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Modeling Scenario

3-064-GearTrain-ModelingScenario

Author(s): Lukasz Grabarek

Keywords: friction gear spur gear gear train torque gear ratio angular acceleration angular velocity moment of inertia double reduction gear

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Abstract

Resource Image Students model an input-output mechanical system of gears with a second order, non-homogeneous, ordinary differential equation with constant coefficients. The model incorporates friction and moments of inertia of the gear train components.

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Description

In this scenario you will model a series of interfacing gears, often called a gear train (see Figure 3). Your model will involve a second order linear differential equation with constant coefficients. The coefficients will encode the physical properties of the system such as moments of inertia of the gears and rotational friction.

Students should have some experience working with torque.

First approximation: gears with no teeth as an example of approach.

We are at this point only interested in the rough geometry of the problem, so let's smooth out the scenario and remove a complication: teeth. To this end, consider two disks of different radii, r1 and r2. Let us suppose that the smaller disk of radius r1 is driving the larger disk with radius r2. If you are able to build a model, fix your disks to a base so that they contact at a point on their circumferences and are able to rotate about their centers. You will rotate the smaller (driving) disk and observe a rotation in the larger (driven) disk. Let theta1' and theta2' be the rates, i.e. angular velocities (revolutions per minute), at which the disks revolve, respectively.

If you have access to a physical model, experiment with it. Otherwise, you may simply imagine such a set up or use an online tool like Gear Generator to aid your investigation.

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Authors

Author(s): Lukasz Grabarek

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