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Slinging theories/explanations "internal ballistics" (Read 14547 times)
Mersa
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Re: Slinging theories/explanations "internal ballistics"
Reply #90 - Jul 9th, 2020 at 7:19pm
 
Noooooooooooooo put this thread back in the archive
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wanderer
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Re: Slinging theories/explanations "internal ballistics"
Reply #91 - Jul 10th, 2020 at 3:58am
 
Mersa wrote on Jul 9th, 2020 at 7:19pm:
Noooooooooooooo put this thread back in the archive


No! Don't do that yet.

I missed most of this at the time, and I feel the arguments that were being made were along the right track.

A very long time ago there was a paper by "George Alsation" accessible. I can't seem to locate a non-Forum home page, which existed at one time. That contained a number of little examples trying to get to grips with the mechanics of the sling, and Apo's diagrams seem to have been illustrating one of Alsation's points.

It looks to me like the dialog between him and JudoP broke down over the description of forces and (probably) some language matters.

The nub of all this is that to increase the speed (kinetic energy) of the sling stone you have to do work on the 'hand' end - what would be the support point if this were a 'high school physics' simple pendulum.

For that you need to move the support point (the hand) , and you also need the pendulum bob to be traveling in a curve in order to tension the cord. If you move the support point appropriately you couple energy into the slingstone and hence increase its speed.

On Apo's diagrams, he was dealing with the motion of the slingstone from W (west) via S and then finally to E, or thereabouts. Throughout this region the sling is pulling against the hand such that movement of the hand towards the north (as Apo was describing) will do mechanical work on the system, increasing the sling stone speed.

Apo also touched, as far as I can make out, on the view of the sling as like a simple pendulum where instead of just a constant gravitational acceleration there is instead a variable acceleration which is due to the movement of the support point. This view is confirmed if you grind through to the Lagrange equation of motion.

I have to admit I wondered whether Apo was actually "George Alsatian", so similar was the basis of his arguments, but who knows?

Apex-apoc = Apo  Wink
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Re: Slinging theories/explanations "internal ballistics"
Reply #92 - Jul 10th, 2020 at 4:26am
 
wanderer wrote on Jul 10th, 2020 at 3:58am:
A very long time ago there was a paper by "George Alsation" accessible.


This one?

http://web.archive.org/web/20070101032007/http://www.slinging.org/29.html
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Re: Slinging theories/explanations "internal ballistics"
Reply #93 - Jul 10th, 2020 at 4:27am
 
wanderer wrote on Jul 10th, 2020 at 3:58am:
Apo also touched, as far as I can make out, on the view of the sling as like a simple pendulum where instead of just a constant gravitational acceleration there is instead a variable acceleration which is due to the movement of the support point. This view is confirmed if you grind through to the Lagrange equation of motion.


I dont remember an article like that in this discussion, if you find it please post it again or post the reply#.(I dont have the time to go through it again right now)
The only thing Ive seen close to what you describe is http://slinging.org/forum/YaBB.pl?num=1561512843 reply#4

NooneOfConsequence wrote on Jun 26th, 2019 at 8:28am:
For some reason part of the link cut off. Top result here:
https://scholar.google.com/scholar?hl=en&as_sdt=0%2C44&q=flinger+trebuchet

haven't read it yet, I still need to up my physics game.

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Re: Slinging theories/explanations "internal ballistics"
Reply #94 - Jul 10th, 2020 at 4:33am
 
Jauke ich bin auch ein Höhlenmensch. Lass uns slingen gehen. Theorie ist für Theoretiker. Slingen ist was für Höhlenmenschen. 😁 😂
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Re: Slinging theories/explanations "internal ballistics"
Reply #95 - Jul 10th, 2020 at 5:50am
 
Sarosh wrote on Jul 10th, 2020 at 4:27am:
I dont remember an article like that in this discussion, if you find it please post it again or post the reply#.(I dont have the time to go through it again right now)
The only thing Ive seen close to what you describe is http://slinging.org/forum/YaBB.pl?num=1561512843 reply#4


It's the one Teg just posted. Strange how I never have the wayback machine at the front of my brain for these things.

