By Greg Sitek
A major technical development, by Michelin, takes the air out of tires, improves safety, wear, traction and does it without maintenance…
What’s a Tweel? That was exactly what I said the first time I encountered a video of a car riding on Tweels around 6 years ago. I did a double take and watched the video for a second and third time. I don’t know if this is the same one but it’s close enough. If you’d like to see what I saw,
After watching the video I had to contact Michelin and find out when it would be coming out and when could I see it and when could I get pictures. You get the picture. I wanted to see the Tweel. I literally bugged the Michelin marketing and PR people and finally, at a recent trade show they said it would be out late 2012.
To answer the question, the Tweel is a revolutionary new tire design developed by Michelin. It is airless and has no sidewalls so it can’t go flat or have a blowout. The Tweel’s hub connects to flexible polyurethane spokes that are used to support an outer rim and assume the shock-absorbing role of a traditional tire’s pneumatic properties.
Tires have always played a major roll (pun intended) in our world of motion. Everything that moves, moves on wheels and for the most part they are tired wheels. In construction they can put serious dent in the bottom line because of the costs involves. Tires demand maintenance but Tweels don’t. Tires on a skid steer loader wear quickly because of the machine’s skid-steer design so Michelin’s using the skid steer loader for the first commercially available Tweels will prove the validity of the design – how about three to five times the wear life?
Mary Ann Kotlarich, commercial public relations director, Michelin North America arranged for me to talk to Tim Fulton, vice president, Tweel Technologies and
Jack Olney, key account manager/business segment manager, Tweel Technologies about the Tweel, its development and Michelin’s plans for its future. We started our discussion by taking a quick trip to http://www.michelintweel.com .
Fulton says, “Tweel is a single simple bolt-on assembly that replaces the traditional tire-wheel assembly, which includes the tire, rim, wheel valve stem and anything that needs to be included in that assembly. Tweel has all the advantages of an air-filled tire without having air in it.”
In explaining how the design concept came into existence Fulton notes, “ Our engineers were asked to identify the characteristics that made the air-filled tire the dominant technology on the planet and they came back with four things. One of them is low contact pressure, which makes tough soil mobility road paving possible. The next thing is low vertical stiffness, which reduces the shock to the machine and the operator. Third low rolling resistance over rough surfaces. Solid tires or wagon wheels, for example, loose all their energy on the backside of the obstacle and have to rely on the engine to overcome the resistance. An air filled tire absorbs the energy and gives it back on the other side. The other thing is that an air filled tire has minimal or low mass for the load that it carries.
“ Air filled tires have been the dominant technology for well over a 100 years. Radial ply tires have been the emerging technology taking the place of bias ply tires for the last 65 years.
“At the same time they were asked to define the characteristics of an air-filled tire that made it the dominate technology they were asked to design something that had the same characteristics without air. What they came up with is the Tweel that we have today.”
Fulton defines the developmental timeline, “they started with prototypes in the late 90s; patents began to be issued on various aspects of it in 1999, 2000 and 2003 and in 2005 the invention reached maturity and it was publicized around the world, on the cover of Time Magazine and at the various auto shows. The company was ready to introduce the skid steer models but, as you know, the world economy collapsed. At that time the company didn’t feel it was in the position to make the commitment that was required to launch a totally new technology into a very large and mature tire industry.”
Olney and Fulton point out the fact that in 1946 Michelin introduced the radial tire and that it is still an emerging technology. For years cars were not design-optimized to take advantage, the radial advantage. Construction equipment was even less optimized for the radial advantage. The change required a massive investment on the part of tire manufacturers as well as the vehicle manufacturers.
The Tweel, like the radial tire, offers manufactures the opportunity to redesign to optimize the contact with the ground. “If you look at your car,” Fulton explains, “there are four patches, the size of your palm, that make contact with the ground. It’s those four patches that make your car a useful device. Without those four patches it would be pretty useless. Those four patches are connected through a vey complex system the suspension the braking, steering dynamics can all be re-engineered with different degrees of freedom with Tweel technology.”
