**MACHINE SHOP CALCULATION - OD1640 - LESSON 2/TASK 2**

EXAMPLE

A 24 inch pulley fixed to a live shaft which makes 400 revolutions per

minute (rpm) is belted to a 6 inch pulley, as shown in figure 8 on the

following page. Find the rpm of the smaller pulley.

This is what the problem looks like:

A is the driving pulley, B is the driven pulley.

Then, X : 400 :: 24 : 6

(b) *Rule 2*.

The speed of gears

running

together

is

inversely

proportional to their number of teeth.

EXAMPLE

A driving gear with 48 teeth meshes with a driven gear which has 16 teeth.

If the driving gear makes 100 rpm, find the number of rpm of the driven

gear.

3.

Pulley Trains and Gear Trains

a.

In the previous paragraph, we discussed the meanings and methods of

solving ratio and proportion problems.

In this paragraph, we will apply

these methods to help determine the size to which a pulley or gear should be

machined in order to enable it to rotate at a given number of revolutions

per minute (rpm) for efficient operation of the machinery pulley train or

vehicle gear train.

A pulley train is a series of pulleys connected by

belting as shown in figure 9 on page 47. A gear train is a series of gears

running

**45**