[Phys-l] Bump Keys (was FCI answer?)

[Brian Whatcott <betwys1@sbcglobal.net>]

Bill Nettles wrote:
> .. I said "Oh, this is vector addition." But a closer look makes me think of "instantaneous" perpendicular impulse.
>  
> What do you think is intended?
>  
> Bill
This reminds me of bump keys, though their way of passing an impulse to 
the five pins of a cylinder lock
is not completely relevant.

It turns out, that for a great majority of American house keys, a choice 
of  six or seven key blanks will suffice to open them. They are first 
cut to the lowest depression offered for each pin, with a saw tooth  to 
the next pin position of the five usually fitted.
This guarantees that the key will completely enter a cylinder lock of 
that profile.
Then with the key pulled back half a pin space, the key is bumped 
forward with a mallet, toffee hammer, wood block, or whatever. The pins 
resting perpendicular to the long axis of the key and its surrounding 
cylinder,
are set into motion outwards by the key's saw tooth impulse. Meanwhile 
the operator, applying a slight turning torque to the key, ensures that 
the transverse momentum of the locking pins is stopped at the junction 
of the rotary cylinder and the outer stationary pins. With all pins set 
to the parting surface, the cylinder can turn - and does. So much more 
accessible than skeleton keys so called, or lock-picks.

BrianW