Constraints often involve tradeoffs as opposed to money. I don't know much about cars, but I am an active rock climber. Climbing is probably unique in that th

Constraints often involve tradeoffs as opposed to money. I don't know much about cars, but I am an active rock climber. Climbing is probably unique in that these sorts of engineering tradeoffs concerning life and death are part of the sport. Perhaps the best example is found in the gear used and its placement. Cords, slings, and webbing (short pieces of tubing or cord used to build anchors or fix gear) were typically made of nylon back in the day. Military grade plastics [1] entered the climbing scene by the 90s. These plastics are both much stronger and lighter than nylon. For that matter, they are actually stronger than steel. In practice, they are so much stronger that they don't stretch at all. The obvious effect is that falls exert a much larger force on both the climber and the gear. Gear rarely fails, but it does punch holes through rock ripping its way out. The other effect is that dyneema effectively sheds redundancy from anchors. A bit of background is in order. Anchors are typically attached to the rock via more than one piece of pro(tection). A cordelette (short cord 20 feet in length) is attached to all the pro and tied into a knot (the master point). Depending on the position of the pro, the legs of the cordelette can be doubled (or more) to make a stronger anchor. A cordelette made of nylon stretches enough that the total weight it holds is nearly additive of the number of independent legs. Dyneema, on the other hand, will break at the tensile strength of a single leg no matter what. In the concrete, 5mm dyneema may hold up to 5000 pounds, while a 7mm nylon cord will hold 2800 pounds or so per leg. In most cases, an anchor of nylon is both stronger and more forgiving because it stretches more. If we didn't have enough to consider already, space age plastics rapidly loose strength under very moderate weighting cycles and degrade quickly in the sun. Which plastic is better? Or better yet, which one would you use? Nylon means falls are typically safer, but you are more likely to take a fall because you will fatigue more quickly. Of course, if you can hit the deck (eg, a ledge below you) or can't double up the cord, you'd want to use dyneema. However, I certainly wouldn't want to take multiple falls in succession on dyneema. | Think about that. It in no way realistically ran into any constraints that were not arbitrary. More engineers, better engineers, and more money can't solve this problem. You have to pick your cords ahead of time and live (or not) with the decision. [1] http://en.wikipedia.org/wiki/Ultra-high-molecular-weight_polyethylene http://en.wikipedia.org/wiki/Ultra-high-molecular-weight_pol...