Dudely locks

[MacGyver101]

I just posted a reply in a PM to Raymond... but realized that the comparison of Dudley and Master combination padlocks might be of interest to other folks. (And, despite the reference to safes, I think this is fine for the open forums, as it is only discussing function, rather than any opening technique...)

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I have to admit, I haven't had a chance to play with an American brand combination lock... but will have to pick one up sometime. I think one of the main differences between the Dudley and the Master (and why you can't shim it) has to do with how the latch interacts with the wheel pack. The Dudley lock works like a direct entry safe lock, where the latch (the "fence") actually has to drop into the gap created in the wheel pack when all of the dials are lined up... this means that it can't be pushed aside by a shim until the proper combination has been dialed. You can see a diagram of the latch here:

http://www.google.com/patents?vid=USPAT1902214

In contrast, the Master lock has a spring-loaded latch that is not directly coupled to the wheel pack. I imagine that they thought this would hamper the ability to decode the gate location (i.e., you can't tension the fence by pulling on the shackle), but it creates the bigger problem that you can shim the lock open. You can see the spring arrangement in the Master patent drawings:

http://www.google.com/patents?vid=USPAT2113864

[Trip Doctor]

I imagine that they thought this would hamper the ability to decode the gate location (i.e., you can't tension the fence by pulling on the shackle.

But when pulling the shackle you DO tension the fence don't you ?

[MacGyver101]

But when pulling the shackle you DO tension the fence don't you ?

I got thinking about that design some more last night, and you're absolutely right.

I was originally (and incorrectly) thinking that the spring-mounted latch (see the Master patent, linked above) would restrict your ability to tension the fence. In reality, of course, the sliding latch will bind after you lift it slighting by pulling up on the shackle. So, the Master lock's latch design simply functions in the same manner as a standard doorknob latch: the spring-mounted latch design allows you to close the shackle even if the padlock is locked.