Calling All Shade Tree Physicists

[Boss .300 winmag]

I seen somthing similar on a hunting channel just a couple days ago?

And what was the outcome?

[TommyH]

I seen somthing similar on a hunting channel just a couple days ago?

And what was the outcome?

It was just a advertisment i think, for a new arrow with a sliding weight in it, I tried to rewind it so i could check it out but I had just turned to that channel so it wouldnt let me rewind far enough. I dont recall the name of the company but i dont think i had ever heard of them.

[jechicdr]

Arrow tube separated by a thin glass divider. In back pressurized gas and a projectile that on impact would shatter the barrier, releasing the gas.  In front a vacuum that would suck the projectile to the front of the arrow.  So instead of relying on the momentum of the arrow to drive the impact on the head, the pressure difference in the arrow would drive the impact.  Of course the recoil might slow the arrow initially, unless you blew out the back of the arrow as well so the escaping gas would also propel your arrow forward to counteract it.  Or just make the entire arrow filled with compressed gas that blew out the back end of the arrow on impact.  I'm a genius.

[Smokey Bear]

Just thinking out loud here. . .

We don't talk much about "knock down" power with a bow, but wouldn't you want the strongest impulse all at once?  NASCAR has crumple zones and safer barriers to absorb the tremendous force and lengthen the time of the impulse, thus protecting the internal organs of the drivers.  Although static friction is very very small considering the razor sharp broadheads we use, I still don't want to "overcome" it twice! 

There has also been talk of how the arrow will fly. . . but just maybe the arrow would fly straighter near impact, with a weight shift to the tip???  I don't know??? 

I applaude questions like this, it's how the next innovations in archery will be born!

   

[RadSav]

jechicdr, ToddID and JPhelps all make an interrelated point that is an important one.  For the RAM to move free within the shaft there will be chatter or rattle robbing energy at a very rapid rate.  If the RAM fits snug within the internal space of the shaft there will be created upon impact an equal vacuum/pressure on each side of the RAM making it only moveable to a point of the amount of compression allowed by the gas within the shaft. (this will happen regardless, but at a much higher extreme if the RAM gives little room for gas to escape around it's surface)   Assuming that impact of the projectile is at point blank and the impact immediately stops the progression of travel of the shaft and the 300 fps 50 grain RAM is then 100% energized for forward momentum the FPE of that RAM completely friction free is about 10 pounds.  Not nearly enough to collapse the vacuum chamber and explode the pressure chamber enough to make any additional impact force against the solid impenetrable object. 

Fact is arrow travel at target is going to be at a speed less than point blank, there is no such thing as 100% friction free travel,  immediate stoppage or transfer of energy of an arrow on impact with ballistic gelatin is not likely, and arrow oscillations will not allow for a tight fitting RAM to travel unobstructed down the length of a shaft externally or internally,  the vibration created will only rob more of the projectiles energy than will be left if and when the RAM actually makes contact with the front of the stationary projectile.   Whewww!

No double tap of any useful benefit if you are able to achieve one at all.  A micro diameter 50 grain tungsten needle might have a chance, but I like your chances of drawing a Washington State goat raffle tag much better than seeing any measurable benefit from even that.  Especially since the "tap" against the back end of the arrow upon release will be at a greater velocity than the "tap" on the front end upon impact.  Thus imparting more decrease in velocity/energy upon the release than you will gain upon impact.  As Todd eluded to in his original post impact of a slower moving 450 grain arrow followed by a second impact of a slower 50 grain RAM would result in less penetration than a solid 500 grain arrow traveling at full speed with no RAM at all (450+50=<500).  And as JPhelps eluded to the energy of a two part arrow traveling at X-speed has the same amount of energy as a two part arrow traveling at the same X-speed.  You can not gain more energy only lose energy due to the additional friction.

[Hunter Dug]

If the object within the shaft was lightly secured to the rear of the arrow, this would stop any rattling during flight.  Upon impact the object breaks free and travels the length of the arrow and slams into the insert, and broadhead.  A small hole in the rear of the nock would have to be drilled to let gases excape from the arrow as the object transfers from the rear of the arrow to the front.  The only issues would be FOC for flight, securing the object within the shaft until impact, and keeping the insert, and broadhead connected to the arrow once the object hit them.

