The Otis King slide rule is a futuristic-looking calculator from the early 20th century that is now available as a 3D-printed replica for makers to assemble and use.
The device works using the principle that adding together logarithms achieves the same result as multiplying the two numbers that the logarithms represent.
This enables the calculator to achieve quick results by using addition instead of requiring multiplication to be carried out.
The comments section of the Hackaday article reveals that the Otis King slide rule is most useful for calculating trigonometric functions, where it is much quicker than other non-electronic methods.
Its use for simple multiplication is less useful because of the need to carefully line up the logarithmic scales before obtaining a result.
