GM_BE TL[1][1].16.0004_Engrg Components Specs - Pulley.doc

Paul McVicar 1 Accessory Drive Pulley Specification DrivenPulleySpecification15JL02 doc 15JL02 GENERAL MOTORS ENGINEERING SPECIFICATION BE TL 16 0004 Components Pulley 1 0 Introduction This specification is intended to cover accessory drive pulleys without integral ball bearings which are covered by an Idler Pulley Specification no BE TL 16 0003 This specification forms an attachment to the Idler Pulley Specification and governs the pulley portion of the assembly 2 0 Construction There are several possible constructions for drive driven pulleys A One piece steel with no hub or integral hub B Two piece steel with welded or brazed hub attachment C Two piece steel with doubler for reinforcement D Aluminum or magnesium one piece E Thermoplastic injection molded with steel hub note that North American applications shall not use plastic backside pulleys because of excessive wear both belt and pulley and manufacturing variation Acceptable quality parts are available in Europe only F Thermoset plastic compression or injection compression molded with steel hub Also not permitted for backside North American application and not recommended for groove side applications Acceptable quality parts are usually injection molded and are available in Europe only 2 1 Web Configuration At the discretion of the supplier supported by F E A analysis based on loading provided by the Powertrain release engineer Holes to provide accessibility to fasteners behind the pulley may be required on some applications Pulley O D offset and pilot hub mounting hole information are supplied by the release engineer as required 2 1 1 Sensitivity To Hub Walking The design of the pulley for high offset or idler applications may be sensitive to the phenomenon of walking off of the shaft even with a correct press fit This is caused by elastic deformation of the hub in the presence of belt load The design of the web section is the most influential in determining the adequacy of the design to resist walking Deflection is inherent due to load and an offset load will increase the deflection The pulley will deflect where it has the lowest stiffness and the hub press can be overcome due to distortion of the bore The bore separates from the shaft locally and will re contact the shaft in a different location due to the offset load effects As the pulley rotates the entire circumference of the shaft in a given plane will advance on the shaft in a spiral fashion and eventually screw itself off of the shaft The supplier shall analyze the deflection of the pulley under load if required assistance will be provided by GMPT to assess what press level will be sufficient to resist the deflection present It must be determined if that required level of press is within the torque to turn and press load requirements elsewhere in this specification Walking tests must be run to verify the analysis Approval of both the analysis and testing must be obtained from the GM Release Engineer and Technical Specialist 2 2 Groove Configuration Must conform to SAE J1459 Rev 2001 dimensioning template including flange configuration supplied with this specification Drawing of part submitted by the supplier must use this dimensioning technique 2 3 Backside Pulleys Intent on backside pulleys is for the belt running surface to be flat No concavity is permissible and any crown must be limited to a height of 0 25 mm across a six 6 groove area of 21 36 mm width and proportionally more less for other pulley widths Paul McVicar 2 Accessory Drive Pulley Specification DrivenPulleySpecification15JL02 doc 15JL02 GENERAL MOTORS ENGINEERING SPECIFICATION BE TL 16 0004 Components Pulley 2 4 Hub Where applicable hub is to made of steel either screw machined or cold formed iron copper powdered metal with machined I D Requires puller groove on pressed on shaft applications with sufficient integrity to withstand 33 4 kN press load on shaft Groove must be 4 5mm wide min and puller lip must be a minimum of 3 8mm thick See page 8 for common hub configuration 2 4 1 Hub Material For screw machined hubs SAE 12L13 12L14 or 12L15 or SAE 1213 1214 or 1215 lead free steel can be used This is equivalent to Opel TDC Specification QS 1109 or DIN 1651 Powdered metal hubs must conform to MPIF Standard 35 F 0005 or FC 0200 as determined by performance requirements Deviations require Technical Specialist approval 2 4 2 Hub Weld Penetration For welded hubs the penetration of the weld must conform to configuration shown on Page 9 2 5 General Specifications 2 5 1 Dimensional Maximum radial and lateral runnout shall not exceed 0 30 mm 0 25 mm max will be the future requirement so sources are encouraged to develop capable processes There may be exceptions for very large diameter high offset applications if approved by the Technical Specialist 3 0 Functional Requirements Each requirement is applicable to some configurations and applies to those only 3 1 Hub Press Interference Hubs whether integral or separate parts must have sufficient press to withstand 68 0 Nm of rotational torque at minimum interference This is based on a maximum power steering required torque of 22 7 Nm and a factor of safety of 3 0 The factor of safety addresses the uncertainty of torsional vibration as well as manufacturing variation Press load must not exceed 33 4 KN at maximum interference This is based on the installation tool capability in the Assembly Plant Please note that these are general design values and that actual application values which are sensitive to hub i d surface finish should be used to set production specifications The supplier must evaluate the interference between the pulley and the hub to ascertain the required pulley i d and tolerance to satisfy these requirements This is accomplished by testing the assembly axial load at the press extremes and the torque to turn in the case of the min press condition A minimum sample size of 3 is required to make this determination A larger