Spur Gear Fundamentals Quiz
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Questions and Answers

What is the term for the distance measured along the pitch circle from a point on one tooth to the corresponding point on the adjacent tooth?

  • Circular pitch (correct)
  • Base circle
  • Clearance
  • Backlash

Which term describes the radius that connects the root circle to the profile of the tooth?

  • Tooth thickness
  • Top land
  • Fillet radius (correct)
  • Addendum

What is defined as the amount that the dedendum exceeds the addendum in gear terminology?

  • Clearance (correct)
  • Backlash
  • Arc of contact
  • Tooth space

What does the term 'diametral pitch' refer to in gear terminology?

<p>The size of the tooth (C)</p> Signup and view all the answers

Which of the following statements about mating gears is true?

<p>They must have the same diametral pitch. (D)</p> Signup and view all the answers

What is the term for the width of the tooth measured along the pitch circle?

<p>Tooth thickness (A)</p> Signup and view all the answers

Which term refers to the amount that the width of a tooth space exceeds the thickness of a gear tooth?

<p>Backlash (C)</p> Signup and view all the answers

What is understood by the term 'arc of approach' in gear mechanics?

<p>Portion of the path from the beginning of engagement to the pitch point (D)</p> Signup and view all the answers

What is the primary function of backlash in gear systems?

<p>To allow sufficient lubrication on the gear teeth (D)</p> Signup and view all the answers

How does a reduction in center distance affect the backlash between gears?

<p>It generally reduces the backlash (A)</p> Signup and view all the answers

What backlash value is recommended by AGMA for certain gear applications?

<p>0.1/Pd (D)</p> Signup and view all the answers

What would be a consequence of gears frequently starting and stopping if backlash is not closely controlled?

<p>Higher wear on gear teeth (A)</p> Signup and view all the answers

If two gears designed with a 20° pressure angle are used, what can happen during operation?

<p>The actual pressure angle may increase beyond 20° (C)</p> Signup and view all the answers

What is the diameter of the addendum circle for the gear with 35 teeth and a diametral pitch of 10?

<p>3.70 in. (A)</p> Signup and view all the answers

What is the clearance for the gear with 35 teeth and a diametral pitch of 10?

<p>0.025 in. (B)</p> Signup and view all the answers

What determines whether two involute gears will mate correctly?

<p>Same diametral pitch and pressure angle (B)</p> Signup and view all the answers

What is the center distance between a pinion with 15 teeth and a gear with 30 teeth both having a 5-pitch?

<p>4.5 in. (C)</p> Signup and view all the answers

Why must the contact ratio exceed 1 in gear design?

<p>To prevent gears from losing contact during operation (A)</p> Signup and view all the answers

For robust gear designs, what is the ideal range for the contact ratio?

<p>1.2 to 1.5 (D)</p> Signup and view all the answers

What defines the base pitch in the context of gearing?

<p>Distance between corresponding points of adjacent teeth on the base circle (B)</p> Signup and view all the answers

What is the deduction for the dedendum circle for a gear with 35 teeth and a diametral pitch of 10?

<p>3.25 in. (D)</p> Signup and view all the answers

What is the primary function of gears?

<p>To transmit motion between rotating shafts (B)</p> Signup and view all the answers

What distinguishes spur gears from other types of gears?

<p>Their teeth are parallel to the axis of rotation (D)</p> Signup and view all the answers

What does the term 'pitch diameter' refer to in gear terminology?

<p>The diameter of the pitch circle (C)</p> Signup and view all the answers

What is the clearance in gear terminology?

<p>The difference between the dedendum and addendum (B)</p> Signup and view all the answers

What does the term 'whole depth' represent in gear design?

<p>The total height of the gear tooth, including addendum and dedendum (C)</p> Signup and view all the answers

How is the addendum defined in gear terminology?

<p>The radial distance from the pitch circle to the top of the gear tooth (B)</p> Signup and view all the answers

What is the purpose of pitch circles in gear design?

<p>To represent the size of a corresponding friction roller (C)</p> Signup and view all the answers

What is the face width of a gear?

<p>The distance parallel to the shaft axis (B)</p> Signup and view all the answers

What is the definition of the module in gear terminology?

