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Re: Bolt Thrust....Big Bore Vs Small Bore on same

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30 June 2004, 03:04
500grains
Re: Bolt Thrust....Big Bore Vs Small Bore on same
Quote:

Your thinking is muddled. Pressure is pressure and the only pressure that matters is PEAK.





Pressure and bolt thrust are two different things. Please do not muddle them together.





Quote:

Bolt Thrust

Bolt thrust is easy to calculate. Only two inputs are required. They are peak chamber pressure in PSI and as mentioned, the inside area of the case head that the gas pressure can work on. The formula then is:



THRUST=AREA*CPSI Where:



AREA=3.1416*(HS/2)^2



HS=the diameter of the inside of the case head.












30 June 2004, 11:35
Mike375
The duration of the pressure really does not matter, only the PEAK pressure achieved

How much is the bolt thrust, 4 or 5 tons. What if a force of 5 tons was applied to the bolt for 12 months...I think that would be considered a greater load on the bolt than firing 10 shots.

Mike
30 June 2004, 15:49
jeffeosso
Pecos,
we are talking loading vs sheer...

you tell me... a wings load rating is FAR less than it's sheer rating, right?

jeffe
30 June 2004, 14:50
Mike375
Ed,

I am aware of what you speak but my question is not relating so much to whether a CZ would have trouble but which calibre puts more load on the bolt. The higher average pressue of the 300 Wby or the lower average pressure of the 458 Lott acting over a longer duration. In other words a 20 pound load on the bolt is greater than a 10 pound load. Although you need 212*F to boil water that does not change the fact that a temperature of 78*F is hotter than 75*F

Mike
30 June 2004, 15:13
ASS_CLOWN
Ed,



What are you talking about? Do you know? Believe me when I say I know of what I speak with regard to fatiguing of steel! Your post is so out of touch with reality, if I am reading it correctly, it isn't funny.



Please explain to me how a statically applied load damages the steel more after setting there for 6 weeks as opposed to only being applied for 1 second.



The answer to the question Mike asked has already been answered. If he requires more information, the links I supplied will provide this data in spades!



ASS_CLOWN
30 June 2004, 13:53
ASS_CLOWN
Mike,



Quote:

How much is the bolt thrust, 4 or 5 tons. What if a force of 5 tons was applied to the bolt for 12 months...I think that would be considered a greater load on the bolt than firing 10 shots.







It simply doesn't work that way. From the bolt's perspective if you apply 5 tons of force for 10 milliseconds or 10 months, it is the SAME 5 tons of force. Of course if, in your example, the bolt was heated to 300 deg F or higher you might see some creep (I would guess on the magnitude of 0.0005" or less). Creep is a funtion of contact pressure, temperature, and the material under load. Steels are relatively creep resistant (compared to aluminum, steel hardly creeps at all). The endurance limit is another area you may find of immense interest. You will also want to work on obtaining a working understanding of the concept of strain energy, and the von Mises theory of strain energy / distortion (effects of combined stresses acting upon a system).



In my last post I stated the facts as tersely as possible. If you NEED a more detailed explanation I suggest you buy some Mechanical Engineering books (Strength of Materials, Machine Design, would be two excellent reference books), or you could go to www.SAE.org and look for fatigue analysis books in their book store. You may also want to review SAE's list of Technical Papers.



I apologize, but it is too blinking hard to try and explain this stuff on a forum chat board. Don't feel bad though, they don't teach fatigue in college very well either, so we get to teach the children about it after they start out in the real world.



Anyway, if you get the textbook or technical papers and have any specific questions I will try and answer them for you, to the best of my meager ability.



Here is a question for you (you may find the answer interesting)



Are any of the following steels significantly stronger / weaker in tensile strength that any of the others?( singificantly would mean a difference of greater than 5% ):



SAE 1040 @ Rockwell C 55

SAE 4140 @ Rockwell C 55

SAE 8640 @ Rockwell C 55

SAE 4340 @ Rockwell C 55



ASS_CLOWN
30 June 2004, 14:01
JefferyDenmark
Steel fatigue analysis 101

Cheers,

Andr�
30 June 2004, 14:07
Grandpasez
Mike--With a regular thrust load of 5 tons,applied steady for a while, the effect wouldn't be any greater than firing a dozen shots with the same thrust. As it is only a third or a quarter of the amount needed to damage lugs, like a Ruger takes 20 tons to break lugs,Mauser 15 tons, etc.
Now if you applied load of 19 tons to ruger for a while you probably would show damage after a while, just as you would
if a dozen shots were fired at 19 tons thrust.Of course 19 tons bolt thrust from any case below BMG size would result in case failures first, before you got built up to that thrust level..Ed