U-lock hollow shackle?

As many U-locks are attacked by bolt cutters, I was wondering about how
they (the locks) have their shackle made. Does anyone know if
manufacturers have tried to make extra-large diameter shackles (1 in=25
mm or greater) to make it so that bolt cutter jaws cannot fit around
them? Now b/f people say that that's insane in terms of weight and
cost, here's my idea. One can have in theory a large diameter shackle
that's hollow. For an equivalent weight of steel, a hollow shackle
would have a greater diameter. It seems to me that as long as the
shackle were strong enough to resist crushing (here a circular cross
section is best), it would be superior to the thin solid shackles. I
wonder if I'm missing something, say in manufacturing difficulties or
something else.

Later,
Nelson Chen
__o Same road Boycott Wal-Mart, union-buster.
_`\,_ Same rights
(_)/ (_) Same rules

wrote:
As many U-locks are attacked by bolt cutters, I was wondering about
how they (the locks) have their shackle made. Does anyone know if
manufacturers have tried to make extra-large diameter shackles (1
in=25 mm or greater) to make it so that bolt cutter jaws cannot fit
around them? Now b/f people say that that's insane in terms of weight
and cost, here's my idea. One can have in theory a large diameter
shackle that's hollow. For an equivalent weight of steel, a hollow
shackle would have a greater diameter. It seems to me that as long as
the shackle were strong enough to resist crushing (here a circular
cross section is best), it would be superior to the thin solid
shackles. I wonder if I'm missing something, say in manufacturing
difficulties or something else.

Later,
Nelson Chen
__o Same road Boycott Wal-Mart, union-buster.
_`\,_ Same rights
(_)/ (_) Same rules

Analogy: aluminum beer can versus an aluminum dowel. Which is easier to get
through?

Just kidding, that analogy is probably inaccurate. Maybe someone can chime
in.

--
Phil, Squid-in-Training

On Thu, 7 Jul 2005 01:06:11 -0400, "Phil, Squid-in-Training"
wrote:

wrote:
As many U-locks are attacked by bolt cutters, I was wondering about
how they (the locks) have their shackle made. Does anyone know if
manufacturers have tried to make extra-large diameter shackles (1
in=25 mm or greater) to make it so that bolt cutter jaws cannot fit
around them? Now b/f people say that that's insane in terms of weight
and cost, here's my idea. One can have in theory a large diameter
shackle that's hollow. For an equivalent weight of steel, a hollow
shackle would have a greater diameter. It seems to me that as long as
the shackle were strong enough to resist crushing (here a circular
cross section is best), it would be superior to the thin solid
shackles. I wonder if I'm missing something, say in manufacturing
difficulties or something else.

Later,
Nelson Chen
__o Same road Boycott Wal-Mart, union-buster.
_`\,_ Same rights
(_)/ (_) Same rules

Analogy: aluminum beer can versus an aluminum dowel. Which is easier to get
through?

Just kidding, that analogy is probably inaccurate. Maybe someone can chime
in.

chime

It's an interesting idea. The can v dowel analogy is a bit extreme
IMHO.

One thing you could do is fill a hollow shackle with a thermoplastic
elastomer loaded with, say, alumina granules.

So you've got a thicker shackle (bad for bolt cutters), and the
alumina (bad for sawing/disc cutting).

------

The elastomer + alumina isn't an original idea of mine, btw. I saw a
safe which some guys had invented where the body and door were cast
out of this stuff on a TV show. They invited people to break in.

A team with an oxyacetalene kiy were confounded as the elastomer
foamed up in the heated zone (it was also self-quenching due to some
additives). This made the already poor heat conductance of the
material even worse, and they never got anywhere.

A guy with a sledgehammer nearly took his own face out as the hammer
just bounced off the safe body.

A disc cutter was used, and the disc just *disappeared* as it ground
against the embedded alumina nodules.

QUite an interesting demo. I don't think the product ever took off
though.

wrote:

As many U-locks are attacked by bolt cutters, I was wondering about how
they (the locks) have their shackle made. Does anyone know if
manufacturers have tried to make extra-large diameter shackles (1 in=25
mm or greater) to make it so that bolt cutter jaws cannot fit around
them? Now b/f people say that that's insane in terms of weight and
cost, here's my idea. One can have in theory a large diameter shackle
that's hollow. For an equivalent weight of steel, a hollow shackle
would have a greater diameter. It seems to me that as long as the
shackle were strong enough to resist crushing (here a circular cross
section is best), it would be superior to the thin solid shackles. I
wonder if I'm missing something, say in manufacturing difficulties or
something else.

