KmuleinAK, some information to help you calculate when you need a second recoil lug.

Impact Strength Izod Procedure:

Scope:
Notched Izod Impact is a single point test that measures a materials resistance to impact from a swinging pendulum. Izod impact is defined as the kinetic energy needed to initiate fracture and continue the fracture until the specimen is broken. Izod specimens are notched to prevent deformation of the specimen upon impact. This test can be used as a quick and easy quality control check to determine if a material meets specific impact properties or to compare materials for general toughness.

Test procedure:
The specimen is clamped into the pendulum impact test fixture with the notched side facing the striking edge of the pendulum. The pendulum is released and allowed to strike through the specimen. If breakage does not occur, a heavier hammer is used until failure occurs. Since many materials (especially thermoplastics) exhibit lower impact strength at reduced temperatures, it is sometimes appropriate to test materials at temperatures that simulate the intended end use environment.

Reduced Temperature Test procedure:
The specimens are conditioned at the specified temperature in a freezer until they reach equilibrium. The specimens are quickly removed, one at a time, from the freezer and impacted. Neither ASTM n or ISO specify a conditioning time or elapsed time from freezer to impact - typical values from other specifications are 6 hours of conditioning and 5 seconds from freezer to impact.

Specimen size:
The standard specimen for ASTM is 64 x 12.7 x 3.2 mm (2� x � x 1/8 inch). The most common specimen thickness is 3.2 mm (0.125 inch), but the preferred thickness is 6.4 mm (0.25 inch) because it is not as likely to bend or crush. The depth under the notch of the specimen is 10.2 mm (0.4 inches).
The standard specimen for ISO is a Type 1A multipurpose specimen with the end tabs cut off. The resulting test sample measures 80 x 10 x 4 mm. The depth under the notch of the specimen is 8mm.

Data:
ASTM impact energy is expressed in J/m or ft-lb/in. Impact strength is calculated by dividing impact energy in J (or ft-lb) by the thickness of the specimen. The test result is typically the average of 5 specimens.
ISO impact strength is expressed in kJ/m2. The test result is typically the average of 10 specimens.
The higher the resulting number, the tougher the material.

Equipment used at Plastics Technology Laboratories, Inc.:
TMI Impact Tester

**Please note that this test description is intentionally generic in nature and aimed at providing a descriptive summary to enhance test understanding. For more information please contact a PTLI Technical Representative at ptli@ptli.com . Due to copyright restrictions, we are not able to provide copies of standards. Standards can be obtained from www.astm.org, www.iso.ch/iso/en, www.sae.org or other appropriate standards authorities.

Impact Strength of Woods
[URL=http://www.cwru.edu/cgi-bin/edocs/fetch.pl?
item=2665]Link to Impact Strengths of Woods part 1[/URL]

Impact Strengths of Woods part 2

Calculating recoil energy you must only use the mass of the barreled action DO NOT INCLUDE THE STOCK.

Axel

holly shit tard, the Izod test will not determine shit related to wheather you need a second recoil lug or not. Are you even a engineer?
Lets digress a bit. There becomes a point in time in engineering when the calculating failure of material can only tell you where you *shouldnt* be, like with wood, and not *when* failure is going to occure.The complexity of finding a failure point in these calculations is "chaotic" Wood like you said, varies greatly, and magical numbers and turning points have little use whereas experiance stands in this field. With wood and many other materials if you dont add a serious safty factor to your calculations you would be flirting with failure. I beg you to "give me a number" in determination. I couldnt.

I forgot to talk a bit about the IZOD test.
At school we use the IZOD mainly for looking at grain structure after failure, and testing homoginized materials, mostly steel. It is a impact test. The test appliciable here, I would think would be a compresion test with a very similar response curve to the recoil. It would be hard to do and even harder to calculate due to the nature of wood.
But then again I am just young and dumb this is just my opinion.

Not to mention the fact that most stopper stocks, even wood stocks, are a composite structure, comprising the wood, steel crossbolt and bedding compound.

Just because someone can calculate failure, does not mean the numbers will be useful in the real world. Calculations need to be correlated to the real world to prove useful. I spent one summer working in the NASA Ames wind tunnels as an engineering student. There is a reason that windtunnels are still used, and computational fluid dynamics calculations aren't solely relied upon. Calculations get one close, and reduce itterations of experiments, but they still need to be correlated to reality.

smallfry, thank you for the kind words. As you said you are young and IGNORANT! Impact strength is exactly that! I suggested using a safety factor of 2 or better yet 3! Just because YOU do no know how to manipulate the data does not mean it cannot be done. For your information, young man, we conduct highly accurate fatigue life predictions everyday. As with all things in nature there is a certain randomness to failure, even with you homogenous material STEEL. Therefore we utilize statistical modelling to predict life to failure.

