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stock replacement rod bolts pages 32-36 72-74 hi-performance for competition aftermarket replacement rod bolts page 30-31 distributor hold-down studs pages 57 60 harmonic balancer bolts page 58 intake manifold bolts pages 55 62 70 camshaft bolts page 59 thermostat housing bolts pages 56 61 valve cover bolts studs pages 50 62 rocker arm adjusters page 49 rocker arm studs page 48 assemble your engine the right way with arp fasteners front cover studs page 53 header studs bolts page 51 flywheel/flexplate bolts pages 64-65 water pump bolts pages 53 61 wheel studs pages 68-69 drive plate bolts page 68 4 800-826-3045 torque converter bolts page 65[close]
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fasteners and street air cleaner studs page 56 rod bolts index accessory rear cam drive 54 air cleaner studs 56 alternator bolts 61 alternator studs 60 71 apparel 99 assembly lube 93 bellhousing stud kits 54 66 blower studs 57 brake hat bolts 67 70 bulk fastener bins 86 camshaft bolts 59 cam sprocket bolt kits 78 carburetor float bowl bolts 57 carburetor studs 55 71 carrier fasteners 67 chrome moly bolt 5-packs 79-85 clutch cover bolt kits 65 coil bracket bolts 56 60 cylinder head bolts 43-44 distributor studs 57 60 drive pins 68 drive plate bolts 68 engine accessory kits 63 flexplate bolts 65 flywheel bolts 64 front cover bolts and studs 53 front mandrel bolts 71 fuel pump bolts 53 61 fuel pump pushrods 58 general purpose nuts 87-88 general purpose washers 91 harmonic balancer bolts 58 head bolts 43-44 76 head studs 37-44 75-76 header bolts studs 51 hex nuts 88 insert washers 92 intake manifold bolts 55 62 70 main studs bolts 45-47 77 metric exhaust/accessory studs 78 motor mount bolts 53 66 nyloc nut 5-packs 88 oil pan bolts studs 52 62 oil pump drives 59 perma-loc adjusters 49 plate nuts 89 porsche specialty fasteners 78 pressure plate bolts 65 rear end cover bolts 66 ring compressors 96 ring gear bolts 67 rocker arm studs 48 rod bolt extensions 95 rod bolt stretch gauge 96 rod bolts 30-36 72-74 spark plug indexer 95 special purpose washers 90-91 stainless steel bolt 5-packs 80-85 stand-off brackets 92 starter bolts 54 thermostat housing bolts 56 61 thread chasers 95 thread sealer 94 torque converter bolts 65 torque specs 24-26 transmission pan bolts 65 valve cover bolts studs 50 62 water pump bolts 53 61 weld bungs 92 wheel studs 68-69 pages 30-36 replacement and aftermarket cylinder head pages 37-44 48-51 75-76 head studs bolts rocker arm studs adjusters valve cover header engine block carburetor studs pages 55 71 pages 45-47 52-54 main studs bolts oil pan pump front cover water pump intake system pages 55-57 manifold bolts carb air cleaner blower studs coil distributor header studs bolts page 51 engine components pages 58-59 cam harmonic damper bolts fuel pump pushrod oil pump accessories pages 60-63 complete bolt kits individual bolts from intake to oil pan driveline pages 64-68 flywheel flex pressure plate converter rear end wheel studs head studs bolts pages 37-44 75-76 nascar specialties pages 69-71 special fasteners for nascar competition main studs bolts pages 45-47 77 sport compact pages 72-78 rod bolts head bolts studs main bolts studs cam accessory studs 1863 eastman avenue ventura ca 93003 bulk fasteners pages 79-92 bolt 5-packs washers nuts bulk bins weld bungs stand-off brackets web arp-bolts.com arpdiesel.com e-mail info@arpfasteners.com phone 805-339-2200 fax 805-650-0742 800-826-3045 tools pages 93-97 rod bolt extenders stretch gauge ring compressors thread chasers © 2011 automotive racing products inc 800all rights reserved arp the arp logo wave-loc perma-loc arp2000 arp3.5 and arp ultra-torque are registered trademarks of automotive racing products inc all other trademarks are property of their respective owners apparel page 99[close]
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the company a brief history they say that to be successful you must identify a need and satisfy it back in 1968 racing enthusiast gary holzapfel saw that many of his friends broken engines were caused by fastener failure at the time there were no commercially available studs and bolts up to the challenge so holzapfel called upon his many years of fastener making experience for a leading aerospace subcontractor and founded arp® automotive racing products in the ensuing years the firm has grown from what was literally a backyard garage workshop into a highly diversified manufacturer with five operational gary holzapfel entities in southern california with founder and ceo a combined area in excess of 148,000 square feet these include forging machining finishing and packaging/warehousing facilities in santa paula and ventura california there is even a unique racing-themed restaurant at the main santa paula facility called hozy s grill which is open to the public on hand at the grand opening of arp s new manufacturing facility in santa paula ca were l to r 12-time nhra world champ john force arp s vp sales marketing bob florine founder and ceo gary holzapfel assistant sales manager chris raschke and arp president mike holzapfel arp s state-of-the-art manufacturing facility in santa paula today arp s product line contains thousands of part numbers and has expanded to include virtually every fastener found in an engine and driveline these range from quality high performance oem replacement parts to exotic specialty hardware for formula 1 indycar nascar and nhra drag racing and marine applications as a matter of fact arp s customer list reads like a who s who of motorsports around the world