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mheslep
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The concept of ultralight vehicles is intended to allow greater fuel efficiencies in part by the use of composite structures to reduce mass by 2 or 3x. In several discussions of these vehicles I have seen and heard mention of the supposed additional safety benefit of shorter stopping distances, but I have not found any elaboration on why this is so, implying I fear that I missing something obvious.
Of course I reached for the standard stopping distance derivation: the kinetic energy of the vehicle and the work done by friction are both linearly related to mass, so that stopping distance is independent of mass as shown here:
http://hyperphysics.phy-astr.gsu.edu/HBASE/crstp.html
giving the familiar distance = velocity^2/(2*Cf*gravity)
So is there some other mass related factor here that is, say, a practical result of chassis, suspension, tires, or brake design? Reduced sway?
The ultralight vehicle article is here:
http://www.rmi.org/images/PDFs/Transportation/T95-27_VehicleDsnStategies.pdf
Is lengthy covering several disciplines and I do not mean to introduce it all here. I am referring to the safety section on pg 14:
Thanks for any comments
Of course I reached for the standard stopping distance derivation: the kinetic energy of the vehicle and the work done by friction are both linearly related to mass, so that stopping distance is independent of mass as shown here:
http://hyperphysics.phy-astr.gsu.edu/HBASE/crstp.html
giving the familiar distance = velocity^2/(2*Cf*gravity)
So is there some other mass related factor here that is, say, a practical result of chassis, suspension, tires, or brake design? Reduced sway?
The ultralight vehicle article is here:
http://www.rmi.org/images/PDFs/Transportation/T95-27_VehicleDsnStategies.pdf
Is lengthy covering several disciplines and I do not mean to introduce it all here. I am referring to the safety section on pg 14:
Design and Materials for Safety
Lightweight vehicle design, while presenting new challenges,does not preclude crashworthiness and could even improve it under some conditions. Lightweight design also improves maneuverability and stopping distance, allowing the driver to avoid many potential collisions. Using proven technologies for energy absorption, force-limiting occupant
restraints, and rigid passenger compartment design, even ultralight vehicles can surpass the safety of today’s cars in many types of collisions. The possible exceptions to this are
high-speed head-on collisions with, and side impacts from, a significantly heavier collision partner, though these might be effectively dealt with through innovative and careful design.
Thanks for any comments
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