Q. Does Tweel technology give you a bigger on the ground footprint than radial or bias-ply technology?
A. Fulton responds,” Tweel technology gives us the ability to optimize that contact patch beyond what we’re able to do with Radial technology. That’s one of the things we see in the skid steer application. We’re able to give a very nice contact patch on the ground that delivers a level of performance that’s magical for the operator; it give them the precision, the ride comfort that’s beyond what they can get with another product.”
Fulton adds, “The Tweel is designed to operate as if it had air in it, so the contact pressure and ride would feel just like you had air in the tire. You have a similar ride comfort where as the improvement is in the stability of the machine. Air in a tire, especially under the torque experienced in skid steer, has a propensity to create torque and give the energy back and the air-filled tires will hop around a little bit.”
Continuing Fulton says, “with the air-filled tire when you put torque on it the air builds up energy on the tire that is experiencing the most torque transfer that energy want to be retuned to the other side of the machine. An air-filled tire is just like a balloon in that it wants to give the energy right back once compressed. With Tweel technology it uses the
Polyurethane spokes to absorb the energy and then give it back in a very different way, which allows the machine to be stable. It can turn where it sits without hopping; the stability improvers the operator’s productivity.
Q. How does wear on the Tweel compare to a bias-ply tire and a radial tire?
A. “Against a bias-ply tire,” Fulton responds, “ it’s two to three times the wear because of the optimized footprint. There is a lot of squirm connected with bias-ply construction with a lot of movement in the contact patch and as a result of the movement you have wear that you didn’t need. We try to eliminate that moment and we do some of that with radial technology and we do it in an optimal way with Tweel technology with the wear begin as low as it can be for that 30 seconds of turning so the wear is much less than it is with a bias-ply tier.”
Back to the invention of the Tweel
Bearing in mind the four characteristics that make air-filled tires the dominant technology the Michelin engineers came up with a tire that mimics these four characteristics without air and with out having the inherent risks associated with either or high low air pressure or rapid air loss. “You don’t have instantaneous failure mode with a Tweel that you would have with a tire that low on air an all of sudden quits and is done,” Fulton elaborates. “With a Tweel damage will be progressive and not spontaneous, no blowouts or sidewall failures.”
The Twell’s construction starts with what is called a “shear band” which is a series of rubber and steel layers with the rubber being laid at a 90-degree angle in the direction of the Tweel’s rotation (See cutaway illustration). Fulton explains, “there’s a protector ply, a layer of steel, another layer of rubber, another layer of steel; these work very much like an I-beam with two pieces of parallel steel having a third piece welded in between, which gives it its strength. The shear band works very much the same way. Basically what we’ve done is replaced the welded steel in the center of the I-beam with rubber. It’s the layering of the steel and rubber that gives it its strength and creates our shear band or beam, the outer ring on which we place a tread, which is very much like the tread on our skid steer loader tires (30.5/32 tread rubber)
“During the manufacturing process we integrate the hub assembly, which is a standard universal 8-hole heavy-gauge steel hub and integrate that with the polyurethane spokes. When we’re done we have one-piece that can be delivered to the jobsite, dealer or customer where it can simply be bolted onto the machine. It doesn’t require any filling, balancing, valves or anything like that.”
The polyurethane spokes are replicating the characteristics of a suspension bridge. Fulton continues to explain, “as you’re rotating the skid steer Twee through its cycle the polyurethane spokes allow it to disburse the forces all the way around the tire radially much the same way air does in an air-filled tire. The engineers who designed the tire say you implicate the entire structure via the use of the connecting polyurethane members.”
Fulton describes the polyurethane spokes, “This is not the same kind of polyurethane you normally see, it’s structural polyurethane. When you look at these you’ll notice that there are very many of them. This is by design. They’re very strong, they don’t break easily, and well actually they don’t break at all. They last the life of the Tweel. In fact we have tried to damage and destroy them even by throwing a hand grenade under them, which we did for the military and still didn’t destroy them. You can damage quite a few spokes before you impact the function of the Tweel. There is a lot of redundancy designed into them.”
