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The King of Kings ...There is only 1...
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Very interesting topic I would have to go in favour of the phyisics aspect of this. :naughty: I will try some testing tomorrow with my crony to see if I get differing results.
 
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The force that the bands exert is proportional to the extent to which they are stretched. To understand this experiment, it is NOT just the draw length that matters ... that is, the distance from the pouch to the middle of the fork. One must also consider the extent to which the bands are being stretched by the two slingshots.

To determine the extent to which the bands are being stretched, what IS important is the distance from the pouch to the fork tip. So to maintain constant force from one slingshot to another, one needs to draw each so that the pouch to fork tip distance is the same in each case. Then if elementary physics still operates, the wider fork width will yield slower velocities; consider the force vector along one band as being resolved into 1: a component from the pouch to the middle of the fork tips, and 2: a component perpendicular to the first, along a line from the middle of the forks to the tip to which the band is connected. The wider the fork, the greater 2 will be and the lesser 1 will be. It is 1 that actually drives the ammo. In other words, the wider your forks, the more band power is being wasted.

As a graphic illustration of this point, suppose in the extreme case you made the fork tips of the wider slingshot so wide that the bands were stretched to the draw length of the narrower slingshot. Then to keep the band stretch the same for the two slingshots, you would not be allowed to draw the pouch back at all. Hence, the ammo would go nowhere ... zero velocity. All the force in the wide slingshot would be directed along vector 2.

However, if you always use the same draw length, then the bands on the wider fork are actually being stretched more than the bands on the narrower fork. That extra stretch will mean the bands will exert more force on the ammo, although a bit of it will be wasted along vector 2. If the extra stretch outweighs the loss due to vector 2 above, then the wider forks might indeed give higher velocities.

In Bill's case, he was using the same draw length each time, so the bands on the wider fork were being stretched more than when the same bands were on the narrower fork.

Cheers .... Charles
 

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HOBBYIST-SOPHOMORIC-JACKA$$
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The force that the bands exert is proportional to the extent to which they are stretched. For this experiment, it is NOT the draw length that matters ... that is, the distance from the pouch to the middle of the fork.

What IS important is the distance from the pouch to the fork tip. So to maintain constant force from one slingshot to another, one needs to draw each so that the pouch to fork tip is the same in each case. Then if elementary physics still operates, the wider fork width will yield slower velocities; consider the force vector along one band as being resolved into 1: a component from the pouch to the middle of the fork tips, and 2: a component perpendicular to the first, along a line from the middle of the forks to the tip to which the band is connected. The wider the fork, the greater 2 will be and the lesser 1 will be. It is 1 that actually drives the ammo. In other words, the wider your forks, the more band power is being wasted.

As a graphic illustration of this point, suppose in the extreme case you made the fork tips of the wider slingshot so wide that the bands were stretched to the draw length of the narrower slingshot. Then to keep the band stretch the same for the two slingshots, you would not be allowed to draw the pouch back at all. Hence, the ammo would go nowhere ... zero velocity. All the force in the wide slingshot would be directed along vector 2.

However, if you always use the same draw length, then the bands on the wider fork are actually being stretched more than the bands on the narrower fork. That extra stretch will mean the bands will exert more force on the ammo, although a bit of it will be wasted. If the extra stretch outweighs the loss due to vector 2 above, then the wider forks might indeed give higher velocities.

In Bill's case, he was using the same draw length each time, so the bands on the wider fork were being stretched more than when the same bands were on the narrower fork.

Cheers .... Charles
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tumblr_lstib8AOYb1r4wscto1_500.gif


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too much science and over thinking for me . im a hobbiest, not an engineer . to each their own .
 
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Physics rules the world.........well, sometimes chemistry........which one might argue must obey the laws of physics.
 

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*sighs* the words I'm looking for are "fair* test please"

It is as Charles has put it...

A wider fork, increase the draw distance, but the cosine of the angle times the new distance remains the same... no gaining something for nothing.

Hence what REALLY happens? Firstly strain has increased (so more distance!) and (gee) because it's coupled* the force has ALSO been increased, so more energy being put in.

FORCE:

Before:

13Kg*constant/(2*30mm*t)=stress of strain... say 2.513 (SR)

-Stress of strain is going to a something erm something 'nasty'

After:

Increase the strain and solve for force: 2.513*1.05 (say 5% more strain)

Force is now 13.5Kg

-Trust me it's a curvy function... good luck.

