11. Designing the mechanical drive

A mechanical drive is drawn in two projections to scale 1: 4. 11.1. Draw the main structural units of the mechanical drive. Among them there are electrical motor , coupling with rubber-bushed studs , gearing of open drive, speed reducer.

11.1. Design the 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

Assume d=55mm

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 d₂=d₁ + 2·t₁ =55+2·5=65mm

The next portion of the output shaft is necessary for installation of conveyer sprockets. Diameter of this portion is d₃ = d₂ + 2·t₁=65+2*5=75

The 4^th portion of the shaft is used to fix sprockets in axial direction.

d₄ = d₃ + 2·t₁=75+2*5=85mm

The last portion of the output shaft is for mounting the second bearing. The diameter of this portion is d₂.

11.2. Design supports of the output shaft.

Double-row radial ball bearings (GOST 28428-90).

Lightweight series, mm

Type designation	d	D	B	r	Cr, kN	C0, kN	Y for
							e	<e	>e	Y0
1213	65	120	23	2.5	31.2	17.2	0.17	3.71	5.73	3.68

Standard уm series bearing housings (gost 13218.3-80), mm

Bore diameter D, mm	D1	d	d1	A	B	B1	L	L1	H	H1	h
120	145	M12	17	210	48	48	260	175	179.5	92	32

11.3 Design the welded frame.

Welded frames are used for mounting assembly units. They should correspond to certain requirements of accuracy to provide needed relative disposition of assembly units. Besides, the welded frame should have high rigidity.

Welded frames are obtained as a result of welding steel rolling elements such as channel bars, angle (L) bars, strips, sheets and others. Channel bars are used more frequently.

The height of the channel bar is determined from the following condition:

H ≈ 0.1∙ L_max=0.1*1896.92≈ 189.6 mm

where L_max is the maximum length of the mechanical drive.

Obtained value of H should be rounded off to the greater side according to standard series given in table.

In order to simplify fixation of assembly units to the frame channel bars are mounted with outside flanges. For aligning the base surface for the bolt head we use skew plates

Channels (GOST 8240-72 )

Number of channel	Dimensions, mm
	h	b	s	t
20a	200	80	5.2	9.0