70021 Morning Star Posted February 12, 2015 Share Posted February 12, 2015 . IF YOU'RE THINKING OF FITTING A SMOKE-GENERATOR, HOW DO YOU PROTECT YOUR PLASTIC LOCOMOTIVE? The problem with these things is that they generate a huge amount of heat, and the smoke oils are likely to attack the plastic of your prize locomotive. I've just fitted a Seuthe 27 to my prize Castle locomotive and, within minutes of switching it on for the first time, I have a melted chimney ! I think there are ways around this problem, and I'd appreciate discussing ideas here. The problem with my 4-6-0 Castle is that it's fitted with a brass chimney cap. It is the top half of the chimney - the lower part being plastic - but has a fitting tube that extends to the full depth of the chimney. As a result, the brass parts took heat from the Seuthe 27, as it heated up, and melted the lower part of the chimney. Not good, considering the manufacture claims this is for plastic locomotives. Well, I wasn't totally surprised. I have a few ideas I'd like to discuss, as I think we can safely use smoke-generators in our plastic locomotives, we just need to do a little preparatory work. But, before I share my ideas, I'd like to hear from other RMWEB members. Awaiting your thoughts, Rick Link to post Share on other sites More sharing options...
34theletterbetweenB&D Posted February 12, 2015 Share Posted February 12, 2015 A question before going any further would be the softening point temperature of the plastic used for the moulding, vs the temperatures generated by the Seuthe unit in that location. If the smoke unit warms the plastic in near proximity close to the softening point (or exceeds it) then the project is a non-starter for any longevity in that form. Even the trick of lining the smokebox interior with as heavy as possible copper tube as combined heatsink and support won't fully do the job, it may stave off deterioration for a while at best. (You want copper as the rapid conduction ensures that the heat dissipates into the full mass as swiftly as possible.) Substitute all metal construction for the heated zone would be one solution. Link to post Share on other sites More sharing options...
70021 Morning Star Posted February 12, 2015 Author Share Posted February 12, 2015 Hi TLBBB&D, Yes, absolutely correct. What I think has happened here, is that the smoke-generator hasn't just heated itself up to temperature, but also had to heat the brass chimney, until they both reached whatever temp is needed to generate smoke. Result: the bottom of the chimney, which is a bit of plastic that acts as a holder for the chimney, melted. I'm thinking to build a self-contained unit that fits inside the plastic body. I'm not going to say what that is, just yet, because I want other ideas. Elsewhere on RMWEB, someone tried something similar using copper pipe (bad idea, as copper is a great heat-conductor), but my thinking is thermal insulation. Everyone: thoughts / ideas, please. Meanwhile, I'm continuing my research of what I hope is a simple and cheap solution. Rick Link to post Share on other sites More sharing options...
ajaxjones Posted February 12, 2015 Share Posted February 12, 2015 What about e-cig components? All the connectors and heater heads are available as individual components Link to post Share on other sites More sharing options...
John Tomlinson Posted February 12, 2015 Share Posted February 12, 2015 An excellent subject to raise. At exhibitions I've looked at locos fitted with these units and the area of the smokebox always seems a bit odd, as if the paint has faded or flaked - not surprising really. I have thought of fitting such a unit in one of my white metal bodied locos, but then there would be even more angst if that melted as well! The idea of setting a Seuthe unit in some form of insulation seems a good one, but the issue then becomes one of whether there is space for it to be effective. The problem with any trial is that the results if negative are likely to have trashed one's loco. John. Link to post Share on other sites More sharing options...
70021 Morning Star Posted February 12, 2015 Author Share Posted February 12, 2015 E-cigarette components, eh. That's something new. I'll have to investigate what's in them and how they work. Not sure about 'white metal'. I know a lot of people replace the plastic chimneys with white metal ones for use with smoke-generators. But, I've always understood it has quite a low melting point ( though I've no idea what that is). My thinking is to create a completely new - heat proof - boiler and chimney section, a 'capsule' that contains and heat isolates all the smoke generation equipment. This would 'drop in' to the front of the boiler. Paint. Hmmm, I'll need heat and chemical resistant paint, at least on the front black painted section of the boiler and chimney. Rick Link to post Share on other sites More sharing options...
70021 Morning Star Posted February 13, 2015 Author Share Posted February 13, 2015 . LOWEST THERMAL CONDUCTIVITY FIREPROOF INSULATOR = FIBREGLASS Been doing some Googling. It appears that those rolls of Fibreglass Wool loft insulation have the lowest thermal conductivity and are fireproof. Also, I've a free supply in my loft, easily sufficient for my needs. Chemical Metal, which I'm using as a modelling construction material, is ok for temperatures up to 160°C. So, filling an aluminium tube with loosely-packed fibreglass wool will contain the heat inside the unit, and mounting the brass chimney in an appropriately modelled lower chimney of Chemical Metal, then mounting the Seuthe 27 smoke-generator inside the aluminium tube in a low heat conductivity plaster support, should meet my needs. I've still got to find a suitable matt black heatproof paint. Rustin's matt black Stove Paint is looking promising; it's a water-borne acrylic. In any case it'll be disguised somewhat by the smoke weathering on the smokebox, and will only be applied over the aluminium boiler tube, the brass chimney, and the Chemical Metal. ==> Don't suppose anyone has a small quantity of matt black Stove Paint they could send me? Rick Link to post Share on other sites More sharing options...
