As engineers, we tend to get excited about little things in life that are often taken for granted, like how an internal combustion engine works or how the buttons are manufactured on a TV remote. When playing with robotic bug toys, we can’t help but take them apart to see how they work. To help inspire some appreciation for the mechanical things in our everyday lives, we’d like to share 5 awesome mechanisms that you use without even realizing it. Plus, we’ve got animations!
One of the most iconic noises when watching a movie in a theater is the rhythmic whirring and clicking of the film projector. You have the Geneva Drive to thank for that. According to Wikipedia, the Geneva Drive “translates continuous rotation into an intermittent rotary motion.” It is composed of two wheels, one with a pin, and one with evenly spaced slots. The wheel with a pin is driven by a motor, and as it spins, the pin enters and exits the slots, creating intermittent rotary motion in the second wheel by advancing it a step at a time.
Film is just a series of still pictures that are shown frame by frame to create the illusion of motion. This means that the images must each be shown for a certain duration of time before showing the next image. Film reels have cutouts in the sides of film strips for just this purpose. The Geneva Drive shows 24 frames per second, advancing each frame at a constant rate.
Geneva Drives are also used for indexing equipment, such as paper bill counters, and in watches, to prevent overwinding.
Four Bar Linkage
While Strandbeests may not be practical, they sure are awesome. The brainchild of Theo Jansen, a Dutch artist, Strandbeests are kinetic sculptures that are self-propelled using wind power. These majestic creatures can be seen crawling across the beaches of the Netherlands. They work by converting the horizontal force of the wind to a walking motion using four bar linkages.
In a four bar linkage, four links are joined together to form a loop. Different paths of motion are created by altering the lengths of the linkages and the combination of which joints are driven and which are constrained. In the case of Strandbeests, many four bar linkages are joined together to emulate a walking gate.
The four bar linkage is used in many mechanical applications because of its ability to replicate interesting motions and create mechanical advantage. The robotic bug toys in the featured image aren’t that different from Strandbeests. And guess what? There’s even a four bar linkage in your knee!
Vroom! Driving down the tollway at 80 mph in your automatic transmission vehicle, it’s easy to take that hard working engine for granted. Did you know that your engine uses planetary gears to change gears? This makes for a smooth transition and great automatic driving experience.
A central sun gear is surrounded by planetary gears, and an outer ring gear captures the planetary system. The gear ratio between the ring and sun gears converts the rotation to the necessary speed, and this motion is transferred to the wheels of the car. So the next time you leave work, just picture this beautiful mechanism rotating around in your engine.
In addition to being an important part of your car engine, planetary gears are also used in mechanical pencil sharpeners and gas turbine engines. Pretty cool stuff, isn’t it?
Have you ever borrowed a friend’s bicycle and needed to change the seat height? In a pinch, you pull a lever back, slide the seat up or down accordingly, then push the lever shut. Wasn’t that easy? No wrenches, no screws, just a simple cam mechanism. Keep an eye out for cams whenever you lock or unlock your windows.
In addition to tightening things with ease, cams are also used to change rotary motion into reciprocal motion. Cams are comprised of a cam shaft, typically an irregularly shaped cylinder, and a follower, that is pushed by the cam shaft to create reciprocal motion. Just like a four bar linkage, cams are great at creating unique motions.
Back in the days before powered pumps, if you needed to move water out of a low-lying body of water, it would need to be carried by hand. Enter the Archimedes screw. With a simple cranking motion, water was easily transferred from the body of water to an irrigation ditch or other location. The Romans used the Archimedes screw to drain water out of mine shafts. The Netherlands uses Archimedes screws to pump water and keep themselves from flooding.
More industrially, injection molding machines use the Archimedes screw to mix and move molten plastic to the mold, allowing us to quickly and cheaply manufacture plastic parts. In short, the Archimedes screw is an incredibly useful application of the screw mechanism.
But you know the most important application? Chocolate fountains. The chocolate has to be pumped to the top somehow!
Hopefully you’ve enjoyed learning about these mechanisms and will keep an eye out for how things work in everyday life. We here at Produktworks definitely find it fascinating! If you’re interested in learning more about mechanisms, check out Five Hundred and Seven Mechanical Movements, a great website that has many animated mechanisms to browse.