newtonian mechanics - Are all machines linearly scalable?

For all machines (cars, elevators, computers, etc), when size, power requirements, dimensions are scaled by a constant N, will it work just as is?

Will a car with all its parts 10x larger still work like a normal car, just larger?

Answer

This is a great question. An influential early discussion of it was given in a 1959 talk by Richard Feynman, There's Plenty of Room at the Bottom. Basically the answer is no, machines are not linearly scalable. For example, lubrication doesn't work for very small machines. A general way of looking at this is that we have various physical quantities, and they scale in different ways. For example, area is proportional to length squared, while volume goes like length cubed. Because different things scale differently, what works on one scale doesn't work on another. A good example is the animal world -- after all, animals are a type of machine. A spider the size of an elephant would collapse under its own weight. This is because the strength of the animal's limbs go like the cross-sectional area, while the weight the limbs have to support is proportional to volume.