sample size may be required if variation is deemed excessive The resulting pulley i d must then be placed on the detail drawing by the supplier and submitted to the release engineer 3 2 Finish Steel pulley finish must not be deleterious to belt break in such that pilling in the belt grooves is exacerbated beyond that experienced without a finish at all or to industry standards of best performance in this regard The groove surfaces shall not exceed an Ra of 1 6 microns Testing is required to verify this characteristic by normal break in on vehicles for 1000 miles with periodic inspection of belt condition There are two specific applications with different finish requirements 3 2 1 Finish For Pulleys Without Bolts Without bolted joints there is no sensitivity to finish creep relaxation so more economical finishes are recommended These are baked on enamel and powdered Paul McVicar 3 Accessory Drive Pulley Specification DrivenPulleySpecification15JL02 doc 15JL02 GENERAL MOTORS ENGINEERING SPECIFICATION BE TL 16 0004 Components Pulley epoxy The epoxy shall only be used on backside pulleys The detail drawing callout is as follows Clean phosphate and paint black with powdered epoxy or enamel conforming to GM 4350M A168 3 2 2 Finish For Pulleys With Bolted Joints In these applications there is sensitivity to creep relaxation in the bolted joint and therefore a different requirement for finish It is called out on detail drawings as cathodic ELPO 9984120 Type IV 3 3 Corrosion Must meet GM4350M Class A168 for steel parts including hubs but not the hub I D which is to be paint free Plating in the bearing bore of idler pulleys is permissible under some circumstances depending on the plating material and the process Approval by GMPT is required on a case by case basis White corrosion on aluminum or magnesium is permissible The paint shall not exceed 50 microns in thickness Autoferritic coatings are not permitted 3 4 Wear Belt wear surfaces must not be post machined after forming on steel pulleys Aluminum magnesium pulley grooves are normally form machined Exceptions to this requirement for large pulleys with significant offset and backside configuration require consideration for wear when the skin of the pulley is removed and softer material is exposed with some processes Approval by GMPT is required in these cases 3 4 1 Wear on Non ferrous Pulleys Must not exceed wear level of a machined billet SAE 1008 1010 steel pulley by comparison testing 3 4 1 1 Aluminum Pulleys Must be hard anodized to a depth of 100 microns minimum to 400 Vickers hardness minimum These applications are chip prone and groove tips are typically not hardened homogeneously In general this material is discouraged since post anodize sanding is required to achieve surface finish requirements Wear testing in large size hard sand is required to validate an application Equivalent performance to billet steel must be validated High silicon piston alloy material is a better alternative No hardening of this material is required 3 4 1 2 Magnesium Pulleys Must be composite with a wear resistant filler material to achieve wear property Composite material and percent composition is optional but must be specified and pre approved by the release engineer prior to source selection by purchasing Wear must be tested with a billet steel pulley as the control and equivalent performance is required 3 4 1 3 Plastic Pulleys Wear testing must be done at 100 C in a chamber with agitated Arizona coarse sand Steel billet pulley must be run in same chamber in same location although not necessarily at the same time for comparison 3 5 Balance Balance is a function of pulley diameter and offset from a manufacturing perspective and application sensitivity from a performance perspective Pulleys which are mounted on accessories with internal construction involving high inertia components and high speeds i e generators or mating components sensitive to clearances i e A C compressors will require a greater control of balance to avoid exacerbation of noise Balance is inherently tied to runout which can add a further degradation of N V performance depending on vector direction Paul McVicar 4 Accessory Drive Pulley Specification DrivenPulleySpecification15JL02 doc 15JL02 GENERAL MOTORS ENGINEERING SPECIFICATION BE TL 16 0004 Components Pulley 3 5 1 Small Pulleys Since small pulleys 150 mm Diam over balls and those with significant offset this may require a balance operation not necessary lower speeds with smaller lower offset pulleys In these cases sensitivity testing for belt span vibration accessory noise steering shudder etc may have to be performed to assess the need for such an added cost 3 6 Flanges Flanges are not permitted on backside pulleys but are required on both sides of grooved pulleys as an assembly aide to center the belt in the pulley These must have a 6 0 mm greater diameter than the diameter over balls 3 6 1 Self Correcting A flange must also be self centering correcting meaning that if the belt is installed one rib off center it will move over to the centered position upon rotation In order to achieve this characteristic the flanges required on both sides of the pulley must be of a diameter 6 0 mm greater than the diam over balls Depending on the manufacturing process used for the pulley the thickness of the flange and its configuration must be such that there will be no damage to the belt if it is mis installed one rib off center before it self corrects This typically means a minimum width of 2 0 mm and a smooth surface 3 6 2 Alternative Design Should the above be impossible to package an alternate design must be developed which will self correct This usually involves a wider flange 3 0 mm with a surface tapered toward the grooves however regardless of the configuration it must be demonstrated to be effective The ideal design has both the diameter and the width so that even a two rib mis installation will self correct 4 0 Validation 4 1 Fatigue Resistance Represents