Shocker of an idea

April 6, 1998

12 Min Read
Shocker of an idea

Beaverton, OR--Mountain-bike enthusiasts will love it. Design engineers with no mountain-bike experience will appreciate it. The it? An innovative add-on rear-suspension system designed to optimize a mountain-bike rider's power and performance, while offering added speed, control, and comfort.

"Shockster APS is the next significant advance in mountain-bike suspension technology," says Lester Erlston, president of BikeControl(TM), the Oregon firm that pioneered the just-introduced system. He adds: "For retailers, we have a new product for which there is a tremendous built-in demand and excellent profit margin. For consumers, it's a breakthrough solution both in terms of performance and price."

"This design is nothing short of revolutionary, since, prior to its introduction, the prevailing wisdom in the bike industry was that an add-on rear suspension was not achievable," adds Bob Laman, BikeControl's vice president, sales and marketing.

A key to making the system profitable for everyone concerned, according to Erlston, is that "until now, you had to buy a new bike to get full suspension. Our solution is not only affordable, but offers outstanding performance. All you have to do is install it on the mountain bike you already own."

Others seem to agree. After debuting the concept at last fall's Interbike trade show, Bicycle Retailer and Industry News reported that the add-on garnered favorable comments from testers who liked its price and performance. "Shockster rode well under a variety of extreme conditions," Ray Teleng of Insane Cycles, told the trade journal. "Downhill fire roads were no problem. And climbing was a breeze. The overall ride was nice." In addition, Jim Rennie's Sports Letter called the Shockster "the hottest new product at Interbike."

No more pogo. Shockster's simple design addresses the disadvantage of many original-equipment, full-suspension bikes by eliminating the undesirable "pogo" effect (pedal-induced suspension movement common to many full-suspension bikes), while remaining fully active. And it weighs only 2 3/4 lbs.

Shockster mounts onto the rear dropouts and the rear brake bosses of most standard 26-inch-wheel mountain-bikes. However, 100% of the suspension load is borne by the bike's dropouts. The rear wheel and derailleur fit onto the system's dropouts, while the brakes mount on Shockster's cantilever bosses.

But its Shockster's U.S. and foreign patent-pending active pivot system that highlights the design. Not only does the system eliminate the pedal-induced suspension travel, but it allows 3 1/2 inches of fully active vertical movement.

Simply put, Shockster converts a "hardtail" bike (one with front-suspension only) into a full-suspension bike. Thus, a bike owner who already has a hardtail bike, but would like full-suspension, can upgrade it to meet this need at a reasonable cost. Typically, a new full-suspension bike retails for $1,500 and up.

Moreover, the system permits users to tune the suspension to their weight and riding preference. A preload dial with 1 1/2- inch preload at the bottom of the springs makes this possible. In addition, the user has a choice of normal or hard springs from which to select. The springs will accommodate riders who weigh anywhere from 100 to 250 lbs. Changing springs takes only a few minutes.

But what about the price, you ask? The rear-suspension system with coil springs and oil damping retails for $329. And it installs in about 30 minutes.

Mastering materials. As in any design, materials played a major role in making the system come alive. This was especially true in Shockster's case, considering it comes with a one-year warranty and must survive repeated rugged use.

Structural components, which include a U-brace, struts, and wheel dropouts, are made from high-pressure, die-cast aluminum alloy. Carbon-fiber, glass-fiber, and PTFE-filled thermoplastic composite injection moldings are used for the system's pivot points and sliding surfaces.

In considering which parts to produce from plastics and what plastics to use, the main issues revolved around durability, weatherability, low friction, and low wear. The BikeControl project team presented them to LNP Engineering Plastics (Exton, PA) technical personnel to identify the right materials.

For instance, a carbon-fiber reinforcement (Lubricomp(reg) RCL, a PTFE lubricated nylon 6/6) allowed sufficient strength in very small wall sections to reduce weight and create small design features without risk of failure. The material, specified for the system's trunnions, active pivot slots, slider strips, and sliders, gives the components maximum creep resistance, low wear, and low coefficient of friction.

