Kelly Posted June 22, 2011 Share Posted June 22, 2011 So I've a perhaps somewhat whacky plan to scratchbuild a 4DD unit. As the windows curve into the roof in a distinqtive manner, getting the roof profile right is very important. Presently I'm toying with printing out plans for sides/roof onto paper and then using those to form side-roof-side on either plasticard or brass sheet. The question I am trying to get around in my head planning such is how to correctly form the curvature/profile of the roof with either material? I'm looking at needing more than one possibly, so was also thinking of using such scratchbuilt plasticard/brass bodys to form the basis for moulding in resin perhaps. Kelly Link to post Share on other sites More sharing options...
billbedford Posted June 22, 2011 Share Posted June 22, 2011 So I've a perhaps somewhat whacky plan to scratchbuild a 4DD unit. As the windows curve into the roof in a distinqtive manner, getting the roof profile right is very important. Presently I'm toying with printing out plans for sides/roof onto paper and then using those to form side-roof-side on either plasticard or brass sheet. The question I am trying to get around in my head planning such is how to correctly form the curvature/profile of the roof with either material? Don't. Think Different Form the body out of a clean material such as acrylic sheet and cut a vinyl overlay to get the windows. Link to post Share on other sites More sharing options...
Pugsley Posted June 22, 2011 Share Posted June 22, 2011 I'd agree with Bill - clear plastic would be the ideal thing to form the body from. Consider making a wooden former, then forming the body over that by heating in boiling water. The vinyl overlay could be used to get door gaps, as well as the windows. Link to post Share on other sites More sharing options...
Kelly Posted June 22, 2011 Author Share Posted June 22, 2011 Thanks for the replies. Will consider suggestions. Link to post Share on other sites More sharing options...
Colin parks Posted June 22, 2011 Share Posted June 22, 2011 Hi Kelly, Scratch-building a 4 DD sounds like an interesting project. I can't think of any advice for the building of these units. I do know that using plastic patterns to form resin moulds is not the best method. Brass is a much better bet, though you will still end up with over-thick sides. Printing onto a clear material or using an overlay sounds more practical, but making a clear acrylic body to the exact profile of a 4 DD? Who has done that?! Good luck. If I think of anything that might help I will let you know. Colin Link to post Share on other sites More sharing options...
Mark Posted June 23, 2011 Share Posted June 23, 2011 Many years ago, I made quite a few coaches using styrene sheet and the method that I eventually adopted for forming the curves on rooves and tumblehomes was to score the inside of the plastic with the tip of a knife so that you form a series of 'V' shaped parallel grooves. I used to do these around 2mm apart for the sharper part of the curve and further apart for the shallower areas. After cutting out all the apertures for windows etc, I then used to clamp the plastic between a pair of Steel Rules stiffened up with a couple of pieces of vertical shelf bracket supports and then bend the material to shape one groove at a time using another rigid straight edge to support the unclamped part of the plastic, working from one side to the other. In doing this, you form the shape you require. I also used to make up a series of formers to check against and ultimately to hold everything in the final shape. It was then a simple case of taking a sanding block with some fine wet and dry and then profiling the outside to achieve a smooth profile. This method used to work fairly well and I found the plastic was far less likely to distort over time after the model was completed. Hope this helps. Regards Mark Humphrys Link to post Share on other sites More sharing options...
Engineer_London Posted June 23, 2011 Share Posted June 23, 2011 I recall someone building small-scale trams with pre-printed clear sheet for the body. Could have been Liverpool streamlined cars, meaning that the problems of single- and double-curvature had been tackled. Will see if I can find out a bit more. Link to post Share on other sites More sharing options...
dasatcopthorne Posted June 23, 2011 Share Posted June 23, 2011 Guys I've been making SR EMUs for a good few years now by sticking an overlay onto pre-curved Perspex sides. It works well until you come to something like the DD. I've struggled with ideas for making one of these on and off for 30 + years and I cannot find a method I'd be able to use at home. The trouble is, it's easy enough to bend Perspex with heat, the problem comes with keeping in shape whilst cooling down. Yes, you can wrap it around a former but it needs to be faily tight, this thens brings the problem of stretching the material and ending up with a mis-formed shell. It's easy enough with just the curve of a Bulleid or BR standard side but a DD needs those windows that stretch up into the roof panels. I'll get there one day. I hope. I've got drawings of the roofs and the special low profile motor bogie so may be I will make it. Dave Link to post Share on other sites More sharing options...
