WHAT MAKES US BETTER
Most roller skis are made from a metal extrusion that is fabricated in such a manner that you can mount roller ski wheels. When not equipped with pneumatic tires or shock absorbing wheel forks, aluminum shaft roller skis can be uncomfortable, especially when skiing on poor pavement. For skis with solid rubber wheels, the vibration damping is mainly a function of the shaft construction and the design of the wheel forks. For roller skis that have larger pneumatic tires, the primary vibration damping is the air in the tire, so there is no need to use the composite shafts and composite wheel forks.
HISTORY OF V2 COMPOSITE SHAFTS
COMPOSITE FIBERS: Over the last twenty years we have tested most of the commercially available synthetic fibers, including the many variants of Carbon, S glass, E glass and Aramid. All of these fibers have strengths and weaknesses. Aramid fibers have high tensile strength, dampen vibration and are extremely abrasion resistant. But Kevlar™ (Aramid) is very weak in compression. Carbon is extremely stiff and strong in both tension and compression, but breaks very easily from impact, which is why so many Carbon ski poles break in sprint races and mass start races. Carbon is a great material, but to prevent impact failure Carbon fiber shafts need a core with good energy absorbing properties, and to endure the carbon should be combined with other impact resistant fibers.
THE CORE: The core material is the foundation of a roller ski shaft and we have tried about every material available, including a variety of metal cores. We have used organic cores like Baltic birch, Italian poplar, balsa and many synthetic cellular cores. We know from extensive experience that for roller skis, cellular cores are superior to vibration damping metal cores. The new XLC uses the best core we have tested to date. The only drawback with the core is that it is time consuming and expensive to make.
BONDING: Composite structures need a very strong bond to both the fibers and the core. Bonding high strength fibers to a metal core can be more difficult than bonding to a porous cellular core. The metal must be aggressively etched for the fibers to bond properly. The cellular core we use has thousands of microscopic pores per square centimeter and the epoxy penetrates and bonds extremely well. The epoxy that binds the fibers to themselves and to the core has a tensile strength about 3X greater than good conventional epoxies. The epoxy we use is the strongest commercially available.
XLC and XLA WHEEL FORKS AND WHEELS
The XLC/XLA wheel forks with fenders are produced in DuPont’s™ toughest thermoplastic and strengthened with the addition of short carbon fibers. The non-metallic wheel forks also help in reducing vibration, and for improved safety all V2 skis accept the patented speed reducers and brakes. The XLC / XLA skate is available in four (4) different speeds: fast, medium, medium-slow and slow. The XLC/XLA classic ski is available in 3 speeds: medium-fast, medium and slow The weight of an XLC98M skate ski is only 1620 grams a pair and the aluminum XLA98M 1850 grams. The classic XLC900 weigh just 1725 grams and the aluminum XLA900 1890 grams.
ALUMINUM SHAFT SKIS
The aluminum shafts are made in 6061 T6 and are produced by an extremely competent US extruder. When working at our previous company we designed many aluminum products used in military aerospace applications. The supplier we use for V2 aluminum shafts was the only extrusion company that met the stringent requirements of one of the primary military contractors.
ALUMINUM WHEEL FORKS FOR XL AERO AND XLC / XLA 9848
All V2 forks are made in a monolithic U shape, which makes them stronger than individual left and right forks mounted to the shaft. On the 150mm XL Aero aluminum skis the forks are welded to the shaft, which is one of the strongest methods of securing aluminum to aluminum. U shaped forks are designed to protect the shaft. On V2 skis that have been used by novice skiers, who have not yet learned how to ski properly, we see a lot of damaged wheel forks.
Most of us are not anatomically balanced, so even though the wheels and bindings are perfectly aligned, the ski might pull in one direction. Few roller ski manufacturers provide a method for wheel alignment and some suggest that you to bend the wheel fork if the ski pulls to the right or left. Bending is not very precise and can weaken the forks. On the XL150S, 150SC and XLC/XLA 9848 we use a unique wheel alignment device. Draw a pencil line along the side of the alignment lever, loosen the nut slightly and if the ski pulls to the right move the lever forward and if the ski pulls to the left move the lever backward. It’s simple and it works. On the XLA and XLC that use the composite wheel forks one bolt hole is oblong while the other hole is round with a very snug fit. If the ski tracks to the right loosen the nut on the bolt just enough so you can move the bolt forward. If the ski tracks to the left move the bolt backward.