in the past several years virtually every major championship on the planet has been won with engines prepared by arp customers these include nascar sprint cup irl formula 1 nhra top fuel funny car pro stock nascar nationwide series and camping world truck series and so it goes arp works closely with many many teams as a supplier of engine and driveline fasteners and has clearly become recognized as the preeminent source for serious racers in addition to its core automotive business arp has an aerospace division and is one of the very few companies in the world fully licensed by the united states government to manufacture ms-21250 fatigue rated fasteners arp also manufactures a variety of industrial fasteners on a contract basis and is known for its ability to promptly provide efficient solutions to problems at hand packaging warehousing and sales operations are handled out of ventura all metal finishing operations are done in this santa paula plant 4 arp s new forging facility in santa paula california this facility is home to arp s heat-treating operations 800-826-3045[close]
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the company the manufacturing process in order to ensure optimum quality control arp has grown to be exceptionally self-reliant and now controls all aspects of the manufacturing process all operations are performed in-house and closely monitored this is how arp has been able to establish a reputation for zero defects quality throughout the industry the process begins right at the mill where arp orders only premium grade materials including several proprietary alloys the ever-popular 8740 chrome moly steel for example comes from the mill in four distinct grades the lowest is commercial which is followed by aircraft quality arp uses only the top two grades sdf and chq which cost twice as much but provide the foundation for defect-free fasteners these materials come in bar stock for studs and huge coils for bolts transforming raw material into a fastener begins with hot and cold heading processes material is fed into powerful devices and cold forged or induction-heated and formed under tons of pressure material comes from the mill in large coils which subsequently will be fed into cold-headers and formed into bolts some bolts begin as induction-heated lengths of bar stock that are forged on huge presses with the desired head shape arp s bank of cold-headers can handle material up to 5/8 diameter and form bolts in a multi-phase operation an overview of part of arp s expansive machining operations the shop is laid out for optimum efficiency lengths of bar stock are automatically fed into special machines and cut to the appropriate length 5 800-826-3045[close]
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following the basic shaping material is heat-treated to desired levels this crucial process is done entirely in-house to assure total quality control arp uses special vertical racks to hold each piece individually and assure complete 360° penetration this is far superior to commonly-used methods of dumping items into a large bin and batch-treating studs are centerless ground to guarantee concentricity the thread rolling operation to mil-s-8879a specs is done after heat-treat which accounts for a fatigue strength up to ten times higher than fasteners which are threaded prior to heat-treat arp manufactures nuts in a multi-step process that begins with raw material being fed into a giant forming device that blanks the hex and 12-point nuts and continues with highly sophisticated automated threading equipment tapping each nut with an accuracy of .001 which is five times higher than the aerospace standard this ensures an exceptionally closetolerance fit between the bolt/stud and nut metal finishing is also performed in-house at arp operations include black oxide coating of chrome moly or polishing stainless steel to a brilliant luster the company the grinding department is where all studs are centerless ground to ensure that they are perfectly concentric as many as ten machining steps are required to achieve this level of accuracy powerful cold-forging equipment is used to make arp s hex and 12-point nuts multi-stage dies are employed to precision-form the finished blanks a series of cnc-threading machines are employed by arp to accurately tap the threads in nuts tolerances held are 5 times better than aerospace standards 6 heat-treating is critically important in obtaining the correct tensile strength fasteners are placed in special vertical racks to ensure complete 360° penetration arp performs the thread rolling operation after heat-treating which results in a fatigue strength up to 10-times higher than fasteners with threads rolled prior to elevating the material s tensile strength 800-826-3045[close]
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the company a bank of cnc machining centers are employed at arp to perform specialty operations also on the premises is a fully-equipped lab for r&d and quality control it has everything required to ensure that arp products measure up to the company s ultra high standards some of the tests that arp personnel perform on a daily basis include proof loading using a 120,000 lb capability tensile machine fatigue cycle amsler and hardness rockwell visual inspections include use of an optical comparator to check thread root contour etc fixtured micrometers and microscopic grain flow analysis the computer-controlled fatigue cycle testers allow arp to take fasteners to a failure point in millions of cycles as opposed to the aerospace norm of 65,000 average to 130,000 cycles maximum this allows arp engineers to verify the design specifications of each fastener and prove its ability to provide superior long-term service finished products are packaged and warehoused in arp s ventura facility which is also home to the firm s customer service technical and sales office contemporary edm technology is used to perform special operations such as hex-broaching the nose of a unique short-run fastener arp s popular stainless steel engine accessory fasteners are polished to a brilliant luster using this specialized equipment fasteners are shot-peened after heat-treatment to improve overall external integrity the finishing touch for most chrome moly fasteners is the black oxiding operation fasteners go through a series of baths 7 800-826-3045[close]
