We put up with a lot from our pneumatic tires, from punctures and blowouts, to slashings and the certainty of relatively frequent, inconvenient replacements and giant piles of waste rubber. The current technology seems well overdue for a revolutionary overhaul, if you'll pardon the pun, and yet despite dozens of fascinating attempts to reinvent the wheel, nothing seems to have found traction yet. Boy, I'm on a roll here.
The latest idea to come across our desks, though, makes a compelling business case for itself as well as offering some interesting dynamic capabilities. Meet the Air Suspension Wheel (ASW), from Global Air Cylinder Wheels out of Chandler, Arizona.
Like a regular pneumatic tire, the ASW is air-suspended, but in this case, it's not by an inflated tube. It's a full hub and wheel replacement that separates the outer tread and rim from the hub using a set of eccentrically mounted, pneumatic air cylinders.
These air shocks are tuneable to give you whatever level of tire deflection you choose, from super-firm to softer and squishier than a regular deflated tire can handle. Likewise, you can design in whatever degree of lateral flex suits your application, and even whatever level of torque flex you'd like, which allows the wheel to flex a little on the axle before it turns. This allows it to act as a soft torque coupler and gives a touch more traction in very difficult circumstances before the wheel spins, as well as slightly isolating the drive train from damaging torque forces in the rough stuff.
As far as treads go, the sky's the limit. Treads bolt directly onto the outer rim piece by piece, and there are a bunch of options to choose from, including a range of pre-molded road retread options by companies such as Michelin that bolt on in sections, or a plethora of heavy-duty industrial options that use polyurethane, urethane or steel pieces in a range of different configurations for serious off-road grab.
Large-scale mining applications – where the dollars make the most sense
The company has set its sights on large mining operations to get things moving; a market where time is money, costs can be projected across decades and gigantic, short-run tires for enormous equipment can cost tens of thousands of dollars each.
Take the mammoth Caterpillar 797F Mining Truck (pictured above), which stands more than 25 ft (7.6 m) tall and weighs in at 1,375,000 lb (623,700 kg). Each of the big Cat's six monstrous 59/80R63 tires stands over 13 ft (4 m) tall, weighs about 12,000 lb (5,440 kg) and costs somewhere in the range of US$38,000 each.
Making a bunch of assumptions about usage, you're up for a set of six of these huge hoops a year plus a spare, giving you a 10-year tire budget of around $2.66 million per truck. (These figures are adapted from the ASW company's own comparison spreadsheets, which use rubber tire pricing of $110,000 each from 2009. These tires are now much cheaper according to our research.)
A set of ASW wheels, on the other hand, will cost you more upfront but last something like 13 times longer – out to the service life of the truck itself. Your first set of six wheels in this case will run you about $1.705 million, but over 10 years you'll likely only need two tread replacements at around $55,000 a pop, giving you a 10-year budget of $1.815 million and a $845,000 saving.
Things turn even further in the favor of the ASW system if you factor in punctures, blowouts, tire fires and how long a truck has to be out of service each year while those monster tires get changed. ASW treads are bolt-on, bolt-off chunks that can be changed with very little gear, without even jacking any wheels up, and done in sections during shift changes and lunch breaks so the truck's never out of service due to tires. They can also ship much more cheaply, since the whole assembly can be broken down into bits that easily fit in a regular shipping container.
Not to mention, they're virtually invulnerable to sabotage, as they can't be slashed, and their inner workings are protected both from malicious acts and from mud, dust and water by big metal plate covers. So they can also be made bulletproof for military vehicles.
Smaller applications, like wheelchairs
The Global Air Cylinder Wheels team has also sent us a bunch of video detailing the advantages of a much smaller scale ASW for wheelchairs. Because of the built-in suspension effect, you'd likely experience more ride comfort, as well as a vastly superior ability to negotiate uneven ground without any of the wheels lifting off and losing stability.
The suspension effect also makes it much easier for a wheelchair user to negotiate steep curbs, both nosing down and backing up, as the suspension effect takes much of the steepness out of the exercise.
It's unclear at this point whether you'd lose any forward motion energy due to torque flex, but that can be tuned out of the system if required in any case. It's also unclear how much a pair of wheelchair-sized ASWs would cost at this point. We assume they're not cheap compared to a regular rim and tire setup. Here's some annoyingly infomercial-style video comparing regular wheelchair wheels to an ASW setup over curbs and grassy, uneven terrain.
It does seem clear the Air Suspension Wheel is unlikely to take over as a car tire replacement any time soon. But its unique set of capabilities do seem to offer some compelling advantages in certain applicarions, and we look forward to seeing how things progress.
Source: Global Air Cylinder Wheels
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