[SCA] How many PSI is a "good" shot?

Hrogn · Post by **Hrogn** » Fri Jul 14, 2006 5:50 pm

Has anybody looked into that in any quasi-scientific way? I completely understand that the answer will vary depending on Kingdom, weapon, etc. But if you have looked into it in anyway, I would be interested in your story.

Maeryk · Post by **Maeryk** » Fri Jul 14, 2006 6:02 pm

The quantity required to make Logan say "GOOD" should work in any kingdom.

I would call that a "metric dukeload"

For say, Michael of Bedford, it would be an "imperial Dukeload".

:twisted:

Marvin · Post by **Marvin** » Fri Jul 14, 2006 6:23 pm

Maeryk wrote:I would call that a "metric dukeload"

Dude, I've got to find a use for that term. Just as soon as I pump the Diet Mt. Dew outta my sinuses.

Richard Blackmoore · Post by **Richard Blackmoore** » Sat Jul 15, 2006 7:43 am

Maeryk wrote:The quantity required to make Logan say "GOOD" should work in any kingdom.

I would call that a "metric dukeload"

For say, Michael of Bedford, it would be an "imperial Dukeload".

I prefer the more scientific term Loganeter. A single loganeter will kill an normal man or a knight and should not be used on newbies. 1 1/2 loganeters take out most problem children.

But a Bedfordeter (2 loganeters) would be used for serious headcases and should only be used when all other available means have failed and the opponent has a good helm and health insurance.

Disclaimer: The measurements above are purely meant to describe the level of force typically delivered by their Graces blows and not the level of force they require to call a blow good

Kilkenny · Post by **Kilkenny** » Sat Jul 15, 2006 8:36 am

In a serious vein, responding to the question - The closest I'm aware of was a study conducted by Count Sir Pieter Van Doorn (spelling? someone from the Middle please correct me).

Pieter ran the semi-famous "bowling ball test", wherein people were given the opportunity to knock a 16 pound bowling ball off of a stand set at an appropritate height for the person. First he gathered data for a couple of years at a variety of events, including Pennsic. People were asked to strike a flat snap into the ball and to give "light","good" and "excessive" shots. Mis-hits were not counted.

The data was then used to develop a range of what was considered light, good and excessive was developed. Pieter came around again with the setup but this time had the ranges marked in circles around the stands. Naturally an awful lot of people came up this time looking to see how far they could launch the ball.

The test is inherently flawed in various ways. I watched and listened as Duke Baldar explained one of the flaws - he stepped up and hit the bowling ball *very* sharply, an enormously fast and focused blow probably aimed about an inch into the ball. There was a quite loud crack and the ball pretty much fell off the stand, not moved much more than a couple of inches. No doubt in my mind the blow was "Good" but the bowling ball test displays driving force rather than impact. My "moderate force good" carried the ball well into excessive, in part because I follow through on shots and there's a long period of contact and drive.

Expressed in foot pounds ? No one has measured that to my knowledge.

Gavin

Rev. George · Post by **Rev. George** » Sat Jul 15, 2006 11:59 am

PSI will tell you the amount of force used. But force isnt all there is. In fact, I would say impact force has about 30% or less to do with a blow. The rest? momentum and Energy. Kinetic energy to be precise. The old explanation goes:

Momentum knocks you off the barstool, and Kinetic energy breaks your jaw.

How hard is it to push a heavy bag out of the way? How hard is it to punch a heavy bag hard enough to move it a similar amount?

Some equations:

Force= mass X acceleration
Momentum= Mass X velocity
KE= 1/2 (Mass X Velocity^2)

The data for SCA blows could be determined using computer tracking- Motion Sensors placed in the "off edge" of a sword to determine the velocity of the sword, its acceleration (and deceleration at impact), couple this with impact sensors to determine the impact and you woudl have everything you want to know about a good blow.

