Activity: Low Gear/High Gear

Nick getting ready to race.

On SCOPE's Racing Car Science episode, you saw Nick head to the track to test out some gearings.

What you need

Two go-karts, each with different gears (one high, one low), alternatively you could do the experiment with two bikes, one set on a low gear, one set on high.

What to do

1. Try racing the 2 karts over different distances or courses such as:
• A short drag on the straight
• A longer race on a fairly straight track
• A longer race on a very curvy track

1. Is the same kart (or bike) always the winner?

What's happening?

In racing there are hairpin turns, straights, pit stops and chicanes (tight serpentine curves). Every race track is a different combination of slow windy sections and fast straight sections, so finding the right gear ratio for a race is vitally important.

The karts have a motor that drives a cog on the rear axle. The toothed cog is fixed to the axle and attached to the motor with a chain. As the motor runs the gear system it turns the axle and the wheels, pushing the kart forward. Tim's kart had a small cog or high gear on the axle and Nick's kart had a large cog or low gear.

Low gears are used for accelerating quickly over short distances, and are ideal for windy tracks when the car is always slowing right down to turn then speeding up again. But a low gear will also mean a lower top speed. A higher gear is great for speed, but it take s a lot to get it moving so acceleration is not very quick. Higher gears are used for straighter tracks where the kart will not need to slow down much.

In racing cars, as opposed to karts, there is more than one gear, so drivers use the low gears for starting off and turning corners and the high gears for the straights. Even so, the engineers will change the gears in the car depending on how straight or windy the track is, to give optimum performance.

There's a lot more to racing than putting your foot to the floor!