The square root unit of the Friden SRW automatic square root mechanism

The Friden automatic square root model SRW is a five-species calculating machine based on the model STW: a fully automatic machine equipped with split stepped drum according to the patent of Carl M. Friden. It was and is the only mechanical calculator that is capable of taking square roots completely automatically. In addition to the four basic arithmetic operations, the SRW automatic square root calculator is also capable of taking precise square roots from numbers with up to ten digits.

The fully automated square root calculation is implemented using a modified Toepler method (5-method). Grant Clawson Ellerbeck is the inventor and designer of the mechanical addition required for this. Taking the square root - a time-consuming operation on all other calculators - is done on this machine after setting the radicand by pressing one of the small buttons located in front of the full keyboard.

In his Bachelor's thesis, Daniel Meyer modeled the sophisticated mechanics of the Friden square root machine in three dimensions based on two-dimensional construction sketches using Fusion 360 software and then didactically processed and clearly explained the square root machine in a video.