1. The Flywheel rotates at several times the speed of the main Camshaft, with which it is coaxial. Yes, the reduction gearing of the Countershaft implies this (and so does the speed of the Flywheel in the few videos of Barths in operation), but I hadn't thought about it before.
3. There are two separate actuations of the Choker Valve in this size Barth. (See the Choker Valve Cam for evidence of this.) They're synchronized with the two successive drops of the Pump Cam. This is further evidence that the two-part drop explained in great detail in Type Speaks! (1948) is a complete fantasy. The Choker Valve closes between the two successive drops. This further reinforces Greg Walters' correct explanation of multiple independent Pump strokes for agitating the metal in the casting cavity when casting large types (see his ATF Newsletter, No. 40 (March 2015), pp. 17-18.
Both activations of the Choker Valve can be seen in the photo of the Choker Cam, below. As seen in the photo, the cam turns clockwise. The first activation is the shorter recessed portion of the periphery of this cam, at about th 1 o'clock position as shown here. The second activation follows soon after and is much longer (running from 12 o'clock counterclockwise to 9 o'clock, as seen in the photo here).
4. Why is this all so interesting to me? Because I'm a typefounding geek, of course - but what's the fascination in that? I'm still a long way from casting type. To a large degree, it's because of accuracy. For a century, when people described the Barth casters, they have done so only in very general terms - often mythic terms, and often incorrectly. Even ATF couldn't correctly describe the operation of this machine by 1948. This is a chance, finally, to get it right and to do so in detail.
There's also a human aspect. This isn't "just a machine," and it isn't an alien artefact. It's a machine built by real people over a century ago. Everything you see in it represents their thoughts, frozen into cast iron.
5. Something very dangerous is happening. It happens to me every time I acquire a big, old machine. At first, they're huge and terrifying. But after a while, once you get to know them, they shrink. They seem smaller, and more human. Now I look at an early Linotype - say, my Model X or an early Model 5, and think "awww, it's cute." As it is. The same thing is now happening to this Barth. This is something to beware of. They're cute, but they bite hard.
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