Mad McCann Posted January 29, 2015 Share Posted January 29, 2015 Folks. I'm about to leap into the world of scratch-building, or at least partly so. I'm going to roll the boilers of my intended victims and with a borrowed roller and relevant tuition I'm raring to go. There is one thing currently holding me back which prompts this question. How do you translate the dimensions of your boiler onto the piece of flat brass you intend to fold? I'm sure I'll be bowled over by the simplicity of the formula when it's pointed out to me but I'd genuinely appreciate some initial guidance. Thanks in anticipation. Link to post Share on other sites More sharing options...
micknich2003 Posted January 29, 2015 Share Posted January 29, 2015 For any circle, the circumference is: 3.141592... × the diameter. Link to post Share on other sites More sharing options...
Adrian Posted January 29, 2015 Share Posted January 29, 2015 or 22/7ths which makes it really simple if modelling in 7mm scale. Link to post Share on other sites More sharing options...
RMweb Premium ianmaccormac Posted January 29, 2015 RMweb Premium Share Posted January 29, 2015 or make it out of paper and cut to size with a pair of scissors and then unroll the paper, pritt stick it to the metal and cut that! Cheers Ian in Blackpool, remembering seeing the brilliant early designs by Malcolm Mitchell being done precisely that way. Link to post Share on other sites More sharing options...
Guest Lyonesse Posted January 30, 2015 Share Posted January 30, 2015 Or if you want to be more accurate pi times ( scaled diameter of the boiler - thickness of the metal ) since the unrolled length is ( 1 / pi ) times the diamteter halfway between the outer and inner surfaces of the rolled boiler. You do have some vernier calipers to measure it with, don't you? I find the essential requirement is true circular profiles which can be insered into the ends of the boiler, since it is not possible to roll a true cylinder with simple hand tools. Link to post Share on other sites More sharing options...
Mad McCann Posted January 31, 2015 Author Share Posted January 31, 2015 Good Lord! An old maths lesson held the answer for me back in 1978. If Bill Campbell's on here anywhere he'll be over to kick my arse shortly as he taught me in the first place! Link to post Share on other sites More sharing options...
John Tomlinson Posted January 31, 2015 Share Posted January 31, 2015 Before you start rolling be aware of the disparity between quoted boiler diameters and the outside diameter with the cladding. The former often refers to the actual boiler and doesn't allow for cladding, but to us modellers it is the size over cladding that matters. I've seen it written that the difference may be around 3 inches or more, which in 7mm is certainly significant, and I wonder if any of our skilled builders could comment. John. Link to post Share on other sites More sharing options...
buffalo Posted January 31, 2015 Share Posted January 31, 2015 Indeed, John. Insulation plus cladding sheets are often 3-4" thick so the overall diameter difference is twice that. I would have thought that most would consider an extra mm to be significant in 2mm scale, 2mm certainly is in 4mm scale. Nick Link to post Share on other sites More sharing options...
micknich2003 Posted January 31, 2015 Share Posted January 31, 2015 As the attached drawing shows, there is typically a 3 1/2gap between the boiler and clading. Link to post Share on other sites More sharing options...
Mad McCann Posted January 31, 2015 Author Share Posted January 31, 2015 So, in 4mm, I'm assuming that's going to add 3mm to my overall diameter then. So many hidden pitfalls! Link to post Share on other sites More sharing options...
micknich2003 Posted January 31, 2015 Share Posted January 31, 2015 Mr Mad, if you are working to a decent "Scale" drawing, simply take the outside dimension off the drawing and multiply that figure to arrive at the circumfrence. The previous comments related to, and for example "XX" locomotive having a 5ft diameter boiler, this is the diameter of the actual boiler which you don't see. You see the clading which adds a further 6ins or so to the overall diameter. Link to post Share on other sites More sharing options...
Londontram Posted February 1, 2015 Share Posted February 1, 2015 In 00 I've always added 2mm ie. the cladding being about 3 inch if you take into account that the 3 inches is all round so the overall out side width is a total of 6 inches greater. so in 00 scale of 4mm to the foot that 6 inches = 2mm extra over the quoted boiler diameters Link to post Share on other sites More sharing options...
Mad McCann Posted February 17, 2015 Author Share Posted February 17, 2015 I'm going to decipher the drawings in the CRA Jumbo book. I should get some fairly definitive numbers from there. Also found myself a copy of Guy Williams' treatise on the subject so I think I should be OK now. Thanks for all the assistance and I'll stick up some images if efforts bear useful fruit. Cheers. D. Link to post Share on other sites More sharing options...
RMweb Premium Nig H Posted February 19, 2015 RMweb Premium Share Posted February 19, 2015 Have you considered using brass tube for the main part of the boiler? From the drawing above, you would need 18mm diameter tube. I model in 2mm scale and this is how I always make boiler/ smokebox units. The smokebox can be built up with a series of overlays made from thin sheet - say 5 thou each. I would have thought that this way might be easier than rolling the whole boiler and more likely result in a perfectly round boiler. Also adding the smokebox wrapper might be easier, though this would still need to be rolled. When I do this, I roll the wrapper by feeding it between two lengths of brass rod which are rolled against each other, thus pulling the wrapper between them and forming a curve. Its worth practising with bits of scrap from etches etc. before having a go with the real thing. Maybe someone who models in 4mm scale could comment on my suggestion. Some pics showing the operation. Regards, Nig H Link to post Share on other sites More sharing options...
RMweb Gold Donw Posted May 31, 2015 RMweb Gold Share Posted May 31, 2015 It is suprising what can be done with a single rod and a mouse mat or even ones thigh. Don Link to post Share on other sites More sharing options...
sej Posted May 31, 2015 Share Posted May 31, 2015 Hi: I'm a big fan of brass tubes and various wrappers in 4mm. Although I do enjoy a good home-rolled one occasionally. Cheers Simon Link to post Share on other sites More sharing options...
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