Machine Kinematics

Toothed Gearing

Question 1
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 2
Marks : +2 | -2
Pass Ratio : 50%
Involute profile is preferred to cyloidal because
the profile is easy to cut
only one curve is required to cut
the rack has straight line profile and hence can be cut accurately
none of the mentioned
Explanation:
The face and flank of involute teeth are generated by a single curve where as in cycloidal
Question 3
Marks : +2 | -2
Pass Ratio : 100%
When the addenda on pinion and wheel is such that the path of approach and path of recess are half of their maximum possible values, then the length of the path of contact is given by
(r + R) sin φ/2
(r + R) cos φ/2
(r + R) tan φ/2
(r + R) cot φ/2
Explanation:
In case the addenda on pinion and wheel is such that the path of approach and path of recess are half of their maximum possible values, then
Question 4
Marks : +2 | -2
Pass Ratio : 100%
For a speed ratio of 100, smallest gear box is obtained by using
a pair of spur gears
a pair of helical and a pair of spur gear compounded
a pair of bevel and a pair of spur gear compounded
a pair of helical and a pair of worm gear compounded
Explanation:
None.
Question 5
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 6
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 7
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 8
Marks : +2 | -2
Pass Ratio : 20%
The size of a gear is usually specified by
pressure angle
circular pitch
diametral pitch
pitch circle diameter
Explanation:
Pitch circle diameter is the diameter of the pitch circle. The size of the gear is usually specified by the pitch circle diameter. It is also known as pitch diameter.
Question 9
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 10
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.