KalKat Posted February 13, 2015 Share Posted February 13, 2015 Aluminium is also a very good thermal conductor........ Link to post Share on other sites More sharing options...
70021 Morning Star Posted February 13, 2015 Author Share Posted February 13, 2015 Hi KalKat, While it's true that aluminium is a thermal conductor, my options for a tube are somewhat limited. Plastic, no. Copper, no. Or aluminium, which is a relatively poor conductor that's not going to be affected by heat. The job of the aluminium is to hold the brass chimney and smoke-generator, which will get hot, and to keep that 'hot spot' away from the plastic parts of the boiler. I'm thinking to reduce the heat transference along the aluminium by 'honeycombing' the top of the aluminium boiler section by drilling it full of holes. These holes can then be shallow surface-filled - so I'll get a smooth paint finish - with low-conductivity plaster or Chemical Metal. I'll try to find time to produce an engineering drawing of what I'm planning, hopefully, sometime today or over the weekend. The key feature is separation of the hot spots from the vulnerable plastic, and to ensure that excess heat cannot easily transmit along the material I'm using to hold the hot smoke-generator and chimney. In this respect, honeycombed aluminium and fibreglass wool look very promising. I hope to come up with a cheap solution that is simple enough to be within the capabilities of all modellers. Keep your thoughts coming, Rick Link to post Share on other sites More sharing options...
34theletterbetweenB&D Posted February 13, 2015 Share Posted February 13, 2015 Rick, I can see the way you are thinking, but the heat of the evaporator is only half the problem. The oil vapour contains heat energy too, and will deposit that energy in anything it condenses on, and then there is the chemical interaction between the oil and any materials it contacts in vapour and liquid phases. You therefore also need to look at the material and paint coating on the exterior of the model, for resistance to the effects of the condensing vapour. Link to post Share on other sites More sharing options...
John Tomlinson Posted February 13, 2015 Share Posted February 13, 2015 Rick, I can see the way you are thinking, but the heat of the evaporator is only half the problem. The oil vapour contains heat energy too, and will deposit that energy in anything it condenses on, and then there is the chemical interaction between the oil and any materials it contacts in vapour and liquid phases. You therefore also need to look at the material and paint coating on the exterior of the model, for resistance to the effects of the condensing vapour. This appears to explain why many smoke fitted locos at exhibitions look a bit of a mess around the smokebox. John. Link to post Share on other sites More sharing options...
70021 Morning Star Posted February 13, 2015 Author Share Posted February 13, 2015 . LESS IS MORE - AVOIDING BOILING SMOKE OIL DAMAGING YOUR LOCOMOTIVE Actually, part of the problem is people overfilling the smoke-generators. Once the smoke-generator is hot enough, the smoke oil is evaporated as 'steam vapour', so shouldn't be dropping hot oil onto the locomotive. The problem is that people overfill the reservoir, so the smoke oil boils, rather than vaporizes - that characteristic spitting and spluttering is a warning something's wrong - and we're seeing deposits of boiling (plastic corrosive) smoke oil droplets thermally and chemically burning onto the locomotive. The old saying "less is more" was never more true; and you'll get better, thicker, 'smoke' vapour if the smoke-generator isn't having its heating element drowned in an excess of smoke oil. I also suspect that the smoke-generator will run slightly cooler if it's only vaporizing a small quantity of smoke oil, rather than heating a bath of the stuff ! This raises some interesting questions for how we design a larger smoke oil reservoir, to permit longer periods of smoke (should I say 'vapour') generation, without overwhelming the heating element. I'm thinking maybe we need to build a micro feed 'wicking' system (like we see on those plug-in air fresheners), rather than using a direct pipe connection. Either that, or a 'capillary action' micro control feed ? ...but, that's for phase two of this project. Rick Link to post Share on other sites More sharing options...
70021 Morning Star Posted February 13, 2015 Author Share Posted February 13, 2015 . DARN - BROKEN SMOKE-GENERATOR WIRES In taking the smoke-generator out and removing the black insulation off the Seuthe 27 - as per the enclosed instructions - the two wires have come adrift. I've identified where one goes, and successfully soldered it back on. But am not sure where the second wire should be connected. The one I've reattached is slightly off centre on the base of the unit. There's also what looks like a very small tube - 1mm or less - surrounded by what may be metal, exactly dead centre in the base. I'm thinking this is where the second wire goes. ==> Yes, it does. I've removed the material from the bottom of the chimney, and bulled out the heater. One wire solders the side of the tube. The other pushes up into it, into something that may be graphite paste. It may be possible to insert a wire and hold it with Chemical Metal. We'll see tomorrow. Anyway, I now have a replacement on order. At least my new mounting system will make it easy to take things apart without breaking anything. Thanks, Rick Link to post Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.