Greetings to the Forum.
I started to look at the Band Calculator on Jörg Sprave's forum. I know it considered obsolete, however curiosity has gotten the better of me.
I will try to explain what I have discovered. I have some programming experience and I am trying my best.
![Image]()
Below is part of the code for the graphical user interface pictured above.
A = document.ss_calc.var_a.value; // Draw length
B = document.ss_calc.var_b.selectedIndex + 1; // Elongation
O = document.ss_calc.var_o.selectedIndex + 1; // Tappering ratio
E = document.ss_calc.var_e.value / 10; // Ammunition diameter
M = document.ss_calc.var_m.selectedIndex + 1; // Ammunition Type (Steel, Lead & Glass Marbles)
A is the draw length in centermeters
B is the stretch ration (Elongation)
O is the tappering ratio
E is the Ammunition diameter
M is the Ammunition Type
This is the next part of programming. It determines the stretch ratio of the bands
if (B==1) C=A/3+3; // Elongation
if (B==2) C=A/3.31+ 3;
if (B==3) C=A/3.62+3;
if (B==4) C=A/3.93+3;
if (B==5) C=A/4.24+3;
if (B==6) C=A/4.55+3;
if (B==7) C=A/4.86+3;
if (B==8) C=A/5.17 + 3;
if (B==9) C=A/5.48 + 3;
An example of my draw length with max band life selected, the first line;
C= 67.5cm divided by 3 + 3 = 25.5cm
The last line;
C= 67.5 divided by 5.48 + 3 = 15.3175cm rounded by the programming code
it will be out put here later in the code
// This is the some of the code behind the output information.
document.getElementById("outputline1").innerHTML = "Your ammo weighs " + N + " gramms." ;
document.getElementById("outputline2").innerHTML = "Cut the bands " + C + " cm long." ;
document.getElementById("outputline3").innerHTML = "Band width at the fork is " + K + " cm." ;
document.getElementById("outputline4").innerHTML = "Band width at the pouch is " + L + " cm." ;
document.getElementById("outputline5").innerHTML = "You need " + J + " bands per side." ;
The last three outputs I have not determine exaclty how they work. They are linked to ammo weight and draw weight required.
I will give you the percentages that can be selected for elongation.
Elongation for draw length:
264.7% // Max band life
312%
334.5%
356.7%
378.4%
399.6%
420.4%
440% // Max power
Next are the tapper ratio's. This is connected to the ammo wieght, draw weight required for that ammo. Using Theraband gold old or new formula?.
if (O==1) D=1; // Tapper
if (O==2) D=1.19;
if (O==3) D=1.38;
if (O==4) D=1.56;
if (O==5) D=1.75;
if (O==6) D=1.94;
if (O==7) D=2.13;
if (O==8) D=2.31;
if (O==9) D=2.5;
These tappers in ratio for are:
1:1
1.19:1
1.38:1
1.56:1
1.75:1
1.94:1
2.13:1
2.31:1
2.5:1
The next is how the ammo weight is calculated.
if (M==1) N=E*E*E*3.14159/6*7.8; //Steel
if (M==2) N=E*E*E*3.14159/6*11.3; //Lead
if (M==3) N=E*E*E*3.14159/6*2.2; //Glass marbles
The first line is for Steel, second line is Lead and the third is Glass marbles.
An example for 10mm steel
10x 10x 10x 3.14159 / (divided) by 6x7.8 = 4,084.067 on the output will be 4.08 grams
The next part gets beyond me as I have only deciphered the draw weight required by the ammo weight
// This calculates the draw weight. factor is 0.4kg per gramm, + 6,2 kg (fixed).
F=0.4*N+6.2; // 0.4 x (N)ammo + 6.2
G=F/1.30; // G = ammo / 1.3
H=(G/(D+1))*D; // H = G / tapper + 1 * tapper
I=G-H; // I = G-H
I have only worked this part out so far
F=0.4*N+6.2; // 0.4 x (N)ammo + 6.2
This is 0.4 x (10mm steel (4.08067 weight in grams) + 6.2 = 7.832268 kg's of draw weight is required to propell 10mm steel.
The next parts start to round the numbers, determines wether one is to use single, double or tripple bands and the correct amount for each tapper.