-+G

justus · Post by **justus** » Sat Jul 15, 2006 12:07 pm

What we need is big light that mounts on top of the helm, like the ones on kids firemens helmets! it's conected to pressure sensitive sensors mounted all over the body, and it has three colors,

yellow=light,
green=good,
red=excessive

It would have to have a three way selector switch: light, medium, and Atlantia (which also disables the red flasher)

It would be great!, you could even have a built in speaker that called out the blow, "Light!" "Good!" "HOLY SH*T!"

:twisted:

The above is written in jest, because sometimes people just don't get it. :twisted:

-Justus

Kaliban · Post by **Kaliban** » Sat Jul 15, 2006 2:50 pm

i hope this thread keeps going because i am rolling ... great stuff guys

Kilkenny · Post by **Kilkenny** » Sun Jul 16, 2006 8:42 am

Rev. George wrote:PSI will tell you the amount of force used. But force isnt all there is. In fact, I would say impact force has about 30% or less to do with a blow. The rest? momentum and Energy. Kinetic energy to be precise. The old explanation goes:

Momentum knocks you off the barstool, and Kinetic energy breaks your jaw.

How hard is it to push a heavy bag out of the way? How hard is it to punch a heavy bag hard enough to move it a similar amount?

Some equations:

Force= mass X acceleration
Momentum= Mass X velocity
KE= 1/2 (Mass X Velocity^2)

The data for SCA blows could be determined using computer tracking- Motion Sensors placed in the "off edge" of a sword to determine the velocity of the sword, its acceleration (and deceleration at impact), couple this with impact sensors to determine the impact and you woudl have everything you want to know about a good blow.

-+G

Ok, help out an old man who hasn't used this stuff in far too many years.
KE is a result in what units ?

Because I just did some numbers off the top of my head with a couple of datapoints I happen to know and came up with 202,500 as the value for KE....
2 kilogram sword moving at 450 miles an hour. And yes, it's not the entire sword moving that speed, so the figure isn't valid in any case, but.. we calculated tip speed on my sword from a flash photo once many years ago, so I happen to have a couple of datapoints - sword mass and speed. Corrections obviously needed for the fact that the entire mass is not moving at that speed, but those are *waaaay* beyond me

Gavin

edited to replace missing word - proof I was over my head :oops:

Mac Thamhais · Post by **Mac Thamhais** » Sun Jul 16, 2006 9:01 am

Rev. George wrote:The data for SCA blows could be determined using computer tracking- Motion Sensors placed in the "off edge" of a sword to determine the velocity of the sword, its acceleration (and deceleration at impact), couple this with impact sensors to determine the impact and you woudl have everything you want to know about a good blow.

-+G

Now this sounds like a right fine idea. Be there any engineers or the like here amongst our number on the archive who would be willing to have a go at this sort of setup?

Rev. George · Post by **Rev. George** » Sun Jul 16, 2006 7:27 pm

Energy of every variety is measure in joules (in SI).

-+G

Samuel · Post by **Samuel** » Sun Jul 16, 2006 10:50 pm

oh great.. thers gonna be engineers reading this and totally missing the joke... welcome to strip fencing you comedians:D

Nissan Maxima · Post by **Nissan Maxima** » Mon Jul 17, 2006 9:28 am

It is more complicated.

Sword velocity and attitude and mass are only part of the picture. The grip strength and style (tight vs. loose) and even the weight of the arm are important. As Gavin indicated Peters set up would be affected by extended contact of follow through. Thrusts against the bowling ball would yield distances grater than strikes. Are they harder?

Recording impact force is non trivial. The event duration is so short that data acquisition is difficult as peak force is easy to miss. I have had some success with pressure sensitive films to detemine the force related to childhood impact trama (Mom, Billy hit me) but heat and humidity must be carefully controlled for this technique. (http://www.prescale.com/E/E.htm)

Realistically I think we remain limited to the Ow! Damn that hurts! (TM) evaluation method.

Mark G. · Post by **Mark G.** » Mon Jul 17, 2006 9:36 am

Well, I've always wanted to try the "reactive armour" approach, where an impact at or above a certain level will set off the reactive explosive, blowing the rattan sword into smoking splinters. At that point the person who got hit will say "Good!"

