Hub Brake Keeps Skaters in Control

Once considered cutting edge, inline skating is now mainstream with more than 24 million people taking part, says the National Sporting Goods Association. However, many others might be turning away from the sport because of the inherent lack of control, especially speed control and stopping in traffic or on steep downhills. That's the feeling of Robert Brandriff, president of Concept Sports LLC, whose patented SmartWheels brake system allows eased braking by using a "snowplow" type maneuver or by flexing the ankles outward.

Traditional heel brake pads require balancing on one skate while the other leg is extended to contact the pad with the road. This maneuver is problematic when water or sand is present. Other techniques, all external to the wheels, involve cables, hand grips, etc., which affect balance when trying to activate.

The SmartWheel houses a disk brake module in its hub consisting of six alternating rotating and stationary alloy steel disks interleaved with Kevlar-backed nitrile pads mounted on the stationary inner hub (see figure). A keyed sleeve retains the brake module within the wheel bearings on both sides of the skate wheel. An elastomer ring provides a threshold for brake actuation.

When a skater pushes (as in a snowplow), so that force acts on the wheel rim from the outside of the boot inward, the pads are compressed, with friction-induced braking torque proportional to the side load. The brake can be installed on most inline skate brands.

While the SmartWheel concept sounds simple, especially regarding actuation with tactile ice-skating-like movements easily learned, Brandriff says a major hurdle to be overcome was the "absence of workable space within the wheel hub to dissipate heat." The first attempts tried to use a single wheel on each skate for braking-but the heat generated was too intense. The solution was to limit the brake torque per wheel and use three wheels out of four on a skate for braking. This spread the heat dissipation and allowed brake force to be more easily modulated. The front wheel on a skate is not braked for control reasons because, "If a skater falls forward, you don't want the skate to stop or have one wheel lock and form a flat spot," Brandriff adds.

The brake design underwent "quite a bit of material iteration," according to Brandriff. "We started with precise alloy steel disks but the nitrile/Kevlar pads were not accurate in thickness. Now we pre-burn-in a brake stack to burnish the pads to known dimensions to get rid of inconsistencies," he says.

The inner brake shaft has about 3-5 thousandths of an inch "slop," relative to the wheel, which it must move through before braking occurs. Brandriff notes that if this gap was tightened, it would be easier to assemble the wheels, but the clearance is enough to keep most dirt from accumulating in the mechanism, and is thus allowed.

While not everyone will want to roller blade on the SmartWheels, the idea may find use in materials handling equipment.

Contact Robert C. Brandriff, Concept Sports, LLC, 22 Dewey Ave. #3, Warwick, RI 02886; Tel: (401) 736-9071; Fax: (401) 736-9076; E-mail: [email protected]; or Enter 554; www.smartwheelsinline.com.