Machine Kinematics

Toothed Gearing

Question 1
Marks : +2 | -2
Pass Ratio : 40%
The contact ratio for gears is
zero
less than one
greater than one
none of the mentioned
Explanation:
The theoretical minimum value for the contact ratio is one, that is there must always be at least one pair of teeth in contact for continuous action.
Question 2
Marks : +2 | -2
Pass Ratio : 20%
The maximum efficiency for spiral gears is
sin (θ + φ ) + 1/ cos (θ − φ ) + 1
cos (θ − φ) + 1/sin (θ + φ ) + 1
cos (θ + φ ) + 1/ cos (θ − φ ) + 1
cos (θ − φ) + 1/cos (θ + φ ) + 1
Explanation:
ηmax = cos (θ + φ ) + 1/ cos (θ − φ ) + 1
Question 3
Marks : +2 | -2
Pass Ratio : 50%
The maximum length of arc of contact for two mating gears, in order to avoid interference, is
(r + R) sin φ
(r + R) cos φ
(r + R) tan φ
none of the mentioned
Explanation:
Interference may only be prevented, if the addendum circles of the two mating gears cut the
Question 4
Marks : +2 | -2
Pass Ratio : 20%
Interference can be avoided in involute gears with 20° pressure angle by
cutting involute correctly
using as small number of teeth as possible
using more than 20 teeth
using more than 8 teeth
Explanation:
None.
Question 5
Marks : +2 | -2
Pass Ratio : 100%
If the module of a gear be m, the number of teeth T and pitch circle diameter D, then
m = D/T
D = T/m
m = D/2T
none of the mentioned
Explanation:
Module, m = D /T.
Question 6
Marks : +2 | -2
Pass Ratio : 50%
The ratio of face width to transverse pitch of a helical gear with α as the helix angle is normally
more than 1.15/tan α
more than 1.05/tan α
more than 1/tan α
none of the mentioned
Explanation:
None.
Question 7
Marks : +2 | -2
Pass Ratio : 50%
Mitre gears are used for
great speed reduction
equal speed
minimum axial thrust
minimum backlash
Explanation:
When equal bevel gears (having equal teeth) connect two shafts whose axes are mutually perpendicular, then the bevel gears are known as mitres.
Question 8
Marks : +2 | -2
Pass Ratio : 33%
Which is the incorrect relationship of gears?
Circular pitch × Diametral pitch = π
Module = P.C.D/No.of teeth
Dedendum = 1.157 module
Addendum = 2.157 module
Explanation:
None.
Question 9
Marks : +2 | -2
Pass Ratio : 50%
The type of gears used to connect two non-parallel non-intersecting shafts are
spur gears
helical gears
spiral gears
none of the mentioned
Explanation:
The two non-intersecting and non-parallel i.e. non-coplanar shaft connected by gears. These gears are called skew bevel gears or spiral gears and the arrangement is known as skew bevel gearing or spiral gearing. This type of gearing also have a line contact, the rotation of which about the axes generates the two pitch surfaces known as hyperboloids.
Question 10
Marks : +2 | -2
Pass Ratio : 33%
The radial distance of a tooth from the pitch circle to the bottom of the tooth, is called
dedendum
addendum
clearance
working depth
Explanation:
Addendum is the radial distance of a tooth from the pitch circle to the top of the tooth.