Bike Lock Combining Strength and Flexibility
What can be done when someone is riding a bicycle in a large metropolitan area, and when they reach their destination they find that there either is no bike rack, or the rack is already full. For bikers who prefer the security of a standard U-lock, this means having to leave to find another rack elsewhere or leave your bike unlocked. This situation is the why there is a need for a bike lock which can combine the security of a U-lock, with the flexibility and size of a chain. This project solves the problem by using a hardened steel chain, comprised of long sturdy chain links connected by stainless steel rivets. This allows for a bike to be locked to a telephone pole or tree about a foot in diameter, while still protecting the bike from the threat of bike theft. This was accomplished through the selection of a strong steel with good hardenability, followed by forces analyses to determine what shape and size is required to prevent tampering from standard bike theft tools, such as hacksaws, bolt cutters, and pry bars. These analyses resulted in a necessary chain link cross-section of 1.250 inches by 0.250 inches, to resist bolt cutters, and a length of each link being 15 inches in total. The required hardness to resist cutting from a hacksaw is above 65 on the Rockwell C Scale, and the design includes washers to prevent a pry bar from fitting between the links.