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the company behind the scenes there are a number of important elements in the production of specialty fasteners not the least of which are materials design and manufacturing as you read further into this catalog you will get a better idea of the extraordinary steps taken by arp to produce the very finest products of their kind on the market today the key to success in all areas is personnel and here s where arp s cadre of highly qualified and dedicated specialists shines brightly two valuable resources in the design of arp products are dr kenneth foster and russell sherman p.e both men have extensive backgrounds in mechanical engineering metallurgy and stress analysis their academic credentials are substantial and real world experience equally impressive dr foster has a ph.d in engineering mechanics from cornell university and has taught at several colleges he was formerly the head of stress dynamics at hughes aircraft space systems division mr sherman has been awarded a fellowship from a.s.m international a technical achievement award from fastener technology international and holds a number of fastener patents kenneth foster phd consulting engineer russell sherman p .e consulting engineer robert logsdon q.c consultant some of the most valuable work done by foster and sherman includes analyzing various aspects of engine chassis and driveline structural loads and coming up with solutions to the problems at hand in this manner the arp research team is able to continually expand the company s product line arp has added robert logsdon to its cadre of consultants he comes to arp with vast experience in the area of metrology quality control manufacturing acquisition and configuration management logsdon is a graduate of the u.s naval academy of metrology engineering the defense management college high powered magnifiers are used to carefully inspect critical components arp s quality control team is relentless a series of special checking devices are employed to monitor the quality of threads for every thread size there is a checking device 8 a computer-controlled instron tensile machine is used to determine the ultimate tensile strength of studs and bolts arp has two of these highly sophisticated amsler fatigue machines which check fasteners through millions of cycles 800-826-3045[close]
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the company and u.s air force institute of technology additionally arp has one of the industry s most complete in-house r&d/qc facilities and a wide variety of testing equipment through the combined efforts of logsdon and arp s management team the iso 9001 level 1 quality manual level 2 quality system procedures and level 3 work instructions documentation has been finalized and is being implemented arp is now iso 9001 and as9100 registered arp also enjoys a solid working relationship with many of the most respected professional engine builders and race teams from the world over including those involved in formula 1 nascar nhra ihra world of outlaws and a host of others constant interaction with these racing experts to provide fasteners for a wide variety of competition applications enables arp to stay on the cutting edge of fastener technology development you will find arp fasteners sold by leading performance retailers and professional engine builders from coast to coast these firms know that arp fasteners are the standard of the industry and smart consumers will accept no substitutions as you can see all arp fasteners are proudly made in the usa to the industry s highest standards arp also supports racers through generous contingency awards programs with many racing programs arp is a long-time nhra major sponsor what arp can do for you in addition to manufacturing a comprehensive array of cataloged fasteners for automotive and aerospace applications arp thrives on the challenges of developing fasteners to solve unique problems racers pro street enthusiasts and street rodders have over the years approached arp about manufacturing special fasteners for unique applications and the company has responded with innovative solutions arp can provide complete r&d services including metallurgical research product design prototype machining and extensive laboratory testing moreover arp has experience manufacturing fasteners from a wide variety of materials all work can be performed under the strictest confidence arp is well versed in facilitating proprietary research and custom manufacturing for corporations the world over it is for good reason that arp is recognized as the world leader in fastener technology the finished goods are given a protective coating and stored in sealed containers awaiting packaging millions are in stock arp fasteners are prominently featured at leading performance retailers worldwide after final packaging the kits are placed in storage racks and are ready for order fulfillment thousands of sku s are warehoused components for each kit are placed on the appropriate display cards sealed and labeled through-put has been significantly increased 9 800-826-3045[close]
