|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
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 |
Ads |
#2
|
|||
|
|||
U-lock hollow shackle?
|
#3
|
|||
|
|||
U-lock hollow shackle?
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. |
#4
|
|||
|
|||
U-lock hollow shackle?
|
#5
|
|||
|
|||
U-lock hollow shackle?
|
#7
|
|||
|
|||
U-lock hollow shackle?
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 |
#8
|
|||
|
|||
U-lock hollow shackle?
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. |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Any suggestions for a simple bike lock | [email protected] | General | 44 | December 22nd 04 06:23 AM |
Kryptonite tubular lock exchange | Dan Daniel | General | 20 | September 28th 04 06:25 AM |
Movie of picking a Kryptonite U-lock in 15 seconds with a ballpoint pen | Phil, Squid-in-Training | Techniques | 53 | September 21st 04 03:49 AM |
Combination lock | Jose Capco | Techniques | 4 | August 23rd 04 08:53 AM |
Bike lock advise and recommendation | David | Techniques | 2 | November 13th 03 12:31 AM |