Muzzle Velocity of Spring Loaded Musket Ball: 64.26m/s

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Discussion Overview

The discussion revolves around calculating the potential muzzle velocity of a musket ball when using a compressed spring instead of gunpowder. Participants explore the theoretical implications of using spring mechanics to achieve velocities comparable to traditional firearms, considering factors like spring constants, energy equations, and the physical dimensions of the musket and ball.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant calculates the muzzle velocity using the spring potential energy formula and arrives at 64.26 m/s, questioning the validity of this result compared to traditional musket velocities.
  • Another participant suggests working backwards from known exit velocities to determine the required spring constant for achieving higher muzzle velocities, proposing a new spring constant of 2979.1 Nm.
  • A later reply discusses the implications of changing the number of active coils and the potential need for a different spring constant to match traditional musket velocities, indicating a calculated muzzle velocity of 310 m/s.
  • Concerns are raised about the feasibility of achieving a spring constant of 2979 Nm with the specified dimensions, suggesting that the calculations may not align with practical constraints.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the calculations and the feasibility of the proposed spring constants. There is no consensus on the accuracy of the calculations or the practicality of the proposed spring dimensions.

Contextual Notes

Participants note potential limitations related to elasticity issues and the assumptions made regarding friction and gravity. The discussion does not resolve these uncertainties.

Who May Find This Useful

This discussion may be of interest to individuals exploring the mechanics of springs in relation to projectile motion, as well as those curious about alternative propulsion methods in historical weaponry.

howdybilly
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disclaimer: bizarre question from physics novice

Using a smooth bore classic musket (approximately 1m length of barrel, musket ball (.0173m diameter)), what would the potential muzzle velocity of the musket ball be if the powder charge were replaced with a compressed spring?

PE=1/2kx^2

KE=1/2mv^2

Using a spring with k=128 Nm (used a calculator on engineer's edge where modulus of ridgity G was 25x10^6, wire diameter d was .2 inches, mean coil diameter D was .48 inches and number of active coils n was 40). Not sure if this is kosher or not.

Assuming friction and gravity are negligible - the musketeer keeps the weapon well lubed and is on the moon, if he pulls the trigger which releases the "charged" spring, what will the muzzle velocity be of the musket ball when it leaves the musket? Let's also assume that the spring when uncompressed, is the full length (1m) of the barrel.

PE=1/2*128*1^2=64 joules?
KE=64=1/2*.031v^2 so v=64.26m/s

64.26m/s, long way from a 1700's .69 caliber musket firing around 310m/s

Could that be right? What am I messing up?
 
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howdybilly said:
64.26m/s, long way from a 1700's .69 caliber musket firing around 310m/s

Could that be right? What am I messing up?

Given you know the exit velocity of the rifle, you may want to work it backwards - get the KE, stick it into the PE equation and see what spring you would need.

Then you can see if the required spring matches what you've got now.
 
jarednjames said:
Given you know the exit velocity of the rifle, you may want to work it backwards - get the KE, stick it into the PE equation and see what spring you would need.

Then you can see if the required spring matches what you've got now.

I did it backwards and entered the new spring constant k as 2979.1 Nm, plugged it into the spring calculator on the engineering website and keeping the diameters and modulus of ridgidity the same, I came up with a change in the number of active coils from 40 to 5.82.

I think there are probably some nature of elasticity issues that I'm neglecting but not sure.

so, rewritten - given a 1m long musket, standard .69 cal musket ball (approx .031kg) and a spring under compression with a constant of 1489 Nm (modulus of ridgitity 25x10^6psi, .25in wire diameter, .43 mean diameter and 5.82 active coils), a muzzle velocity of the musket ball could match the 310 m/s of a traditional powder musket.

PE=1/2*2979*1^2=1489.5 joules
KE=1489.5=1/2*.031v^2 so v=310 m/s

?? not sure if I'm using the right calculations. is a spring constant of 2979 Nm possible?

thanks
 
howdybilly said:
?? not sure if I'm using the right calculations. is a spring constant of 2979 Nm possible?

Not sure, but I'd say definitely not with the dimensions you're talking about.
 

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