They have a knack for sneaking into our homes via newspapers, bundles of mail, and cut flowers, and then multiply like rabbits in the drawers. The flimsy-looking rubber bands don’t have the same operational value as some of the other household stationary like duct tape. Yet the physics-defying knick-knacks are an easy fix to some exasperating troubles and the simplest means to bear-hug anything you want held together as a group.
The bands are made of rubber, which is one of those ingenious hacks that was in use even several thousand years ago in everything from sandals to jewellery. It wasn’t called rubber until several centuries later when famed British chemist Joseph Priestley (who also discovered oxygen) accidentally realised that this material could erase pencil marks on paper.
Thomas Hancock then began mass-producing rubber and turned it into a commercial product by 1819. The following year, Thomas Hancock patented rubber springs for various types of clothing. He commercialised rubber by inventing the rubber masticator, which was a machine that had revolving teeth to tear up rubber scraps. These shredded bits adhered into a solid mass that could then be pressed into blocks or rolled into sheets.
However, things made from rubber back then weren’t durable and had a tendency to melt in warmer weather. It wasn’t until 1839 that Charles Goodyear discovered the vulcanisation process by heating a rubber and sulphur mixture to end up with a material that was elastic and strong. He patented the process in the US in 1844. But when he applied for a patent here in the UK, it was challenged by Hancock who had patented a similar method a year earlier in 1843. After a tedious court battle, Hancock came out on top.
We have Stephen Perry to thank for the modern-day rubber band. In 1845, Perry began slicing the vulcanised rubber tube into elastic bands. However they weren’t mass-produced until 1923 when William Spencer cut bands from discarded rubber products to wrap newspapers to prevent them from blowing across his lawns. Soon after, standards for rubber bands were defined in the United States in 1925, which governed things like the tensile strength and elongation of the bands.
Throughout history, two types of rubber have been used to manufacture rubber bands: natural rubber or latex from rubber trees, and synthetic rubber. A majority of the rubber these days comes from crude oil. In general, to make synthetic rubber, by-products of the petroleum refining process called butadiene and styrene are combined in a reactor containing soap-suds. This creates a milky-looking liquid latex, which is coagulated into lumps that can be melted down and used.
Modern-day rubber bands are created by extruding this rubber into long tubes of varying thickness and diameter. These elastic tubes are then sliced into the circular bands that we’re all familiar with.
Rubber Band Heat Engine
Project Maker: Adam Micolich
Who better to demonstrate the thermodynamic properties of rubber bands than a physics professor? In a superb video, Adam Micolich, an Associate Professor in the School of Physics at the University of New South Wales, Sydney, builds a rubber band-powered heat engine to convert heat energy into mechanical motion.
You’ll need a bike rim and bolt cutters to cut through a small section of the aluminium spokes. Bend both of the ends of the remaining spoke into hooks and stretch a rubber band between them. Do this for all the spokes. You’ll then have to rebalance the wheel so that the centre of mass is at the axle. Adam found this to be the most frustrating part of the project: “The worst part is, because the bands are a bit flexible, the centre of mass wanders a bit, so when you think you have the wheel true, a small shift means it might not be.” Once the wheel is balanced, he places a lamp close to the rubber bands and after a while the wheel starts to turn.
When heated by a hot lamp, rubber bands, unlike metals, will contract and become smaller. As they contract, the centre of mass will shift towards the outer rim of the wheel, which makes it unbalanced. This causes the weight to shift and the wheel begins to spin. And this is how the heat energy from the lamp is converted into mechanical motion.
Rubber Band-Cooled Refrigerator
There’s another thermodynamic property of rubber bands that Ben Krasnow harnessed to build a refrigerator. Ben works at Google’s Verily Life Sciences research labs and hosts the Applied Science channel over at YouTube.
Ben noticed that rubber bands get hot when stretched and cool when released. This seems to defy the second law of thermodynamics that states that things, like gases, should get hotter when compressed. As Ben explains in this video, it’s the rubber band’s molecular structure that’s responsible for this strange behaviour.
He put this property to use by fabricating a refrigerator with a wheel that stretches rubber bands outside the fridge and releases them inside. He uses a couple of fans to transfer the thermal energy from the bands and circulate inside the fridge.
Ben models his parts in SolidWorks and then cuts them with a hand-held CNC router. He cranks the wheel for five minutes and uses a thermal camera to show that the air inside the fridge does cool by a couple of degrees. Again, like Adam’s heat engine, the rubber bands aren’t efficient enough to replace the traditional refrigerant, but Ben’s fridge is a nice demonstration of the rubber band’s thermodynamic properties.
Rubber Band Gatling Gun
Project Maker: Mark Stevenson
Tired of shooting your pals with rubber bands from your fingers? With a weekend and some very detailed instructions from Mark Stevenson, you can build and assemble a hand-held Gatling gun which will help you dominate any crucial rubber band duel. Instead of using CNC machines or laser cutters, Mark cut out the gun using a drill and a jigsaw to make the project more accessible.
He has also published all the templates, in PDF format, for the four main components, along with videos to help you fashion them with relative ease. Once you have crafted your gun, you can load over a hundred rubber bands in its barrels and unload them as fast or as slow as you want. Be merciless.
Rubber Band Helicopters
Project Maker: Lance Akiyama
Lance Akiyama loves to demonstrate science concepts to kids with hands-on engineering projects. One of the easiest to replicate is the rubber band helicopter. All you need is a plastic propeller that you attach to a craft stick. Bend and attach a paper clip on the other end and stretch a couple of rubber bands between the two ends.
The most crucial bit is the piece of paper cut-out that helps create lateral drag. When you wind the rubber bands and release the helicopter, instead of all the energy travelling down and spinning the craft stick, a majority is diverted towards the propeller and the helicopter takes flight.
Every time Lance teaches the project to kids, someone’s helicopter would inevitably land on the roof and they’d feel both distress and pride: “I like to believe that experiences like that are what they think back on when they’re thinking of a time they needed to show some grit” says Lance.