# 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?

• For a very simple case, consider a body that generates heat relative to its volume, but can only transfer heat relative to its surface area. As you scale it up, it will get hotter and hotter until it breaks down. – raptortech97 Oct 7 '14 at 1:15
• Same question but for animals: physics.stackexchange.com/questions/72641/… – user10851 Oct 7 '14 at 6:01
• A car that is 10 times bigger doesn't 'work' because you can't reach the pedals. An elevator that is 10 times bigger wouldn't 'work' because it would occupy all stories of the building at once. A computer with a transistor that is 10 times bigger is probably comletely useless because the electricity has to travel through a very long path. – Dennis Jaheruddin Oct 7 '14 at 10:16
• even worse, a car that's 10 times as large in size has a volume of material that's 1000 times as large while not having 1000 times as much engine power... And the same with most things when scaled up. – jwenting Oct 7 '14 at 14:29
• Perhaps a better question would be "are there any machines which are linearly scalable which remain useful"? Consider the lever - a ten-foot-long lever might be very useful for moving something. A 100-foot-long lever? Maybe not so much... – Bob Jarvis Oct 7 '14 at 22:48

• tl,dr: Weight scales like $\text{length}^3$ but strength of an e.g. bone scales like cross sectional area $=\text{length}^2$. Therefore, as you make an animal or machine bigger, the strength to weight ratio goes down. – DanielSank Oct 7 '14 at 1:12