IsoTruss-tubed Delta 7 bikes look funny, but boast high strength to weight ratio
By Ben Coxworth
February 2, 2010
Go ahead, stare. It’s OK, they want you to. Delta 7 Bikes currently manufactures two of the most unusual-looking bicycles on the market, the Arantix hardtail mountain bike and the Ascend road bike. Their open-lattice spider-web tubes incorporate patented IsoTruss geometric design, wherein carbon fiber and Kevlar are woven into a network of isosceles triangles. The triangles join together to form pyramid-shaped trusses, which provide incredible structural support while using a minimum of material. If you’re a bicycle-maker looking for something with a great strength-to-weight ratio, it’s hard to beat.
IsoTruss was developed at Utah’s Brigham Young University (BYU), for use by NASA. BYU still owns the patent, but granted a license to Advanced Composite Solutions to develop, produce and market products using IsoTruss technology. Advanced Composite Solutions owns Delta 7, hence the funny-looking bikes. IsoTruss is most commonly used to build things like masts, towers, beams and pillars - although it can also be used to make flat objects.
While Delta 7 uses carbon fiber, IsoTruss products can be made using just about any type of weavable fiber (including bamboo) and resin. Because it uses less raw material than conventional methods, IsoTruss can legitimately be called an environmentally-friendly and cost-effective process. Unlike materials such as metal and wood, IsoTruss products won’t rust or rot, they have low wind resistance, and don’t require toxic preservatives. And, despite its complex appearance, IsoTruss is possible to produce using automated techniques.
How it applies to bikesInterestingly enough, one of the items that BYU students made to showcase IsoTruss was a mountain bike - the bike that became today’s Delta 7 Arantix. So, what makes IsoTruss particularly well-suited to high-end bike-building?
- Fantastic strength-to-weight ratio - it can be up to 12 times stronger than steel, while weighing ten times less (depending on the application)
- Because of the redundant nature of its grid system, damage to one section of the frame remains isolated and can be repaired, as opposed to conventional frames that usually have to be entirely replaced
- Frame design can be fine-tuned by adding more fibers on the sides for better lateral stiffness, or using less on the top and bottom for more vertical give
- High-stress areas can be reinforced by using thicker fibers and/or more trusses
- It reportedly gives a very stiff, responsive ride
You want one?
Because Delta 7 used to weave all of their frames by hand, the Arantix was likely the world’s most expensive production mountain bike, at $US11,995. Now, thanks to in-house, mechanized production, the price has dropped to a slightly more reasonable $8,495, or $4,895 for the frame only. The Ascend road bike will set you back $10,995, or $5,995 for the frame only. Both frames weigh in the neighborhood of 1050 grams (2.5 pounds)... and that’s without the dirty Lizard Skins.
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