How To Build A Steam Engine From Scratch — 5

Now we move onto THE CHIMNEY construction

For the chimney, there are two options available to you. One is easy to produce but provides no way for the spent steam from the engine to be concealed as per normal traction engine fashion. For that reason, a steam tube needs to be attached to the rear of the chimney to provide this vent, and looks a little odd.

For this method this chimney is simply a solid rod, with washers (again not shown on the drawing) soft soldered to it (it’s safe to use soft solder here) to give the impression of flanges for bolting joints, sitting a little above the top of the chimney saddle, with a brass ring near the top for show purposes, and threaded at the lower end for a nut.

With this solid version the original intention was to install a belly tank at the front of the fire-box and to divert the exhaust steam into that so water recovery could be accomplished, along with oil recovery, meaning the water could be used again, that way making this model a lazy-mans traction engine – but for now we’ll stick to the basics and simply vent it to atmosphere – perhaps we’ll cover that in a later chapter if the need arises.

The second option is to use a tube and channel the spent steam up this tube in a conventional manner, although in the end this method was used and the steam was sent up the chimney in the normal steam engine fashion.

But firstly, we will deal with the easy option.

As the chimney is not needed for its usual function, the chimney is can be left solid, apart from the top inch, so take a 7 inch (175mm) length of 1¼ inch (32mm) steel rod, centre drill one end and reduce the outside diameter of the centre-drilled end to 1⅛ inches (28mm) for a length of three-quarters of an inch (19mm), this will be the position of the chimney brassware which will be soldered on.

Once this is done, bore out the centre to around seven-eighths inch (22mm) wide for an inch deep (nothing hard and fast here for dimensions).

Next, turn the rod around end to end in the chuck, centre drill the end and supporting the chimney on the newly cut external diameter in your 3 jaw chuck, you need to turn the tailstock end down to ¼ inch (6mm) diameter for a length of ½ an inch (13mm) and thread it ¼ x 40 (or alternatively you could use a 2Ba thread here).

The remainder of the bar now needs a taper cutting on it (as an aside, it could be left as it is, but a taper looks much more in keeping with traction engine designs of the past).

By turning your top slide over by one-and-a-quarter degrees from square, and using your top-slide only to cut the taper, you will find that this is approximately right in making the top end of your chimney slightly wider than the bottom, although you may have to increase the angle slightly, but beware, the slightest movement can cause a large variation over the length of the chimney.

(If you end up with two different angled tapers on your chimney, then just round it off with a file in the lathe. Many traction engines had rounded tapers on their chimneys, so it would be nothing unusual.)

 

Leave a small lip for the brass-work to sit against the top of the chimney’s taper (the chuck end).

Next you need to file an arc at the lower end of the chimney stack so that the base of the chimney sits flush with the smokebox outer diameter,

What is needed now is a steel washer, or alternatively two (to give the impression of a flange – normally sitting a short way above the chimney saddle).

 

This is basically a steel, circular plate, at ³/₁₆ inch (5mm) thick by 1⅜ inch (35mm) diameter, simply turned in the lathe, with a groove turned in the outside centrally to give the impression it is two chimney flanges (two washers) joined together, and with a hole bored in it so that it slides to a position at ½ an inch up from the saddle top. It is basically like a big washer, and needs soft soldering into place.

Bolts can be added to this to make it look more realistic if you feel you want to be finicky, but to save time, this was not done.

 

The second method is similar except you use a tube of similar dimensions rather than a solid bar, with a plug soldered into the bottom with the same screwed thread sticking out so that it may be attached with a nut as in the solid version. The washers, in this case, need to be silver soldered on as we shall be using the chimney as the main vent for the exhaust stream, which means a great deal of heat is generated here.

 

For this method, do not be tempted to taper the outside diameter of the tube, otherwise you may have no thickness in the wall at the base of the chimney.

Keep the plug at the base to no more than ½ an inch high as the steam exhaust pipe will need to be inserted just above the saddle height, but this part will be done as the top plate is installed and is governed directly from your engine height. Shape the bottom to be a good fit to your smoke-box as in the first method.

The short video below shows the simpler version of steam venting where the exhaust is blown up a tube attached to the rear of the chimney – stop the video just as the engine passes you to see it more clearly, but it is not so obvious to the onlooker.

 

 

The builder of this slightly modified version of PYRTE being used at a car meet for its first public airing can be seen in the background wearing the hat and grey overalls (the usual steam enthusiasts uniform) and using a remote control for the steering at around the 8-second mark, with the exhaust more obvious at the 11-second mark. 

He installed another two short videos entitled:

Traction Engine Doris #2 and Traction Engine Doris #3 to see more of this engine in action.

 

If you are wanting the full instructions to build PYRTE, it is available from Amazon as a frighteningly expensive kindle download at $2.99 or there is also a soft-backed printed version available for workshop use by clicking this blue tab.

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