Check request - calculating force from weapon recoil.

[Mechbob1]

Hi, I'm a recently graduated engineer who's working on calculating the force exerted on a rigidly mounted weapon mount as a result of recoil. I'm hoping someone can have a look and see if I'm on the right path, and that what I'm doing makes sense for an approximation.

Using a bunch of variables, I was able to calculate the weapon's recoil velocity. Then, I calculated the kinetic energy from the weapon's velocity and the mass of weapon.

Now, I have an answer in Joules, but am unsure how to use that to calculate a force. Anyone able to advise?

As I was stuck there, I then tried, instead, using impulse and momentum and the following forumla:

F * change in T = m*v(initial) - m*v(final).

This gave me a force, but I'm unsure if it's a correct way to do it. Anyone have anything to add?

First post, so please advise if I need to add anything else.

Thanks.

 

[hydtools]

Mechbob1:
"That said, I have since realised that using the momentum method I ignore the rifling friction force, which I’ve read is ~10%. Also the pressure of the gas leaving the barrel (though this is comparatively tiny)."

When using impulse-momentum in this case, friction in an internal force in the system. No additional accounting is needed. The friction force acting opposite the projectile motion is matched by the opposing friction force reaction on the barrel.

Ted

 

[Mechbob1]

Thanks, hydtools!

Just to 'close this off', I ended up realising that the momentum method only works for linear acceleration. As a round doesn't act in this manner, I used the data given to make a 'best estimate' as I don't have access to velocity profiles in the barrel. At max acceleration, it was around 2.5x the average acceleration, which multiplied the force accordingly. Haven't received any feedback on the numbers yet, so I'm going with 'no news is good news'.
Thanks for all the input - lots of things I hadn't considered.