And now we come to the SADDLE of your Traction Engine PYRTE, a really simple part to make in the how to build a Traction Engine From Scratch series.
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The saddle is made from either copper or brass sheet and needs silver soldering together. Mine was done in copper as that was to hand, and also I wasn’t too sure whether to leave the smokebox and the saddle on show as polished copper or not. In the end it was painted.
Pieces of the 13 gauge sheet of copper that were used on the boiler are great here.
Start off with a rectangle of copper or brass sheet at 4¼ inches x 1½ inches (115 x 37mm), nicely squared, with a centre line marked along the longer length, and a centre line crossing it at 90°.
Centre punch this crossing point and drill it out at ¼ inch (6mm).
Next, you need a block of wood turning to a 1¾ inch (44mm) diameter by 4 inches (100mm) or more long, with a ring marked around the circumference with a pencil or biro. This circle now needs dividing into 4, with each quarter marked. A hole is then drilled in at ¼ inch (6mm) on one of the points, sitting back from the front edge by around 2 inches (50mm).
The surplus needs trimming off from each side.
Now mark ½ inch (13mm) in from the tail ends, and this is where the tails are to be bent outwards to take the same shape as your smokebox barrel (as in the sketch – note there are 5 bolt holes showing on the sketch as these were just randomly placed to show what is needed, but on the original model there were 4 bolt holes, as in the picture above.).
You may need to grip the copper in the vice, with the timber still attached, to accomplish this, but don’t forget to use your soft vice clamps made previously, as this part is on obvious view.
Try it against the top of the firebox, and run a ¼ inch (6mm) bolt through the top of the saddle and into the hole already in the top of the firebox, add a large soft washer, ¾ inch (19mm) copper or brass is great, and then a nut, but do not tighten it much, finger tight is plenty for now. You may need to jiggle it about a little to get it sitting centrally and with the outer flaps where the bolts will secure it later, sitting nicely on the surface.
What you need now are 2 pieces of copper, 13 gauge again, measuring 1 inch by 2 inches (25 x 50mm).
Take one piece – the front face – and file it along the bottom to the same shape as the firebox shell, to sit in front of this bolted part you have just made, and it must be a very close fit to the shell. A line now needs scribing around the outside arc, level with the top of the saddle and the surplus removing. Trim the front face to just push into the saddle, as this will need silver soldering in place. The same needs to be done with the rear face.
Once you are happy with the fit, undo the bolt and silver solder the three pieces in place. Trim the edges and corners round to produce a smooth saddle.
Next you need to make the hole for the chimney to sit in, and this will be a nadgers over 1 inch (25mm) in diameter because of the taper of the chimney (if you are using the tube method, then the diameter will be 1¼ inches – 32mm). It needs to be a tight fit as there is no solder on this part. The chimney is simply held in place by the ¼ inch (6mm) screw thread and a nut and washer underneath. (So don’t us the chimney as a lifting or pushing point, as many unsuspecting, inexperienced folk do.)
If you want the added benefit of solder, it means you may have to undo more nuts and bolts to take the chimney off, if you need to.
The brass ring (cowl) sitting at the top of the chimney.
Take a 1½ inch (37mm) diameter rod of brass, ½ inch (12mm) long, and bore it out to match the top of your chimney (should be 1⅛ inch or 28mm).
I used 2 pieces of ¼ inch brass plate I had spare at around 2 inches square and silver soldered them together, held them in the 4 jaw and bored them out before inserting a carrier and skimming the outside down to the right size.
With a piece of broom handle forced inside the brass, the metal was lightly turned to shape, using the soldered joint as my dividing line, I turned a concave arc on one side and a convex one on the other. The concave was done finally with a round file as it was spinning slowly in the chuck, and the other was done with a fine flat file, after the bulk of the metal was removed.
By doing it with files, well away from the chuck and at a low speed, with the broom handle sat in the chuck, my file followed the shape of the brass, allowing for any deviation caused by the broom handle being uneven, and a good result was achieved, as can be seen in the photo above.
The brass cowl should be slipped on the top of the chimney and can be soft soldered in place, resting on the lip, with around ⅜ of an inch (10mm) of the chimney steelwork sticking through. The concave part of the ring needs to be at the bottom.
The next job is to mark the bolt holes for the saddle to be secured with.
A line was scribed parallel to the outer edges at ¼ inch (6mm), that way sitting centrally on the flat face to be bolted, and from the front edge a mark at ³/₁₆ inch (5mm) was the first hole, the second was ⅜ inch (10mm) beyond that, with the third a further ⅜ inch (10mm) and the fourth ⅜ inch (10mm) again. This left ³/₁₆ (5mm) to the rear of the rear edge of the flat bolting face to match the dimension of the front.
To make mine look a little less plain, I decided to round off the bottom edges a little and have the bolts sitting in a similar arc. It’s nothing spectacular, but all I did once the edges were rounded off, was to open my caliper to ¼ inch (6mm) and locked it at that, and used the caliper to scribe a line parallel to the outside edge (see 2 pictures up).
All holes were drilled with the 3.6mm drill to suit the 4ba bolts, although this time the bolts are ½ inch(12mm) long.
Now is the time to sight along your traction engine to make sure the chimney is sitting upright compared to the firebox. If it’s looking good, then remove the chimney (leaving the saddle in place) and the smokebox from the boiler and we shall proceed to the perch bracket for mounting the steering underneath the smokebox.