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fastener tech john carroll smith a tribute there are many of us who can say we knew john carroll smith in life carroll smith was known around the engineering shops as a design and development engineer he was known on race circuits as a team manager driver coach and racing guru and before that he was known for his 30 years of racing experience driving in scca events as well as on circuits in europe including the targa florio and le mans even more of us know carroll smith through his books his to win series of books brought technical acclaim as they became staples for amateur and professional racers while his engineer in your pocket are today highly regarded as engineering handbooks we re never surprised to find his name on or featured in books on race car design preparation engineering and tuning among his peers at the society of automotive engineers he served as a judge for the formula sae competition one of his proudest honors was the society s excellence in engineering education award carroll smith was a race engineer and special motorsports consultant with automotive racing products for more than decade the pages of our catalog alone bear the mark of his enormous contributions to our efforts here at arp as elsewhere carroll smith s mission was simple he was determined to impart the encyclopedic knowledge of racing and the machinery of racing that he learned during those decades on the world s racetracks around those shops and among his engineering peers he left us at arp with a significant engineering inheritance much of what we now know from carroll will ensure we remain the world leader in the field of racing fasteners it is our way of reciprocating for what he gave us that we impart his expertise and experience in the form we know best superior engineered products as an engineer carroll smith had successes in formula 5000 numerous gt and sports car races and with the ferrari formula 1 team he is best known however for his work with carroll shelby and the ford gt40 program which he helped develop into a winner at le mans ford has recently announced it is bringing back the gt40 its signature race car and a vehicle which even forty years later bears carroll s fingerprints to those of us who knew him in person and through his work the return of the gt40 is just another indicator of the enormous contribution to race engineering that john carroll smith continues to make even after his passing carroll smith passed away at his california home on may 16 2003 from pancreatic cancer smith are you implying that the aerospace fastener manufacturers cut corners in order to win contracts no it s a matter of manufacturing goals and simple economics the aerospace market is price dominated in order to get the contract the fastener manufacturer s goal is to meet the specification at the least cost not to produce the best possible part this means that they are going to use the least expensive steel and manufacturing processes that will meet the specification there is nothing wrong with this approach it certainly does not mean that certified aerospace fasteners are unsafe in any aspect they will do the job for which they were designed there is another factor airframe and aircraft engine manufacturers design their components to a very high margin of safety further aerospace structures are designed to be fail safe there is a back up or second line of defense for virtually every structural component so that an isolated failure will not lead to disaster they are also subjected to frequent and rigorous inspections this spring was wound from un-shaved material it failed on the seam line the aerospace quality myth in areas from hose ends to engine fasteners the terms aerospace material and aerospace quality have become buzz words implying the very best in design materials and quality control it isn t necessarily so says gary holzapfel founder and ceo of santa paula california based arp inc arp automotive racing products supplies extremely high strength and fatigue resistant threaded engine fasteners to nascar irl nhra and formula one engine builders and manufacturers holzapfel explained his reasons in an interview with carroll smith smith gary do you believe that the term aerospace quality is over rated in the specialty fastener industry yes i do first of all the term is meaningless any ams aerospace material specification material must be matched to the specific application as an example some airframe bolts an3-20 are legitimate aerospace parts and are very well suited for the low stress applications for which they were designed but with a minimum ultimate tensile strength of 125,000 psi and a relatively low temperature limit they would be completely unsuitable for use in a racing engine we started out in the aerospace fastener business and we understand it that s why we re not in it any longer what is not generally understood about aerospace fasteners is that the fastener manufacturers do not design the product the nuts bolts and studs are spec d by the airframe or engine designers and put out for bid as long as the supplier certifies that the product meets the minimum requirement of the specification and it passes the customer s inspection procedures low bid wins smith what s different about motor racing quite a lot really while the demands for strength fatigue resistance and quality control can be similar and the assembly and inspection procedures in racing can 10 800-826-3045[close]
