Pneumatic tyres have been around for quite a while and were responsible for an incredible revolution in the tyre industry. Despite the advantages they offer, a major drawback with pneumatic tyres has been their over-reliance on air for their performance and functioning.
It's a fact that pneumatic tyres work best only on specific air pressures and are prone to blowouts and punctures that are very inconvenient, not to mention dangerous at high speeds.
Airless tyres were thus proposed as a concept to design a tyre that retains all the advantages and capabilities of the pneumatic tyre while functioning independently of pneumatics. This prompted tyre manufacturers to set out on a journey to construct the perfect airless tyre that is able to replicate the cushioning and shock absorption of a pneumatic tyre without relying on air.
The Design
We might be generalising here but almost all of the airless tyre designs that have been produced till date are quite similar and follow a common philosophy.
The designs of all the airless tyres use polymer spokes rather than an air-filled interior to absorb shocks. These polymer spokes are then connected to the hub as well as an outer rubber ring which makes up the tread of the tyre.
There are several companies like Michelin, Bridgestone and Sumimoto who have used this design philosophy to make their own prototype airless tyres
The First Airless Tyre: "The Tweel"
In fact, Michelin was the first company to produce a prototype and manufacture an airless tyre that was called "The Tweel". It was one of the first airless tyre designs to be showcased to the world. In fact, it fascinated so many people that Time Magazine named Michelin's Tweel as "one of the most amazing inventions of 2005".
The Tweel used polyurethane spokes with each pair arranged like a wedge that was connected to an inner hub and an outer shear band. The tyre tread was then attached to the shear band for external contact with the road. The polyurethane spokes were the shock absorbers that were used to replicate the effects of air in pneumatic tyres. The inner hub structure could also be engineered in a way so as to absorb shocks by being more flexible.
Also See: What Is A Pneumatic Tyre?
Both the spokes and the shear band could be engineered in different ways to adjust the handling as well as the load-carrying capacity of the tweel and the outside tread was customisable just like those in pneumatic tyres with different patterns for different uses. It was also replaceable.
The tweel was a massive hit across the world. It succeeded in captivating science fanatics and technological firms who somewhere hoped that this signified a new beginning in the tyre industry. It even got NASA's attention, who contacted Michelin to develop a similar airless tyre for their Lunar Rover. As a result of which, the Lunar Rover Scarab's wheels were born.
The world greeted the airless tyres with excitement that was unfamiliar for a tyre but it signified how much an airless tyre meant to every industry. From space application to the military to tyres in wheelchairs, every industry wanted to know more and recognized the airless tyre as the beginning of a new era. It brought forward the massive importance of tyres in the world we live in today and how something so simple could be so revolutionary.
The latest prototype releases in the airless tyre segment have again been from Michelin who showcased their UPTIS design in 2019. The new UPTIS airless tyre has a chevron shape to the spokes and the company is currently testing the product in partnership with GM (General Motors).
Conclusion
Well, there's no doubt that consumer opinion will likely take some time to come around to the idea of airless tyres. Pneumatic tyres have been the norm for over a century, and airless designs are a radical departure from what has been used before. It will likely take significant effort on the part of manufacturers to help customers grow accustomed to the quirks of the new technology. There will be inherent, unforeseen limitations, and the designs need to be suitable to fit existing vehicles.
It's unlikely that these issues are unsolvable. However, to overcome these problems, and to take a new design to the point where it is ready to be attached to any car will take a huge amount of engineering effort. Michelin appears to be leading the field, and have been slowly grinding away on the project since the late 1990s.
