Percy Ludgate wrote about the engine in 1914 and published his own design for an analytical engine in 1909. It was drawn up in detail, but never built, and the drawings have never been found. Ludgate's engine would be much smaller (about than Babbage's, and hypothetically would be capable of multiplying two 20-decimal-digit numbers in about six seconds.

In Essays on Automatics (1914), Leonardo Torres Quevedo expanded upon Babbage's ideas by proposing