I only know some programming, I am not a professional.
Members may be able to augment this information and refine these forumlas with what they find to provide the best performance.
I will see what I can do. I measured a broken single sheshou guru band set 50x20 to a 675mm draw and it was 6.2kg I am guessing a made up band set would have made a 12.4kg draw weight.
I measured a Yellow snipersling 0.8 50x20mm tapper and the draw weight was 8.2kg at 675mm draw distance. Just over the the recommended draw weight for 10mm steel.
The Calculator does not go beyond a band width of 4.28cm (42.8mm) then it will go back down and ask the user to use double or tripple bands.
So in conclusion Band life ratios are:
264.7%
312%
334.5%
356.7%
378.4%
399.6%
420.4%
440%
Tapper ratios are:
1:1
1.19:1
1.38:1
1.56:1
1.75:1
1.94:1
2.13:1
2.31:1
2.5:1
Ammo weight calculator is
N=E*E*E*3.14159/6*7.8; Steel (Diameter) x (Diameter) x (Diameter) x 3.14159 divided by 6 x 7.8 = e.g 10mm steel 10x10x10x 3.14159/6x7.8= 4,084.0 (4.08 gramms)
N=E*E*E*3.14159/6*11.3; Lead (Diameter) x (Diameter) x (Diameter) x 3.14159 divided by 6 x 11.3 = e.g 10mm lead, 10x10x10x3.14159/6x11.3 = 5,916.6 (5.92 gramms)
N=E*E*E*3.14159/6*2.2; Glass marbles (Diameter) x (Diameter) x (Diameter) x 3.14159 divided 6 x 2.2 = e.g 10mm glass, 10x10x10x3.14159/6x2.2= 1,151.91 (1.51 grams)
Draw weight required is
0.4 x (ammo wieght in grams) + 6.2 = Kilograms required in draw weight.
I hope other members, present and future find this information useful. I hope it can be refined and improved. Undoubtedly. Any unproductive comments will be dealt with appropriately. Constructive criticism is always welcome, it will help refine our sport. Obviously most shooter use a elongation of 500%.
All credit to Jörg Sprave and Helmut Sprave.
Salutations.
I started to look at the Band Calculator on Jörg Sprave's forum. I know it considered obsolete, however curiosity has gotten the better of me.
I will try to explain what I have discovered. I have some programming experience and I am trying my best.
Below is part of the code for the graphical user interface pictured above.
A = document.ss_calc.var_a.value; // Draw length
B = document.ss_calc.var_b.selectedIndex + 1; // Elongation
O = document.ss_calc.var_o.selectedIndex + 1; // Tappering ratio
E = document.ss_calc.var_e.value / 10; // Ammunition diameter
M = document.ss_calc.var_m.selectedIndex + 1; // Ammunition Type (Steel, Lead & Glass Marbles)
A is the draw length in centermeters
B is the stretch ration (Elongation)
O is the tappering ratio
E is the Ammunition diameter
M is the Ammunition Type
This is the next part of programming. It determines the stretch ratio of the bands
if (B==1) C=A/3+3; // Elongation
if (B==2) C=A/3.31+ 3;
if (B==3) C=A/3.62+3;
if (B==4) C=A/3.93+3;
if (B==5) C=A/4.24+3;
if (B==6) C=A/4.55+3;
if (B==7) C=A/4.86+3;
if (B==8) C=A/5.17 + 3;
if (B==9) C=A/5.48 + 3;
An example of my draw length with max band life selected, the first line;
C= 67.5cm divided by 3 + 3 = 25.5cm
The last line;
C= 67.5 divided by 5.48 + 3 = 15.3175cm rounded by the programming code
it will be out put here later in the code
// This is the some of the code behind the output information.
document.getElementById("outputline1").innerHTML = "Your ammo weighs " + N + " gramms." ;
document.getElementById("outputline2").innerHTML = "Cut the bands " + C + " cm long." ;
document.getElementById("outputline3").innerHTML = "Band width at the fork is " + K + " cm." ;
document.getElementById("outputline4").innerHTML = "Band width at the pouch is " + L + " cm." ;
document.getElementById("outputline5").innerHTML = "You need " + J + " bands per side." ;
The last three outputs I have not determine exaclty how they work. They are linked to ammo weight and draw weight required.
