Mechanical computers for fire control where the standard solution until very recently. Here's a very interesting video about them: https://www.youtube.com/watch?v=s1i-dnAH9Y4
I don't think I'd really call that a computer any more than I'd call an old watch a computer.
The some of the targeting computers aboard the USS Iowa worked in part by the same principles. (The Mk 8 Rangekeeper)
The continuous control mixing of the XC-142 tiltwing (1960's version of the V-22 Osprey) as it changed from vertical to horizontal mode, was all done with cams, gears, and levers.
I understand it to have been essentially a proof of concept, not something that was intended to provide motive power to a machine. Given that, its simplicity would likely have been more valuable than its efficiency.