Weiss / Walton Ceramic Burners for Model Steam Boilers

1. Auflage 2020
ISBN: 978-1-78500-766-8
Verlag: The Crowood Press
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 112 Seiten

This book covers the materials needed to make ceramic burners and explains how to silver solder them. It discusses LPG and holding tanks, as well as connecting pipework and electronic and mechanical automatic gas-control systems to monitor the boiler pressure. In addition, there is advice on how to set up, install and operate each burner to provide optimum heating to the boiler. A summary of the Boiler Test Code Volume 3 that applies to home-made gas tanks is included, together with a list of useful suppliers with their contact details. This book provides all the information you need to build and operate: three burners, with one variant, for boilers with 42mm, 35mm and 28mm horizontal flues; two round burners for vertical boilers with fire boxes; two different sizes of rectangular burner, with one variant, for use in horizontal water-tube or pot boilers and finally, one small round and one tiny oblong burner for use in Mamod and Wilesco boilers. The burners described are straightforward to make and simple to use to heat the water in boilers that meet the 3 bar litre limit in the UK Boiler Test Code.

Alex Weiss established a model engineering workshop over forty years ago and has written numerous books and articles, mainly about model making. All the burners described in this book have been designed, built and tested in working boilers by Alex and Kevin Walton, who has provided extensive technical support.

Autoren/Hrsg.

Weiss, Alex

Walton, Kevin

Leseproben

1	Materials and Tools

THIS CHAPTER DESCRIBES ALL the tools and basic ready-made items that can be purchased, as well as the raw materials that will also be required to build the burners described in this book. It also covers the workshop facilities, including machine tools, that are likely to be needed. It does not include what is needed for silver soldering, which is covered in Chapter 2.

Building ceramic burners is not a difficult task, but does require a few items not normally found in many modellers’ workshops. One unusual tool is required, a ceramic saw, as well as high-temperature adhesive/ filler and high-temperature paint. These are easily obtained either from DIY or specialist suppliers, or on eBay. Building burners also requires a range of machine tools, some of which are fairly normal such as a lathe, and a few that are slightly less common, but that you may need depending on which burner you decide to build, such as a vertical milling machine and a rotary table. Likely to be found in the scrap box are short lengths of brass rod and possibly some pieces of copper tube.

COPPER AND BRASS

Two metals are predominantly used in the construction of all the burners in this book: copper and brass. Copper is not simple to machine or drill but is very malleable and easy to bend into shape. Drilling is best done with a special copper-drilling bit that looks similar to a wood drill. Brass, on the other hand, is straightforward to machine, though drilling can be awkward at the point of breakthrough. Brass is readily bent but not as easily as copper. Annealing either metal makes bending relatively simple. Brass needs an etch primer if you wish to paint it, but to date there are no heat-resistant etch primers.

It is important to realize that lengths of copper pipe from plumbing suppliers will be a different size from those purchased from model engineering suppliers, so it is important that where end caps and short lengths of tube are needed, they will fit into each other.

Cutting Lubricant for Copper

A number of lubricants are recommended for use when machining copper: sulphur-free cutting oil, dry soluble oil, lard oil, and paraffin or mineral lard oil. A practical tip I learned from Martin Gearing in his articles on the ME vertical boiler is to use original bright-green Swarfega Classic as a lubricant when drilling copper. A can is illustrated in Figure 15. It cleans off easily and has no negative effect on silver soldering. It is an excellent cutting fluid, or rather a jelly, for copper. It is still widely available both from Screwfix and Amazon. For drilling and milling, the bit can be dipped into some Swarfega, whilst for turning, a brush will prove ideal for applying it. Although it is also ideal for cleaning hands at the end of a session, do keep two separate containers to prevent polluting the hand cleaner with swarf.

FIG. 15
Swarfega Classic, the original hand cleaner, is a fine lubricant when machining copper.

BURNER BODIES

The bodies of the round burners described in Chapter 3 are made from copper plumbing end caps of different sizes, and short lengths of copper plumbing tube. Likewise, all the round burners in Chapters 4 and 5 involve the use of plumbing end caps. A number of different-size end caps can be seen in Figure 16. It is essential that these end caps are not the Yorkshire type, as these contain a ring of soft solder that will make silver soldering impossible. As all copper plumbing materials are only available in metric dimensions, imperial sizes are not normally quoted by suppliers.

FIG. 16
A small selection of copper plumbing end caps, the two left-hand ones for making large circular burners, the right-hand pair for making burners to fit horizontal flues.