Prevents excessive blow force that way AND you know when a GOOD blow has been struck. No more "Light, tippy, skippy stuff."

It'll be entertaining to the people watching as well. :twisted:

Hmmm, I wonder whether I can get that into the next rules update....

:twisted:

Kevin O'Shaughnessy

Maeryk · Post by **Maeryk** » Mon Jul 17, 2006 10:11 am

Realistically I think we remain limited to the Ow! Damn that hurts! (TM) evaluation method.

Those "new" crash test dummies could probably get the readings you want, at least on a head shot..

Now we just need someone to volunteer the use of one, when about 10 people of varying levels can get together and take a swing at it, and someone to interpret the readouts.

Put a helm on it, and smack it.

I doubt you will hurt the dummy.. they are, after all, designed to be crashed in cars.

Hrogn · Post by **Hrogn** » Mon Jul 17, 2006 10:16 am

Just for clarification, I was asking this questions for a material properties reason, rather than for a rule change. I was trying to get a very rough estimate about how thick aluminum, spring steel, Ti, etc. would have to be to not deform when getting hit in our game. My engineering buddy tells me that he can figure that out if I can give him a good guess about psi or newtons/square meter. I figured that we would be more likely to know about psi than newtons/square meter.

Nissan Maxima · Post by **Nissan Maxima** » Mon Jul 17, 2006 10:23 am

Here is a resource for how thick a peice of aluminum you can dent by hitting it with your head.

http://64.233.167.104/search?q=cache:F- ... =clnk&cd=5

Those crash test dummies can tell youu what kind of an injury will be sustained, but not really how much KED was absorbed.

Maeryk · Post by **Maeryk** » Mon Jul 17, 2006 10:28 am

Those crash test dummies can tell youu what kind of an injury will be sustained, but not really how much KED was absorbed.

Well, they can actually measure flex of joints, G's and acelleration/deceleration through neck flexing and such.. they have come a LONG way in a relatively short period of time.

(I watch too damn much Learning and Discovery channel.. course, those dummies, and the computer, run about 100K a piece)

Nissan Maxima · Post by **Nissan Maxima** » Mon Jul 17, 2006 11:00 am

I have one in child size. I push it off of playground equipment to see it go splat. I have whacked it with a stick but it doesn't catch the peak reliably.

Maeryk · Post by **Maeryk** » Mon Jul 17, 2006 11:06 am

I have one in child size. I push it off of playground equipment to see it go splat. I have whacked it with a stick but it doesn't catch the peak reliably.

How new a model is it?

Kilkenny · Post by **Kilkenny** » Mon Jul 17, 2006 11:08 am

Nissan Maxima wrote:I have one in child size. I push it off of playground equipment to see it go splat. I have whacked it with a stick but it doesn't catch the peak reliably.

I have all sorts of amusing visions from this information. Nissan smacking a child sized crash test dummy with a stick is funny, but there's just something really wrong in a sick and twisted funny sort of way about the abuse of the poor child dummy.

Gavin

Nissan Maxima · Post by **Nissan Maxima** » Mon Jul 17, 2006 11:21 am

2004 NHTSA Hybrid 3 model. It has 2 accelerometers in its head and a force and a moment sensor in its neck. It is good for crashes but it just is not instrumented for the fast transient nature of whack in the head with a stick scientific inquiry. It would be ideal for proving that a heavy helmet is better than a light helmet for safety. (If you were a fightin' toddler) but not so good for how hard was the shot, except in the relative measurement of, this hit was harder than that one. But not so good for the absolute, this shot was x hard.

Nissan Maxima · Post by **Nissan Maxima** » Mon Jul 17, 2006 11:27 am

Kilkenny wrote:
Nissan Maxima wrote:I have one in child size. I push it off of playground equipment to see it go splat. I have whacked it with a stick but it doesn't catch the peak reliably.

