Sat Jun 03, 2017 1:02 pm by tarboxb
I suppose that would be a mighty fine idea Martin.
The Yale friction fence uses a gear driven, friction clutch fence. There is no spring like most locks have. The drive cam is located closest rather than furthest away from the dial and has a gear attached to the bottom of it. This gear drives a second gear, seen in the right of the internal picture. This gear drives the fence through a friction clutch. The rotating clutch is designed with a spring tensioner inside which transfers the gear's motion to the fence until resistance is present on the fence. At this point, the clutch slips and the gear continues to move. When the dial is turned to the left, the gears and friction clutch pull the fence down to the wheel pack, which is mounted onto the back cover so it can test the wheels. If the gates in the wheels and drive cam are correctly aligned, the fence penetrates into the wheel pack and drive cam gate. The still rotating drive cam pulls the fence which rotates and the dogear of the fence retracts the bolt. If the gates aren't aligned, the clutch slips and the gears spin freely along with the dial, keeping light tension between the fence and wheel pack. This design can only be opened when the dial is rotated left. Unlike a spring fence lock, rotating into the drop in point from the incorrect direction will give no sign of drop in. This is due to the design of the friction fence mechanism which only ever brings the fence into contact with the wheels when the dial is rotated left. Another side effect of this design is that there is only a single contact point and it is only ever felt when rotating the dial left. The correct opening sequence for the lock is Right, Left, Right, Left to open though it is possible to open it Left, Right, Left as long as you rotate right past the drop in area and then back left to actually open the lock. Manipulation tends to be difficult due to the feel of the gears, the single contact point, and the minimal indications often seen due to wheel pack accuracy and the shape of the fence and drive cam gate.
