Expansion link

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The eccentric rod provides motion to the expansion link (7) which is pivoted in a central location back to the body of the locomotive. The expansion link holds the radius bar (8), captive by a die block which is integral with the radius bar but is free to move vertically in a constrained curved path along the expansion link.

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Machining

The North American Live Steamer, Volume 1 Number 9, 1956.

David Mackie

Ashland, Wisconsin

It is a rather difficult job to cut the slots in a link with a file and keep a true curve. The method I use is to first rough out the slots with drill and file before profiling, then fasten the piece on the faceplate of the lathe, having the distance from the center line of the slot to the center of the lathe the same as the length of the radius rod. Now, with the tool post grinder and a stone small enough to work in the slot, grind the slot to size by working the faceplate back and forth by hand, being careful not to stop until the end of slot is reached, otherwise there will be a groove where you stopped. Make the link blocks in the same manner, using enough material to make both blocks at the same time.

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