How much power does the action consume

[smokey-seven]

Once more into the breech

terraformer asked:

Point once where I said the slide NEVER moved. Once. Please.

terraformer in post 116 of this thread said:

Once the bullet is out and the pressure on the barrel to go forward is begins to wane, the barrel is now free to pivot on it's barrel link pivot. The slide is then able to swing back and the cycle begins to occur. ie; the rearward movement of the slide overcomes the forward force of the barrel.

There, right there in your words you state the bullet leaves the barrel before the barrel and slide start to move to the rear.

terraformer said:

I finally got you to admit that with no bullet and just gas pressure can push a slide in recoil.

I'll find the quote, but you are the one that stated a blank would not work in a 1911 and I refuted that.

terraformer said in post #125:

OK, then answer me this. To fire a blank cartridge out of a real semi auto handgun*, you need to restrict the gas flow out of the barrel.

I replied in post #128:

In a word, no. This is not correct. I can fire a blank out of a 1911 and if I load the blank up to a point that it will cycle the action, it fires and cycles just fine.

Again from your #116 post:

To summarize, in very simple terms, the forward pressure on the barrel keeps the slide locked until that forward pressure is relieved (which can't happen until the bullet leaves the barrel). Once it is relieved, the barrel can move backwards allowing the slide to cycle. That's how the locking mechanism works.

And I am saying that the barrel and slide are in motion rearward all the time that the bullet is in the barrel. They unlock after the bullet leaves the barrel but they move rearward together during that .0007 seconds.

terraformer said:

See, there are only 500 or so ft lbs of energy in a 230 grain bullet. Do you think that a 1911 only sees 500 ft lbs of energy in recoil?

Any force imparted to the bullet is also imparted to the weapon in an equal and opposite direction.

terraformer said:

Why can't you admit that after the bullet leaves the barrel the 20K PSI of gas pressure has an effect on the slide/barrel as it leaves the barrel?

I never said it did not, but in the .0001 of a second after the bullet is out of the barrel, the pressure is no way near the maximum number and the slide and barrel have been moving to the rear over the previous .0007 seconds.

terraformer said:

The longer the barrel (within bounds and subject to diminishing returns), the longer that expanding gas has to push on the bullet to accelerate it.

Longer barrels do have an increase in frictional resistance. There is a point in all loads where the length of the barrel will actually slow the projectile down in comparison to a shorter one. Pressure curves in different ammo and various barrel lengths are a little more technical that just saying a longer barrel accelerates a bullet more than a shorter barrel. It is not the barrel length that is doing the acceleration.

terraformer said:

So, by fixing the barrel to the slide, you are ensuring that the full amount of the energy of the expanding gas is directed in one direction, out of the muzzle.

No. The pressure is being converted to mechanical energy in an equal and opposite direction than that of the bullet. It's what is driving the slide to the rear while the bullet is in the pipe! The full amount of energy is being transferred in all directions at the same time. The barrel restricts it all to forward and rearward forces. The slide is being pushed to the rear by the cartridge case attempting to accelerate rearward and opposite to the bullet with an equal force. The barrel moves rearward due to the lugs locked to the slide and the toggle gives the timing to open the barrel from the slide.

terraformer said:

This is energy that NEEDS to be accounted for and is PART OF recoil.

Great... I'll give you a couple foot pounds but until you prove to me how much it actually is, I'll say it's negligible in the overall scheme of things. It all happens after the barrel and slide have unlocked and pressure is dropping off very rapidly. Don't forget to subtract the residual gas energy that comes from the chamber end.

You are stating an increase in muzzle velocity in a Thompson. I'll grant you the 50 fps, but now stretch it out to the 29 inches I originally stated and you will lose that 50 fps and some more. Not all longer barrels will increase muzzle velocity.

Since we now have a .3" distance bullet travel that achieves maximum pressure, I will expect that you will agree now, that a rearward slide / barrel travel is in action by this time.

 

[smokey-seven]

Bump up

Seems that the other party has left for some reason.

 

[maee]

Conservation of momentum. In a semi-auto, the slide/bolt goes back when the bullet leaves the barrel. The means that the bullet MUST be traveling slower in a semi-auto than in a bolt action. The difference is likely small, but is must be traveling slower or the laws of physics would be violated.

m_s*v_s + m_b*v_b = 0, where _s is for the slide and _b is for the bullet. m is mass and v is velocity.

The second equation is conservation of energy. Lets say the energy in the cartridge is Ec, then:
Ec = 1/2*m_s*v_s^2 + 1/2*m_b*v_b^2.

Now, you have two equations, so you can have two unknown variables. Let see what you do know:
Ec - energy in powder
v_b - muzzle velocity, you can measure this with a chronograph
m_b - simply the bullet weight
m_s - simply the weight of the slide

Now, what don't you know?
v_s - the velocity of the slide

So actually, if assuming you chronograph the bullet, you only have one unknown, v_s, and you can use either equation. But lets say you don't have a chronograph. Well, then you don't know v_s or v_b, but with the two equations, you can still solve for both.

So lets do this calculation for a 1911 shooting a .45 ACP:
Ec = 559 J (165 gr (10.7 g) Federal Premium Low Recoil JHP)
v_b = 320 m/s
m_b = 10.7 grams
m_s = 250 grams (approximately)

Well, doing the math, v_s = 14 m/s. Therefore, the energy wasted on the slide is Es = 1/2*m_s*v_s^2 = 24.5 J, or about 5% of the total energy.

