Designing the mechanical drive

A mechanical drive is drawn in two projections (as a rule, front view and top view) to scale 1: 4 or 1:5.

13.1. Draw the main structural units of the mechanical drive. Among them there are electrical motor (table 9.1), coupling with rubber-bushed studs (tables 9.7), belt drive, speed reducer, chain coupling (table 9.8), flanged coupling (table 9.9), chain drive. Dimensions of all mentioned above elements and units have been found.

13.2. Design the output shaft of the mechanical drive (Fig.13.1).

Fig.13.1. Output shaft of the mechanical drive

Determine the minimum diameter of the output shaft. For this purpose we use the same formula as for the other speed reducer shafts

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If the output shaft of the mechanical drive is joined with the speed reducer shaft by the coupling, the minimum diameter of the mechanical drive output shaft is equal to the minimum diameter of the speed reducer output shaft.

On the cantilever portion of the output shaft half coupling, sprocket or gear may be mounted. They should be fixed in the axial direction. That is why it is necessary to provide the shoulder on the shaft. Then the diameter of the second portion of the shaft is determined as d ₂= d ₁ + 2· t ₁ (t ₁ is chosen from table 9.2).

The second portion of the output shaft is for mounting a bearing. That is why the diameter of this portion should be ended by 0 or 5.

The next portion of the output shaft is necessary for installation of the drum or conveyer sprockets. Diameter of this portion is d ₃= d ₂ + 2· t ₁.

The last portion of the output shaft is for mounting the second bearing. The diameter of this portion is d ₂.

13.3. Design supports of the output shaft.

As a rule, supports of the output shaft are mounted in different housings. In order to compensate inaccuracy and misalignment in assembly self-aligning double-row spherical radial ball bearings of the light–weight series are used (table 13.1). Owing to the race spherical surface of the outer ring, these bearings can handle the shaft misalignment of up to 2 or even 3.