Mark Posted June 26, 2014 Share Posted June 26, 2014 Having been working on a kit for a Great Western covered footbridge, which I have designed specifically for Brent with additional parts to make it more generic, I have today received the etches laid out in the photo below, all eighteen sheets of them! I hope to use this thread to post images of the bridge as it develops over the coming few weeks. Regards Mark Humphrys 16 Link to comment Share on other sites More sharing options...
RMweb Gold gwrrob Posted June 26, 2014 RMweb Gold Share Posted June 26, 2014 That looks very nice Mark.Any prices been quoted for it yet please. Link to comment Share on other sites More sharing options...
Kenton Posted June 26, 2014 Share Posted June 26, 2014 Must be 4mm? That looks scary - lots of long thin bits to cut out, keep flat and the solder without heat bends. Going to be interesting to see this grow into 3D. Link to comment Share on other sites More sharing options...
Horsetan Posted June 26, 2014 Share Posted June 26, 2014 Mark is the same fella responsible for a 3D printed-plus-etched "Western", I believe.... Link to comment Share on other sites More sharing options...
Mark Posted June 27, 2014 Author Share Posted June 27, 2014 (edited) This is the work from the last couple of days. Firstly embossing the rivets in the main span, tinning the rivet overlays on the fret and then soldered in place for. There has been no difficulty in removing the parts, or distortion when soldering. The etches are 0.3mm Nickel Silver, so they are more forgiving of heat than brass. In should complete the main spans tomorrow and then start on the legs. Edited June 27, 2014 by Mark 9 Link to comment Share on other sites More sharing options...
RMweb Premium Siberian Snooper Posted June 28, 2014 RMweb Premium Share Posted June 28, 2014 Mark That looks fantastic, if you decide to market them I for one would be interested. I also learnt something, I had never thought to tin and add bits whilst they were still on the etch. Cheers SS Link to comment Share on other sites More sharing options...
Mark Posted June 28, 2014 Author Share Posted June 28, 2014 Today's work has focussed on the lower web for the main span after fitting the overlays for the rivet detail yesterday. I have half etched these parts to make provision for the angle bracket that joins the sections together on the prototype. I have done a pair for the lower edge and another pair for the top edge of the sides. Being half etched, there are two ways of forming the bends for the staircase. One is to etch small holes where the bend is required, and the other way is to design a jig with the fold line half etched in the frame. The idea being that the bends are formed in the jig and the side can be soldered in place whilst still in the jig, which makes it easier to keep everthing square and not get burnt fingers!. The problem with this method is that the metal isn't fully supported when the bend is formed meaning you could get a radius bigger than required. The solution I came up with was to stick some brass shim on the surface of the part with Pritt Stick to bring it up to the same height as the frame before clamping it in the bending bars. The bend was then formed and the brass shim removed and used for the other end. The Pritt Stick stops the metal moving when it is being adjusted in the bending bars. Once the bends were formed, I had to use a broach to open the slots slightly to enable the tags on the side to locate properly. The sides were soldered into the lower web before removing it from the Jig one at a time. The final image is the assembled part after cleaning up. 3 Link to comment Share on other sites More sharing options...
Mark Posted June 28, 2014 Author Share Posted June 28, 2014 Thanks. I am planning to do it as a kit later on, but this is the test build of the etches. I have been working on this for the last six months, so hopefully I have flushed out most of the issues during the design phase. I have designed the kit to be for South Brent, or as a generic Great Western plate footbridge. The kit can be built with a hipped roof, curved roof, staggered entrances, with or without roof. I have also made it 4mm too high so the legs can be properly seated in the platform. Regards Mark Humphrys 2 Link to comment Share on other sites More sharing options...
Mark Posted June 29, 2014 Author Share Posted June 29, 2014 Today's work has focussed on the upper web for the sides and a start on vertical stiffeners. Forming the upper web took around an hour and the first attempt at attaching to the first side was a bit difficult, because I had kept the part on the folding jig. For the second side, I removed the part before soldering and it was much easier to do. I have been trying to use the same side for the first operation of each stage so I have one with defects in it and one with improvements. The images are for the side with all the defects in. I have also included some rendered images from the cadds file that I created a few years ago showing the bridge in its intended setting. Regards Mark Humphrys 7 Link to comment Share on other sites More sharing options...
