And now we come to the heating arrangement for your model traction engine First off, let s take a look at the gas fuel we can use... Here in the UK there are two readily available gas types that will do the job. Both are available in the smallish 1 4 kg size (2.2 8.8 lbs) Propane Butane Both are readily available in gas bottles of varying dimensions that may suit a trailer, although the propane bottles tend to have a large handle sat on top for carrying purposes which takes up far too much of the trailer height and would make the trailer look totally disproportionate to PYRTE. Propane, being at a higher pressure in the bottle needs a regulator to reduce the pressure for burning purposes, again usually sat on top of the bottle more often than not sat within the confines of the handle for safety s sake, and produces a far fiercer flame at the burner end and for that reason generates more heat than Butane... Wait for it... There s a BUT... It also uses up the gas far quicker than Butane and is harder to light as it needs a flame for combustion to take place. Butane on the other hand has a flatter profiled bottle which suits the trailer size better and does not need such a great reduction in pressure = a smaller regulator = less height involved and merely needs a spark for ignition to take place. For the same amount of gas being used, apparently Butane is supposed to burn hotter than Propane. Now here s the BUT... And believe me, it s a GREAT BIG BUT! Here in the UK, and all over Europe too (I ve not explored the US yet, so I m afraid that will be up to someone else to tell you on that score), our Butane bottles have regulators with a pressure level set to suit camping gas stoves, barbeques and the likes, and this barely gives enough pressure to light PYRTE s burners, especially when it is trying to supply four, so that is pointless. It can be seen that with the awkward size of the Propane bottles and the reduced pressure with the Butane regulators, a compromise is needed. On the practical side, for economies sake, larger bottles would be used; but for our convenience we need to turn to the disposable gas cartridges that are readily available. They contain, generally speaking, 70% Butane (for ease of lighting) and 30% Propane. These give off a slightly higher pressure of gas and burns far more fiercely than neat Butane without the need for a large regulator.
There are generally three sizes of canister to choose from, but as we are to be using four burners, then the largest, around 450/500 gm (almost 1 lb) is the most suitable for our purposes. Do be careful though... These canisters tend to have a variety if fittings for the top for the gas outlet some with internal screw threads, others with external, some are a push-on fittings, and all with a confusing array of different thread sizes just to make it more awkward. And the worst part of it is, when you go to a supermarket or wherever for you gas purchase, the threads are protected by a plastic stopper so you can t see what you need to see to get the right match for your own fittings unless you actually buy the can. What I suggest you do is first of all get hold of your gas can valve from www.clevedonsteam.co.uk (one of our most highly recommended suppliers especially for the heating side of things any problems, Gerry s the man to ask) so you have something to start with. The thread on the gas bottles is a very odd-ball one, and making your own fittings for the bottle connections is really a non-starter + you need to consider the safety aspect of this also. It s just a matter of taking the fitting with you and asking for help in your local shop to find the matching gas bottles. You can go down the single gas can valve route if you wish, but the single narrow pipe connected to this valve limits the amount of gas flow to your burners, which tends to give a weaker flame. I tried one for a time when running four burners until I realised the rear two burners were well fed with gas, but the front two only half did what they were supposed to. It appears one can and its regulator is fine for 3 burners with number 5 gas jets, but not 4 burners. The simple answer was to be running on two bottles of gas with two gas can valves feeding into one pipe connection which fed the burners. Fine, light her up on one gas bottle, then add the other to get the steam pressure up before regulating the gas flow by reducing the gas from one bottle or both. Et voila... Perfect flames all the time. Sorry... I m telling porky s here. The two gases in these containers tend to be released at different stages, unless they are being shaken (mixed like when you are trundling along under steam). The Butane comes off first with easy combustion and a hot flame, and when you are down to the last 30+% you get the propane being introduced and the flame becomes less heated, less productive, often referred to as a lazy flame. With the four burners in place and two cans in use this is not a problem, but when I tried PYRTE with three burners and a single can, she had just enough heat produced to get up steam when the can was almost empty, but it seemed to take forever, and when a load was added (like pulling me around) she failed miserably.