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the company ing fasteners from at least 10 different steel alloys from 8740 chrome moly to the very high strength chromium-cobalt-nickel alloys such as custom age 625 we also use stainless steel and titanium with utss ultimate tensile strength from 180,000 to 270,000 psi we can suit the material to the job and the customer s cost restraints we are continually researching and experimenting with new alloys and manufacturing processes some with all around better strength and fatigue properties arp s mike holzapfel and russ sherman discuss a fastener s alloy smith once the design work is done and material has been selected what s next next comes the actual process of manufacturing it goes without saying that all high strength bolts must have rolled rather than cut threads and that the threads must be rolled after heattreatment but there is more to it the old saying to the effect of if you are doing something in a particular way because that s the way it has always been done the chances are that you are doing it wrong holds true in fastener technology technology advances and we have to advance with it all of the manufacturing processes should be subject to continuous experimentation and development as an example with some alloys cold heading produces a better product than hot heading and vice versa the number and force of the blows of the cold heading machine can make a significant difference in the quality of the end product excessive numbers of blows can lead to voids in the bolt head arp in fact holds significant patents on cold heading procedures for the higher nickel and cobalt based alloys in a typical aerospace manufacturing process these alloys are hot headed from bars reduced in diameter from 48 to 50 by cold drawing resulting in a hardness of about rockwell c46 which is too hard for cold heading so the blanks are locally induction heated in a very narrow temperature envelope and hot headed if care is not taken the process can reduce the hardness of the bolt head and the area immediately under it as much as 3 to 5 points on the rockwell c scale subsequent heat-treatment does not restore this partially annealed area to full hardness and strength therefore the final result can be a relatively soft headed bolt this process is not preferred by arp our patented process begins with a softer wire that can be cold forged the process work hardens the head and the under head area to the desired hardness we then power extrude the front end to achieve the reduction and hardness in the shank resulting in a bolt with even strength and hardness from end to end the same is true of thread rolling temperature and die speed must be controlled and changed for different alloys many bolt manufacturers who meet the aerospace specifications don t come close to meeting our standards we consistently go beyond standard aerospace specs our concern with the manufacturing processes extends to the details of heat-treating shot-peening fillet rolling and grinding down to the frequency of dressing the grinding wheels in the arena where aerospace standards are a starting point and random failures are unacceptable i feel arp stands alone as a primary be as rigorous as aerospace in professional racing very few parts are over designed and there are no fail safe features there are no back up provisions for component failure a failed or even loosened nut or bolt in a racing engine means disaster instant catastrophic failure an expensive engine is destroyed and a race is lost that is why random failures are unacceptable in motor racing and why aerospace standards should be only a starting point this means that a specialist in the production of high performance engine fasteners must design and manufacture the very best fasteners that can be produced smith so where does the production for a new racing fastener begin the design process begins with the customer s requirements the operating conditions and loads to be expected the packaging constraints and the weight and cost targets this allows us to select the optimum material for the part and to do the initial mechanical design there is more to material selection than simply choosing the best alloy it means using only the cleanest and purest steel available which in turn means researching to identify the best and most modern steel mills it means working closely with the mills both to insure consistent quality and to develop new and better alloys 5 stage cold header used in the production of arp bolts there are not only a myriad of alloys to choose from but for each alloy there are several grades of aircraft specification steel wire from which fasteners can be made we believe that only the top and most expensive grade shaved-seamless guaranteed defect-free is suitable for racing engine applications we also believe that samples from each batch should be subjected to complete metallurgical inspection smith how many alloys do you work with we are currently produc 11 800-826-3045[close]