Caveat: this assumes you have a perfect grip on the pistol (no limp wristing or arm movement). It also ignored friction in the mechanism and the tilting of the barrel. It also assumed the bullet has left the barrel before the slide compresses the recoil spring much.

 

[44marty]

I can't believe this thread is still going. You are making this way too complicated. When the cartridge charge is detonated, forces act in two directions. In the forward direction, forces expel the bullet and gases out of the barrel. In the opposite direction, forces drive the handgun rearward. These forces are equal and opposite. The portion of the force used to operate the slide is part of the rearward, recoil force. Working the slide does not reduce the bullet velocity.

Remember that when the powder is detonated, the cartridge expands to seal the brass against the chamber walls before the bullet leaves the cartridge.

 

[smokey-seven]

maee said:

In a semi-auto, the slide/bolt goes back when the bullet leaves the barrel.

No, and this is why the thread is still ongoing.

The movement of the slide and components starts to the rear as soon as expanding gas has created enough force to drive it to the rear. That is well before the bullet leaves the barrel. It is not, "when the bullet leaves the barrel"

I will cease posting to this thread as soon as people stop saying that nothing happens until the bullet leaves the barrel.

 

[terraformer]

terraformer asked:

terraformer in post 116 of this thread said:

There, right there in your words you state the bullet leaves the barrel before the barrel and slide start to move to the rear.

Inartful simplification on my part and it's not what I meant to say but you can read it that way if you take it in absolutes. I admit it was not good wording.

Longer barrels do have an increase in frictional resistance. There is a point in all loads where the length of the barrel will actually slow the projectile down in comparison to a shorter one. Pressure curves in different ammo and various barrel lengths are a little more technical that just saying a longer barrel accelerates a bullet more than a shorter barrel. It is not the barrel length that is doing the acceleration.

I never said other things don't have a causal relationship to it.

Great... I'll give you a couple foot pounds but until you prove to me how much it actually is, I'll say it's negligible in the overall scheme of things. It all happens after the barrel and slide have unlocked and pressure is dropping off very rapidly. Don't forget to subtract the residual gas energy that comes from the chamber end.

You have to give me more than a few foot pounds. Just read that email I found and you have to give me 25 - 50.

You are stating an increase in muzzle velocity in a Thompson. I'll grant you the 50 fps, but now stretch it out to the 29 inches I originally stated and you will lose that 50 fps and some more. Not all longer barrels will increase muzzle velocity.

Which is what I said when I caveated "within bounds and subject to diminishing returns" but I guess it's more fun to imply that I didn't say that.

Since we now have a .3" distance bullet travel that achieves maximum pressure, I will expect that you will agree now, that a rearward slide / barrel travel is in action by this time.

But without the barrel, how much would it be. That is the bit I have been arguing.

 

[Admin]

Can we kill this abortion of a thread?

You guys took beating a dead horse to a whole new level.

 

[terraformer]

Seems that the other party has left for some reason.

The other party has a life and is on vacation not checking in as much. Also, I was looking forward to TheRoland's update. He is going to try to answer the OPs original question.

 

[TheRoland]

Can we kill this abortion of a thread?

You guys took beating a dead horse to a whole new level.

I'm more or less done with it. I think we've all said our peice a few times.

However, this is probably one of the longest, most fun, and least hostile non-political threads I've ever seen here! I secretly (or not so secretly now) regret giving up my physics major for a more practical engineering major back in college.

The other party has a life and is on vacation not checking in as much. Also, I was looking forward to TheRoland's update. He is going to try to answer the OPs original question.

I haven't had time to do this yet, but still will, after the NER match.

 

[HooVooLoo]

Actually, I think it could go up a few more levels before it implodes via invocation of Godwin's Law. Let it fly.

 

[maee]

maee said:

No, and this is why the thread is still ongoing.

This is still a good assumption because the slide is so much more massive than the bullet, that its velocity is only about 14 m/s. Therefore, the bullet is long since out of the barrel by the time the slide has moved a short distance.

 

[TheRoland]

This is still a good assumption because the slide is so much more massive than the bullet, that its velocity is only about 14 m/s. Therefore, the bullet is long since out of the barrel by the time the slide has moved a short distance.

But the short distance is the point. Short distance != 0.

Also, your signature banner is going to cost me a good deal of money if I can find a convenient place to fly.

 

[Admin]

 

[maee]

But the short distance is the point. Short distance != 0.

In engineering, short distance = 0. Something small is almost always zero to engineers. Mathematicians, well, thats another story. Makes me remember the story about the mathematician who was told he could sit in a chair 100 feet from a very, very attractive blond woman. Every 30 seconds, he could move his chair closer by half the distance. After thinking about it, he decided he would wouldn't do it because he'd never actually reach a distance of zero. On the other hand, the engineer said "Thats fantastic, to think, after only a few minutes I'll be closer to a woman like this than I've ever been before!!!" and jumped at the opportunity. Once he got close enough, he called it zero.

By the way, if you need a place to fly, check out this website with a list of flying fields:
http://www.modelaircraft.org/clubsearch.aspx

Personally, I fly at this place: http://charlesriverrc.org/newsite/Fields_davis.html