Spring-Loaded shock absorbing roller ski ferrule
G5, THE V2 FERRULE THAT REDUCES ELBOW & SHOULDER INJURIES (Patent Pending)
Many skiers have reported injuries, and more frequently aggravation of old injuries, from the shock of the ski pole hitting the pavement. For this reason, some pole companies introduced shock absorbing roller ski ferrules. But skiers told us the carbide tips on the shock absorbing models often broke after a short period of use.
For twenty-five years V2 has had a worldwide reputation for good roller ski ferrules. When we decided to make a shock-absorbing ferrule, we knew from experience that spring loading the carbide tip housing was not the answer. To be durable, the carbide tip must be securely embedded in the plastic housing, and the housing firmly fastened to the ski pole. We decided to use an independent damping system so if it should fail, the carbide tip would still be intact, and the skier would be able to pole home.
Most skiers liked our first damping ferrules. The plunger was nylon with a drive screw for the tip. But many skiers told us that more damping would make the ferrule even better. To me more damping made sense because for a long time I have had serious right shoulder problem. Being active all my life it’s impossible to pinpoint the cause of my sore shoulder but I believe one reason is forty years of roller skiing. More damping required a metal plunger and a stiffer spring. We chose a grade 12/9 bolt, the hardest 4mm available, but with the increased spring pressure against the pavement, the head of the bolt abraded long before the carbide tip wore down.
Why are paved roads so abrasive? Asphalt is a waterproof bitumen that binds sand and crushed stone. The amount of asphalt in newly paved roads and recreational paths is less than 10%, so over 90% of the road material consists of silica particles in sand and crushed stone that are harder than any metal. The tungsten carbide we use in V2 ferrules is hard, but only slightly harder than silica. On the Mohs hardness scale, talc is the softest material with a value of 1 and diamond, the hardest of all known materials, a value of 10. The hardest steel on the Mohs scale is 7, while the silica particles are 8 and the tungsten carbide in V2 ferrules 9. Alumina, Al2O3 is 9, the same as tungsten carbide. Old and chip sealed pavement is more abrasive due to less asphalt and more exposed silica.
G5 FERRULE: To be as durable as the carbide tip, the end of the bolt had to be harder than silica. There is no metal hard enough and tungsten carbide bolts are cost prohibitive for this application. Our solution was to machine a cavity in the head of a stainless-steel bolt and encapsulate a 5mm alumina ball. Al2O3, is as hard as tungsten carbide and has a very low coefficient of friction. The ball shape also lowers sliding friction reducing the abrasive wear from the silica in the road. Durability data on springs showed that the stiffer, smaller diameter springs might fatigue before the carbide tip wore down. For highly stressed springs fatigue life is hard to predict. Some springs can last a long time while others in the same manufacturing lot have a much shorter life span. Because of this unpredictability every pair of G5 ferrules comes with two extra springs.
“After using the ferrules for about 250 kilometers, the spring mechanism is as good as new, no looseness / play noted. I did not need to do any tightening. I can say that the ferrules do a good job of absorbing the shock! You chose a good test subject in that I have some tendonitis on the inner part of my left elbow. So, what I’ve been able to do is to evaluate the amount of soreness after rolling with the spring-loaded ferrules one day to the amount of soreness after using my Swix Triac the next. There has consistently been much less soreness after using the spring ferrules. I also feel that using the shock absorbing ferrules has a positive impact on my technique. I find myself applying more force in my poling. Also, because the spring extends beyond the carbide tip, I find myself coming up higher with my hands and hips, putting my body in a better position for power and balance.” – Dave Johnston (1st place in the 10k freestyle, 2nd in the 15K and 5th in the 30K at the 2019 World Masters Championships)
“We consider V2 ferrules to be hands down the best ferrules on the market. Over the entire duration of the trip, we only broke one tip. The only reason it broke is because I ran straight into it with the roller-ski while it was planted in the ground. We have yet to find another brand of ferrules that matches up to V2’s.” – Santi and Carolyn Ocariz, elite ski racers who used V2 Roller skis and ferrules to roller ski over 5,000 kilometers from South Carolina to San Francisco.