Colin parks Posted June 23, 2011 Share Posted June 23, 2011 Hi Kelly, I 've had a look at the plans for the 4 DD again. The "bending and heat" method could be a possibilty. As the body is slab-sided, the shape is a lot simpler than most SR EMUs. But as Dave has said, modelling the windows on the curve in the roof would be a hard. I did have a few chats with the late owner of No Nonsense Kits. He was very heplful and informative on how he made his 2 EPBs. He said that the windows were punched out of the aluminium sheet first and then rolled to form the roof/side and solebar. Just how much trial and error was invovled I do not know. It would perhaps be better to make the (clear) plastic body in three parts: each side incorporating the roof up to the water strip above the upper windows, and a roof section the width between those strips. I seem to recall the 4 DDs were painted in the body colour up to that point anyway, so that would be the natural place for a join on a model. (In my opinion etc. etc.!) Off topic, but relevant, is: how would you - or anyone else for that matter, get the motor bogies to swivel enough to negotiate curves of less than prototype radii? Colin Link to post Share on other sites More sharing options...
coachmann Posted June 23, 2011 Share Posted June 23, 2011 The DD's are an interesting project but not an easy call. I can see how the sides could be etched on 12thou brass with many grooves on the insides to aid bending the top windows onto the roof. The remaining roof section would be a plain arc. But the trouble lies in bending the glazing. One would need to experiment with different types of material as some will frost over, others will show stress lines and others would be too thick to be if any use. Link to post Share on other sites More sharing options...
RMweb Gold Adam1701D Posted June 23, 2011 RMweb Gold Share Posted June 23, 2011 Sounds a bit like the concept I've used for the 4mm Southern Region Mk1-based EMU overlays. Basically, they are pre-cut vinyl that mounts on clear acetate sheet that is thin enough to easily form to the correct profile for the donor coach. No reason why I couldn't do pre-nationalisation designs (apart from lack of time at the moment ) Link to post Share on other sites More sharing options...
Engineer_London Posted June 23, 2011 Share Posted June 23, 2011 Looked up the reference to small-scale trams, in a journal as long ago as 2005. Alas, not much in the article on shaping the clear shells to form the tram body, other than mention of local heating for bends, and filing the roof profile from solid. The maker used computer-printed vinyl laid on the shell to finish the vehicle. So alas, not too much new information for you. Only other thing I've remembered is an old kit for a trolleybus stored somewhere, made from vacuum-formed clear plastic. Don't think vacuum-forming is going to be useful either. Link to post Share on other sites More sharing options...
Southernboy Posted June 23, 2011 Share Posted June 23, 2011 If it's any help, Worlsey Works offer to produce etches for "any of the Southern Electric Multiple Units shown in Brian Golding Book" , and the DDs are featured on pp157, 158 and 171 - 174. The etches are usually sides, ends and floor only, but could provide a good basis to start from. I have an A3 sheet of thin clear plastic bought from the 4D Model Shop which bends to quite acute curves with no problem for use in buildings with curved windows, so would probably suit carriages as well. Sorry, don't have a reference number or product name for it, but I'm sure they'll be helpful if you contact them. Link to post Share on other sites More sharing options...
stadman Posted June 23, 2011 Share Posted June 23, 2011 Isn't one of the original vehicles still in existence somewhere? You may be a ble to take a look to aid your modelling. Link to post Share on other sites More sharing options...
Kelly Posted June 23, 2011 Author Share Posted June 23, 2011 Thanks for the replies, plenty of interesting options to try. I'll have to get some wood and wood working tools sometime I think to form a roof profile on that to shape by (or resin cast from perhaps). Interesting about Worlsey Works, though I suspect my very limited budget would preclude such an option sadly. May be that brass sheet might be easiest for me to work with with tools I already have and a bit of trial and error with a smaller subject to test various principles etc before moving onto the DD itself. Link to post Share on other sites More sharing options...
L49 Posted January 6, 2012 Share Posted January 6, 2012 I was commissioned to make one a long while ago as the master for an ill fated resin kit (it looked Ok until it sat in my clients workshop for a couple of weeks in the summer, and then it looked like a 25mm wide banana!). I used 20thou plasticard with all the windows cut out and doors scored while it was still flat, rolled over a wooden former turned for me by my brother in law on his wood lathe. It was held in place with a sheet of paper to keep the tops of the upper deck windows from springing up and making little 'hoods' over the windows, while I heated it with a craft heat embossing tool (nicked from my wife's card making box!) The basic model looked really nice, just don't use solvent to add the strengthening, and don't let anyone leave it in a warm place! I remember the anticipation of the first one coming back from CMA for test fitting, and being told that there might be a little bit of work to do on it. It was a truly horrible feeling to open the box and see the frankly bizarre misshapen lump that sat before me. I think a few might have made it onto the market, but it is the one model I have had a hand in which I deliberately avoided keeping a sample of! Link to post Share on other sites More sharing options...
justin1985 Posted January 7, 2012 Share Posted January 7, 2012 An interesting perspective on modelling from clear arcylic sides: http://www.svensktmjforum.se/forum/index.php?topic=3718.0 (In Swedish, but Google translate does a reasonable job) Jorgen Edgar has used this technique to create a vast collection of models in N scale - including pretty much every BR type! http://jorgenedgar.se/eng/galleri/storbritannien.html Link to post Share on other sites More sharing options...
RMweb Premium ianmaccormac Posted January 8, 2012 RMweb Premium Share Posted January 8, 2012 http://www.marcmodels.co.uk/html/in_the_tunnel.html No one seems to have seen the above web link? They are producing one. You may get ideas from this. Cheers Ian Link to post Share on other sites More sharing options...
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