Free Spirit: the world’s lightest wheelchair
May 13, 2008 Drawing on a background that ranges from experience as an aerospace technician to a stint in research and development on the Williams F1 team, Marcus Cunnington has designed and built the 6.3kg (around 13.9 pounds) Free Spirit - a carbon fiber composite design that claims the mantle of the world's lightest manual rigid wheelchair.
Cunnington has released the Free Spirit line through his company Future Chairs, with two models available - ‘standard’ and ‘ergo’.
In addition to high performance characteristics including lightness, rigidity, durability, and shock absorption, carbon composites can be varied through different fiber angles, different plies, different ply thicknesses, and different combinations of materials. This means the end product can be tailored to precise specifications and customized for varying degrees of stiffness in a way that steel, aluminum or titanium can not.
The stiffness to weight ratio of composites is also very impressive. The 6061 and 7000 series aluminum used in some wheelchairs is roughly one-third as heavy as steel, one-third as stiff, and, at best, is about 80% as strong as the 4130 steel used in wheelchairs. Titanium is roughly two-thirds the weight of steel, one-half as stiff, and about 60% as strong as steel. Carbon fiber composite is less than one-quarter the weight of steel, but it is about as stiff (which makes it almost four times as stiff on a weight-to-weight basis), and it is roughly four times as strong in tension.
The Free Spirit line of chairs comes with 100% carbon fiber composite main tubes; choice of five color finishes; colored anodized backrest; carbon fiber splash guards; height adjustable backrest; Spinergy wheels as standard or Glance Alloy Billet wheels as extras and colored casters. All of the chairs from Future Chairs are custom hand built using strict design, inspection and assembly process similar to processes used by Formula One teams, with attention paid to detail like the use of alloy blanking caps for the caster pots and backrest tubes. Chairs take between eight to 12 weeks to build and prices start from UKP2595.
Cunnington isn't alone in having made the transition from F1 to wheelchair design. In 2006, Formula One car part designer Mark Spindle launched the off-road Trekenetic K2 wheelchair.
Future Chairs are currently only available in the UK, but the company plans to expand later in the year following interest from Ireland, Spain and Canada.