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[ 11-01-2002, 07:09: Message edited by: Roger Rothschild ]

ask ToadE... he knows everything
jeffe

Hello Roger

The worst case calculation is quite easy.

The maximum bolt thrust (lb)= Combustion pressure (lb/in^2)x inside base area of cartridge (in^2).

This assumes zero headspace and teflon coated brass.

Since no design engineer would risk designing the containment (bolt face, lugs etc) for less than about 5 - 8 times the maximum figure, there is no need to worry about the effects of case taper.

Let the flames begin - cheers edi

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[ 11-01-2002, 07:09: Message edited by: Roger Rothschild ]

[ 11-01-2002, 17:05: Message edited by: Zero Drift ]

As pointed out before, calculate for worst case (pun alert! ) and go from there.

Roger,

Go ahead and post what you and your proffessors have decided consititutes the correct equation.

I will not argue with you. I don't care anymore. My first hand experience with the determination of a thrust force created by an expanding gas is my work with SI engines. I have several years experience in that arena. I simply applied what worked there, and arrived at my simple understanding of the forcing function called "bolt thrust force".

Personally, I think that the case taper itself means nothing. What is important is the difference between the internal case taper (created by the drawing die) and the external taper. This difference can generate a SMALL additional or more frequently reducing force. There is that enough to get you to post?

So please post away. I am very interested to see what you all have come up with. I just hope these simpletons don't torment you too badly if your solution doesn't fit into their opinion, WELL.

TEG

Roger - Many years ago in college I had a physics professor who I think gave the best possible answer for your question. It was as follows:

"What do you want to know for...it's not on the final exam?"

This answer seemed to satisfy the curiosity of the entire class.

And now I will leave the arena and let the totally discredited TEG expound on this subject and tell you where the dearly departed P. O. Ackley went terribly wrong during his life of firearms development and research.

I suppose it's a blessing Ackley isn't here any longer for he would surely laugh himself to death reading TEGGY's pompus bullshit.

Your show, TEG. Make a fool out of yourself once more. I've got my glasses on so your bullshit won't get into my eyes.

Am I missing something here? I thought that Roger was going to post a credible set of thrust force equations that the average joe like myself could understand. I check in today and all his posts have gone away. What gives?

Casey

I'll tell you why Roger withdrew. He was trying to start a fight with the Toad. Unfortunately for all of us, the Toad was correct so Roger went running home with his tail between his legs.

Why can't we all just behave like grown-ups and get along. Is there somekind of mental illness, which is causing all of you to have to be right all the time, while the other guys is wrong!

This has always been my problem, but I have finally gotten professional help. I am now a recovering know-it-all-know-nothing-prick. It isn't easy staying on the wagon, but I am.

RAB

RAB - Your idiot spigot is open again...

What gives? Is there another part to the original post somewhere else?

No one was slating P.O. Ackley. He was perfectly correct - reduced case taper results in reduced bolt face thrust and longer case life.

If my memory is working, Roger asked for the formula to calculate the thrust on the bolt face. This figure is of critical importance to the designer of the action and as I wrote in my post - the maximum thrust will occur with zero headspace and a teflon coated cartridge - ie there is no reduction in thrust due to the interaction between the brass and the walls of the chamber.

The action is designed to withstand this maximum thrust with an adequate safety margin.

In the real world the friction of the brass against the wall of the chamber and the straining of the case due to headspace help to reduce that thrust and slightly increases the safety margin.

Hope this helps - cheers edi

Edi,

The intellectual level of this forum has been allowed to fall over the past couple of months. Ever since the individual poster found multiple proxy software that allows the illusion of posting from a different IP address and the lack of "moderation" in any way, shape or form.

The second part here is no moderation would be needed if the obviously well-educated, mature (I would have hoped) men on this board simply stopped replying and began ignoring the troll. Until these things happen I have no interest in attempting to post anything serious since it will only degrade to kindergarten playground name-calling. With all the name-calling and profanity the aforementioned "adults" engage in, it is embarrassing and shameful, giving definition to the phrase, "ugly American". I want no part of this.

A bit of "moderation", a fingertrace program and a letter to the IP provider would nip this short quite quickly.

Sounds to me like a cop out to me. If you really have the information Roger, please share it with us. Screw the trolls. If you don't post this information, guess what, the damned trolls with! Come on post it.

