Thank you for your informative reply. It really was an eye opener how
you showed how the 12.7 mm solid rod has the same amount of material as
a 25 mm tube that's only 1.74 mm thick. I even checked the math myself
:-). Might be better against bolt cutters, but very vulnerable to
crushing attacks. Also, I'm glad you pointed out that hollow tubing is
really expensive compared to the solid rod.
In terms of economics, I believe that there is always the question of
demand. If I'm not mistaken, the makers of today's top locks (Abus,
Kryptonite, Onguard, etc.) mark up their top designs a lot. I just saw
the New York 3000 for sale today at a LBS for $80. People willing to
pay that much for those locks probably will pay top dollar for
something *truly* shown superior. How much of the cost is really the
material cost, and how much is the locking mechanism and fabrication
cost? Thought just dawned on me how concrete is very good against
crushing. How about a concrete filled shackle? Wait, that would be very
heavy though.
This thread is making me wonder if we should have a discussion on the
*physics* of bolt cutters and cutting - some initial thought convinced
me that it's much more complex than at first sight - issues of
sharpness, pressure, compressive strength, buckling, etc. just to list
a few.
Later,
Nelson Chen
__o Same road Boycott Wal-Mart, union-buster.
_`\<,_ Same rights
(_)/ (_) Same rules
Chalo said:I expect that it is manufacturing issues that keep such a lock off the
market. While it's not exactly difficult to make a tightly bent
thick-walled tube, the economics of producing things for the mass
consumer market make everything other than the cheapest methods
uncompetitive.
I see a lot of merit in your idea, but it would be difficult to make
the weight similar to a normal u-lock without the shackle being
vulnerable to crushing (note that crushing the shackle would not
necessarily make it easier to cut or remove the lock by force).
A 12.7mm solid rod weighs the same as a 25mm tube with a 1.74mm wall
thickness. That's only about twice as thick as an inexpensive bike's
tubing. So it would have to be made of some tough stuff to resist easy
cutting once flattened.
Tubing is expensive compared to rod, and tubing made out of very tough,
high-tensile material is _really_ expensive compared to rod. I imagine
that it would be more cost effective to use a rod of a stronger,
tougher alloy than it would be to make a tubular shackle. Because even
though lock manufacturers love to boast about how strong their shackles
are, the metals used are not that remarkable.
If somebody saw fit to make a lock with a shackle of Carpenter Aermet
100 or Inconel 718, now that would provide some pretty good security.
Best not lose your key, though.
Chalo Colina
