You might be surprised to find mechanical calculators – completely analog computational devices with no electrical parts – competed shoulder to should with their digital counterparts well until the late 1960s, in some respects surpassing them.

Monroe PC-1421 without cover. Credit: Kevin Twomey

Monroe PC-1421 with cover. Credit: Mark Glusker

These devices, like the  Monroe PC-1421 – a high speed multiplication and division device – were among the most complex of their sort ever built. Weighing a whooping 40 pounds, the PC-1421 was at the high end as far as mechanical calculators go. For instance, while early mechanical calculators required an operator to turn a crank by hand in order to add, subtract, multiply, and divide, the PC-1421 did this automatically following each operation via a motor. It was also one of few mechanical calculators with a decimal point button (many others required that users keep track of decimal points in their head).  No, this wasn’t the XVIIth century – this machine made its debut in 1964.

It’s pointless to mention mechanical calculators went out of fashion. Within a couple of years, digital calculators had become a lot more popular thanks to their small size and fewer components. If a digital calculator broke, you could easily fix it by replacing a transistor or condenser, depending on the nature of the malfunction. If your PC-1421 broke, you’d be in a heck of a lot of trouble. It had thousands of parts and one of the broke, the client had to phone the company then the dispatch service would disassemble, reassemble, and recalibrate the entire device in order to incorporate the new part.

Top view of the Monroe PC-1421. Credit: Kevin Twomey

While they’re not useful at all nowadays, I found these machines extremely beautiful in their intricacy.

“It’s kind of a holy grail machine for me,” says Glusker, a mechanical engineer and collector of early calculators (including the PC-1421). “When you’d read the specifications, you’d think, ‘That’s just crazy.’”

Credit: Kevin Twomey

These photos of the PC-1421 along other models in Glusker’s collection were taken by Kevin Twomey, a commercial and fine arts photographer. Twomey took multiple pictures of each calculator using varying focuses and lighting techniques, then melded those images together into a composite to make sure every interconnected part was in high resolution detail.

“These chains, levers, and gears were almost reminding me of how ligaments and joints are working together,” says Twomey.

Credit: Kevin Twomey

Credit: Kevin Twomey

Credit: Kevin Twomey

Credit: Kevin Twomey

Credit: Kevin Twomey

Credit: Kevin Twomey

Credit: Kevin Twomey

Credit: Kevin Twomey

Credit: Kevin Twomey

Credit: Kevin Twomey

Credit: Kevin Twomey

If you thought these mechanical calculators are amazing, wait till you hear about this 240-old beautiful ancestor of the modern computer. [story via Science Friday]