1. Other than the pendulum, what internal mechanisms are important to a clock’s operation?

2. What is a Simple Machine?
A simple machine has few or no moving parts.
Simple machines make work easier

3. Wheels and Axles The wheel and axle are a simple machine
The axle is a rod that goes through the wheel which allows the wheel to turn
Gears are a form of wheels and axles

4. Gear ratios

5. OBJECTIVES To understand and calculate gear ratios
To understand and demonstrate the relationship of torque and rotational speed
To understand and properly express the relationship between the driving and driven gears

6. What is a gear?
A gear is a wheel with teeth that mesh together with other gears.
Gears change the…
Speed
Torque (rot. force)
Direction
…of rotating axles.

7. Different types of gears
Spur gears
Idler gears
Worm gears
Bevel gears
Belts & Pulleys

8. How do you get 4000 lbs of wheels and steel moving from a stop and keep it going without over revving the engine?
Gears! They are used to keep the engine in its ideal RPM range for any given condition
What can be done to get a race car to the end of the ¼ mile faster?
Use a set of low gears (numerically higher ratios)
What would you do to a vehicle to achieve a higher top speed?
Use a set of high gears (numerically lower ratios)

10. Calculating Gear Ratios and Torque
Always divide the driven gear by the drive gear
2 divided by 1 = 2:1 ratio
This ratio is used to calculate the output torque
25 ft-lb x 2= 50 ft-lb

11. Calculate Output Rpm & Torque
Output RPM = Input RPM/GR
1000 rpm divided by 2= 500 rpm
Output Torque = Input Torque*GR
10 ft-lb multiplied by 2= 20 ft-lb
Drive

12. Divide the driven by the drive gear
44 divided by 11= 4:1

13. How many times will the drive gear turn to rotate the driven gear once with a ratio of 4:1?
100 ft-lb of torque is input to a gear ratio of 4:1, how much is output?
400 ft-lb
1000 rpm is input to a gear ratio of 4:1, what is the output?
250 rpm

14. Calculating Transmission Gear Ratios (multiple gear sets)
1. Calculate the ratio of the first set of gears by dividing the driven (output) gear by the drive (input) gear 2. Do the same for the second set of gears 3. Multiply the answer from the first calculation with the answer from the second calculation

15. Two or more sets of gears in mesh- calculate the first set, then the second and multiply together for final ratio
3.63 x 3.52=12.78:1

16. Find the Overall Gear Ratio…
Gear set A-drive gear has 20 teeth, driven has 40, Gear set B drive gear has 30 teeth, driven gear has 40. What is the drive ratio?
2:1 x 1.33:1=2.66:1