DEGREE PROJECT IN MECHANICAL ENGINEERING, SECOND CYCLE, 30 CREDITS STOCKHOLM, SWEDEN 2019 Simulation of CamDrum for Shock Absorbers ADAM OLSSON ANDERS RASK KTH ROYAL INSTITUTE OF TECHNOLOGY SCHOOL OF INDUSTRIAL ENGINEERING AND MANAGEMENT Simulation of CamDrum for Shock Absorbers ADAM OLSSON ANDERS RASK Master of Science Thesis KTH Industrial Engineering and Management Machine design SE-100 44 Stockholm Supervisor: Ulf Sellgren Industrial Supervisors: Carl Hesse & Andreas Bolin Examiner: Ulf Sellgren Approved: 2019-06-12 TRITA-ITM-EX 2019:249 Master of Science Thesis TRITA-ITM-EX 2019:249 Simulation of CamDrum for Shock Absorbers Adam Olsson Anders Rask Approved Examiner Supervisor 2019-06-12 Ulf Sellgren Ulf Sellgren Commissioner Contact person Öhlins Racing AB Carl Hesse Abstract Simulation can play an important role when aiming to streamline extensive and time-consuming tests. It has the potential to save time, money and energy. One of the testing methods used to test shock absorbers (SA), is accelerated life testing using a rolling road, CamDrum. It is therefore of great interest to examine the possibilities to streamline this testing method. This master the- sis is conducted in co-operation with Öhlins Racing AB and the Machine Design department at KTH. The thesis project aims to look into the following: How can the use of simulation software aid in streamlining the test sequence used for shock absorbers in CamDrum? What limitations is there when simulating the CamDrum method using the selected simulation soft- ware? The goal was to develop an adequate model according to specified requirements, to facilitate early testing of new ideas and parameter changes. The delimitations includes, that the project only fo- cuses the test-rig for MTB shock absorbers, the parts of the test-rig are assumed to be rigid and the simulation of the shock absorber is out of scope, since the aim of this thesis is to simulate the test-rig. To succeed with the project, a background research was conducted to gain knowledge about shock absorbers, test method and equipment, dynamics and useful software. The simulation model was verified against data obtained from tests. The tests were performed using the CamDrum with two different MTB shock absorbers and a stiff rod. The aim was to log and verify the change in position for the test-rig, shock absorbers and wheel. In addition the forces acting on the shock absorbers was investigated using strain gauges attached to the test-rig. The mean deviation in % for configuration 70-30-30 [mm] bump: SA MTBM1899, A4: 11.6% - 23.2%. SA MTB1691, A4: 15.8% - 28.1%. Stiff rod, A3: 0.9% - 4.9%, A5: 2.0% - 5.1%. SA Force, 16.1% - 24.0%. The deviation between the simulation and the test environment increases with the velocity. The use of stiff rod verifies the model against the CamDrum regarding the displacement. The resulting force from the use of strain gauges verifies the simulation models force regarding the shape. The Amesim model has the potential to be of great aid when designing tests. Keywords : Amesim, Computer Aided Engineering, Rolling road iii Examensarbete TRITA-ITM-EX 2019:249 Simulering av CamDrum för stötdämpare Adam Olsson Anders Rask Godkänt Examinator Handledare 2019-06-12 Ulf Sellgren Ulf Sellgren Uppdragsgivare Kontaktperson Öhlins Racing AB Carl Hesse Sammanfattning Simulering kan vara en väg till att effektivisera tidskrävande och omfattande tester. Det finns poten- tial att spara såväl energi som tid och pengar. En av metoderna för att testa stötdämpare är rullande landsväg, CamDrum. Det är därför intressant att undersöka hur den processen kan effektiviseras. Examensarbetet utförs i samarbete mellan Öhlins Racing AB och institutionen för Maskinkonstruk- tion på KTH. Det här examensarbetet avser att undersöka följande: Hur kan användandet av simuleringsprogram underlätta effektivisering av testmetoden som används för stötdämpare i CamDrum? Vilka avgränsningar finns vid användande av simulering för CamDrum-metoden med valt simule- ringsprogram? Målet var att utveckla en modell som uppfyller givna krav och underlättar vid initieringsfasen för utveckling av tester för CamDrum. Projektets avgränsningar innebär att enbart riggen för MTB- stötdämpare undersöks, alla ingående komponenter i testriggen antas styva och dämparmodellen som utvecklats är förenklad då målet är att simulera riggen för dämparen. För att lyckas med uppgiften har en förstudie genomförts för att samla nödvändig kunskap om stötdämpare, dynamik, testmetoden och lämplig mjukvara. Simuleringsmodellen verifieras mot data hämtat från utförda tester. Testerna utfördes i CamDrum med två olika MTB-stötdämpare och en rundstång med mål att logga och verifiera rörelser för riggen, stötdämpare och hjulet. Vidare har krafterna på stötdämparen undersökts med hjälp av trådtöjningsgivare monterade på testriggen. Medelavvikelsen i % för guppkonfigurationen 70-30-30 [mm]: SA MTBM1899, A4: 11.6% - 23.2%. SA MTB1691, A4: 15.8% - 