AFAIK most of them are actually broken with a car jack. Power tools are
becoming more popular with the advent of good rechargeable disc cutters.
And then there's the trusty Bic pen ;-)

wrote:
As many U-locks are attacked by bolt cutters, I was wondering about how
they (the locks) have their shackle made. Does anyone know if
manufacturers have tried to make extra-large diameter shackles (1 in=25
mm or greater) to make it so that bolt cutter jaws cannot fit around
them? Now b/f people say that that's insane in terms of weight and
cost, here's my idea. One can have in theory a large diameter shackle
that's hollow. For an equivalent weight of steel, a hollow shackle
would have a greater diameter. It seems to me that as long as the
shackle were strong enough to resist crushing (here a circular cross
section is best), it would be superior to the thin solid shackles. I
wonder if I'm missing something, say in manufacturing difficulties or
something else.

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

wrote:
On Thu, 7 Jul 2005 01:06:11 -0400, "Phil, Squid-in-Training"
wrote:

wrote:
As many U-locks are attacked by bolt cutters, I was wondering about
how they (the locks) have their shackle made. Does anyone know if
manufacturers have tried to make extra-large diameter shackles (1
in=25 mm or greater) to make it so that bolt cutter jaws cannot fit
around them? Now b/f people say that that's insane in terms of
weight and cost, here's my idea. One can have in theory a large
diameter shackle that's hollow. For an equivalent weight of steel,
a hollow shackle would have a greater diameter. It seems to me that
as long as the shackle were strong enough to resist crushing (here
a circular cross section is best), it would be superior to the thin
solid shackles. I wonder if I'm missing something, say in
manufacturing difficulties or something else.

Later,
Nelson Chen
__o Same road Boycott Wal-Mart, union-buster.
_`\,_ Same rights
(_)/ (_) Same rules

Analogy: aluminum beer can versus an aluminum dowel. Which is
easier to get through?

Just kidding, that analogy is probably inaccurate. Maybe someone
can chime in.

chime

It's an interesting idea. The can v dowel analogy is a bit extreme
IMHO.

One thing you could do is fill a hollow shackle with a thermoplastic
elastomer loaded with, say, alumina granules.

So you've got a thicker shackle (bad for bolt cutters), and the
alumina (bad for sawing/disc cutting).

------

The elastomer + alumina isn't an original idea of mine, btw. I saw a
safe which some guys had invented where the body and door were cast
out of this stuff on a TV show. They invited people to break in.

A team with an oxyacetalene kiy were confounded as the elastomer
foamed up in the heated zone (it was also self-quenching due to some
additives). This made the already poor heat conductance of the
material even worse, and they never got anywhere.

A guy with a sledgehammer nearly took his own face out as the hammer
just bounced off the safe body.

A disc cutter was used, and the disc just *disappeared* as it ground
against the embedded alumina nodules.

QUite an interesting demo. I don't think the product ever took off
though.

Ah, yes, but then one would have to focus on the lock mechanism itself...
Sounds like a pretty neat idea though.

--
Phil, Squid-in-Training

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 wrote:
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

Zog The Undeniable wrote:
AFAIK most of them are actually broken with a car jack. Power tools are
becoming more popular with the advent of good rechargeable disc cutters.
And then there's the trusty Bic pen ;-)

Does anyone have any statistics on how common it is to have a U-lock
broken? The reason I ask is because I've had terrible luck with bike
theft, but have never had a U-locked bike stolen. Over the past 8
years, I've had a bike w/a cable lock stolen, two unlocked bikes
stolen, and the wheels stolen off a bike whose frame was U-locked. The
U-lock I've used was a low-end Kryptonite for a while, normal size,
which I got replaced with a similar flat-key model.

My main worry isn't usually whether my frame is going to walk away in
downtown DC, I worry about vandalism and theft of small parts. By the
time I lock down my front wheel, seatpost, remove lights, bags, and
computer... my good commuter road bike is not much fun to deal with
anymore. So I only take the beater when I'm going to leave it outside
unattended for more than 1/2 hour.

Has anyone tried these locking skewers?
http://www.veratomic.com/phpshop/frame.php?p=1 They appear to be a
good deal.