3.Means of coupling

3.1 Centering

  When the motor is directly coupled to driven machine particular attention should be paid to centering . First of all , check the bottom plane of the foot of motor with a level to make sure they are all at the same level . Secondly , fasten the foot to the base with bolts for trial installation . Thirdly , set the dial indicator on the lateral coupling device and rotate the shaft of motor gently to obtain precise dimension of A shown in figure 6 . Fourthly , check the inclination between the shaft of motor and that of the coupled machine by inserting the thickness gauge into gap X shown in figures 6 and  make adjustment , by inserting liners , when necessary to make every B around the disc of coupling device a minimum value possible .

　

The allowance of A, B and X are listed below :

	Rigid Coupling Device	Flexible Coupling Device
A	0.03mm	0.05mm
B	0.03mm	0.04mm
X	0	The value designated by manufacturers

  However , gear coupling or specially designed flexible coupling devices may have greater allowances than those listed above . Please contact the respective manufacturers for information .

3.2 Belt Transmission

  Since V-belts are adopted as transmission means for motors of medium capacities , we take these belts as an example for our following discussion .

  - The ratio of diameters of belt pulleys between motor and its coupled machine is 8 : 1 .

  - The speed of V-belt must be kept under 22 to 23 m/sec . If the belt runs at a speed over 25m/sec., its slip and vibration will be increased and the belt itself will worn out much faster .

  - In case the outer diameter of the pulley is too small , the bending force on the shaft will be increased in inverse ratio . If this force goes beyond the fatigue limit , a broken shaft is impending . in case a wide pulley of small diameter has to be adopted for belt transmission , please consult Tatung sales- engineers when motors are ordered .

  - As to belt transmission , the following procedures will apply .

1.   To insure uniform quality , it is ideal to obtain the belts , for one transmission device , from the same manufacture or the dimension allowance between the belts be kept within 0.2%. Please remember that when belts are selected. In case some of the belts on the same transmission device are damaged or worn out , please replace all the belts there on with new ones , not the damaged or worn ones only . Next , attention should be paid to pulley alignment , i.e. the shaft of motor should be kept parallel with that of its coupled machine; or the shafts be at right angle with belts or belt-pulleys.

2. Proper initial tension on the belts

  If the tension is too large , a damaged , even a broken shaft may be resulted in . On the contrary, if the tension is too small . slip of the belts will occur , desirable power transmission could not be achieved , and the belts and pulleys will become worn out more quickly.

  The initial tension of the belts can be found out easily by means described below : At the middle point between the shafts of the two belt pulleys , as shown in figure 7 , a weight P is hung on the belt to obtain h1 and h2 . The values h1 and h2 are the differences between the deflections before and after the weight is hung . The approximate values of .

  e=2×L/(h1+h2)  are shown in the following table .

Shape of V-belt	P (kg)	e	Transmission condition
			Speed of belts	Output
C	5	35	16m/s	30Kw
D	10	35	25m/s	150Kw
E	10	45	25m/s	150Kw

  You may adjust the adjusting bolts of the base to obtain the tension . the values of e are correlated with the speeds of belts and values of output, and adjustments of the values are necessary .

  Another simpler way of measuring the tension is to measure the elongation of the belt; i.e. when the belt is elongated 0.5%, it is considered to have been mounted with proper initial tension . After the motor has run for ten hours, tension of the belt should be checked once again . After the motor has run for one month , the belt may become permanently elongated , and re-adjustment should be made then .

3. Replacement of V-belts

  When the V-belt is deteriorated it must be replaced; other-wise , desired transmission can not be obtained . Moreover, because of the diminution of friction coefficient , the deflection strength of the shafts will increase relatively . That will adversely affect the bearings . Generally speaking, when the permanent elongation of the belts reaches 1.5 - 2.5% , it should be replaced .

4. Special belts

Presently , nylon and steel wire belts are marketed in large quantities . In case these belts of high initial tension are to be adopted , high anti-flection strength for motor shafts will be required . Please inform Tatung when order is placed .

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