It is required to design a single stage Spur / helical gear reducer (According to the attached table). The gear box has an input power of 4.5 (kW), an input speed of 2500rpm (rpm), a transmission ratio of 2.5, and a service life of 15 (kh). the pressure angle is 20 o and the helix angle may be chosen between 20 o and 30 o . Detail drawings of a similar gear-box are shown on the following pages. The pinion can be integrated with (or mounted on) the driving shaft (5) . The gear is mounted on the driven shaft (3) by means of a feather 6x6x15 (11). Both shafts are supported on the casing through two ball bearings (e. g. D = 35 mm, B = 11). A guffro sealing (e.g. D = 25 mm, B = 7 mm) is used to prevent leakage of oil from both ends of input and output shafts. Covers are fixed to the casing of the gear box through 4 bolts (e.g. M3x8). the upper and lower parts of the casing are fixed together by means of ten M6x18. Also there are two positional pins 3×10 . You are asked to submit the following documents: a) A short technical report including your design and checking calculations. basically i need the first part which is designing a pinion and a gear meshed together and getting me a factor of safety for bending stress between 2.5 to 4~ and a factor of safety for contact stress between 1.2 to 1.4 Im stuck and i thought i could ask for help.