Jol Wilkinson Posted June 30, 2014 Share Posted June 30, 2014 Mark, excellent work. Also a good illustration of why modelling the LNWR has its benefits, their covered footbridge is much more straightforward to model. The more complex(?) and repetitive parts were laser cut in .75mm Rowmark by Jonathan Buckie of Clockwork Ideas and the rest overlaid/built/constructed with Evergreen strip. Jol 6 Link to comment Share on other sites More sharing options...
Mark Posted July 3, 2014 Author Share Posted July 3, 2014 That looks superb! Regards Mark Humphrys Link to comment Share on other sites More sharing options...
Mark Posted July 3, 2014 Author Share Posted July 3, 2014 The last few days I have been putting the external braces on the main span and doing the stairs and deck. The next job over the coming days is to assemble the legs and landing. The first image is the assembly jig for the staircase. On Brent, the stairs on the main span are enclosed behind wooden planks, so the jig incorporates these on the underside. If an open staircase is required, it can be done by removing the planks after soldering the steps in place. The second image illustrated one of the folded steps located in the assembly jig, followed by the stair case balanced on the bridge. The next image is tinning the metal strip that runs along the surface of the main deck on either side before fitting it to the floor, shown in the next image. The remainder are images of all the bits balanced together. Apart from some filling and adding the hand rails to the staircase this part of the main span assembly is nearly complete. Regards Mark Humphrys 7 Link to comment Share on other sites More sharing options...
Isambard Kingdom Brunel Posted July 3, 2014 Share Posted July 3, 2014 Mark, that is awesome. I expect to see alot of GWR Stations in the future with some beautiful Footbridges. I think the fact that there are so many options to how it can be made will make it a best seller Link to comment Share on other sites More sharing options...
Mark Posted July 16, 2014 Author Share Posted July 16, 2014 Progress is being made on the bridge. The last few weeks have focussed on making the legs and I have started on the first flight of steps now. Again the images show the basic formation of the legs and various overlays to create the impression of 'L' section girders. I have also taken the opportunity to balance bits together to start to get a feel for the overall impression. The most important part has been to take plenty of time with each stage. There are some minor issues I have identified, mostly regarding the stiffness of the legs when trying to bend them, so I will make some minor alterations to the tool to make this easier. Otherwise, everything has fitted together remarkably well so far. Regards Mark Humphrys 10 Link to comment Share on other sites More sharing options...
Mark Posted July 27, 2014 Author Share Posted July 27, 2014 I have spent the last week soldering together the main span girders onto the floor and assembling the first staircase sub assembly. The photos show various stages of assembly and then the sub assemblies loosely put together. Each step is individually soldered into a slot in the wall. I was concerned about it going banana shaped, so I soldered small groups on either side to even out the expansion. In the event, I don't think this would have been a problem. There are a some gaps between the landing and the main staircase, because there are dowels that locate it into the landing tower, which are intended to file flush with the inside before the main span is fitted. I haven't the staircase to the landing yet, so the main span is pushing against one of the dowels and forcing the staircase away. The staircase assembly is locked to the landing tower with tabs that locate in slots under the floor. Regards Mark Humphrys 7 Link to comment Share on other sites More sharing options...
RMweb Premium Siberian Snooper Posted July 28, 2014 RMweb Premium Share Posted July 28, 2014 This is turning out to be one heck of a kit, bearing in mind that some of the photo's are very close up the level of detail is fantastic. SS Link to comment Share on other sites More sharing options...
RMweb Premium Gwiwer Posted July 28, 2014 RMweb Premium Share Posted July 28, 2014 Very nice indeed Mark. I wonder how much expansion has to be allowed for in the construction. I would be interested here if it wasn't for the temperature range my model has to endure. I'm stuck with the Hornby plastic equivalent which looks nowhere near as good but has at least proved tolerant of eight years on the model in air temperatures varying between 5C and 50C. Link to comment Share on other sites More sharing options...