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fastener tech number of cycles typically 130,000 cycles with the high tension load at 50 of the uts and the low load at 10 of the high load if all of the test samples last 85,000 cycles per ams 5842d the lot is accepted even though racing fasteners are not continuously subjected to their maximum design load at 18,000 rpm 100,000 cycles takes just 5 minutes thirty-four seconds except for drag racing measured in seconds no race lasts just 5 minutes therefore we consider this aerospace standard to be inadequate at arp we fatigue test to elevated loads 10 above aerospace requirements and to a minimum cycle life that exceeds 350,000 cycles the majority of samples are routinely tested to one million cycles during material development and in the case of extremely critical new designs we test to destruction thread rolling is the last mechanical operation in our manufacturing process for each production run the thread rolling machine is shut down after a few parts these parts are inspected for dimensional accuracy and thread quality and are physically tested for both strength and fatigue before the run is continued random samples are inspected and tested throughout the run extremely critical components are individually inspected for dimensional integrity smith what about out sourcing engineering and manufacturing source for specialty and custom fasteners for use in motorsports it is important to realize that simply quoting an ams aerospace material specification number without strength and percentage of elongation numbers is meaningless statements that the use of a particular material will in itself result in extreme strength and resistance to fatigue can be misleading in the world of high strength alloys whether they are used for bolts or for landing gears the manufacturing processes are at least as important as the material specification some in our industry claim to inspect materials at the molecular level in metallurgical terms molecules are not necessarily part of the vocabulary our engineers tell us that talking about molecules is misleading when reference is made to metal it is typically in terms of atom structures we routinely check metallurgical features microscopically by the way the same is true for claims of manufacturing to zero tolerance our engineers tell us that this is technically unrealistic economics often dictate that many processes in the manufacture of aerospace fasteners are out sourced or farmed out in fact 30 plus years ago arp began as an out source thread rolling shop over the years however we have found through experience that the only way to maintain the quality we require is to keep everything in-house from heading through machining grinding heat-treat thread rolling and shot-peening to black oxide treatment we perform every operation in house on our own equipment with our own employees smith gary one of the things that i am hearing is that every aspect of the manufacture of racing engine fasteners is more expensive than that of similar aerospace items true but the bottom line is that we have to look at the cost aspect of the very best fastener versus the cost aspect of a blown engine and a lost race in the end the manufacturing of fasteners for racing comes down to a matter of attitude a refusal to accept published standards and procedures as the best that can be done and most of all a determination to learn and to make still better products smith how does the actual process work at arp for each new design we produce a number of prototype parts using different design aspects and sometimes different methods we inspect and test after each process choose the best design and method of manufacture and then freeze the design and write the manufacturing specification smith you have mentioned the importance of fatigue resistance is there a difference in the procedures for strength and fatigue testing between aerospace and the specialty racing industry yes while the ultimate tensile strength testing is the same fatigue testing is different aerospace fasteners are fatigue tested to the relevant specification of fluctuating tension load and 12 800-826-3045[close]
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fastener tech there are literally hundreds of standards and specifications for all types of applications from bridges to spaceships none are however as critical as those required for real-world motorsports applications in an environment where lighter is faster there is clearly no room for redundancy systems like those found in military and aerospace applications the mere nature of motorsports requires designers to produce fasteners that are light yet produce toughness fatigue and reliability factors that extend far beyond other acknowledged application standards the design and production of fasteners exclusively for racing clearly involves many complex factors some so special no standards or design criteria exist and so everyone at arp is totally dedicated to the development and analysis of appropriate bolt designs exclusively for special applications designs that take into account the special loads and endurance that must be carried the material selection processing and the methods of installation that will continue to deliver arp quality and reliability the focus of the following material prepared by the arp engineering staff could be called motorsports fastener engineering for the non-engineer it is hoped that by providing an overview of the engineering design and production forces arp applies daily you as the end user will be better equipped to evaluate your initial fastener requirements effectiveness and performance design procedures for automotive bolts presented by dr kenneth foster phd the design of automotive bolts is a complex process involving a multitude of factors these include the determination of operating loads and the establishment of geometric configuration the process for connecting rod bolts is described in the following paragraphs as an example the first