I have all sorts of amusing visions from this information. Nissan smacking a child sized crash test dummy with a stick is funny, but there's just something really wrong in a sick and twisted funny sort of way about the abuse of the poor child dummy.

Gavin

Well then you should see me shove stuff down in their airways, strangle, suffocate and burn them. (Not the NHTSA CT dummy, But the purpose built robots for this other mayhem) I also do poke in the eye research but I use pigs for that.

Maeryk · Post by **Maeryk** » Mon Jul 17, 2006 11:34 am

I also do poke in the eye research but I use pigs for that.

Have you programmed the testing machines so it goes "DING! NYUK NYUK NYUK!" when the test run is finished?

Euric Germanicus · Post by **Euric Germanicus** » Mon Jul 17, 2006 1:31 pm

NEWS FLASH: NISSAN MAKES CLONE ARMY TO FIGHT THE EAST

More at 11!

Akseli · Post by **Akseli** » Mon Jul 17, 2006 4:14 pm

My first post here but simply had to reply to this thread.

I've been pondering a way to get scientific data about blows. So far the only way I've figured one way with equipment possible to get from somewhere. There's a very simple device which has some fancy name I can't remember at the moment that is used in measuring velocities of projectiles. Basicaly you hang a wooden block from a string from the roof. Then you whack the piece of wood with your stick with a force of a solid good blow, or you ask some duke to hit it even harder. The thing you measure is the difference in height the block will undergo after the blow.

This can be done by computer sensors. Or with a video camera. Though, the block needs to be heavy enough so that it will move slow enough. Place a scale behind the block and watch the video frame by frame to determine the highest point.

You will have to know the mass of the block and the mass of your stick. At this point we will asume that the string doesn't take any energy to move. When you know the amount of motion of the block in the y-axis and the mass of the block you can calculate the potential energy of it (Ep=mgh)

The potential energy should (in this harmonic situation) be equal to the kinetic energy (Ek=0.5mv^2) of the block right at the start of the motion right after the blow has landed. This is the amount of energy the blow transfers to the body it strikes. This, however, is not the kinetic energy of the stick in motion due to the fact that when the stick squeezes and bends during the energy trasfer, it consumes a lot of energy.

However, the velocity computed from the kinetic energy is the same as the velocity the block starts to move before any of the energy is transfered to potential energy. From this velocity is possible to calculate the momentum of the block (p=mv). This momentum is the same as the one in the stick at the moment of the blow. Knowing the mass of the stick we can now compute the speed of the stick at the moment of the strike.

It should be noted however, that stick is in somewhat circular motion. This means that the stick has only constant angular velocity. The velocity of a point in the stick dependes of the distance from the centre point of the motion aka your hand. If you use paint or something in the wooden block you can determine the point of the stick in which the shot has landed. Knowing this you can quiet easily make some sort of estimates of the velocity in different part of the sticks.

This is still theory, I've never tested this out but I do inted to.

Nissan Maxima · Post by **Nissan Maxima** » Mon Jul 17, 2006 4:23 pm

Akseli,
If I hold the sword rigidly in my hand and strike the block it will move further than if I hold it loosely in my hand and strike the block, all other factors( sword mass, velocity and point of contact) being equal.

Indeed, if I merely follow through my blow the block will move further.

It is complicated.

raito · Post by **raito** » Mon Jul 17, 2006 4:27 pm

Kevin O'Shaughnessy wrote:Well, I've always wanted to try the "reactive armour" approach, where an impact at or above a certain level will set off the reactive explosive, blowing the rattan sword into smoking splinters. At that point the person who got hit will say "Good!"

Prevents excessive blow force that way AND you know when a GOOD blow has been struck. No more "Light, tippy, skippy stuff."

Kevin O'Shaughnessy

Yeah, but you also want to run around the woods at night with wet armour and flaming weapons. :shock:

adamstjohn · Post by **adamstjohn** » Mon Jul 17, 2006 5:06 pm

Oh boy, just wait till Agilmar sees this thread. And tells Hagen. :shock: