Lever Systems and Torque

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Questions and Answers

What is the first step in designing a motor system to meet specific speed requirements?

Calculating the gear ratio required

Determining the output torque of the gearbox

Choosing the type of motor to use

Calculating the load the motor must be under (correct)

What is the formula to calculate the torque load that will cause the motor to exceed a certain current?

Torque Load = (Given Motor Current – Free Current) x Stall Torque / (Stall Current – Free Current) (correct)

Torque Load = (Given Motor Current x Free Current) x Stall Torque / (Stall Current x Free Current)

Torque Load = (Given Motor Current / Free Current) x Stall Torque / (Stall Current / Free Current)

Torque Load = (Given Motor Current + Free Current) x Stall Torque / (Stall Current + Free Current)

What is the purpose of calculating the torque load in a motor system?

To determine the output torque of the gearbox

To determine the maximum torque the motor can handle (correct)

To determine the motor current required

To determine the gear ratio required

What is the relationship between the output torque and input torque of a gearbox?

Output Torque = Input Torque x Gear Reduction Signup and view all the answers

Why is it important to consider the gear ratios available when designing a motor system?

To ensure the gear ratio required can be achieved with the available gears Signup and view all the answers

What is the primary goal when designing a compound gear reduction?

To achieve a gear ratio greater than the required minimum Signup and view all the answers

What is the result of not being able to achieve the exact gear ratio required with the available gears?

The motor system will not meet the design criteria Signup and view all the answers

What is the purpose of calculating the gear reduction required?

To determine the gear ratio required to meet the design criteria Signup and view all the answers

What is the torque applied to the output of the lever system in the example above?

8 N-m Signup and view all the answers

What is the resulting force on the output of the lever system in the example above?

1 N Signup and view all the answers

How do gears work in terms of mechanical advantage?

They are a series of levers, where the larger diameter gear has a longer lever. Signup and view all the answers

What happens to the torque when a small gear drives a large gear?

Torque decreases Signup and view all the answers

What happens to the speed when a small gear drives a large gear?

Speed decreases Signup and view all the answers

What is the angle of rotation of the 60-tooth gear when the 36-tooth gear is rotated 1 tooth?

6 degrees Signup and view all the answers

How do the speeds of the two gears compare in the example above?

The small gear spins faster than the large gear Signup and view all the answers

What is the mechanical advantage of using gears and levers?

To harness a fixed input force to accomplish a desired output Signup and view all the answers

What is the primary advantage of varying the gear ratio and mechanical advantage in a system?

Improving the versatility of the system to accomplish different tasks Signup and view all the answers

What is the ratio of the sizes of two gears meshing proportional to?

The resulting torque change and speed change between them Signup and view all the answers

What is the Gear Ratio denoted as?

Driven Gear Teeth:Driving Gear Teeth Signup and view all the answers

What is the main issue with the direct drive mechanism from the motor to the lock bar in the scoop bucket prototype?

It is moving too quickly Signup and view all the answers

What software is used to design and test the gear drive in the scoop bucket project?

Autodesk Inventor Signup and view all the answers

What is the formula to calculate the Gear Reduction?

Driven Gear Teeth / Driving Gear Teeth Signup and view all the answers

What is the formula to calculate the Output Torque?

Input Torque x Gear Reduction Signup and view all the answers

What is the primary purpose of the seven videos in the project, including the Overview and Summary?

To review the content and workflow of the project Signup and view all the answers

What is a prerequisite for completing this unit?

Basic understanding of Autodesk Inventor user interface and navigation Signup and view all the answers

What is the formula to calculate the Output Speed?

Input Speed / Gear Reduction Signup and view all the answers

What happens to the speed and torque when the Gear Reduction is greater than 1?

The speed decreases and the torque increases Signup and view all the answers

What is the main benefit of using a gear drive in the scoop bucket project?

Improved control of the scoop motion Signup and view all the answers

What happens to the speed and torque when the Gear Reduction is less than 1?

The speed increases and the torque decreases Signup and view all the answers

What is the relationship between the number of teeth on a gear and its diameter?

The number of teeth is proportional to the diameter Signup and view all the answers

What is the overall gear reduction in a gearbox with twelve 12:60 reductions as part of one compound reduction?

244,140,625 Signup and view all the answers

What is the advantage of using pulleys and belts in mechanical power transmission?

They can transfer torque over long distances Signup and view all the answers

Why is mechanical advantage important in the design of DC motor systems?

It helps the motor stay within its load limits Signup and view all the answers

What is the result of multiplying the gear reductions of each individual gear pair in a compound gear system?

The overall gear reduction is the product of the individual gear reductions Signup and view all the answers

How do sprocket ratios compare to gear ratios?

Sprocket ratios are calculated by counting their teeth, while gear ratios are calculated by comparing their diameters Signup and view all the answers

What is the result of having a compound gear reduction of 25 in a system?

The output shaft is 25 times slower than the input shaft Signup and view all the answers

How long would it take for the output to spin once if the input is spun at a rate of once per second in a gearbox with a compound gear reduction of 244,140,625?

Approximately 7 years and 9 months Signup and view all the answers

What is the purpose of using gear reductions in mechanical power transmission?

To transfer torque over long distances Signup and view all the answers

Study Notes

Mechanical Advantage and Levers

Mechanical advantage can be achieved through the use of levers, which can be used to harness a fixed input force to accomplish a desired output.
The formula for torque is: Torque = Force x Distance from Center of Rotation.
Example: If the input force is 4 Newtons and moves 1 meter, the output will have a force of 1 Newton and moves 4 meters.

Gears and Gear Reduction

Gears work in the same manner as levers, with the diameters of the gears becoming the lengths of the levers.
The resulting change of torque is equivalent to the ratio of the diameters.
Small gears driving large gears result in a torque increase, while large gears driving small gears result in a torque decrease.
The gear ratio is denoted as (Driving Gear Teeth):(Driven Gear Teeth), and the gear reduction is calculated as Driven Gear Teeth / Driving Gear Teeth.
Example: A 36-tooth gear driving a 60-tooth gear results in a gear reduction of 1.67 and a speed decrease.

Gear Reduction and Torque Change

The ratio between the sizes of two gears meshing is proportional to the resulting torque change and speed change between them.
Combining gear ratios can result in a compound gear reduction, which can be calculated by multiplying the individual gear reductions.
Example: A gearbox with twelve 12:60 reductions results in an overall reduction of 244,140,625, almost a quarter of a billion to 1.

Other Types of Reductions

Sprockets and chains, and pulleys and belts can also be used to provide gear reduction.
The same principles apply to these mechanisms, with the ratio being calculated by counting teeth or comparing diameters.

Applying Gear Ratios to DC Motor Systems

Adjustments to mechanical advantage are important in the design of DC motor systems.
The first step is to calculate the load the motor must be under to meet the design criteria.
The output requirements and input limits are then used to calculate the ratio required.
Example: A VEX 2-wire Motor 393 requires a gear ratio of 18.68 to lift a 30 Newton object and not exceed the current draw of 2.5 amps.

Designing a Gear System

A designer's ability to vary the gear ratio and mechanical advantage gives them the versatility to accomplish whatever work needs to be done with whatever motors they have.
The simplest approach is to determine the inputs and outputs, calculate the difference between them, and set the gear ratio accordingly.
This method can be applied to any number of motor/gearing systems.

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Description

Quiz about calculating torque and resultant force in a lever system, with examples of input and output forces and distances.