The MDC PRR boiler is excellent with the correct sand box, but the mechanism needs work to more accurately represent the loco. Very noticeable, the MDC drivers are 75" instead of 80". However since the boiler sits too high with the correct size drivers, it must be lowered about xx scale inches at both cab rear brace and the cylinder saddle.
First for leveling reference, the rectangular hole in the brace is duplicated at the required distance above original by scribing the outline, drilling pilot holes in corners and sawing out the inside. Filing almost to the scribed outline, test for tight fit. The only html line is the top, which sets hight.
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Rear cab brace hole location.
Lowering the saddle is more difficult, but with care can be done by hand tools. A rectangular brass sheet of the desired thickness is cut and rolled to match smokebox curve. A tight html hole is drilled dead center for boiler mounting screw. Using dividers, scribe a line html around all faces of cylinder at the required lowering distance plus the top saddle flange plate thickness. Rough metal removal may be carefully done with a rotary tool burr. Finish with a convex curved face bastard file with a radius smaller than that of the smoke box. Test for fit often as the scribed line is approached. Check level based on rear hole. If lowered too far, a thicker top plate may be used with the edges beveled to disguise thickness or a shim cut to size can be added between cylinder and plate.
Final leveling was done with a SURFACE GAUGE AND PLATE.
As suggested by the late Bob Shinn, the metal removal can be done with a flycutter on a mill. The cutter is set to the smokebox plus plate radius. Cylinder is carefully aligned and securely mounted for a vertical cut. After each cut, it is fed horizontally to increase depth. Setup and final cuts consume much more time than rough cutting.
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Lowering saddle top on vertical mill.
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Side view with 80" drivers and lowered boiler during level testing stage.
The MDC axle gear is removed and placed on a Bowser 80" driver. Bowser valve gear and rods are used. Headlight is replaced with a PRR Sunbeam. Other details are done to taste. The oversized and questionably routed blower pipe may be carefully removed from smokebox left.
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