THIS week I'll fulfil the promise to give the necessary details for building "Ada" as a ten-coupled engine, similar to the latest version in full size. Builders who have not yet started, can make the ten-coupled version by using the drawings which are reproduced here, plus the previous instructions. Anybody who has built an eight-coupled chassis can easily convert it if they so desire.
The new frames are 22 in. long, against the 19¼ in. of the earlier engine. To make a new pair, two pieces of metal 22 in. by 2½ in. and 3/32-in. or 13-gauge in thickness will be needed ; and these must be marked off, and sawn and filed to outline, exactly in the manner previously described. To lengthen an existing pair of frames made for the eight-coupled engine, mark off a vertical line 1½ in. behind the centre-line of the third axlebox opening—that is, the driving one; saw off, and carefully file the cut edges dead square, with the frame plates temporarily clamped or riveted together. Now get two pieces of 3/32-in. steel plate measuring 2½ in. by 8¼ in. ; mark off on one that part of the frame which friend Hambleton would say is astern of the dotted line. Incidentally, I‘d love to read his description of a Drummond "paddle-box"! Rivet the pieces together temporarily, saw and file to outline, separate, and piece one "butt-up" against each portion of the cut-down frames. If anybody who is reading this owns or has the use of an oxyacetylene blowpipe, the butt seam can be welded, either with Sifbronze or by the ordinary fusion-welded process. Otherwise, put a strip of 3/32-in. steel, 2½ in. long and 1 in. wide, half over each piece of frame, on the inside, and rivet in position with two rows of 3/32-in. rivets in each, arranged in staggered formation. Yet another satisfactory alternative would be to use a ½-in. butt-strip of 1/16-in. steel, with just sufficient rivets to hold the two pieces of frame in line, and then braze the joint with an ordinary blowpipe or blowlamp, using Boron compo as flux, and brass wire for a brazing medium.
Beginners, please note: Whether the frames are entirely new or the earlier type lengthened, be mighty careful to cut out the recess for the firebox correctly to outline and dimensions, so as to form a proper cradle. The total length of the opening needed is 4 7/16 in. It starts 1 15/16 in. from the back end, where it is ¼ in. deep. The easiest way to mark-out is to draw a vertical line 4 7/16 in. ahead of the step, and at 11/16 in. from the top of this draw a horizontal line 7/16 in. long. The end of this is the meeting-place of the two diagonal lines, one of which slopes up at a sharp angle to the top of the vertical line just ahead of it, and the other goes up to the bottom of the ¼-in. step at the back. When lengthening existing frames, beginners should leave this job until the extension-pieces are fitted, then clamp or bolt the frames back-to-back, butt strips outside, and cut out the cradle opening in both, at one fell swoop, thus ensuring alignment.
The trailing wheels, axle, axleboxes, hornblocks, and springs are exactly the same as described for the trailing wheels of the eight-coupled "Ada," so no detailed description is needed. The coupling-rods are a little different. Instead of the piece between the third and fourth pairs of wheels having a plain boss at the rear end, it has a tongued extension similar to the one behind the driving crankpin, and the section with the plain boss fits over this, so that there are three knuckle joints altogether, one ahead of the second axle and one behind the third and fourth axles. If the locomotive is going to run on a line with curves of less than 18 it. radius, the flanges should be turned off the middle pair of wheels; that is, the driving wheels. If this is done, she will negotiate any curve that could be traversed by the eight-coupled engine.
The cylinders, guide-bars, connecting-rods, valve-gear, lubricator, feed-pump, and, in fact, everything except boiler and frames, is the same on both eight and ten-coupled engines; so new builders can refer to the full description published in recent issues. The great difference is in the boiler. As previously mentioned, experiences with both the British engines of the original design and their American sisters demonstrated the superior ity of the wide firebox with coal of poor quality ; hence the provision of a boiler of this type on the later full-sized "Adas." In case any beginner who has built the eight-coupled engine has any qualms about the boiler not being able to "deliver the goods," I hasten to add that any shortcomings which may have been found in the full-sized engine, have all been eliminated in Curly's small version of it. This is no idle boast, as all older followers of these notes who have built engines to my specifications will readily confirm.
The Association can supply photocopies of the constructional series to members.
Drawings, castings and some materials are available from GLR Kennions.
The Association can supply the correct pattern driving and coupled wheel castings.
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This page was last changed on 06/05/2016