Teacher's Notes: Difference between Mac and Small Boomer robots Pro Preview

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  • #987
  • 05 Nov 2018

We’ve seen earlier that the inner wheels go a shorter distance than the outer wheels in a turn:

As we have already commented, this makes the outer wheels scuff, slip and wear much faster and the construction becomes very unstable. We’ve seen how to solve this problem by using a differential. Today, we will take a look at another solution – driving only one wheel. Thus, the wheel will go only the set distance while the other wheel will go the distance it should travel.

That was the solution used in the first models of cars: the motor drives only one of the rear wheels.

Discuss with students why this solution was not successful and designers abandoned it. The major disadvantage of vehicles driven by one wheel only is that when the respective wheel goes on ice or in the air, the car can no longer move on.

Locking the differential

Nowadays, most vehicles with a differential face the same problem as the differential transmits the turning force to the wheel with the lowest traction.

In order to avoid tire scuffing, the differential is temporarily locked. Then the engine drives the two wheels equally and the car can move on. However, we won’t go into detail about how to lock and unlock the differential.