Load of inverted Roller Speargun?

[born to hunt]

Hi there

I am planning on making an inverted roller speargun, total length will be 115-120 cm and the barrel-pipe will be 100cm
i am planning on using 3 rubbers bands on each side to 6 total of 14,5 or 16mm 25-30cm each to achieve 280-350% stretch

what would be the workload for the speargun in each scenario in kg or lbs ?
and how to calculate it ? thank you so much in advance

 

[david598ball]

Hi there

I am planning on making an inverted roller speargun, total length will be 115-120 cm and the barrel-pipe will be 100cm
i am planning on using 3 rubbers bands on each side to 6 total of 14,5 or 16mm 25-30cm each to achieve 280-350% stretch

what would be the workload for the speargun in each scenario in kg or lbs ?
and how to calculate it ? thank you so much in advance

Hello,
To calculate the workload (force) of your speargun, use the formula: biglotssurvey.cc

Workload (Force) = Rubber Cross-Sectional Area × Draw Length × Stretch Percentage × Elasticity Constant

1. For rubber area (A): Calculate the cross-sectional area of one band using the formula:
   $$A = \pi r^2$$
   where r is the radius of the rubber (e.g., for 14.5 mm, r = 7.25 mm or 0.725 cm).
2. Multiply by the number of bands (6 total).
3. For draw length (L): This is the distance the rubber is stretched (e.g., from relaxed to fully drawn).
4. For stretch percentage (e.g., 300%): Convert to a decimal (300% = 3.0).
5. For elasticity constant (k): Approximate value for speargun rubber is around 1,000-1,500 N/m.

Finally, convert the result from Newtons (N) to kilograms (kg) or pounds (lbs).
Let me know if you'd like assistance with detailed calculations!

Best Regards,
David Ball

 

[born to hunt]

Hello,
To calculate the workload (force) of your speargun, use the formula: biglotssurvey.cc

Workload (Force) = Rubber Cross-Sectional Area × Draw Length × Stretch Percentage × Elasticity Constant

1. For rubber area (A): Calculate the cross-sectional area of one band using the formula:
   $$A = \pi r^2$$
   where r is the radius of the rubber (e.g., for 14.5 mm, r = 7.25 mm or 0.725 cm).
2. Multiply by the number of bands (6 total).
3. For draw length (L): This is the distance the rubber is stretched (e.g., from relaxed to fully drawn).
4. For stretch percentage (e.g., 300%): Convert to a decimal (300% = 3.0).
5. For elasticity constant (k): Approximate value for speargun rubber is around 1,000-1,500 N/m.

Finally, convert the result from Newtons (N) to kilograms (kg) or pounds (lbs).
Let me know if you'd like assistance with detailed calculations!

Best Regards,
David Ball

Hello
thank you so much for the reply,
can you explain this one more
what are the $$ for? did u use them as " " ?
can you pls give us an example of one rubber to know how to apply it more ?
thank youu

1. For rubber area (A): Calculate the cross-sectional area of one band using the formula:
   $$A = \pi r^2$$
   where r is the radius of the rubber (e.g., for 14.5 mm, r = 7.25 mm or 0.725 cm).