Kenton Posted July 28, 2014 Share Posted July 28, 2014 Very nice indeed Mark. I wonder how much expansion has to be allowed for in the construction. I would be interested here if it wasn't for the temperature range my model has to endure. I'm stuck with the Hornby plastic equivalent which looks nowhere near as good but has at least proved tolerant of eight years on the model in air temperatures varying between 5C and 50C.Given that range is pretty small in the overall metal expansion terms and that it is all same metal construction. Would expansion seriously be an issue. I would not fix the base of the stairs on both sides to the baseboard but allow it some float - the most expansion is going to be along the bridge. I must say I am really impressed with the detail and complexity and am wondering on the build time overall. Link to comment Share on other sites More sharing options...
RMweb Premium Gwiwer Posted July 28, 2014 RMweb Premium Share Posted July 28, 2014 Would expansion seriously be an issue. I use nickel-silver rails. This kit is nickel-silver. I have to allow a 2mm gap at the joins when laying track in cool weather to avoid buckling in the heat. 2mm expansion of a footbridge might be enough to disturb the ground it is seated on even if not fixed. But it's a superb kit and something I would be rather interested in myself. Link to comment Share on other sites More sharing options...
Mark Posted July 28, 2014 Author Share Posted July 28, 2014 Thanks for your kind comment comments. The bridge is made from Nickel Silver and is intended to sit below the surface of the platform by 4mm. I have had a quick look at the thermal expansion for Nickel Silver and it seems to be around 1.6e-5mm/mm/degC. The total width of the bridge is 240mm, so on the assumption that you have a temperature range of 45deg C, then the total expansion is 1.6e-5x240x45 which gives a total deflection of 0.17mm. I suspect the reality is the temperature when the bridge is installed would be around mid range, so you have a deflection of +/-0.085mm. I can't see this being a significant problem. I have probably spent around 100 hours over the last five weeks working on this, but a fair chunk of that time has been spent making notes and maintaining a list of minor things to change for the production tool. The good news is that so far I haven't found anything that requires a radical redesign. Most of the issues revolve around the ease of bending parts, which is easily addressed by making the fold lines less stiff. I would expect to spend a similar amount of time on a loco kit and I am on a learning curve with this as well. Tonight I am planning to build up the staircase on the other side of the bridge. After that, there are some braces to go on the main span before I contemplate soldering the sub assemblies together. After that I can start on the valences. Regards Mark Humphrys 1 Link to comment Share on other sites More sharing options...
Kenton Posted July 28, 2014 Share Posted July 28, 2014 Mark, if you haven't already thought about it - one way I have seen on a few all N-S kits to make fold lines easier is to effectively etch perforations into the half-etched lines. It does tend to make them a little bit more brittle but is a perfect solution for the 180' reverse folds. Link to comment Share on other sites More sharing options...
3 link Posted July 28, 2014 Share Posted July 28, 2014 Hi Mark, I do not know the implications of how easy it would be to scale up to 7mm, but I think the footbridge would sell well in 7mm. I for one would definenately want one, and being of Nickel Silver is even better. Enjoying the build, Martyn. Link to comment Share on other sites More sharing options...
Mark Posted July 29, 2014 Author Share Posted July 29, 2014 I have been asked by others if I would consider a 7mm version. It is quite possible, although I would have to adjust some parts to make sure it scales properly. I think I will get the 4mm version sorted first and see how it goes. I would need four new tools for a 7mm version, so I would need to be confident that I don't end up out of pocket on it. Regards Mark Humphrys Link to comment Share on other sites More sharing options...
Mark Posted July 29, 2014 Author Share Posted July 29, 2014 I haven't found too much difficulty with folds that are in full thickness etches where a half etched line suffices. The problems were with the legs, where the actual leg is half etched. I put a line of small holes in to weaken it for bending, but it was still too stiff, which increased the risk of bending the diagonal braces as result of excessive force so this will be modified to fold along a dashed line rather than a dotted line. Also the small holes etched on the half etch 180 degree fold on the steps needs to be weakened as well to speed up the process of folding 40 individual steps, so I will probably do this with dashed slots as well. Regards Mark Humphrys 1 Link to comment Share on other sites More sharing options...
hayfield Posted July 29, 2014 Share Posted July 29, 2014 Stunning piece of workmanship, pity it will be covered in paint and viewed from a distance. Work of art in its own right Link to comment Share on other sites More sharing options...
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