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In previous posts the following have been noted

1. The HR1 locks by turning the locking knob counterclockwise
2. There is a stop pin under the locking knob that provides adjustment when locking becomes unreliable

Any candidate design for the actual HR1 locking mechanism needs to have these features.

The design shown in the drawing kindly forwarded by Gary http://fer3.com/arc/m2.aspx/Bygrave-Locking-Device-LaPook-feb-2013-g22320 may indeed lie at the heart of the locking mechanism but some its details would need to be changed in order to be consistent with the observed functioning of the HR1. Assuming a right handed screw, the design in the drawing would lock when turned clockwise. Moreover the threaded rod does not pass all the way through the locking knob in the HR1.

In my earlier post http://fer3.com/arc/m2.aspx/HR1-Sliderule-locking-mechanism-questions-Stuart-feb-2013-g22300 I was envisioning a variant of the drawing design in which the rod is attached to the locking knob and threaded through the end cap. This arrangement would lock by turning counterclockwise and the stop pin would work by limiting travel of the knob parallel to the axis of the tubes. Information provided by Brad Morris pretty much rules this arrangement out and it is now not at all clear to me how stop pin acts to adjust the lock.

Unfortunately it appears that at the present time that a full understanding of the actual mechanism will require further information or a new flash of inspiration

Robin Stuart

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