"Lubricomp cut component costs and weight for BikeControl," reports Dan Schultz, LNP technical sales representative. "The material not only offers the parts added strength, but it resists abrasives, such as dirt and sand."

"The lubricity of the material, combined with its strength, allowed us to avoid the need for several extra parts, such as bearings or sliding surfaces, and its low-wear factor indicates the parts will have a long service life," adds BikeControl Design Engineer Michael D. Miles. "These attributes," he explains, "will reduce the need for replacement parts and direct customer support."

Miles cites an example. One of the part shapes involved a slot feature with a flange and wall combination that would ordinarily bow inward due to residual stress from molding. In anticipation of this happening, the part was designed to allow for the expected bow.

"To our surprise," Miles reveals, "carbon-reinforced nylon, because of its rigidity, did not bow. As a result, the feature had to be revised to be compatible with the material's characteristics."

For the Preload Knob (spring tension adjustment knob), BikeControl selected Verton(reg), a chemically coupled, long-glass, fiber-reinforced, heat-stabilized polypropylene. The material had the right toughness, UV stability, and the ability to produce the required surface finish, Miles notes. Other key properties of the material include: high strength, stiffness, and notched Izod impact.

Miles sees more opportunities for weight savings and design optimization through the expanded use of plastics. However, the mountain-biking community, being accustomed metal systems, remains somewhat skeptical of structural bike components made of plastic, he explains. As confidence in the resins and designs grows, Miles feels confident that the use of engineering resins like the LNP materials will become more widespread.

Trials and tribulations. Erlston conceived of the add-on rear suspension system in 1995. Then, over the next two and one-half years, he and Tony Planck, BikeControl vice president of research and development, took the system through numerous design phases, prototyping, and testing. Miles, a private-practice mechanical engineer, joined the team in mid-1997 to finalize the design for tooling and production.

As with any new product, many early design iterations did not work. For example, a parallel linkage system with a single coil spring was prototyped, but then abandoned when it failed to deliver the desired performance.

Once these problems were overcome, the project moved from the bulky functional prototype that proved the operating principle, as well as the preliminary layouts developed by the inventors, to:

- Refining the basic structure that would work best with the preferred fabrication processes (molding and die casting).

- Finalizing a visually appealing design that would attract the target market.

- Encompassing Design for Manufacture and Assembly (DFM/A) principles.

- Reducing overall weight.

- Resolving any last-minute issues to improve system performance and functionality.

Prototyping of the final design began in October 1996. Production operations were finalized in February of this year, with the product hitting the market in March.

CAD considerations. The design team called on CoCreate SolidDesigner (Collins, CA) (v4.52), with utility enhancements and support from Visionary Design Systems (Sunnyvale, CA) (VDS Environment) to finalize the Shockster design. Running on a HP 715/100 workstation with an HCRX-8 graphics card and 160 MB RAM, the system served as a full solids modeling tool for the project. Originally based on the ACIS kernal from Spatial Technologies (Boulder, CO), it comes complete with dynamic pan/zoom/rotate of rendered models.

Models were exported in two forms:

- IGES format as both trimmed parametric surfaces and wireframe.

- STL format for rapid prototyping.

For the most part, the files were sent in Zipped form to fabricators, die makers, and rapid-prototyping bureaus. As a result, the molding and die-casting tools were built using "paperless" data transfer. The tool designers and fabricators used CNC Software (Tolland, CT) MasterCam NC software for this operation. Both the wireframe and surface files gave the tool builders the needed accuracy to design in the complex surfaces for the tools.

The design team employed several modes when it came to producing the prototypes. Selective Laser Sintering (SLS) on a DTM Sinterstation (Austin, TX) was used for some smaller parts to verify the functionality, rigidity, and reduced friction characteristics of the nylon material. Laminated Object Modeling (LOM) (Helisys Inc., Torrance, CA) verified basic part layout, component arrangement, and part appearance.