[KFhunter]

or

the arrow shaft in a complete vacuum

[Hunter Dug]

you could prevent vacum by drilling a thru hole in the slug that was inserted within the shaft.

[konrad]

As I said earlier, I will be using a powdered shot shell buffer media in the first tests…if I can obtain a usable weight and still have free space within the shaft.
The fine buffer media will be free to distribute itself within the shaft by way of centrifugal and inertial forces. My objective is to tilt the shaft upward slightly during the draw cycle to move the media to the rear of the shaft. If the media is not placed in the same relative position prior to each shot, more or less energy would be absorbed by moving the media on launch thereby producing (I believe) variances in launch velocity.

The original concept came from considering methods for balancing lack of wall concentricity in modern carbon composite shafts and the associated rotational imbalances. A shaft’s “spline” or hard ridge along one side of the shaft indicates to me wall thickness variations. If there is in fact a wall thickness variation (or change in mass) there would also be a corresponding weight irregularity. The primary purpose of rifling and fletching is to spin the projectile so that those weight irregularities are “evened out” around an axis of rotation to produce better accuracy (more consistent flight patterns). Of course, a slightly bent shaft will produce the same poor weight distribution described above.

We shall see…

[RadSav]

The original concept came from considering methods for balancing lack of wall concentricity in modern carbon composite shafts and the associated rotational imbalances. A shaft’s “spline” or hard ridge along one side of the shaft indicates to me wall thickness variations. If there is in fact a wall thickness variation (or change in mass) there would also be a corresponding weight irregularity. The primary purpose of rifling and fletching is to spin the projectile so that those weight irregularities are “evened out” around an axis of rotation to produce better accuracy (more consistent flight patterns). Of course, a slightly bent shaft will produce the same poor weight distribution described above.

Are you trying to say that the granules of powder are going to balance out the weight irregularities of spline thus increasing performance, stability and accuracy?

[RadSav]

At times sleep comes easier if you make the leap of faith that sometimes a stick and a string simply shoots another stick.  And leave it at that

[coachcw]

on a different note. what if bow manufacturs listed maximum ke. insted of ibo. for instance what weight arrow creates maximum ke some bows it may be 500 grains other may be six hundred .

[RadSav]

on a different note. what if bow manufacturs listed maximum ke. insted of ibo. for instance what weight arrow creates maximum ke some bows it may be 500 grains other may be six hundred .

Manufacturers would never do such a thing instead of IBO.  Perhaps some would add it to the list, but I would assume most would find it time and effort without return.  KE means quite little in the realm of killing or bow efficiency and thus creates as much confusion as any real life benefit would give them or the bowhunter.  It's why AMO standard speed calculations are never used anymore since the adoption of IBO speed standards. 

Those IBO speed standards, which are easily and often manipulated, serve a single purpose - to sell bows!  Nothing in archery creates as much emotional involvement and aides in the selling of completely backward designed, meaningless advances and poor shootability than does speed.  Creating such a standard has assured that sooner rather than later an archer will feel the need to upgrade.  Not from a lack of success, not from a lack of accuracy and not from a lack of shootability, but due to a growing discontent for numbers.  It assures that bows will not be handed down from generation to generation as would be the case with a classic firearm.  But discarded like trash as would be last years Windows operating system and the computer that only thinks at a rate 1,000 times faster than the human mind.

It is presented to the archery community as a standards of measure.  And while true within the wide spread variables of the AMO, ATA and IBO guidelines manufacturers use it more as a sales tool than any viable standards procedure.  A KE standard of measure would surely be as filled with wide interpretation and manipulation as speed squared.  Without the added benefit of using it to drive sales and emotionally charge a happy archer into discontent.

[WDFW Hates ME!!!]

I think the only difference you will see is different points of impact, due to the different weight distribution of the arrows. 500 grain arrow shot next to another 500 grain arrow but 1 arrow is 450 grains with a 50 grain slider still weighs in at 500 grains and same available energy. You shouldn't lose any to friction as it still weighs in at 500 grains.
I think you would lose accuracy as your media inside your shaft would have to be in the same position at release every time or it would hammer back at release.

[Todd_ID]

Slow Motion Archery Hoyt UltraElite Wendy EX-F1

That is a modern bow and aluminum arrow.  Carbon arrows are worse for the vibration you'll find at impact: worse in that they will be less predictable.