Shifting Gears
When do you shift gears?
A gear system allows you to adjust the driving force that is needed to move the driven wheel. When driving a vehicle, you start off in a low gear and then shift into higher gears at higher speeds.
In which situations is it useful to be able to shift gears up or down?
Build this *Geared Vehicle*.
This vehicle has interchangeable gear trains, which allows us to see the effects of shifting gears!
Do a test run.
Place the model on a solid and level surface. Make sure that both the gear pointer and the reference motor pointer are pointing upwards. Run the program and count the number of rotations by keeping track of the gear pointer. Make sure that you observe its turning direction.
Does the reference motor complete one rotation? Do both motors stop turning at the same time?
Using the Ultrasonic Sensor
The Ultrasonic Sensor generates sound pulses, which form a sound cone in which objects can be detected. When starting the experiment, do not stand next to the vehicle or within the Ultrasonic Sensor's sensing cone; it’s best to stand behind the Ultrasonic Sensor.
Record your results.
Record the experiment number, gear ratio, your prediction of what will happen, the distance travelled and velocity in a testing table. Make sure you leave space for recording other observations.
Perform the experiment using the default gearing, and then repeat the experiment for each of the gear train options that are shown in the ‘Hint’ below.
Running the Experiment
Keep the following tips in mind as you run your experiment:
- The distance travelled (in cm), velocity (in m/s) and rotational speed (in revolutions per second) will be shown on the Display.
- Perform the experiment at least three times for each of the gear train options and use the average value to ensure the most reliable results.
Shifting Gears
Remove the first default gear train:
Build the second gear train using double bevel gears:
Build the third gear train using the same gears:
If you have enough time, use regular gears to build the fourth gear train:
If you have enough time, build this fifth gear train using the same gears:
Summarise your results.
Use the average value for each gear train option to analyse how the gear ratio relates to the vehicle’s velocity and the distance it has travelled.
Which gear ratio would you choose when designing a fast vehicle and which would you choose when designing a vehicle that must move a heavy load?
How did you do?
What did you do well? Is there anything that you could have done better?
Now you know when to shift gears, that’s brilliant. Full speed ahead to the next lesson!