Of course you could use a compression stress model, but that is more than likely going to be far more inaccurate than an impact strength based model. The problem is smallfry that the load is applied in as a "SQUARE WAVE", which is indicative of an IMPACT. Compressive loading is done with defined slope and is more accurately modeled with a "SINE WAVE" type of input. Recoil is most definitely an IMPACT or "SQUARE WAVE" event not some simple gradual increase in compressive force with respect to time. To explain further. During impact the loading goes from 0 to maximum in very small time period, say 10 - 50 milliseconds. While the compressive strength loading from 0 to maximum is applied over a much longer time interval, say 500 - 1000 milliseconds. This time interval differential has a HUGE effect on the load capacity of the material. But then I am a tard as you said.

Paul H, I agree with your comments. Of course the calculation MUST be correlated to the real world. However, a properly executed calculation should get you close to reality. By close I mean within 5% - 20%. So if you were to use a safety factor of 3 times the requirement of a correlation to reality is not really necessary. If you correlated you may find that in reality you only had a safety factor of 2! Still plenty!

Axel

Well mouth... have at it then, sample a piece of walnut in a IZOD tester and calculate your model from there. Must be simple.
Secondly as I have said before when you include a safty factor of say 2 or 3 you are not predicting when and where other then where you shouldnt be.
I apoligize for the harsh words I hit the computer to early after waking up.

Smallfry, testing a peice of walnut in my IZOD tester is not necessary. This has already been done! Actually, smallfry the inclusion of a safety factor does not mean that we do not know the how and when of failure. It means that we are prolonging the lifespan of the component and compensating for some statistical distribution due to variations. See this means that some samples of walnut stocks may well be 3 times stronger than necessary while some other samples of walnut stocks my be just strong enough.

You seem to suffer from the standard American engineering education. That meaning you have NO clue how to apply the principals taught in school since you get no "hands on" application of said principles.

Axel

Safty factor? really?
You also might read your first post Axel, sorry I am so dumb.

Now Guys- Don't be too harsh with Axel! Remember the only second recoil lugs he's ever actually seen are in pictures of rifles from this site! You don't actually believe anything he says do you? Note that his English has gotten much much better lately. He's really Scott Sweet and not a German at all. If I'm wrong Axel, I'm sorry!-Rob

Robgunbuilder, what exactly is so hard to understand about my being able to both be German and speak/write english? Another issue I have with you is your insistance I am Scott Sweet! What did this guy do to you to make you so paranoid? I am not Scott Sweet, the moderators of this site have verified that FACT! BTW, I have seen a second recoil lug in person once or twice! If you are about to have a mental break down let me know and I will stop posting here. I really do not want to be responsible for your failed mental health!

Orion1, there is a fundamental difference is the training of engineers between the US and Germany. In the US it is common knowledge that it takes upwards of 2 years to train a graduate engineer to do his JOB! In Germany this is reduced to a couple of months!!! This is due to apprenticeships programs in Germany. This DOES NOT exist in the US. Besides all of your examples are ANCIENT history! The Japanese and even the Dutch surpass the US in electronics! The US space agency is almost as bad as the Russians with their unsafe shuttles. BTW, the russians had laser and IR precision guided aerial munitions before the US did! You had better deflate that head of your before it pops!

Smallfry, the safety factor comment was made on a thread started by Jeffeosso. Jeffeosso's thread concerned bedding compounds. I started this thread to answer a question from KmuleinAK that was posed on Jeffeosso's thread. I thought you knew this based upon this comment in your first post "With wood and many other materials if you dont add a serious safty factor to your calculations you would be flirting with failure." Upon rereading your post I can see that this was not necessarily the case.

Axel

Interesting, I've worked as an engineer for a dozen odd years, at various companies, with engineers from all over the world, and in foreign countries. What I've experienced in that short time is there are always a few engineers that sound very impressive in their analytical and technical approach to problems. These guys sound like they really know their stuff. What one finds after working with these guys is that it is all a front, and they haven't a clue as to what they are doing.

Our friend here, wherever he may be from, or whoever he may be is a textbook example of such clowns.

Sounds like alot of work for a thought process that takes a few milliseconds:
"This cartridge has alot of power, I better add a second recoil lug."

[ 05-24-2003, 05:30: Message edited by: DanD ]