DISTANCE:

Before:

800mm/(1+SR) = 227.7mm

After:

227.7=828.6mm/(1.05*SR+1)

'POWER': (ok I tried a little harder too)

Before:

(800mm-227.7mm)*13kg*9.80665N/Kg = 73 J (if force could be constant)

=>

25.535J @ 73.497 m/s using 16mm steel

After:

(828.6mmm-227.7mm)*13.5kg*9.80665N/Kg = 79.55J (again "if only")

=>

27.874 @ 76.790 m/s using 16mm steel.

End.

A higher average force should mean higher speeds (equal and opposites and all that)... The truth is there are only a few variables to control or understand, oh "and it's more complicated than that..."

*This coupling holds great speed, power and wealth to those who understand it :p
 

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HOBBYIST-SOPHOMORIC-JACKA$$
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. . . to those who understand it :p
i wish i understood :iono: , :question: im actually envious of those that do . :shakehead:
 

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I got it to work the other way, a great design VS a great design over cooked...

28.263 J @ 91.635 m/s (good set 9/16" steel used, 14.29mm this is well damn close to where I'd put it just add a little more force)

27.276 J @ 90.020 m/s (larger ammo is needed here... This is maxing speed but not the band so more force does not always yield more speed!)

Quite a bit of magic later... 30.179 J @ 88.024 m/s using 15mm steel -If in doubt *bigger* and for comparison 79.902 m/s for 16mm steel. The higher strain used in this set is where the difference in performance can be found.

But the differences are still pretty small, and I swear you can compensate through 'correct' ammo size... but the efficiency has decreased since it is strain related.

Maybe its about right? 13kg VS 13.5kg and 80cm VS 82.86cm... very small change.

I'd hate to go on opinion but band drag and ammo selection? Seems to me if you can put more power in then you must be able to get some of it back out?

please discuss.
 

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Put simply, bands on a narrow fork can be drawn longer easier, wider forks will stress the rubber harder sooner.. the test needs to be done so the bands on both size forks are pulled to the absolute limit, that would mean the narrow frame will gain slightly more draw length..
 

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The thing you guys might be missing is, the same draw length is used... and that's what I said in the video as well.

If one were to pull to the band's maximum pull length, the narrower fork will do slightly better. But and it's a very big BUT, almost nobody ever pulls to the end of the elastic's stretch potential.

Therefore under normal shooting circumstances the wider fork will shoot faster... and the reason is quite simple really... more band stretch at your normal draw and the elastic contraction continues closer to the fork as well.
 

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scooter trash
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So why was John getting slower results? I thought he was using a consistent draw length, too?
 

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So why was John getting slower results? I thought he was using a consistent draw length, too?
I think it was because John was pulling to the bands maximum length, while Bill was pulling to a set draw length for both.

As Bill stated "If one were to pull to the band's maximum pull length, the narrower fork will do slightly better. But and it's a very big BUT, almost nobody ever pulls to the end of the elastic's stretch potential.

Therefore under normal shooting circumstances the wider fork will shoot faster"

So both videos are correct

Ian
 

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Agreement all over the place, especially with Ian. Both videos are correct, but under different circumstances, which are not thoroughly described.

A more complete analysis of the effects would need to include ammo drag and mass and perhaps to match them to the experiment to eliminate any non-linear response. Band drag. The non-linear relationship between draw length and energy conversion, especially approaching the elastic limit.

Pretty tough to do by hand and by feel. A job for Charles' machine perhaps?

Bill's test could be made an order more comprehensive by doing the same again with slightly shorter and slightly longer tubes to see how the proximity to the elastic limit affects the results. The longer the bands (given a fixed draw length) the more linear the response.
 

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scooter trash
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So if a shooter is using a set of bands cut to their drawn length and strength of draw (getting to maximum useful stretch) there is no advantage to a wider fork?
 

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Something so simple to understand is muddled with technical mumbo jumbo. Watch. You adjust the tubes or the flatbands to accomodate your choice of forks in combination with the hold time. Narrow forks with speed of release will knock the snot out of anything else out there. Im certain I will be railed on for this simple truth.

Heres a tip. The ammo leaves tbe pouch at a different point with wide vs narrow. So you go figure the rest out now.
 

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"Mighty Can Smiter"
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?........ You adjust the tubes or the flatbands to accomodate your choice of forks in combination with the hold time......... Narrow forks with speed of release will knock the snot out of anything else out there.....
Heres a tip. The ammo leaves tbe pouch at a different point with wide vs narrow. So you go figure the rest out now.
Not trying to rattle you, unless I am misunderstanding you...

If one adjusts the tubes/flatbands to accommodate your choice of forks, I am lead to believe that the proper set up would knock the snot out of an improper one, and it wouldn't matter the width between the forks???

Which is better, I believe, would be determined on the style and taste of the shooter.

LGD
 
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