you are more than fast enough to be stable at the lower velocities that drag produces.
We start with the assumption is that the bullet is fired with enough spin to be stable to begin with. Any initial yaw not so great as to cause direct tumbling will be about 80-90% damped out after a couple of hundred yards (see Litz's plots of this in his Applied Ballistics for Long Range Shooting, page 156 of the 1st Ed.). Interestingly, that distance does not change with spin rate because while it is true faster spin reduces the number of cycles of coning needed to close in on the final stable orientation of the bullet (assuming constant wind conditions), the greater gyroscopic stiffness of the faster spin makes each one of those cycles slower. The two effects cancel each other out.
As to center of gravity, that determines the location of the transverse moment of inertia, and the axis location of the axial moment of inertia, both of which are critical to calculating minimum stable spin rate at any particular velocity. You can determine both by using a vertical torsion pendulum and a stopwatch. I won't go through the procedure here because you can look at several methods published by physics teachers online. A critical point is that if the CG is not exactly centered in the bullet axis, faster spin of the bullet will introduce helical wobble. Additionally, lateral drift after exiting the muzzle that is due to spinning an off-center CG in the bore will also increase with spin rate. So, when people say, "over stabilized", they are really just saying that it is spinning faster than is strictly necessary for best accuracy, and therefore increasing the chances that a small manufacturing error in the bullet CG location, or an off-center CG caused by a few thousandths of bullet tilt in the barrel, will open the group more than you have if you stuck to a stability factor of about 1.5.
The shockwave formation does, of course, affect drag by creating the sound barrier effect, but that is just a rise in drag that exceeds what Newtons formula predicts. It is not more than you have at still higher velocities. So, again, if you are spinning fast enough to be stable at the muzzle, you are more than fast enough to be stable at the lower velocities that drag produces.
stagpanther
New member
Thanks. It would be cool to have animations of these principals. I feel like I'd need to return to college to understand Litz's calculator. I did actually buy his books years ago but getting through the computer simulations stuff was rough going for me.
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Stagpanther,
I had the same idea, and actually started work on a coning motion animated .gif file when this thread first began. Then the longer I stayed out of it and watched ideas going back and forth, it made me think it would be more useful to do a whole video on why spinning works to stabilize a projectile. Then it occurred to me there are probably already a number of them, and I should just go through them and find one I can refer people to.
It's actually not as terribly complicated as some imagine. Once you get past understanding why precession makes a spinning object turn perpendicular to forces that try to turn its spin axis, all the rest falls out. There are a couple of good explanations for precession on YouTube videos, but I would like to find one that shows tipping momentum flipping around every half turn because that way of looking at it explain nutation as well as stability when you take the time required for a half rotation into account. If I don't find one like that, perhaps I can find time to put one together down the road. The trick is trying to keep it visual. Most folks who don't work with equations regularly tend to see them as formulas rather than descriptions of what is happening, so they sort of zone out when you start laying out the math symbols. And you don't have to be able to see equations to understand the principle. You can get it just by seeing little arrows showing the directions of momentum. The only thing you miss without the equations is a method of quantifying what your mind's eye sees.
I had the same idea, and actually started work on a coning motion animated .gif file when this thread first began. Then the longer I stayed out of it and watched ideas going back and forth, it made me think it would be more useful to do a whole video on why spinning works to stabilize a projectile. Then it occurred to me there are probably already a number of them, and I should just go through them and find one I can refer people to.
It's actually not as terribly complicated as some imagine. Once you get past understanding why precession makes a spinning object turn perpendicular to forces that try to turn its spin axis, all the rest falls out. There are a couple of good explanations for precession on YouTube videos, but I would like to find one that shows tipping momentum flipping around every half turn because that way of looking at it explain nutation as well as stability when you take the time required for a half rotation into account. If I don't find one like that, perhaps I can find time to put one together down the road. The trick is trying to keep it visual. Most folks who don't work with equations regularly tend to see them as formulas rather than descriptions of what is happening, so they sort of zone out when you start laying out the math symbols. And you don't have to be able to see equations to understand the principle. You can get it just by seeing little arrows showing the directions of momentum. The only thing you miss without the equations is a method of quantifying what your mind's eye sees.
stagpanther
New member
If you look at Zeke's link about the motorcycle racing engine development (not that I expect you to do anything like that) which I found fascinating-- I got a "semi I get that" even though it was very technical and moved very fast. That's because the physics of something affecting an object are just easier to understand when illustrating what is actually happening. That said--I'm a visual artist myself and I know I don't have the skills (or patience) to use a CADCAM type program to illustrate the physics.
absolutely. As my mind gets less capable to grapple with this I get mentally lazy.