I will give you the percentages that can be selected for elongation.
Elongation for draw length:
264.7% // Max band life
312%
334.5%
356.7%
378.4%
399.6%
420.4%
440% // Max power
Next are the tapper ratio's. This is connected to the ammo wieght, draw weight required for that ammo. Using Theraband gold old or new formula?.
if (O==1) D=1; // Tapper
if (O==2) D=1.19;
if (O==3) D=1.38;
if (O==4) D=1.56;
if (O==5) D=1.75;
if (O==6) D=1.94;
if (O==7) D=2.13;
if (O==8) D=2.31;
if (O==9) D=2.5;
These tappers in ratio for are:
1:1
1.19:1
1.38:1
1.56:1
1.75:1
1.94:1
2.13:1
2.31:1
2.5:1
The next is how the ammo weight is calculated.
if (M==1) N=E*E*E*3.14159/6*7.8; //Steel
if (M==2) N=E*E*E*3.14159/6*11.3; //Lead
if (M==3) N=E*E*E*3.14159/6*2.2; //Glass marbles
The first line is for Steel, second line is Lead and the third is Glass marbles.
An example for 10mm steel
10x 10x 10x 3.14159 / (divided) by 6x7.8 = 4,084.067 on the output will be 4.08 grams
The next part gets beyond me as I have only deciphered the draw weight required by the ammo weight
// This calculates the draw weight. factor is 0.4kg per gramm, + 6,2 kg (fixed).
F=0.4*N+6.2; // 0.4 x (N)ammo + 6.2
G=F/1.30; // G = ammo / 1.3
H=(G/(D+1))*D; // H = G / tapper + 1 * tapper
I=G-H; // I = G-H
I have only worked this part out so far
F=0.4*N+6.2; // 0.4 x (N)ammo + 6.2
This is 0.4 x (10mm steel (4.08067 weight in grams) + 6.2 = 7.832268 kg's of draw weight is required to propell 10mm steel.
The next parts start to round the numbers, determines wether one is to use single, double or tripple bands and the correct amount for each tapper.
I only know some programming, I am not a professional.
Members may be able to augment this information and refine these forumlas with what they find to provide the best performance.
I will see what I can do. I measured a broken single sheshou guru band set 50x20 to a 675mm draw and it was 6.2kg I am guessing a made up band set would have made a 12.4kg draw weight.
I measured a Yellow snipersling 0.8 50x20mm tapper and the draw weight was 8.2kg at 675mm draw distance. Just over the the recommended draw weight for 10mm steel.
The Calculator does not go beyond a band width of 4.28cm (42.8mm) then it will go back down and ask the user to use double or tripple bands.
So in conclusion Band life ratios are:
264.7%
312%
334.5%
356.7%
378.4%
399.6%
420.4%
440%
Tapper ratios are:
1:1
1.19:1
1.38:1
1.56:1
1.75:1
1.94:1
2.13:1
2.31:1
2.5:1
Ammo weight calculator is
N=E*E*E*3.14159/6*7.8; Steel (Diameter) x (Diameter) x (Diameter) x 3.14159 divided by 6 x 7.8 = e.g 10mm steel 10x10x10x 3.14159/6x7.8= 4,084.0 (4.08 gramms)
N=E*E*E*3.14159/6*11.3; Lead (Diameter) x (Diameter) x (Diameter) x 3.14159 divided by 6 x 11.3 = e.g 10mm lead, 10x10x10x3.14159/6x11.3 = 5,916.6 (5.92 gramms)
N=E*E*E*3.14159/6*2.2; Glass marbles (Diameter) x (Diameter) x (Diameter) x 3.14159 divided 6 x 2.2 = e.g 10mm glass, 10x10x10x3.14159/6x2.2= 1,151.91 (1.51 grams)
Draw weight required is
0.4 x (ammo wieght in grams) + 6.2 = Kilograms required in draw weight.
I hope other members, present and future find this information useful. I hope it can be refined and improved. Undoubtedly. Any unproductive comments will be dealt with appropriately. Constructive criticism is always welcome, it will help refine our sport. Obviously most shooter use a elongation of 500%.
All credit to Jörg Sprave and Helmut Sprave.
Salutations.
