The teeth of the helical gears are cut parallel to the shaft axis.

Consider the following statements: In case of helical gears, teeth are cut at an angle to the axis of rotation of the gears. 1) Helix angle introduces another ratio called axial contact ratio. 2) Transverse contact ratio is equal to axial contact ratio in helical gears. 3) Large transverse contact ratio does not allow multiple teeth to share the load. 4) Large axial contact ratio will cause larger axial force component Which of the above statements are correct?

A

1 and 2

B

2 and 3

C

1 and 4

D

3 and 4

Consider the following statements: 1. In spur gears, the contact occurs abruptly on a line parallel to the axis, and the disengagement too is abrupt. 2. In helical gears, both loading and unloading are gradual, and therefore, these happen more smoothly and less noisily 3. When two gears mesh, any arbitrary shape of the tooth can be chosen for the profile of the teeth of any one of the two gears, and the profile for the other shall be obtained by applying the law of gearing. Which of the above statements are correct?

A

1 and 2 only

B

1 and 3 only

C

2 and 3 only

D

1, 2 and 3

Consider two shafts connected with two gears as per the following options: 1. One on each shaft 2. Through an intermediate gear mounted on an intermediate shaft, and every shaft having one gear only 3. Through an intermediate gear mounted on an intermediate shaft, with the intermediate shaft having two gears, whereas the other shafts have one gear each Which of the above represent(s) a simple gear train?

A

1 only

B

1 and 2 only

C

2 and 3 only

D

1, 2 and 3

For an Oldham coupling used between two shafts, which among the following statements are correct? I. Torsional load is transferred along shaft axis. II. A velocity ratio of 1:2 between shafts is obtained without using gears. III. Bending load is transferred transverse to shaft axis. IV. Rotation is transferred along shaft axis.

A

I and III

B

I and IV

C

II and III

D

II and IV

According to parallel axis theorem, the moment of inertia of a section about an axis parallel to the axis through center of gravity (i.e. $$I$$P) is given by (where, A = Area of the section, $$I$$G = Moment of inertia of the section about an axis passing through its C.G. and h = Distance between C.G. and the parallel axis.)

A

$$I{\text{P}} = I{\text{G}} + {\text{A}}{{\text{h}}^2}$$

B

$$I{\text{P}} = I{\text{G}} - {\text{A}}{{\text{h}}^2}$$

C

$$I{\text{P}} = \frac{{I{\text{G}}}}{{{\text{A}}{{\text{h}}^2}}}$$

D

$$I{\text{P}} = \frac{{{\text{A}}{{\text{h}}^2}}}{{I{\text{G}}}}$$

According to parallel axis theorem, the moment of inertia of a section about an axis parallel to the axis through center of gravity (i.e. $${I_{\text{P}}}$$) is given by (where, A = Area of the section, $${I_{\text{G}}}$$ = Moment of inertia of the section about an axis passing through its C.G. and h = Distance between C.G. and the parallel axis.)

A

$${I_{\text{P}}} = {I_{\text{G}}} + {\text{A}}{{\text{h}}^2}$$

B

$${I_{\text{P}}} = {I_{\text{G}}} - {\text{A}}{{\text{h}}^2}$$

C

$${I_{\text{P}}} = \frac{{{I_{\text{G}}}}}{{{\text{A}}{{\text{h}}^2}}}$$

D

$${I_{\text{P}}} = \frac{{{\text{A}}{{\text{h}}^2}}}{{{I_{\text{G}}}}}$$

Helical gears mounted on parallel shafts are called crossed helical gears.

A

True

B

False

The shaft angle of two helical gears is 60°. The normal module is 6 mm. The larger gear has 50 teeth and the gear ratio is 2. The centre distance is 300 mm. Find the helix angles of the two gears.

A

Ψ1 = 11.68°, Ψ2 = 48.32°

B

Ψ1 = 13.02°, Ψ2 = 46.98°

C

Ψ1 = 10.11°, Ψ2 = 49.89°

D

Ψ1 = 12.21°, Ψ2 = 47.79°

Statement (I): Two non-intersecting and non-parallel, i.e., non-coplanar, shafts connected by gears are called skew-bevel gears or spiral gears, and this type of gearing has a line contact the rotation of which about the axes generates the two hyperboloid pitch surfaces. Statement (II): A hyperboloid is a 3D surface formed by revolving a straight line about an axis (not in the same plane), such that every point on the line remains at a constant distance from the axis.

A

Both Statement I) and Statement II) are individually true and Statement II) is the correct explanation of Statement I)

B

Both Statement I) and Statement II) are individually true but Statement II) is not the correct explanation of Statement I)

C

Statement I) is true but Statement II) is false

D

Statement I) is false but Statement II) is true

For helical gears, the angle between hob’s spindle axis and workpiece’s spindle axis must be _____ as the helix angle of the helical gear.

A

decreased by the half amount

B

increased by the half amount

C

decreased by the same amount

D

increased by the same amount

The teeth of the helical gears are cut parallel to the shaft axis.

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