GETTING POWER AROUND CORNERS 2

摘要

Where the axes of the two shafts are significantly displaced from each other, as for example may be the case in motor vehicles between engine and rear axle it is usual to connect them with a propeller shaft fitted at the ends with universal joints. The simplest and most common of such joints is Hookes coupling as shown in drawing 20. As such a coupling rotates, the speed of the driven member varies cyclically within each revolution; but provided that there are two such couplings with the yokes in line, and that the shaft axes are parallel, then these speed variations cancel out. Provision is also usually made for small longitudinal variations in dimensions, due to the difficulty in achieving precise length fitting, and in the case of vehicles, the relative movement of axle and engine due to road inequalities and vehicle springing. This might take the form of a splined joint allowing the two parts of the joint to move axially, one relative to the other.