All these copper plumbing parts should be to EN 1057 – Type X (previously BS 2871 Table X). They can be bought from plumbers’ merchants or DIY supermarkets, but it is probably easier and cheaper to order them on the Internet. For the 28mm burner a pair of end caps will be needed, one of 22mm and the other of 28mm. The 35mm burner for horizontal flues requires end caps of 28mm and 35mm. Likewise the 42mm burner needs end caps of 35mm and 42mm. In addition, the two larger burners require short lengths of copper tube, of 28mm and 35mm diameter respectively. You might have offcuts yourself, or you may be able to scrounge a short length – 50mm will do – from one of your friends.

It is possible to build the circular burners for boilers with fireboxes from 35mm, 54mm or 67mm end caps, depending on the size of burner required, but the height of the end cap will have to be reduced: this can be easily done in a lathe or using a hacksaw and file.

FIG. 17
The folded copper box that forms the body of the large rectangular burner.

Any of the larger rectangular burner bodies can be made from 1.6mm thick (16 SWG) copper or brass sheet, cut and folded to size as illustrated in Figure 17. The smallest oblong one uses 0.9mm (20 SWG) brass sheet. All the oblong burner housings are then silver soldered at the corners. You will need to drill the bodies, whether round or square, so that the gas-jet housing you have made can be silver soldered into place.

GAS-JET HOUSINGS

It is a relatively straightforward task to make the gas-jet housing. Drill a short length of 1/2in or 12mm brass rod right through, and then, for the smaller burners, turn down one half to a smaller diameter. Carefully cross-drill the holes for primary air, then drill and tap a small hole for a 6BA or M3 bolt in order to secure the jet holder in place and allow its position to be adjusted. Examples of the two main variants can be seen in Figures 18 and 19.

FIG. 18
The type of brass gas-jet housings needed for burners for horizontal flues.

FIG. 19
The different gas-jet housing required for burners that fit in fireboxes.

GAS-JET HOLDERS

While gas-jet holders are widely available from companies that sell gas jets, they are also very easy to make. All that is needed is a short length of 8mm (5/16in) round brass rod. The holder is 25mm (1in) long, and is drilled 4.5mm for a depth of 20mm (3/4in), and then tapped 1BA to match the gas jet. Finally, a 1/8in hole must be drilled for the gas pipe. This can be either cross-drilled near the base of the holder, or through the base depending on how you want the gas pipe to run.

GAS PIPE

The UK standard for gas pipe, suitable for LPG burners that heat model boilers, is 1/8in. It is normally supplied as bending-grade copper tube in a coil. The pipe can be easily straightened and cut to the required length, and then silver soldered into the gas-jet holder. The other end needs silver soldering into the gas-valve connecter to the gas tank. A small pipe bender, such as the one shown in Figure 20, will help to ensure a neat installation of the gas pipe.

FIG. 20
A coil of 1/8in copper pipe and an economically priced pipe bender to enable the making of a neat gas-pipe installation.

NUT SPINNERS

Adjusting the position of the gas jet in the housing is an awkward task – holding the housing, moving the gas-jet holder, and loosening and tightening the bolt that fixes the holder in place in the housing. Trying to do this using an open-ended spanner is almost impossible, so the use of a nut spinner makes a difficult task significantly easier. Figure 21 shows examples of a long and a compact nut spinner used for this task.

FIG. 21
Two alternative examples of 6BA nut spinners, either of which will be found useful when setting up your burner.

GAS-DIFFUSER COMPONENTS

Without any diffusing components, the gas will not be evenly distributed in the larger burners, and the ceramic material in some of them will not burn evenly across its surface when lit, seriously reducing heat output. The burners that plug into the flue have gas-jet holders that extend to within 3mm (1/8in) of the far wall of the burner body, resulting in the gas dispersing across the relatively small surface area of the ceramic.

For the larger round and oblong burners that fit in the firebox, various possible solutions were tested. These included using a tube of mesh fitted across the width of the burner body from the gas/air inlet, a sheet of mesh fitted under the ceramic element, and the use of baffles in the body of the burner. None of these methods worked as well as a strip of mesh to diffuse the gas and a length of spring to give it swirl, which resulted in the gas spreading evenly across the burner body. The two materials that help resolve this issue, springs and mesh, are both made of stainless-steel.

Stainless-Steel Springs

The four largest burners have a length of stainlesssteel spring in their bodies from the gas-jet housing to the other side of the burner body to impart a degree of swirl to the gas/air mixture entering the chamber. This can be easily cut from a short length of 1/2in or 12mm diameter stainless-steel spring of 1.6mm thick wire (16 SWG). The two smallest burners for Mamod and Wilesco boilers use a thinner 3/8in (9 or 10mm) diameter stainless-steel spring of 0.9mm (20 SWG) or 1.2mm (18 SWG) wire thickness. Figure 22 shows examples of both these springs.

FIG. 22
Lengths of 3/8in (9mm or 10mm) and 1/2in or 12mm...