# Machine Kinematics Questions and Answers – Interference

This set of Machine Kinematics Multiple Choice Questions & Answers (MCQs) focuses on “Interference”.

1. Which of the following is a disadvantage of involute gears?
a) Occurrence of interference
b) Non occurrence of interference
c) Pressure angle remains constant
d) Face and flank are generated by single curve

Explanation: The disadvantage of the involute teeth is that the interference occurs. This may be avoided by altering the heights of addendum and dedendum of the mating teeth.

2. By changing the angle of obliquity of the teeth, interference can be avoided.
a) True
b) False

Explanation: Interference can be avoided by changing the obliquity of the teeth or alternatively altering the height of the addendum. Failure to do so will result in the occurrence of interference.

3. The phenomenon when the tip of tooth undercuts the root on its mating gear is known as _______
a) Involution
b) Interference
c) Cycloidal motion
d) Undercutting

Explanation: The phenomenon when the tip of tooth undercuts the root on its mating gear is known as interference. This is generally observed in involute profiles.

4. In which of the following gears, interference occurs?
a) Cycloidal
b) Involute
c) Epi cycloidal
d) Hypo-cycloidal

Explanation: Interference occurs in involute gears which is one of its disadvantages amongst many advantages. This happens when the pinion has a low number of teeth.

5. For the same pitch, which of the following statement is true?
a) Cycloidal gears are stronger than involute gears
b) Involute gears are stronger than cycloidal gears
c) Both cycloidal and Involute gears have equal strength
d) Cycloidal gears are stronger for lower pitch only

Explanation: Cycloidal teeth have wider flanks, as a consequence the cycloidal gears are stronger than the involute gears, provided the pitch is the same. That is why cycloidal gears are used for cast teeth.
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6. If the point of contact between the two teeth is always on the involute profiles of both the teeth, then which of the phenomenon will occur?
a) Avoidance of interference
b) Occurrence of interference
c) Increase in length of path of contact
d) Increase in length of arc of contact

Explanation: The interference may only be avoided, if the point of contact between the two teeth is always on the involute profiles of both the teeth.

7. Given,
Involute profile teeths of mating gear: 20 and 40
Pressure angle = 20°
module = 10mm
The constraint: The addendum on each wheel is to be made of such a length that the line of contact on each side of the pitch point has half the maximum possible length.
Find the addendum height for the larger gear wheel in mm.
a) 6.5
b) 6
c) 6.8
d) 7

Explanation: r = m.t/2 = 100mm
R = 200mm
Using the constraint we find that
Ra = 206.5mm
Therefore

8. Given:
Involute profile teeths of mating gear: 20 and 40
Pressure angle = 20°
module = 10mm
The constraint: The addendum on each wheel is to be made of such a length that the line of contact on each side of the pitch point has half the maximum possible length.
Find the addendum height for the smaller gear wheel in mm.
a) 6.4
b) 6.2
c) 6.3
d) 6

Explanation: r = m.t/2 = 100mm
R = 200mm
Using the constraint we find that
ra = 106.2mm
Therefore

9. Given:
Involute profile teeths of mating gear: 20 and 40
Pressure angle = 20°
module = 10mm
The constraint: The addendum on each wheel is to be made of such a length that the line of contact on each side of the pitch point has half the maximum possible length.
Find the length of path of contact in mm.
a) 56.4
b) 56.2
c) 56.3
d) 51.3

Explanation: r = m.t/2 = 100mm
R = 200mm
We know that length of path of contact = (R+r)sinΦ/2
= 51.3mm.

10. Given:
Involute profile teeths of mating gear: 20 and 40
Pressure angle = 20°
module = 10mm
The constraint: The addendum on each wheel is to be made of such a length that the line of contact on each side of the pitch point has half the maximum possible length.
Find the length of arc of contact in mm.
a) 56.4
b) 54.6
c) 56.3
d) 51.3

Explanation: r = m.t/2 = 100mm
R = 200mm
We know that length of path of contact = (R+r)sinΦ/2
= 51.3mm
Arc of contact = length of path of contact / cosΦ
= 54.6mm.

11. Given:
Involute profile teeths of mating gear: 20 and 40
Pressure angle = 20°
module = 10mm
The constraint: The addendum on each wheel is to be made of such a length that the line of contact on each side of the pitch point has half the maximum possible length.
Find the contact ratio.
a) 1.23
b) 1.52
c) 1.74
d) 1.97

Explanation: r = m.t/2 = 100mm
R = 200mm
We know that length of path of contact = (R+r)sinΦ/2
= 51.3mm
Pitch = πx10 = 31.42
Contact ratio = length of path of contact/pitch
= 1.74.

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