28.1%. Rundstång, A3: 0.9% - 4.9%, A5: 2.0% - 5.1%. SA Force, 16.1% - 24.0%. Avvikelsen mellan simuleringen och testerna ökar med hastigheten. Användandet av rundstången verifierar modellen gentemot CamDrum med avseende på positions- förändring. Den resulterande kraften från användandet av trådtöjningsgivare verifierar simuleringsmodellen med avseende på form. Amesim-modellen har en möjlighet att underlätta vid framtagning av tester. Nyckelord: Amesim, CAE, Rullande landsväg v Preface We would like to thank the following persons for aiding and guiding us during this thesis, the final result would not have been the same without their expertise. Carl Hesse for acting as the head supervisor on site and for making sure we got the help and material needed to perform this thesis. Ulf Sellgren at KTH for being our supervisor and guiding us with a firm and steady hand. Andreas Bolin for acting as the overall knowledge on site and our first contact when we needed assistance. Niklas Klinteskog for aiding us with the use of strain gauges and providing MAT- LAB scripts for extracting the results from the logged data. David Bolander, Jonas Jarlmark Näfver & Michel Chapuis for their valuable help with Amesim and damper dynamics. Johan Jarl, Erik Nordgren & Pär Åslund for helping us in designing tests and analysing results for the MTB dampers used in this thesis. Lars Karlsson for his sharp mind, helping us making it to the end. Fredrik Hedin and Mathias Raine for help with analysis of damper result with their broad experience within the subject. Peter Stridh, Christoffer "Glassen" Andersson, Björn Meland och Tobias Karlsson for helping us disassemble dampers, running tests in the dynos, tips and trix and keeping the office environment cheerful. And all other people that have been involved in this thesis. Adam Olsson Anders Rask Stockholm, June, 2019 vii Contents Abstract iii Sammanfattning v Preface vii Contents ix Nomenclature xiii 1 Introduction 1 1.1 Background . 1 1.1.1 Purpose and Goals . 2 1.1.2 Requirements . 2 1.2 Delimitations . 3 1.3 Methodology . 3 2 Frame of reference 5 2.1 Shock absorbers . 5 2.1.1 Rebound/Compression . 5 2.1.2 Hysteresis - Internal components inertia . 6 2.1.3 General design features regarding shock absorbers . 7 2.2 Front fork . 8 2.3 Rear shock absorber . 10 2.4 Sprung and unsprung mass . 12 2.5 Tyre damper profile . 13 2.6 Linear transducer . 13 2.7 Strain gauges . 14 2.8 CamDrum . 15 2.9 Dyno . 17 2.10 Simulation software . 18 2.10.1 Simulink . 18 2.10.2 Simcenter Amesim . 19 2.10.3 MSC Adams . 21 ix 2.10.4 BikeSim . 22 3 Implementation 23 3.1 Possible solution strategies . 23 3.2 Test configuration . 24 3.3 Shock absorber #1 - MTBM1899 . 27 3.4 Shock absorber #2 - MTB1691 . 28 3.5 Stiff rod . 29 3.6 Tyre model . 30 3.7 Amesim model . 32 3.7.1 Detailed description of the assembly components . 36 3.8 Linear Transducers . 39 3.9 Strain gauge . 40 3.10 Verification . 44 3.10.1 Amesim versus Linear transducers . 44 3.10.2 Amesim versus Strain gauges . 45 4 Results 47 4.1 Displacement result . 47 4.1.1 MTBM1899 . 48 4.1.2 MTB1691 . 50 4.1.3 Stiff rod . 52 4.2 Force result . 54 5 Discussion and conclusions 57 5.1 Discussion . 57 5.1.1 Displacement . 58 5.1.2 Force . 59 5.1.3 General possible sources of error . 60 5.2 Conclusions . 61 6 Recommendations and future work 63 6.1 Recommendations . 63 6.2 Future work . 64 Bibliography 65 Appendices A Risk Management 69 B Test configurations 71 C Pugh Matrix - Simulation Softwares 73 x D Stiff rod drawing 75 E Drawing of modified rod for strain gauge 77 F Drawing of test-rig 79 G Drawing of installation fixture to camdrum 81 H Bump drawing 83 I Strain gauge specification sheet 85 J Complementing displacement results MTBM1899 87 K Complementing displacement results MTB1691 93 L Complementing Force results 99 M MATLAB - Linear transducers 107 N MATLAB - Stiff rod 113 O MATLAB - Force script 117 P MATLAB - TSA for linear transducers 121 Q MATLAB - Force mean and percentage 123 R MATLAB - Theoretical maximum bending stress 125 S MATLAB - Tyre spring calculation 127 xi Nomenclature Symbols Symbols Description c Damping constant [Ns/m] g Gravity costant [m/s2] k Spring constant [N/m] m Mass [kg] x1 Displacement of body 1 [m] x˙ 1 Velocity of body 1 [m/s] 2 x¨1 Acceleration of body 1 [m/s ] x2 Displacement of body 2 [m] x˙ 2 Velocity of body 2 [m/s] 2 x¨2 Acceleration of body 2 [m/s ] p Displacement of ground [m] p˙1 Velocity of body ground [m/s] 2 p¨1 Acceleration of ground [m/s ] Abbreviations Abbreviation Description 1D-3D 1-3 Dimensions A3-A5 Analog03 - Analog05 CAD Computer Aided Design CAE Computer Aided Engineering DoF Degrees of Freedom EOM Equations of motion HMI Human-Machine Interface KTH Royal Institute of Technology MTB Mountain bike OEM Original Equipment Manufacturer SA Shock Absorber TSA Time-synchronous signal average UI User Interface xiii Chapter 1 Introduction In this chapter the background, delimitation and methodology is introduced and stated.