A flat tire can be very inconvenient, especially at high speeds. It also increases the risk of vehicle accidents and reduces driving stability.
A new tyre can eliminate these problems and bring significant changes to the automotive industry. It is based on intelligent materials and structures, which can perceive changes in the environment and internal conditions.
Airless Titanium Tires
We’ve all been there: you’re enjoying a ride when your tire pressure light starts flashing orange. You inspect the flat and find that a punctured nail has caused one of your tires to lose air. Luckily, there may be a solution—a non-pneumatic, nearly indestructible tire that’s flexible like rubber. Developed by NASA and adapted for terrestrial use by the SMART Tire Company, these “space age” tires are powered by an inner skeleton made from a modern material called Nitinol, a shape memory alloy. The lightweight, highly flexible ‘superelastic’ metal stretches like rubber and will always instantly snap back into its original shape, which helps to provide a smooth ride.
While major tire companies have largely given up on airless applications, the SMART Tire Company is working to adapt this technology for bike use. They’re working with Felt Bikes and anticipate their first METL tire for bikes will be available in 2022.
While METL’s radial construction is a step in the right direction, it’ll be difficult to implement this technology on ultra-skinny race bikes—as the company freely admits. Instead, it’s likely that the METL tires will work best on gravel, mountain, or commuter bicycles where preserving every ounce of weight isn’t as important. Those who are interested in trying out these tires can do so through the company’s Kickstarter campaign, where pledges start at $500.
Nitinol Tires
Developed by NASA to help their space vehicles traverse the rough, extraterrestrial terrain of Mars, these tires are airless, durable and will never go flat. Designed to absorb road bumps, they are made of a phase-changing alloy called Nitinol that’s elastic like rubber yet strong as titanium.
A form of nickel-titanium, nitinol is known for its ability to endure large deformations and then instantly return to its original shape. It’s also used to make ultra-tough eyeglass frames and flexible stents in heart valves. But it could be a game-changer in tires: nitinol’s superelasticity helps it to bend and deform to absorb bumps, then spring back into its original shape.
The tires are built with a unique polyurethane outer layer that protects the nitinol coil and keeps out debris, while the inside of the tire is made of a flexible polymer to hold the coil in place and reduce friction against the road surface.The team behind the Carlisle TyrFil claim that their flatproof tires are more durable, elastic, and shock-resistant than rubber tires, and will negate the need for regular pressure checks or sealants since they will never flatten.
The nitinol tires are currently only available for bicycles, but the team plans to expand their market to car and truck tires soon. And although they might not be a cure for all flat tires, these innovative wheels offer a glimpse into a future where run-flat technology can be more widely implemented and a time when flat tires will truly be a thing of the past.
Shape Memory Alloy Tires
NASA engineers designed this next-generation non-pneumatic tire for future Mars and lunar rovers, but it could revolutionize the $300B tire industry on Earth too. The NASA-developed technology uses a shape memory alloy that bends and twists like metal, but is as elastic as rubber, so it will never go flat.
The SuperElastic Tire is a NASA Glenn innovation, comprising a non-pneumatic, compliant tire that utilizes shape memory alloys (mainly NiTinol and its derivatives) as load bearing components. These alloys can withstand an order of magnitude more deformation than conventional tires before they experience plastic deformation.
These shear bands are woven into a unique structural pattern that displaces energy optimally for maximum grip and comfort. The structure also eliminates the need for an inner frame, which simplifies and lightens the tire/wheel assembly.
To test their new tires, the NASA team put them to the ultimate test: driving them on simulated Martian terrain. The tires survived the harsh conditions, going over rocky outcroppings and traversing sand dunes. They even handled a payload, which is an important factor when developing tires for rovers and other exploration vehicles.
Taking the technology to the streets, a startup called The SMART Tire Company is working on a bicycle tire that will be coated/encased in a proprietary material and marketed as a durable, eco-friendly pneumatic alternative to traditional rubber bikes. The airless tires are puncture-resistant and will last the life of the bike without needing air pumps or sealants.
Non-Pneumatic Tyres
Although they do not require air, non-pneumatic tires must still be able to withstand significant forces and impacts. To this end, engineers are working to make them more robust and dependable by optimising their structures. One of the key aspects they must address is vibration.
In addition, they need to ensure that the tyres can withstand the load without suffering damage from shear forces. To achieve this, they are using intelligent materials and structures, which are composite systems that can perceive changes in the external and internal environment. They can then identify and infer information, make reasonable decisions, and drive the responses of the structures.
Specifically, the researchers are using piezoelectric intelligent materials, which can generate electric currents by converting vibration into electricity. These electric currents create a counter-vibration to the initial one, thereby reducing vibration amplitude and improving stability and manoeuvrability.
Another area in which researchers are exploring is the use of metamaterials. These are artificial composites that have extraordinary physical properties that natural materials cannot possess. For instance, they can reshape themselves under stress to prevent the buckling of the tyre shear band.
Non-pneumatic tires are a promising new technology, but it will be some time before they become mainstream. Even so, they have great potential to improve driving safety and comfort. For example, they can eliminate annoying punctures and allow drivers to travel over difficult terrain without worrying about damaging their tyres.
