Tinkering with Messrs. Springer, Woolf, Etc.


| September/October 1991



# Picture 01

1102 Box Canyon Road, Fallbrook, CA 92028

This yarn is inspired because of a happenstance at two consecutive Old Time Thresheree shows I happened to attend in the not-too-distant past. Everything was going along hunky dory with all the exhibitions in full attractive demeanor, right up to the parade sequence, when along labored a fine old steamer with the most terrible case of asthma that I have ever heard in my life! She was pounding on only one end and, had I been blindfolded, I would have taken her for one of those old 1910 Titan gas tractors that could really shake the earth as they rolled by. As this venerable specimen passed our reviewing stand, it became at once evident wherein all the difficulty arose. This fine animal was equipped with a Woolf valve gear and also a rocker shaft to increase the valve throw beyond block drive. As she banged her way along the route leftward in front of us, it became apparent that this rocker was being exercised by an extreme over-length in the adjustment between the rocker and the block drive. This caused the upper section of the rocker to oscillate too far rearward, with the result that only the head end of the cylinder was receiving and exhausting steam; the rear port hardly being uncovered at all which most detrimentally transformed her into a single-action job not at all intended by the manufacturer. A monkey wrench and ten minutes should have brought her back into the 'ball park.' Actually, a good steam man can set a valve very closely by simply adjusting the valve travel in one direction until it is clearly evident that she is coming short on one end; then adjusting travel in the opposite direction until the same unbalance becomes evident. By counting the turnbuckle turns between extremes, and splitting the difference, it will be found that operation is way above reproach. This, of course, is a quick and dirty method to be resorted to in the field in order to keep the crews busy until after closedown when the engineer's duties seem to never end.

But now, to digress a bit in general on valve gears, which, after all, are about the most complicated element of the old steamer other than the injector (which, since it appears to have worn out and will not respond to cleaning any more, must be replaced) and the force-feed lubricator (which at most may require cleaning to remove a bit of debris from under the discharge valve, as evidenced by the fact that it has been pumping oil all day over the sight feed but the reservoir is still full!).

Ever since Watt discovered that a cam or eccentric could replace the labors of an attendant who was originally required to operate the valves on the New comen pumping engines, and engines became double acting, the subject of proper valve setting also became a subject to be mastered by the operating engineer. Now, today, we may take so much for granted. If it be a simple mill engine, all that is required is to equalize the valve travel over opposite ports; then adjust the eccentric for the desired lead. If a tram and marks have not already been provided, it requires but removal of the valve compartment cover and a few course measurements. Rocking valves are a bit more tedious, but true to form while going to Stevenson link motion is a repetition of the first case above requiring only that each end of the link be matched in accordance with direction of motion. With 'open' method of link drive as was common in locomotive practice, it is interesting to note that these old locos would run at speed in either direction with the 'Johnson Bar' hooked up to true center (the ports became slightly uncovered to inlet steam at dead centers).

But, eventually, and originally in marine practice, along came the development of the 'radial' type of valve gear. There are quite a raft of patents applicable to this Rube Goldberg contraption; but they all accomplish the same duty with the same effectiveness. These gears soon became applicable to railway practice because of their accessibility, and were competitive with the Walschaerts type of outside valve gears (which later were often mis classed as of radial type). The Baker and Southern were the only two radial types of locomotive gear in extensive practice. As Stevenson dropped out mostly because of its inaccessibility, Baker and Walschaerts absorbed most of the field. However, Young (who also designed a rotary locomotive valve) did find a small installation for a valve gear which resembled Walschaerts, except that, instead of utilizing a crank drive for the link off the main driver, it utilized the cutoff drive from the crosshead on one side to not only furnish that function but also, through a short connecting link, drive a rocker shaft that extended across the locomotive frame and supplied drive for the valve on the opposite side of the locomotive. All valve drive functions were thus derived from only crosshead source.

It is well to point out here that, if a single fixed eccentric is to be utilized on a reversible engine, it must necessarily be set at 90 degrees from crank position. But an eccentric (alone) set at the position does not allow setting at proper lap of the valve. Hence, since proper eccentric lead is in the neighborhood of 120-135 degrees, an auxiliary motion is required. This is ordinarily supplied by the auxiliary drive off the crosshead. If you recall your plain geometry, the resultant vector derived from two other vectors 90 degrees apart, may result in a final vector anywhere between zero and 90 degrees (depending upon the respective length of the combined vectors). By utilization of a rocker linkage, the resultant vector may become one of 90 to 135 (or more) degrees. Thus, with Walschaerts, we combine 90 degrees off the main crank throw with that of zero (or 180) degrees off the crosshead and wind up with our desired 120-130 degrees.