3D Crank Slider, with 4 revolute joints (hinges), one slider, a universal and a ball joint. The SW model details how they are defined. 1

SW design tree CSmotion IntelliMotion builder, (there is also a browser) 2

Interference checking is very cpu intensive so the parts and the intervals are identified to improve response time 3

Valve, rocker and cam assembly. The moments, forces and torques are indicated as the motion takes place. The spring parameters have to be defined specifically as stiffness and preload, they are not derived from physical dimensions of the spring. The model of the spring shown may be defined but is just decorative. 4

An Excel s.s. generated from a csv file provided by Csmotion. 5

The displacement of the piston, along the horizontal centre line shown, is the sum of the complete oscillatory movement of the crank pin and the partial oscillatory movement of the big end of the connecting rod. The result is in part higher acceleration at TDC (top dead centre) than at BDC. The force transmitted to the main bearings due to the inertia loads has harmonics, the highest component of which is at twice the engine speed. 6

A model of a Mitsubishi engine showing the position of the engine at maximum bending moment in the connecting rod The highest vertical acceleration at the connecting rod little end is at TDC, the next highest is at BDC. The alternating loads on the big end bolts occur at TDC, accelerating the piston up then down. The highest lateral acceleration of the big end is shown at left, for an engine of the given dimensions. The lateral inertia loads on the stem of the connecting rod occur at this point. These may bend the connecting rod. The compression loads may not be damaging unless the engine fills with oil or liquid fuel. 7

A con rod undergoes a number of ‘separable’ motions: it accelerates vertically up & down a). It rotates at variable angular accelerations b) that induce a bending moment in in its stem c). It rotates at variable angular velocities, that result in centripetal forces d). a) b) c) d) 8

Vertical force at the big end with engine running at 8000 rpm 9

Max gudgeon pin vertical acceleration against rpm. The horizontal axis is rpm the vertical is m/sec^2 10

Bending moment in stem at 8000 rpm assuming stem of uniform section along its length. 11

Top right are forked connecting rods for RR Merlins and Griffons. At lower right the master and articulated con rod assembly for a radial engine 12

Con rod assembly and retaining screws for a MB V8 1970s engine 13

The connecting rod experiences tension, compression and a bending moments, while swinging from side to side, fortunately not all at the same time. The loads caused by the combustion process become much smaller than the dynamic loads (F=mass x acc), at a relatively high ~ 7000 rpm. Pressure and force due to combustion at higher rpm 14 Jeri Svec 2003

15 Jeri Svec 2003 UG thesis simulation of 1300 cc Mitsubishi engine Stress analysis of connecting rods under static conditions

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17 Assem Yamak 2013, MeSc thesis Comparing conrods - while being spun at high rpm, the conrod with bolt holes showed a different stress pattern than the one piece conrod. This provides the first insight as why an H rod may be the better design than I for high revving engines.

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Our drag car conrod, end cap screw, piston and gudgeon pin 19

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