So if you are going to be using PYRTE for a good steaming session, I recommend having two cans on the go, with a further two in your trailer for replacement purposes. Right... Next we come to the burners... In my early trials I was struggling to get enough heat under PYRTE s belly to get her to move at all. Recently, however, in the last few years, there has been an explosion (perhaps the wrong word in this case) of interest and demand for ceramic burners and I must admit I tried first one, then two together under PYRTE s belly, being ¾ x 5½ inches long. One barely did anything, not even managing to lift the needle from zero on the gauge any heat being passed into the boiler and water was simply radiating away as fast as it was introduced. What was needed was more heat, so a second burner was bought and installed. Please note: The supplier I used for the second burner you should avoid at all costs. I am speaking from personal experience here. The ceramic burner was ordered from Forest Classics whose web site I shall not show, and the burner took two months to arrive, despite regular contact with them. Car salesman springs to mind here - all flannel and promise, flashy site but very poor service. In the end I had to threaten court action to get the burner delivered. They are most certainly NOT recommended by me. With this extra burner the pressure reached up to 25 lbs/sq inch, just about... It may have got up to 30 the odd time when there was no wind, but as soon as the engine was run under steam, sat on my bench at the time, so under no load, the pressure dropped off and was not replaced, so PYRTE soon stopped turning over. I was getting more and more frustrated with this, until I saw one of Gerry s ads on Ebay (He was using Ebay as his main selling point, this was before he had set up a web site) and I thought I d try two of his burners to see how it went. They are obviously designed to fit Cheddar Models boilers as that s where he started off his steam career, and as Cheddars have gone belly-up, he decided to continue making parts for fellow Cheddar enthusiasts, along with others now. To be honest, I was a bit sceptical about this pair of burners, but when they arrived, my eyes were opened. After all the hype about ceramic burners being so wonderful and being sizzled into my brain over the last few years, and the advertisers jumping on the bandwagon and raising the prices no end, it was refreshing to find a burner that was better than the ceramic ones, around half the price and also less than half the space was needed. Gerry makes these burners himself, and also supplies many other fittings associated with burners and boilers, so you are assured of a good product.
I initially tried fitting one alongside the two ceramic burners and the pressure went up to the 35 mark whilst under no load again and I could plainly see that Gerry s was the better burner owing to the fierce blue flame, so this led me onto installing the two with one ceramic burner it was all trial and error at that time. With the three burners in place PYRTE got up to pressure in around 12 minutes on the bench, but with the motor running she was down on pressure to the 20 mark very quickly. This called for more heat, so I ordered a further two of Gerry s burners and installed them with the disappointing ceramic ones quickly dispatched to the bin. With the four burners in place I found that with the extra heat being produced, I had to open the vent in the top plate a little to accommodate the extra gas flow, that way not creating improper combustion, and this was easily achieved by opening the gap up to ¾ inch wide from its original ⅝ inch. I now use four of Gerry s burners, sitting half an inch under the boiler barrel and run from two gas bottles with the taps connected to a rubber gas hose between the trailer and the manifold, and this gets up steam and ready for the off in around 8 minutes from cold, and then once the steam s up, it s a case of turning off one bottle completely and using a single one, or turning the two down to suit the demand. Like this a single bottle will give almost an hour in running time. One word of caution here though... These fittings, the gas tap outlet thread and the piping nuts all have ¼ x 32tpi threads and for this reason you can either purchase the thread converter (adapter) from Gerry to bring these fittings to match the ¼ x 40tpi you are generally using, or you can source your own taps and dies (I suggest MaccModels) at ¼ x 32tpi to make up the manifold. Right... Enough of the waffle... Take your firebox base at 6 x 6 inches x ¹/₁₆ inch mild steel sheet and mark along two opposite sides a line at ³/₁₆ in from the edges. Along this line from each end make a mark at 1¼ inches in and drill through with a 3.5mm at these four points and sit the two ⅜ square brass rods you already have from your tender sides to sit flush with the ends and across the top of these and using the base as a guide, mark the brass rods for drilling purposes and drill right through. Now you need two 6 inch lengths of 1 inch x ⅛ section steel and drill a 3.5mm hole through the ends centrally, but at ³/₁₆ from the end and thread a 1 inch 4ba bolt through each hole from the bottom of the base plate, up through the brass rod and through the 1 inch x ⅛ support plates. This will leave you with ¾ inch of brass rod showing at either end, but do not worry about the middle bolts showing along the brass rods for now. (The above picture does not show this clearly or to scale as in these early trials with the gas heating, the brass rods here were simply butted together rather
