Figure 10-25.--Bevel gear differential.

meshed gears can be found by using the following

of the several simple machines that make it up. In this

case, you considered the winch as being two

formula:

machines--one having an M.A. of 6 and the other an

M.A. of 2. Therefore, the overall theoretical M.A. of

the winch is 6 x 2, or 12. Since friction is always

present, the actual M.A. may be only 7 or 8. Even so,

In which,

by applying a force of 100 pounds on the handle, you

To= number of teeth on driven gear

could lift a load of 700 to 800 pounds.

Ta= number of teeth on driver gear

THE GEAR DIFFERENTIAL

In this case,

As you have seen, gears have a variety of

Then,

functions, and as an IC Electrician, you will work with

all types of gear trains. One type of gear train that is

used extensively is the gear differential. It is capable

of adding and subtracting mechanically. The gear

differential adds the total revolutions of two shafts, or

Now, the theoretical arrangement for the other

subtracts the total revolutions of one shaft from the

part of the machine, which is a simple wheel-and-axle

total revolutions of another shaft, and delivers the

arrangement consisting of the crank arm and the drum,

answer by positioning a third shaft. The gear

can be found by dividing the distance the effort

differential will add or subtract any number of

moves-- 2R--in making one complete revolution, by

revolutions, or small fractions of revolutions,

the distance the cable is drawn up in one revolution of

continuously and accurately.

the drum--2r.

Figure 10-25 is a cutaway drawing of a bevel gear

differential, showing all its parts and how they are

related to each other. Grouped around the center of the

The total, or overall, theoretical M.A. of a

mechanism are four bevel gears, meshed together. The

compound machine is equal to the product of the M.A.

two bevel gears on either side are called end gears. The

Figure 10-25.--Bevel gear differential.

10-13