Exam Question

(a) The bedplate which is the base of the engine is attached to the tank top by holding down bolts and chocks. The holding down bolts fix the engine in correct position and chocks is used for good alignment so that there will not be any uneven load on bearings, and also provide a clamping force so that the friction between bedplate, chock and ship’s structure resist the propeller thrust.
If there is any relevant movement between the bedplate and tank top the studs will bend and subsequently fail due to fatigue. In order to reduce the risk, long studs with distance tubes are often employed. The effective length of the stud is the length of stud plus length of tube. For the same amount of relative movement between tank top and bedplate the long stud will bend to a larger radius of curvature and will therefore be subject to a lower stress and less risk of fatigue failure.
Side chocks are fitted adjacent to each transverse girder. These are welded to the foundation plate to hold the engine in correct horizontal alignment and to prevent sideways movement due to movement of the vessel and the sideways component of thrust from the crank and running gear.
(b) The sketch below shows main engine friction type top bracing which is fitted between the engine topmost part and to a very stiff location the ships side.