1. The problem statement, all variables and given/known data I have an assignment which is asking me to calculate the minimum diameter of a shaft. Shaft length is 300 mm. The shaft is held between two bearings with one on the left hand side and one on the right 220 mm away. At 143 mm there is a spur gear and at 300 mm(at the end) is a keyway. I know how to find the minimum diameter using DET or MSST but the problem I am facing is I need to find the reactions on the bearings first and there are no forces given at all. All I know is that 40 kW of power is transmitted at 7000 RPM which gives a torque of 55 Nm. I have posted an example (Fig.1) my lecturer has given me but the forces at the gear(G) and pulley(P) in z and y direction are already given in the example. A and B are bearings. 2. Relevant equations See Fig.1 3. The attempt at a solution My attempt at the solution is to first find out what the forces on the spur gear are in the z and y direction. Can I use the torque transmitted by the shaft to calculate these forces assuming the shaft is driven by the gear? Thanks for the help! I have attached the generic data I have been given for the shaft in my assignment as Fig2.