<p>The ratio of pitch diameter to the number of teeth. (D)</p> Signup and view all the answers

Which pressure angle is currently most commonly standardized for gears?

<p>20° (A), 25° (C)</p> Signup and view all the answers

What factor does the pressure angle influence in gear design?

<p>The relative shape of the gear teeth. (C)</p> Signup and view all the answers

What happens when the pressure angle is reduced in gears?

<p>Higher radial loads on the bearings. (D)</p> Signup and view all the answers

How is the involute curve of a circle constructed?

<p>By unwinding a taut wire from a base circle. (A)</p> Signup and view all the answers

What occurs at the portion of the gear tooth that is inside the base circle?

<p>It is not designed to be contacted by a mating gear tooth. (A)</p> Signup and view all the answers

In a 20° full-depth involute spur gear with 35 teeth, what is the purpose of the base circle?

<p>To serve as the starting point for generating involute profiles. (A)</p> Signup and view all the answers

What is the diametral pitch of a gear with 35 teeth and a pitch diameter of 3.5 inches?

<p>10 (B)</p> Signup and view all the answers

What is the contact ratio calculated for the given pinion and gear?

<p>0.59 (A)</p> Signup and view all the answers

Which condition indicates that interference is not a concern for the gears?

<p>If 30 is less than 45.489 (B)</p> Signup and view all the answers

What is one way to avoid interference during gear operation?

<p>Increasing the number of teeth in the pinion (B)</p> Signup and view all the answers

What is undercutting in the context of gear operation?

<p>Removing material on the gear tooth to avoid interference (D)</p> Signup and view all the answers

What effect does undercutting have on gear strength?

<p>Decreases the strength of the gear (A)</p> Signup and view all the answers

What is meant by backlash in gear mechanics?

<p>The amount a tooth space exceeds the thickness of a gear tooth (B)</p> Signup and view all the answers

In the given scenario, how many teeth does the pinion have?

<p>15 (A)</p> Signup and view all the answers

What would occur if a small gear pairs with a much larger gear without considering design constraints?

<p>Higher risk of gear failure due to interference (D)</p> Signup and view all the answers

Flashcards

Spur Gear

A type of gear where the teeth are parallel to the axis of rotation.

Pitch Circle

The circle that represents the size of the gear.

Pitch Diameter

The diameter of the pitch circle.

Addendum

Radial distance from the pitch circle to the top of a gear tooth.

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Dedendum

Radial distance from the pitch circle to the bottom of a gear tooth.

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Whole Depth

The height of a gear tooth (Addendum + Dedendum).

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Clearance

The difference between dedendum and addendum of meshing gears.

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Face Width

Length of gear tooth parallel to shaft axis.

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Base Circle

The circle from which the curved shape of the gear tooth is constructed.

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Base Diameter

The diameter of the circle from which the gear tooth profile is derived.

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Backlash

The difference between the width of a tooth space and the thickness of a gear tooth, measured on the pitch circle.

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Fillet Radius

The radius that connects the root circle to the profile of the tooth.

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Tooth Thickness

The width of the tooth measured along the pitch circle.

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Tooth Space

The width of space between two adjacent teeth, measured along the pitch circle.

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Diametral Pitch

The number of teeth per inch of pitch diameter.

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Pressure Angle

The angle between the line of action and the tangent to the pitch circle. It influences tooth shape and force transmission.

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Addendum Circle

The circle that defines the outer boundary of the gear tooth.

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Dedendum Circle

The circle that defines the inner boundary of the gear tooth.

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Pinion

The smaller gear in a gear set.

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Bull Gear

The larger gear in a gear set.

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Center Distance

The distance between the center of the shafts of two meshing gears.

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Contact Ratio

A measure of how much of a gear tooth is in contact with its mating tooth at any given time.

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What is the Formula for Contact Ratio?

Contact ratio (m) is calculated by dividing the length of the contact path (Z) by the circular pitch (p).

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Interference

A condition that occurs when gear teeth collide, causing a jamming issue due to incorrect gear design.

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Undercutting

A manufacturing technique to avoid interference by removing material on the gear tooth to allow for proper meshing.

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Why is Backlash Necessary?

Backlash allows for some flexibility in the gear train, preventing binding and wear due to manufacturing tolerances and thermal expansion.