DUAL DENSITY RUBBER WHEELS
In June of 2018 we received the first dual density wheels for the XLC/XLA 9848. For skis with solid rubber wheels a soft wheel is much smoother, especially on rough pavement or dirt roads. One of my favorite wheels many years ago was very soft. But being so soft the wheel wore down in less than 20 hours. The new 9848DD has about 3mm of 80-shore hard rubber over much softer rubber that makes the wheel absorb vibration better. We applied a load of 75 pounds (330Newton) in a press to a standard 9848 wheel and a 9848DD wheel to measure deflection. There is a lot more give in the dual density wheel, which makes for a smoother ride.
ROLLING RESISTANCE OF WHEELS AND KINEMATIC DAMPING
The rolling resistance of tires is a function of the amount of energy the tire absorbs. Bearings have minimal influence on the rolling speed of a wheel. A fast tire absorbs very little energy and uses a “high rebound” material. A slow tire absorbs a lot of energy and the tire can become very hot. On a warm sunny day, when the pavement is much hotter than the air temperature, a very slow rubber compound will wear rapidly and can actually disintegrate like truck tires do on the highway on a hot day. V2 roller skis do not use low rebound rubber. To slow the wheels we use a patented system based on kinematic damping. On the W98RS, the slow wheel on the XLC/XLA98S skate ski, we use the same rubber composition as on the W98RM, but slow the wheel with a recently patent- approved, lightweight (10 gram) internal kinematic speed reducer called the ISR. The ISR is exactly the size of a 22 mm bearing, and on the slow wheels we simply increase the depth of the bearing bore to accept both the ISR and the bearing. This system increases the rolling resistance by about 15 -20 %. The heat generated by the ISR is dissipated through the aluminum bearing tube and the bolt.
If you spin a wheel with your hand on an in-line skate or roller ski with bearings that are lubricated with lightweight oil, and the bearings do not have contact seals, the wheel can spin for several minutes. Contact sealed bearings with grease lubrication will stop in less than five seconds. The conclusion that most people reach is that the free spinning bearings will make the roller skis a lot faster. This is an incorrect assumption. In order to accurately test the rolling resistance of the wheel, the wheel must be under similar load as when the roller ski is being used. We have developed a sophisticated test machine that accurately measures the rolling resistance of wheels under load. The wheels are driven at a constant speed of 30 kilometers per hour. The machine works just like the cruise control on a car. As you encounter a hill more gas is supplied to the engine to maintain the speed. Our engine is a precise electric motor and we measure the current required to keep the wheel speed at 30 kilometers per hour. The energy required to maintain the speed is measured to 1/1000 of an ampere so the test machine is extremely accurate. We have found that, under load, the non-sealed oil lubricated bearings are only about 2.0% faster than permanently sealed greased bearings.
SPEED REDUCERS AND BRAKES
V2 roller skis have become world famous for the patented speed reducers. Over the years the concept has been modified and improved numerous times. The latest generation speed reducers for the Aero XL150 skis work so well that you can ski in almost any terrain. At first, top ski racers felt that the use of speed reducers and brakes was only for “sissies”. Not any more. Many of the world’s best skiers are now using speed reducers and several we know use both brakes and speed reducers.
Our first brake, introduced in the mid 90’s, was not an elegant solution. In 2005 we developed a simple, better brake that really works. In 2007 we introduced an improved version for all XL model skis. By mounting the brake to the wheel fork we were able to eliminate several parts and make the system both stronger and lighter than the Universal brake unit. (The US Patent Office granted the Patent for our brake system in 2010.) For 2020 we have introduced a new improved brake arm and leg yoke. (See the Brake section)
AERO ROLLER SKIS
In the summer of 1999 we introduced the first reliable pneumatic tire roller skis. We dubbed them the Aero. The Aero roller skis have been sold to over thirty countries and over the years we have made many improvements. With the Aero you can roller ski on both paved and non-paved roads. Since the Aero will roll over objects and cracks in the pavement that stop other roller skis, most skiers consider the V2 Aero safer than any other roller ski. Many users have told us they spend a lot more time roller skiing on the Aero than they do skiing on snow and many have also told us that without the security of the Aero equipped with brakes and speed reducers they would not roller ski.
V2 HAS ROLLER SKIS FOR ALL SURFACES
The 2020 XLC are the best solid rubber roller skis for paved surfaces you can buy. For dirt roads and rough pavement nothing can beat the V2-Aero pneumatic tire skis or the XLC9848 with dual density wheels. With the patented brakes and speed reducers you can now roller ski just about anywhere.