The paper you posted looks like a barrel of laughs. Perhaps the culmination of several semesters of classical mechanics.  Wink

But... equation (12) in there is the one I had in mind, but maybe looks less offensive in polar coordinates.
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Re: Slinging theories/explanations "internal ballistics"
Reply #96 - Jul 10th, 2020 at 8:40am
 
wanderer wrote on Jul 10th, 2020 at 3:58am:
The nub of all this is that to increase the speed (kinetic energy) of the sling stone you have to do work on the 'hand' end - what would be the support point if this were a 'high school physics' simple pendulum.

For that you need to move the support point (the hand) , and you also need the pendulum bob to be traveling in a curve in order to tension the cord. If you move the support point appropriately you couple energy into the slingstone and hence increase its speed.

On Apo's diagrams, he was dealing with the motion of the slingstone from W (west) via S and then finally to E, or thereabouts. Throughout this region the sling is pulling against the hand such that movement of the hand towards the north (as Apo was describing) will do mechanical work on the system, increasing the sling stone speed.



What you say seems correct to me, the contention was that you cannot simply add v_hand to the current angular velocity of the sling projectile. In fact you cannot really apply force at all in the north/south direction when the sling is in the 9 o'clock position, since the cord is orthogonal with N/S direction.

Instead you apply force inwards across the whole movement which converts into greatly increased angular velocity. It may not feel like this in practice, but if you sling you can feel the tension pulling always directly outwards along the cord, and the force you apply to the projectile via the cord is simply working against this. In fact the only force you CAN apply is radially inwards.

Quote:
Apo also touched, as far as I can make out, on the view of the sling as like a simple pendulum where instead of just a constant gravitational acceleration there is instead a variable acceleration which is due to the movement of the support point. This view is confirmed if you grind through to the Lagrange equation of motion.

I have to admit I wondered whether Apo was actually "George Alsatian", so similar was the basis of his arguments, but who knows?

Apex-apoc = Apo  Wink


It does seem likely in reading both posts. The sling has a lot of similarities with a pendulum, it is basically the same system with different forces applied. It seems plausible to me that the movement (acceleration specifically) of the support point could be reformulated as an external (pseudo) force, though you may see extra complication as I expect that the pivot hand force will change through time to be applied directly along the line of the sling, compared to gravity which is a constant. Overall this seems a much more promising approach than what I think he was trying to explain to me around adding velocities. Unfortunately I think any allusion to this was lost in translation for the original thread.
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Re: Slinging theories/explanations "internal ballistics"
Reply #97 - Jul 11th, 2020 at 8:37am
 
Oh no. What have you done? Cast it into the fire! Destroy it!

But seriously, I stopped even trying to follow this one.
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Re: Slinging theories/explanations "internal ballistics"
Reply #98 - Jul 12th, 2020 at 10:39pm
 
Teg wrote on Jul 10th, 2020 at 4:26am:
wanderer wrote on Jul 10th, 2020 at 3:58am:
A very long time ago there was a paper by "George Alsation" accessible.


This one?

http://web.archive.org/web/20070101032007/http://www.slinging.org/29.html


LOL ...Ok, I probably enjoy the theory discussions more than most people, but it’s hard to take this seriously when his physics-based advice includes “run to the side and cover your head”

He doesn’t need math, he needs more practice!  ... and maybe a different sling.
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Re: Slinging theories/explanations "internal ballistics"
Reply #99 - Jul 13th, 2020 at 11:03am
 
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Re: Slinging theories/explanations "internal ballistics"
Reply #100 - May 17th, 2021 at 3:51pm
 
Ah my favorite thread, this video is great for studying sling slowmotion shots, I can watch it over and over
https://youtu.be/qm--RIJH0p0
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Re: Slinging theories/explanations "internal ballistics"
Reply #101 - May 17th, 2021 at 4:01pm
 
Can someone start a tangent on this thread about which is worse for society hunting with the sling or socialism? Apparently this thread needs to go nuclear before it can be locked and forgotten. Seriously, this is one of the most painful to read threads on this site.
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