Well, yes. If someone hands me a Rubik’s cube, I’m not going to be satisfied if they tell me the subcubes are just attached at the faces and slide across each other in a peculiar way. I know there must be some internal axle or bearing system.
Well, I’ve only read a handful of Discworld books, though that does include Thud!. I’m not sure if they’re described in more detail elsewhere. Here is the actual book passage, which includes more detail than the link above:
“It spins once every 6.9 seconds but the torque is immense! It broke the clamp! What powers it?”
“No one seems to know,” said Carrot. “In Uberwald-”
“Excuse me, what is this about?” said Lord Vetinari, holding out a hand imperiously.
The man glanced at him and then turned to Carrot. “Who’s this?” he said.
“Lord Vetinari, ruler of the city, may I present Mr Pony of the Artificers” Guild?" said Carrot quickly. “Please let his lordship see the Axle, Mr Pony.”
“Thank you,” said Vetinari. He took the thing, which looked very like two cubes, each about six inches on a side, joined together on one face, like a pair of dice joined at the sixes. In relation to the other, one turned - very, very slowly.
“Oh,” he said flatly. “A mechanism. How nice.”
“Nice?” said Pony. “Don’t you understand? It won’t stop turning.” Carrot and Pony looked expectantly at the Patrician, who said:
“And that’s a good thing, is it?”
Carrot coughed. “Yes, sir. One of these drives one of the biggest mines in Uberwald. All the pumps, the fans that move the air, the trucks that haul the ore, the bellows for the forges, the elevators … everything. Just one of those. It’s another type of Device, like the cubes. We don’t know how they’re made, they’re very rare, but the other three I’ve heard of have not stopped working for hundreds of years. They don’t use fuel, they don’t need anything. They appear to be millions of years old. No one knows what made them. They just turn.”
It doesn’t really rule out there being a rod in there somehow. Vetinari assumes it’s a fairly ordinary mechanism to start with.
Relevant facts:
- Spins every 6.9 seconds (8.7 rpm)
- Two cubes about 6 inches on a side
- Essentially infinite torque
- Only 4 known Axles total
- Already runs one of the biggest mines in Uberwald