When you go for a swim in the pool or the ocean, a pair of flippers can help you move faster though the water.

After a day’s swimming however, they can lead to sore ankles, and their floppiness makes it hard to walk with them on when you step back onto land.

Australian inventor Marc Lee has come up with a solution to both problems: the shinfin™. Instead of attaching to the end of the foot – where they often cause the leg to pivot from the knees and ankles – Marc’s invention is worn around the base of the shins, covering the ankles and spreading over the top of the foot instead of underneath it.

When doing a scissor kick in the shinfin™, your legs act as third class levers. Your muscles provide the effort, your feet pushing against the water create the load, and your hips are the pivot. Because the flippers are at the base of your shin, they place the load at a much stronger point on your leg, reducing the soreness you can get from other kinds of flippers. Even better, because the bending at your knee is reduced, the lever’s “arm” (your legs) is lengthened making it easier to move to the force: you through the water.

Because shinfin™s are worn on your shins instead of under your feet, they’re much easier to walk around in too.

While traditional flippers may flop, there’s no way Marc’s invention is going to!

How do levers make life easier?

When the fulcrum (the pivot point) is in the middle of the lever – like a see-saw, a pair of scissors, or a set of pliers – the lever can either magnify force or magnify distance, depending on which arm is longer! They can also be used to change the direction of a force. These are considered “first-class” levers.
When the load is in the middle, such as in a wheelbarrow, spanners, and doors, the lever can magnify force. The longer the lever arm, the greater the force magnification. Try pushing open a door at a point near the doorknob, then try pushing it from near the hinge. These are “second-class” levers.
When the effort force is in the middle, the lever magnifies movement. When you sweep with a broom, use a pencil or spoon, or swing a cricket bat or golf club you use them like a lever to magnify movement and gain a greater reach. These are all “third-class” levers.

At the Factory’s Lifting with Levers exhibit, you can see just how powerful a lever’s magnifying force is. While your friend holds a rope at one end of a lever, you can try and lift them by tugging on a rope at the other. The further you are from the fulcrum when you pull the rope, the easier it’ll be to lift them off the ground!

Learn more

Want to learn more about levers? You can download background notes from our page of Educational Materials.