Complete strike and repeat control assemblies, quarter and hour racks - July 2011                         

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This month Buchanan continues with the fabrication of the strike train control systems and now proceed with the fabrication of the quarter and hour strike racks. These are made of both brass, for the tail portions - that part which contacts both the associated snail cam as well as meshing with the pinion of the rack let down fly, and steel for the saw toothed rack itself. The steel portion will be later polished and blued.


These photos show the initial blank for the hour strike tail in paper. Notice how the paper is rotated to check for full movement between the first and second photos.


Next that paper blank is positioned on the brass blank. The outline is next scribed. The next photo shows the mill cutting the teeth into the tail. These teeth will mesh with the fly let down pinion.


Next the quarter rack tail paper blank is tested for clearance within the movement. As with the hour paper blank, it is then transferred to brass stock and this is now mounted to the mill. This part has internally cut teeth and these are cut in the same fashion as the internally cut teeth for the repeat function initiator assembly.


Notice the support given near the area where the reciprocating blade cuts the internally toothed tail piece. The next photo shows a close up of this process.



Next the brass hour strike tail is fabricated as well as the actual rack from steel, first two photos. The next two show the rough hour and strike racks in place on the movement being checked for fit.



In the left column of photos are the rough quarter and hour rack assemblies. To the right are the design drawings depicting the finished design form.


Both the the brass and steel portions of the rack outlines are cut with a hand fret saw. All of the steel components are cut with an old fashioned fretting saw, all by hand with lots of elbow grease. Once again contributing to the hand-built nature of this project.

The photo above is the quarter strike rack. The actual teeth are cut by machine to retain meshing accuracy. The part is then tested for functionality within the movement below. Note how the sector gear is highly raked to compliment the general curvature of that part of the component. It almost disappears within the curve. Some finish filing has been done to enhance the part.


The lower two photos above show the graceful outlines of the rack tails. Notice external and internal toothed meshing surfaces for the hour and quarter rack tails. We needed this since both racks operate in the same reciprocating direction but need to mesh with pinions attached to fly fans which will turn in opposite directions to each other. We do this to maintain the the left-right 'handedness' of the three paired fly fans in this movement. They are the two remontoire, the strike and these rack let down fans. 



We now begin the hour rack lifting pawls using the same allegorical bird design used for the quarter rack. First the rough parts are made and the pivots inserted in the appropriate places. The third photo shows the assembly in the movement to test for fit. Next is a drawing depicting the final outlines to be cut for the pawls.



Once again these parts are cut with the hand fret saw. The next two photos show the completed assembly in place. The last photo shows an additional lever attached to the quarter rack tail which is used to release the hour rack at the end of the quarter strike sequence (part attached to lower jeweled roller). When the quarter rack is near the end of the sequence it puts that additional rocking lever, which has two pins, into a position where those pins simultaneously pull away the pair of bird pawls (not shown) holding the hour rack in place; allowing it to fall and begin the hour strike sequence.



The strike lever work is now complete. The large and numerous jewels within these assemblies are a nice touch. The feathers on the strike detent birds are only a preliminary trial of seeing how we will attach these detents to the racks. If one looks closely at the quarter strike (right hand) bird's feathers, and last photo close up, you can see a pin protruding between the uppermost and next lower feather. This pin is connected to the quarter rack tail and moves that detent downward until intersects the fly fan's whip.

Below are three YouTube videos showing the strike trains and the action of these linkages and their epicyclical fly fans. Depending on your security settings you,  may need to allow your browser to run active-x controls to see these videos. Otherwise you can visit my YouTube channel at:

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