If you’ve been lucky enough to fly business or first class on an overseas trip, you may have noticed just how complex the seats have become from a linear motion standpoint. The most advanced seats now fold completely flat and offer numerous neck, back, and leg adjustments.
These super seats, which consist of up to 5,000 parts and cost more than $250,000 each, can incorporate as many as 8 different linear guides. A couple of technical key factors have emerged as the most important when selecting linear guides for seating applications.
The Right Weight. Notice we said “right” and not “light.” It’s an important distinction in this application. Thanks to its strength-to-weight ratio, titanium has traditionally been perceived as the ideal material for interior structural parts. Sourcing difficulties and high costs, however, have made it less and less attractive in seats. Increasingly, steel linear guides get the nod in seat applications.
Steel linear guides, many of which are off-the-shelf components, are widely available and offer a comparable strength to titanium at roughly one-fourth the cost. Steel does weigh roughly twice as much as titanium. Yet steel’s weight penalty is minimal in the context of a super seat. On a 300-lb seat, for example, the steel rails represent less than 1% of the total weight.
Long-term Reliability. Aircraft seats have to be robust to pass the industry’s extreme testing regimen and hold up to years of passenger abuse. The airline’s expectation of these seats is that they will last for 5 to 7 years with few maintenance issues.
As the seats rely more heavily on linear motion, one of the growing threats to seat reliability is linear guide misalignment. Misalignment produces excess friction that can makes seats difficult to operate and, ultimately, wear out before their expected lifecycle.
Traditionally, seat engineers have addressed misalignment problems during the assembly process. They specified rails and bearings separately, leaving the alignment up to assembly technicians. However, this approach is time consuming, costly and error prone.
An alternative approach has emerged recently. Rather than “assemble-in” the guide alignment, seat engineers are instead picking self-aligning, preloaded linear guides. Our Compact Rail system, for example, can absorb rotational positioning errors, misalignments between lateral planes and longitudinal parallelism errors — all while maintaining the original preload setting.
Compact Rail linear guide systems have additional benefits in seat applications, including noise reduction and a high dynamic load capacity. For more detailed information, download our white paper on linear motion for aircraft interiors.