than overlapped at the corners, but make a point of getting the rods the right way round as these need to be bolted to the inside of the firebox base). So you now have a base plate that can be mounted underneath the firebox and can be held in place with 6 x 4ba bolts. To make the all brass manifold, take 2 x 2 inch lengths of ¼ o/d brass rod and drill them through with a ⅛ drill. (You may need to drill in from both ends to complete this operation, although you can reduce the length of the rod, but it will mean the feed pipes for the burners being pulled into tighter bends to achieve this). The ends are threaded ¼ x 32 to accept the burner fittings (or alternatively ¼ x 40 with the adaptors from Clevedon Steam). Next you want 2 x 1¾ inch pieces of brass at ⅜ diameter with a ³/₁₆ hole bored to 1 inch deep. In the undrilled end a hole needs boring across the ⅜ rod to allow the ¼ tube to be inserted and silver soldered into place. Once this soldering is done, then a ³/₁₆ drill is used to continue the hole already started and to go through the side of the ¼ tube and marry up to the ⅛ holes in that tube, that way allowing gas to enter the larger diameter and escape at the two smaller ends and on to the burners. The hex rod is ¾ inch across the flats (I used hex as it was available and is easier to drill through sideways than round bar) and is 2 inches long with around ¾ inch turned to ¾ diameter (this is not really needed). A hole needs boring through across the flats at ½ an inch from the end for the ⅜ tubes to be soldered in place and from the round end of the hex rod a ¼ hole is needed to marry up to the ⅜ tubes. Open this ¼ hole out to ⅜ for a depth of ¼ inch to take a ⅜ brass tube which is soldered to it and held in place by the brass brackets supporting the burner stems. The supporting tube is again soldered to a length of 9 inch length (variable) ¼ inch o/d copper piping to allow easy access for coupling up the rubber gas hose from the trailer. This was achieved through a brass ferule being soldered on the end and a jubilee clip clamping the rubber tube to the ferule.
The burners themselves were purchased from Clevedon Steam and were simply clamped in place by the ⅜ inch square brass rods (remnants of the reinforcing rods in the fire box build). These rods were bolted to the raised 6 inch length of 1 inch x ⅛ section steel at the rear. block off the air inlet holes. You ll notice that lumps have had to be cut out to allow nuts to be placed on the bolts in the picture, plus some drilling will need to be done to get the burner necks to fit, but do make sure you do not In the above picture you can see an upper hole level with the two burner gas inlet points. This was the original mounting for the manifold and the flame sat far too low below the boiler, so the extra packing was installed to get the burners sat at around ½ an inch below the boiler bottom. You will also see that the ⅜ support tube for the gas supply is hex and has a threaded adapter for the copper tube - this was purely for my convenience and is not really needed. The piping for the gas is the same as supplied by caravan retailers, being re-inforced rubber hose with an internal diameter of just under ¼ inch (6mm I think). Because of this the end of the pipe sitting underneath the traction engine needs to be made to fit this and I made a simple brass ⅜ end soldered onto the ¼ inch pipe, with a reduction down to ¼ for the hose and bored through with a ³/₁₆ drill. On the bottle side of the equation, if you want to try a single gas bottle, then you need to make an adaptor with a ³/₁₆ diameter hole through it to go from the ¼ x 32 fitting on the end of the gas delivery tube from the bottle, onto a ¼ insert for the end of the rubber tube. This will not be too successful as you will see the gas delivery tube is ⅛ copper tubing with an internal diameter of ¹/₃₂ or there abouts, and as the pressure is not too high in these bottles, then this piping will restrict the amount of gas being fed to your burners. This size just about copes with 3 burners, but struggles with the 4 we are using for PYRTE. A simple T adaptor sitting in your trailer is all that s needed with a ¼ leg for the rubber tube end and two gas bottles individually feed the top arms of the T so that double the gas volume is available when needed. The arms are ¼ o/d with a bore of ⅛ and the leg is ¼ o/d with a bore of ³₁₆. At start-up both bottle are needed for the initial heat surge, but when she s warmed up a bottle can be turned down or off on the can and a single one provides enough heat for steady running. With the burners pointing towards the central axis of your boiler, all that s needed now is to connect your gas supply and light the burners so that you can adjust the flames properly. This is done by undoing the screw on the side of the gas inlet and sliding the jet holder either forwards or backwards to produce a large and neat blue flame what this does is to allow the correct amount of
air in the air hole by partly blocking it off (and causing some turbulence for better mixing at the same time). We next move on to the insulation and painting of your model.