fatigue resistance for actual number of cycles based on 525 10 6 crankshaft revolutions per 150K miles 250k km Only steel pulleys with a well defined S N curve can be tested to 3 10 7 cycles and assume infinite life Requirement for 150K miles 250k km must be multiplied by pulley drive ratio involved Non ferrous pulley testing must be run at 100 C in a chamber with circulated air Non ferrous pulleys are best designed to very low stresses so fatigue failure is impossible 4 1 1 Rotary Fatigue Test Dead weight test run at equivalent load based on system duty cycle supplied by release engineer Can be run at each load speed condition if equivalent damage relationship is unknown Equivalent damage is developed from test data at different loading levels and temperatures to develop an S N curve except in the steel case For plastic parts S N curves are required over a range of temperatures including the approximately 100 Deg C underhood ambient Paul McVicar 5 Accessory Drive Pulley Specification DrivenPulleySpecification15JL02 doc 15JL02 GENERAL MOTORS ENGINEERING SPECIFICATION BE TL 16 0004 Components Pulley 4 1 1 1 Non Ferrous Materials Fatigue in non ferrous materials does not behave like steel with a predictable S N curve It has two requirements Design F E A model stress not to exceed 35 MPa for plastic pulleys and 100 MPa for aluminum magnesium pulleys and or Rotary fatigue must be run to actual number of cycles in life of part if no equivalent damage model exists A model can be established by testing to failure over a range of stresses and temperatures to develop s n curves for the material The test plan must be approved by the Powertrain HRC Technical Specialist 4 1 1 2 Plastic Materials Fatigue resistance depends on homogeniety of material throughout the part Where process parameters effect local density variation such as knit lines test parts must reflect worst case settings possible within production variation Mold screw temperatures Mold cycle time Mold pressure Preform mass Raw material fines particles at bottom of bags Regrind usage of plastic composite is not allowed A review of these parameters and settings is required with the HRC Release Engineer prior to rotary fatigue testing 4 1 1 2 1 Reground plastic Thermoset and thermoplastic plastic pulleys shall be made of 100 virgin polymer and must be called out as such Thermoplastic parts must have a note on the detail drawing designating the permissible level of regrind even if zero The note shall read Regrind content Re XXHS max per GM7400M Levels for any plastic part will vary depending on the nature of the composite reinforcement and the length of fiberglass fibers when used No callout presence shall default to 100 virgin material No post industrial or post consumer material shall be used but rather home scrap runners sprues from the same process when allowed See GM502M Recycling Design Guide for more information 4 2 Contamination Resistance Parts must withstand exposure to salt sand and mud 4 2 1 Salt Corrosion Must meet requirements of GM 4350 M class A168 4 2 2 Dust Non Ferrous Only Wear must not exceed that of a like pulley with the groove area made from billet SAE 1008 1010 steel The dust Arizona course must be agitated in a chamber of optional construction with the control steel pulley also tested in the same chamber Some applications require a more aggressive sand i e Thailand applications 4 2 3 Mud Non ferrous only Must withstand mud spray of water 0 3 salt NaCl with 5 clay powder added repeated for 100 hours followed by a soak of 14 days 336 hours Clay is to be hydrous Paul McVicar 6 Accessory Drive Pulley Specification DrivenPulleySpecification15JL02 doc 15JL02 GENERAL MOTORS ENGINEERING SPECIFICATION BE TL 16 0004 Components Pulley aluminum silicate with 80 composition of 10 micron maximum particle size available from the Kentucky Tennessee Clay Co Flow 15 L min Pressure 0 5 0 7 Bar 4 7 Materials Material specifications shall be limited to North American controlled GM GMW SAE ASTM MPIF International standards such as DIN JIS and the like are not acceptable nor are supplier internal standards except in the case of those required by this specification Copies of GM W can be obtained thru Global Engineering Documents 800 624 3974 4 7 1 Restricted and Reportable Substances All component parts must meet GMW 3059 This includes but is not limited to hexavalent chrome free finishes 4 7 2 Part Cleanliness Every detail drawing must call out Parts as delivered to assembly plant shall be clean and free of debris residual abrasive material and corrosion products adversely affecting function or appearance 4 7 3 Coatings Platings Finishes All finishes must be called out on the detail drawing to a GM 998 series number or GMW specification If an ELPO or powder epoxy finish is used the following are options Clean zinc phosphate and paint black by cathodic electrodeposition conforming to 9984120 Clean zinc phosphate and paint black with powder epoxy conforming to GM4350M A168 4 7 4 Metals Callouts are required on the detail drawing as follows Die Cast Aluminum Shall employ GMW5 specification A380 is equivalent to GMW5M Al C Si8Cu3Fe and A383 is equivalent to GMW5M Al C Si10C2Fe1 Note that the GMW5 callouts follow ISO9002 based on chemical symbols applicable to all the light metals and their alloys International symbols are used in GMW5 to cover the major alloying elements and significant residual elements Alloying elements defined as those with an upper and lower limit other than zero in the chemical composition are listed left to right in order of decreasing content or in alphabetical order in the case of equal percentages Each chemical symbol is followed by whole numbers denoting the nominal percent present in the alloy Steel SAE 1008 1010 with the finishes in 4 7 3 4 7 5 Polymers Callouts are required on the detail drawings using applicable GM W ASTM or SAE specifications for example the ASTM specification for injection molded polyamide is D4066 Include info