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Why is Undercutting a Problem?

Undercutting weakens the gear tooth, potentially reducing its overall strength and making it more susceptible to failure.

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How to Prevent Interference

Choose the right number of teeth for each gear based on their pitch and pressure angle to avoid interference.

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Module (m)

A measure of gear tooth size. It's calculated by dividing the pitch diameter by the number of teeth.

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Pressure Angle (φ)

The angle between the pitch line and the pressure line, which is a line perpendicular to the tooth surfaces at the point of contact.

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What is the significance of pressure angle?

The pressure angle influences the shape of the gear tooth. It affects the efficiency of torque transfer and radial loads on bearings. Different gears must have the same pressure angle for proper meshing.

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Involute Curve

The path traced by the end of a wire unwinding from a base circle. It's used to form the gear tooth profile.

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How does pressure angle affect the base circle?

As the pressure angle increases, the distance between the base circle and the pitch circle also increases.

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What happens if gears have different pressure angles?

They won't mesh properly, leading to inefficient operation and potentially gear wear.

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Why is the portion of the tooth inside the base circle not designed to be contacted?

Contacting this portion leads to interference, making it useless and potentially damaging the gears.

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What is backlash?

The amount a gear can rotate without its mating gear rotating. It's necessary for lubrication.

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Why is backlash important?

Backlash affects gear operation. Continuous gears need more backlash, while gears that start/stop or reverse need controlled backlash.

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How does center distance affect backlash?

Changing the center distance between gears alters the backlash. Reducing the distance decreases backlash and vice versa.

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What is the formula for ΔB?

ΔB = (0.4/Pd) - (0.1/Pd) = 0.06. This represents the change in backlash.

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How does operating pressure angle change?

The actual pressure angle during operation can be different from the designated value. Increasing the center distance increases the angle.

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Study Notes

Spur Gear Fundamentals

  • Spur gears are the simplest gear type.
  • Teeth are parallel to the axis of rotation.
  • Commonly used to transmit motion between parallel shafts.

Gear Function

  • Gears transmit motion from one rotating shaft to another.
  • Often used to increase or decrease speed, or change the direction of motion.

Gear Terminologies

  • Pitch circle: Represents the size of a friction roller that could replace the gear.
  • Pitch point: Point of contact between two pitch circles.
  • Pitch diameter (d): Diameter of the pitch circle.
  • Addendum (a): Radial distance from the pitch circle to the top of a gear tooth.
  • Dedendum (b): Radial distance from the pitch circle to the bottom of a gear tooth.
  • Whole depth (h₁): Height of a gear tooth (addendum + dedendum).
  • Clearance (c): Difference between the dedendum and addendum.
  • Face width (F): Length of the gear tooth parallel to the shaft.
  • Circular pitch (p): Distance measured along the pitch circle from a point on one tooth to the corresponding point on the adjacent tooth.
  • Base circle: Circle from which the curved shape of the gear tooth is constructed.
  • Base diameter (d₁): Diameter of the base circle.
  • Backlash (B): Amount the width of a tooth space exceeds the thickness of a gear tooth on the pitch circle.
  • Top land: Surface of the top of the tooth.
  • Fillet radius: Radius connecting the root circle to the tooth profile.
  • Number of teeth (N): Total number of teeth on the gear.

Gear Interactions

  • Center distance (C): The center-to-center distance between two mating gears.
  • Contact ratio (m₁): Average number of teeth in contact at any instant.

Interference

  • Interference occurs when a small gear mates with a much larger gear.
  • The largest number of teeth to avoid interference is determined by a formula.

Undercutting

  • Removing material to avoid interference.
  • Reduces gear strength.

Operating Pressure Angle

  • Actual pressure angle during operation differs from designed value.

Diametral Pitch (Pd)

  • Tooth size standard for gear specifications.
  • Number of teeth per inch of pitch diameter.

Module (m)

  • Commonly used gear parameter in the SI unit system.
  • Ratio of pitch diameter to the number of teeth in the gear.

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Spur Gear: A Comprehensive Guide PDF

Description

Test your knowledge on spur gears, their functionalities, and key terminologies. This quiz will cover essential concepts like pitch circle, addendum, dedendum, and more. Perfect for engineering students and enthusiasts alike!

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