The fabricator that performed the NC machining of the first structural prototypes had LOM on site. This made it convenient for the shop to see the parts, prototyped from a block of LNP's Lubricomp(reg) RCL, a glass-fiber-reinforced lubricated polyphenylene sulfide (PPS), in solid form during programming and priorto machining.

On the horizon. As is the case with most inventors, BikeControl principals are happy with their results, but know there is always room for improvement. "At present," says Erlston, "we are experiencing no performance problems with the product. Yet, there are certain characteristics inherent in the design that could be greeted with mild skepticism. That's always the case with new, revolutionary products."

Some future refinements might include the use of elastomers as a spring or as a damping unit, or the use of carbon fiber and titanium to produce even lighter-weight, longer-wearing components, according to BikeControl's R&D President Planck. Also under consideration is a downhill version of the rear-suspension system that will increase vertical travel anywhere from five to seven inches. The company also hopes to entice OEM mountain-bike manufacturers to use Shockster in their production models, as well as create other mountain-bike accessories.

"However, we feel that once the consumer is educated on all the features and benefits of Shockster, we will have a world full of believers," Erlston predicts.

Setting design targets

In bringing the Shockster APS to market, BikeControl principals set these design goals for the project:

- Had to fit a standard 26-inch mountain bike without any modifications to the bike frame.

- Had to weigh less than 3 lbs.

- Had to be pogo-free and fully active.

- Had to be affordable for the consumer.

Company on a mountain high

As with many design projects, BikeControl's began with the principals talking over ideas and diagramming them on napkins "over a few brews." Next came design modeling in a graphics form. This was followed by a series of prototyping and testing activities, more revisions, more prototypes, and more tests. Throughout the prototyping phases the main objective remained achieving pogo-free, fully active pivot points that move along a predetermined axis. This took about 18 months of the 2 1/2-year incubation period. Once the design was finalized, BikeControl was formed by a "consortium" of investors. The company now employs about a dozen people. However, if all goes well, the introduction of other patented products now under development (traction and braking components, among them) could make the little Oregon company a major player in the fast-growing mountain-bike accessory marketplace.

A mountainous market

In 1996, the U.S. bicycle industry recorded $5.2 billion in sales, according to the Bicycle Market Research Institute. These figures represented the sale of some 10.9 million bikes in 1996. Of this number, mountain bikes (26-inch-wheel size) accounted for 57% of the bikes sold through dealers and specialty retailers. The National Bicycle Dealers Association (NBDA) reports that the mountain bike success story has been the focus of much of the industry in recent years. With fat tires and upright seating positions, these all-terrain bikes appeal to both the casual recreational and off-road trail riders. Looking at sales from another angle, specialty bike dealers commanded a vast majority of parts and accessories sales in 1996, and virtually 100% of the service market, NBDA reports. They dominated the market in bicycles selling for $250 and up. This speciality dealer network is made up of about 6,800 dealerships. Of these, some 25% concentrate on the high end, referred to as "pro shops." Their popularity is not too surprising. According to NBDA, margins on parts, accessories, and service are generally higher than those for bicycles (46% gross margin). In fact, parts, accessories, and services presently account for about half of these dealers gross sales. Considering the profitability of this bicycle venue, it appears that BikeControl did its homework before introducing the Shockster to the marketplace.

What this means to you

Many engineer/inventors would like to bring their "revolutionary" products to market. Here's how BikeControl principals made that a reality:

- Found a market niche that no one presently filled.

- Reviewed carefully the potential market for the product and the retail price that would make the venture profitable.

- Set realistic goals to meet and a reasonable timeframe to accomplish them.

- Pulled together a design team within and outside the company with the skills needed to bring the goals to fruition within the given time period, setbacks included.

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