To see just how functional the Tweel is take a few seconds and watch the video:
Onley points out, “Some people look at the Tweel and think of the solid tires that have apertures through them that are just holes. The important difference between the Tweel and other tires that don’t have air in them is every one of those carries the load from the hub to the contact patch and are called bottom loaders. As a result, they get very high contact pressure, which results in poor traction and not a very good footprint.
“What the Tweel does is act like a bicycle tire or radial tire in that it’s pulling the spokes downward and from the outside of the structure to implicate the shear band, which is a semi-rigid product. It pulls on all of those and hangs the load from the top and creates a large footprint. It’s a top loader just like an air-filled tire. The hub wants to send the load to the ground with a load on it but the polyurethane spokes when put under tension don’t allow that to happen. At the same time they put a spring force around the outside of the shear band, which deforms the shear band slightly and creates our footprint, which ends up being a very low contact pressure footprint providing good traction and mobility.”
Skid steer market
“Skid steer manufacturers equip the machine with air-filled tires and when they reach the jobsite operators start experiencing flats and costly downtime,” Olney says. “So many users have gone out and replaced their air-filled tiers with tracks, solid tires or have foam-filled them. In each instance they’ve taken the suspension off the machine completely, they’ve reduced their contact pressure and the efficiency of their machine, and put a lot more weight on the end of that wheel assembly than needs to go there.
“If you look at the list of options available for skid steers,” Olney notes, “it’s obvious that skid steer users are looking for a solution so they don’t have to cope with the downtime. We think the value proposition for the customer is that they can arrive at the job and not have to worry about downtime or be concerned about having tire problems.”
The customer value proposition with the Tweel is obvious in that the user no longer has to be concerned about downtime due to a loss of tire pressure or other tire related problems. The other fact is that because of the footprint it is very good on wear compared to a bias ply tire and foam-filled or solid tires. From san operator standpoint, safety is improved, as is productivity.
Michelin ride and drive demonstrations confirmed the validity of the Tweel concept. End-users, after seeing and the differences between the machines on semi-solid tires vs. the Tweel weren’t interested in operating the semi-sold equipped skid steers. The bottom line is that once the Tweel in installed it requires no maintenance. None. No pressure checks. No sidewall inspections. No balancing. No valve problems. A better ride that is safer. Control that is more positive. Improved wear life. Improved saferty.
Michelin is now distributing the MICHELIN® X-TWEEL™ SSL, a non-pneumatic mobility solution for skid steer loaders in the landscaping, construction, contracting, refuse/recycling and agricultural industries.
The MICHELIN 12N16.5 X-Tweel SSL hub design is universal and can be fitted on most skid steer loaders. It is available in the U.S. and Canada as a no compromise solution for skid steer owners.
Introduced by Michelin in 2005, the Tweel (a tire and wheel assembly) is a single unit replacing the current tire, wheel and valve assembly. It replaces the 23 components of a typical radial tire and is comprised of a rigid hub, connected to a shear band by means of flexible, deformable polyurethane spokes and a tread band, all functioning as a single unit.
“This is a very exciting time for Michelin,” said Tim Fulton, head of Michelin Tweel Technologies. “Michelin captured the fascination of the world with the concept of the Tweel; now landscapers, contractors and other skid steer loader operators will have the opportunity to use this innovative technology in their everyday businesses and experience the advantages first-hand.”
Skid steer loaders with pneumatic tires typically experience several flat tires per month. To reduce downtime from flats, many users fill their pneumatic tires with foam or replace them with solid tires, resulting in machines with inadequate traction, handling and ride comfort.
The MICHELIN® X-TWEEL™ SSL solves this problem by delivering no maintenance, no downtime and no compromise. The TWEEL provides the advantages of no maintenance of air pressure, easy mounting, damage resistance, increased operator comfort, reduced operator fatigue, improved productivity, longer wear life than pneumatic tires, and excellent traction. The Tweel has years of field testing in the most demanding work site environments.
To learn more about the MICHELIN Skid Steer Tweel, visit www.michelintweel.com. (Insert Tweel Promo QR Code)