Compass cart
An antique transportable direction indicator is known as a compass car. Unlike a compass , it is not dependent on geomagnetism , but rather it records the different rotations of two parallel wheels of the same size with the help of a subtraction gear , the structure of which is similar to a differential gear . With the differential, the translation between the two half-axes is opposite (i = -1) and the sum of the revolutions of both shafts is applied to the drive shaft, with the compass car the two half-axes are translated 1: 1 (i = 1) and the direction indicator shows the difference the revolutions of the two wheels.
The compass cart is a cart with two wheels connected by a planetary gear , on which a pointer is attached that always points in the same direction.
The first verifiable construction is ascribed to the Chinese inventor Ma Jun (around 200–265), although as early as 2600 BC. The Chinese ruler Huáng Dì is said to have used such a device. At that time the compass cart was used to keep one's bearings in armed conflicts even in fog.
Web links
- Simple mathematical considerations on the compass cart
- AMS: Compass car from the metal construction kit
- Sciencemuseum: Chinese South-pointing chariot (with picture)
- Antiquark: South Pointing Chariots (with picture)
- South Pointing Chariots (with picture)