step in the process of designing a connecting rod bolt is to determine the load that it must carry this is accomplished by calculating the dynamic force caused by the oscillating piston and connecting rod this force is determined from the classical concept that force equals mass times acceleration the mass includes the mass of the piston plus a portion of the mass of the rod this mass undergoes oscillating motion as the crankshaft rotates the resulting acceleration which is at its maximum value when the piston is at top dead center and bottom dead center is proportional to the stroke and the square of the engine speed the oscillating force is sometimes called the reciprocating weight its numerical value is proportional to a typical value for this reciprocating weight is in the vicinity of 20,000 lbs for purposes of bolt design a rule of thumb is to size the bolts and select the material for this application such that each of the 2 rod bolts has a strength of approximately 20,000 lbs corresponding to the total reciprocating weight this essentially builds in a nominal safety factor of 2 the stress is calculated according to the following formula so that the root diameter of the thread can be calculated from the formula it is seen that the design load the reciprocating weight depends on the square of the rpm speed this means that if the speed is doubled for example the design load is increased by a factor of 4 this relationship is shown graphically below for one particular rod and piston this formula shows that the thread size can be smaller if a stronger material is used or for a given thread size a stronger material will permit a greater reciprocating weight the graph see page 14 shows the relationship between h beam-deformed thread size and material total translation strength it must be realized that the direct reciprocating load is not the only source of stresses in bolts a secondary effect arises because of the flexibility of the journal end of the connecting rod the reciprocating load causes bending deformation of the bolted joint yes even steel deforms under load this deformation causes bending stresses in the bolt as well as in the rod itself these bending stresses fluctuate contours for loading in tension due to acceleration forces at 8000 rpm 13 800-826-3045[close]
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fastener tech significantly greater than the bolt tension strength this problem is especially important in bolts used in aluminum rods because of the fact that the shear strength of aluminum is much lower than the shear strength of steel finally although not a design parameter the subject of bolt installation preload must be addressed it is a fundamental engineering concept that the force in a bolt in an ideal preloaded joint will remain equal to the preload until the externally applied force exceeds the preload then the force in the bolt will be equal to the external force this means that fluctuating external forces will not cause fluctuating forces in a preloaded bolt as long as the preload exceeds the external force the result is that fatigue failure will not occur in a non-ideal joint such as in a connecting rod the bolt will feel fluctuating stresses due to fluctuating rod distortions these are additive to the preload so that fatigue could result in connecting rods precise preloads are required because if they are too low the external forces the reciprocating weights will exceed the preloads thus causing fatigue if they are too high from zero to their maximum level during each revolution of the crankshaft the next step is to establish the details of the geometric configuration here the major consideration is fatigue the fracture that could occur due to frequent repetition of high stresses such as the bending stresses described above several factors must be considered in preventing fatigue attention to design details is essential fatigue failure is frequently caused by localized stress risers such as sharp corners in bolts this would correspond to the notch effect associated with the thread form it is well known that the maximum stress in an engaged bolt occurs in the last engaged thread by removing the remaining non-engaged threads the local notch effect can be reduced this leads to the standard configuration used in most arp rod bolts a reduced diameter shank and full engagement for the remaining threads providing a local fillet radius at the location of the maximum stress further reduces the local notch effect thus this configuration represents the optimum with respect to fatigue strength the reduced diameter shank is helpful in another sense it reduces the bending stiffness of the bolt therefore when the bolt bends due to deformation of the connecting rod the bending stresses are reduced below what they would otherwise be this further increases the fatigue resistance of the bolt a typical bolt configuration is shown below they provide a high mean stress that combines with the fluctuating stresses due to rod distortion again fatigue is promoted the objective then is to preload a bolt so that it just exceeds the external load and no higher to sum up both insufficient preloads and excessive preloads can lead to fatigue failures appropriate preloads are specified for each arp bolt these preloads can be attained in a connecting rod by applying proper torque using a torque wrench or by measuring the amount of stretch in the bolt using a stretch gauge it is known that a bolt stretches in proportion to the tension in it the torque method is sometimes inaccurate because of the uncertainty in the coefficient of friction