A nautilus gear is an odd shaped non-circular gear that follows a logarithmic spiral.

Nautilus gears only work in pairs where both gears are the same size, this results in a 1:1 gear ratio but the delivery of this ratio is quite unusual. If you rotate the driver gear at a constant speed, the driven gear will rotate at a constantly varying speed.

One of the uses of the nautilus gear is on oil and gas pumps where a long throw of the piston needs to be finished with a final high-pressure slow purge at the top of the valve.

The nautilus gear gets its name from Nautilus, which is a marine mollusc. The Nautilus lives in a beautiful spiralled shell divided into increasingly larger chambers. When it first hatches from the egg, it has 4 chambers already formed. As it grows, it moves into the next largest space in the shell and builds a wall to seal off the old chamber. The shell of nautilus is a symbol of proportional perfection. It is also the perfect paradox – having survived relatively unchanged for millions of years, the Nautilus Shell is, oddly enough, a symbol for expansion and renewal as it grows increasingly larger chambers throughout its life.  

It is also considered as a symbol of strength since this shell can withstand very high pressure. This is why the Nautilus is the only shell that managed to survive past the dinosaur era—the exact reason why it is often referred to as a ‘living fossil.’

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