Casey

Roger - Thanks for your reply. It's a pity that there are some people who actively and vehemently protest against learning anything new. I'm sure that they are greatly outnumbered by those who are only too willing to learn.

My father's formal schooling ended when he was about 11. At the age of 81 he made his engineer son dig deeply into his notes on atomic power by enquiring "How does the neutron bomb differ from the enriched uranium bomb that was dropped on Hiroshima?" During our discussion I came to realise that he had a fairly deep understanding of how these things worked. A bit humbling.

cheers edi

This entire thread was started so Roger could have some fun with TEG. It is rather obvious that Roger and his Professors came up with the identical formula that Axel/TEG did sometime ago. This being the case Roger could not have fun since HE was in fact in agreement with Axel/Todd E/TEG/etc/etc.

Roger, I suggest you grow up a little bit and stop this childish trolling behavior. Everyone saw through your attempt from the very beginning of this thread.

I will search out the Axel formula and example problems to refresh your memory.

Here is what the Axel handle posted as an example problem. Looks pretty close to correct to me, but then I am only a Doctor. TEG stated above that the external body taper doesn't matter. What matters is the difference between external and internal body taper. That would seem to be the only correction needed for Axel's equation. That in and of itself, is only a measured parameter correction, the fundamental equation is still sound.

"Nickudu, the pressure of the gases reacts pependicularly to the internal surfaces of the case. So the largest single component of bolt thrust will be the force generated by the internal case pressure acting upon the case's internal diameter at the case head.

The case taper will allow some additional thrust to occur because of the radial force vectors acting upon the walls of the case. To determine the magnitudes of these vectors in the direction of the bolt thrust is a simple thing.

First you must calculate the radial force acting upon the case wall. The thrust force component due to the taper angle of the case is then equal to:

Radial force on case wall * sin(body taper angle).

Example:
Operating pressure: 55000 psi
Case internal base area: 0.125
Case base OD: .54"
Case base ID: .39:
Case wall thickness midlength: 0.035"
Case diameter midlegnth: .52"
Case body taper angle:0.6 degrees
Axial bolt thrust: 55000*.125 = 6875 lbs
Radial force on case wall: 8800*sin(0.6 deg)= 92.2 lbs

Total thrust force is = 6875 + 92.2 = 6967.2 lbs

The radial force is: pressure time the cross sectional area of the case.
Radial force = 55000 * 0.16 = 8800 pounds

So Nickudu, as I said the body taper's contribution to trust force is insignificant. Additionally, we have assumed that there is not friction acting between the chamber wall and the case. If we were to apply a static coefficient of friction of 0.3, which is unrealistically high the thrust force due to body taper would be equal to 92.2 * 0.3 = 27.7 pounds. Even less significant!"

RAB

[ 11-03-2002, 17:21: Message edited by: RAB ]

The maximum bolt thrust (lb)= Combustion pressure (lb/in^2)x inside base area of cartridge (in^2).

This assumes zero headspace and teflon coated brass.
_______________________________________________

Since you are assuming zero head space, what does "friction" have to do with anything? Afterall, the case is in contact with the bolt...it doesn't have to move, correct?

Hello Sniper - in the real world of stresses there is no such thing as a rigid body, so when the load comes onto the boltface it compresses slightly and moves backwards until the receiver strains to compensate for the load to which it is being subjected.

Any friction between the brass and the chamber serves to reduce the boltface thrust load - so I threw in the teflon coated case to make the point that the maximum thrust happens when there is no friction between case and chamber.

Hey - why don't we coat our brass with MoS2? It will look nicer, won't shine and alert the game, will resize easier, won't pick up dust and score the chamber, eject easier .....

I wonder what will happen to the MoS2 coat when you have to anneal the case - and how do judge when it needs annealing? At present I wait for the neck to begin sooting up - and then anneal. Probably a bit sooner than needed - but what the hell it helps to pass the time.

cheers edi

Has anyone else noticed that I really don't know what I am talking about? But you just got to love all the insignificant math that I can throw into a discussion.

Hello Rab - sorry about not repeating the significant maths - here it is.

The worst case calculation is quite easy.

The maximum bolt thrust (lb)= Combustion pressure (lb/in^2)x inside base area of cartridge (in^2).

In the event of a case separation the area used ie the chamber diameter at the point of break.

cheers edi