at the interface between the bolt and the rod this inaccuracy can be minimized by using the lubricant supplied by arp other factors equally as important as design include material selection verification testing processing and quality control these aspects of bolt manufacturing are discussed elsewhere in this document the foregoing discussion concentrated on the design of bolts the same considerations apply in the design of studs once the bolt configuration has been established the manufacturing process comes into play this involves many facets which are discussed in detail elsewhere here however one process is of primary interest with respect to bolt fatigue strength thread rolling is a major consideration threads are rolled after heat treating this process which deforms the metal produces a beneficial compressive stress in the root of the thread it is beneficial because it counteracts the fluctuating tensile stresses that can cause fatigue cracking if heat-treatment were to occur after rolling the compressive stresses would be eliminated this would therefore reduce the fatigue resistance of the bolt an additional factor must be taken into account in defining the bolt configuration the length of engaged thread if too few threads are engaged the threads will shear at loads that are lower than the strength of the bolt as a practical matter the thread length is always selected so that the thread shear strength is 14 800-826-3045[close]
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recognizing common failures there are six types of metallurgical failures that affect fasteners each type has unique identifying physical characteristics the following chart is designed to be used like a spark plug reading chart to help analyze fastener failures while few of us have access to sophisticated analysis equipment a standard bausch and lomb three lens magnifying glass will generally show 98 of what we want to see several of the photos below have been taken utilizing a scanning electron microscope sem and are presented to simply illustrate typical grain configurations after failure 1 typical tensile overload in a tensile overload failure the bolt will stretch and neck down prior to rupture one of the fracture faces will form a cup and the other a cone this type of failure indicates that either the bolt was inadequate for the installation or it was preloaded beyond the material s yield point fastener tech 1 2 torsional shear twisting fasteners are not normally subjected to torsional stress this sort of failure is usually seen in drive shafts input shafts and output shafts however we have seen torsional shear failure when galling takes place between the male and female threads always due to using the wrong lubricant or no lubricant or when the male fastener is misaligned with the female thread the direction of failure is obvious and in most cases failure occurs on disassembly 2 3 impact shear fracture from impact shear is similar in appearance to torsional shear failure with flat failure faces and obvious directional traces failures due to impact shear occur in bolts loaded in single shear like flywheel and ring gear bolts usually the failed bolts were called upon to locate the device as well as to clamp it and almost always the bolts were insufficiently preloaded on installation fasteners are designed to clamp parts together not to locate them location is the function of dowels another area where impact failures are common is in connecting rod bolts when a catastrophic failure elsewhere in the engine debris from failing camshaft or crankshaft impacts the connecting rod 3 4 cyclic fatigue failure originated by hydrogen embrittlement some of the high strength quench and temper steel alloys used in fastener manufacture are subject to hydrogen embrittlement l-19 h-11 300m aeromet 100 and other similar alloys popular in drag racing are particularly susceptible and extreme care must be exercised in manufacture the spot on the first photo is typical of the origin of this type of failure the second is a sem photo at 30x magnification 4 5 cyclic fatigue cracks propagated from a rust pit stress corrosion again many of the high strength steel alloys are susceptible to stress corrosion the photos illustrate such a failure the first picture is a digital photo with an arrow pointing to the double origin of the fatigue cracks the second photograph at 30x magnification shows a third arrow pointing to the juncture of the cracks propagating from the rust pits l-19 h-11 300m and aeromet 100 are particularly susceptible to stress corrosion and must be kept well oiled and never exposed to moisture including sweat inconel 718 arp 3.5 and custom age 625 are immune to both hydrogen embrittlement and stress corrosion 5 6 cyclic fatigue cracks initiated by improper installation preload many connecting rod bolt failures are caused by insufficient preload when a fastener is insufficiently preloaded during installation the dynamic load may exceed the clamping load resulting in cyclic tensile stress and eventual failure the first picture is a digital photo of such a failure with the bolt still in the rod the arrows indicate the location of a cut made to free the bolt the third arrow shows the origin of the fatigue crack in the second picture an sem photo at 30x magnification that clearly shows the origin of the failure 1 and the telltale thumbprint or beach mark 2 finally 3 tracks of the outwardly propagating fatigue cracks and the point where the bolt unable to carry any further load breaks-away 6 15 800-826-3045[close]
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