Lady_Ava_Hay Posted May 26, 2011 Share Posted May 26, 2011 I have completed a long wall on one side of a cutting that contains four running tracks and one of the station turnoffs. Fairly sharp curves all at standard Tillig centres. Part of the plan is to construct a road bridge across this cutting. Intermediate piers are not an option as the coaches will clout it unless it is so thin and narrow as to be basically puny. This means an unsupported bridge that is probably 400mm long in 00gauge. There is ample room under the road for substantial beams. I think I would like to construct a bow string through truss bridge and have no qualms about that. What is best though? Use of brass sections, plasticard or plain thick card? Rivets or welded style? Can I design this on Inkscape and get etches made or construct it purely from pre made sections cut to length from the drawings? Any pics out there? I have Googled up a few and they look ideal. Link to post Share on other sites More sharing options...
Guest jim s-w Posted May 26, 2011 Share Posted May 26, 2011 Hiya 400mm is only 30 meters in the real world. Thats not a large span by any means. A normal verigirder bridge would be fine. HTH Jim Link to post Share on other sites More sharing options...
Lady_Ava_Hay Posted May 27, 2011 Author Share Posted May 27, 2011 Hiya 400mm is only 30 meters in the real world. Thats not a large span by any means. A normal verigirder bridge would be fine. HTH Jim Looked at your Jim and yes I can see what you mean. I reckon your span is very much what I am looking at and yours is a good deal lower in height above rail. This bridge though, needs to be a bit spectacular. It is almost the first thing you will see as you walk in to the train room and I want it to be the focal point for the eye. This is why I fancied a truss bridge. I also recall that a lot of the London railway bridges were heavy versions of this style of bridge. I think one of them was badly damaged in the Lewisham disaster or at least one of the crashes in that area. i know that rail bridges have to be much more substantial than mine which is a road bridge but the whole layout stretches the imagination anyway and I have a taste for the spectacular. I shall try this image Link to post Share on other sites More sharing options...
Glorious NSE Posted May 27, 2011 Share Posted May 27, 2011 Inspiration? http://maps.google.co.uk/maps?f=q&source=s_q&hl=en&geocode=&q=london+liverpool+street&sll=53.826597,-4.042969&sspn=5.992167,27.641602&ie=UTF8&hq=&hnear=Liverpool+Street,+Greater+London,+United+Kingdom&ll=51.521515,-0.078524&spn=0,0.003374&t=h&z=18&layer=c&cbll=51.521562,-0.078692&panoid=rAzmX7ZDhFNySc1_a4VWkA&cbp=12,298.75,,0,-11.88 or http://maps.google.co.uk/maps?f=q&source=s_q&hl=en&geocode=&q=london+paddington&aq=&sll=51.521562,-0.078691&sspn=0.000784,0.003374&ie=UTF8&hq=&hnear=Paddington,+Greater+London,+United+Kingdom&ll=51.543413,-0.155225&spn=0,0.013754&t=h&z=16&layer=c&cbll=51.542695,-0.155232&panoid=wcaBdxCrirMkPSMGD3Ryhg&cbp=12,53.24,,0,-1.54 or http://maps.google.co.uk/maps?f=q&source=s_q&hl=en&geocode=&q=london+paddington&aq=&sll=51.521562,-0.078691&sspn=0.000784,0.003374&ie=UTF8&hq=&hnear=Paddington,+Greater+London,+United+Kingdom&ll=51.525353,-0.234382&spn=0,0.013754&t=h&z=16&layer=c&cbll=51.525457,-0.234404&panoid=9EBMyxv-IiiHBcBkqmLZrg&cbp=12,338.92,,0,0.98 If it's something that old (and I think it would have to be, or they would have just used a more modern simple girder in steel or concrete) then in answer to your question or riveted vs welded - rivets and lots of! Construction-wise, are there any continental kits that could get you the girder elements of the right length? Link to post Share on other sites More sharing options...
Lady_Ava_Hay Posted May 27, 2011 Author Share Posted May 27, 2011 Inspiration? http://maps.google.c...98.75,,0,-11.88 or http://maps.google.c...,53.24,,0,-1.54 or http://maps.google.c...,338.92,,0,0.98 If it's something that old (and I think it would have to be, or they would have just used a more modern simple girder in steel or concrete) then in answer to your question or riveted vs welded - rivets and lots of! Construction-wise, are there any continental kits that could get you the girder elements of the right length? First one is too fussy and square. Second one is better. Then I Googled it and up came this:- © Copyright Jonathan Thacker and licensed for reuse under this Creative Commons Licence. With complete provenance ( Brunel ), just the right shape and roughly length ..... i will investigate further. Yes I know it is rail over river and possibly single track but a thing of beauty is a joy forever. Link to post Share on other sites More sharing options...
RMweb Gold The Stationmaster Posted May 27, 2011 RMweb Gold Share Posted May 27, 2011 With complete provenance ( Brunel ), just the right shape and roughly length ..... i will investigate further. Yes I know it is rail over river and possibly single track but a thing of beauty is a joy forever. It is a double track structure David (with a large pipe now on the side where the other line was removed in 1963) but is also has a third girder arch in the central '6 foot' space as well although whether it would fall down if that wasn't there I don't know. (For those who don't know it is one the ex GWR Windsor branch and the design is attributed to Brunel; the original material was wrought iron and it was made by Hempnett of Bristol being transported by rail to the site in sections no longer than 15ft. The riverine span was reported as 167ft at the time of opening but one source gives the length as 200ft while another says 202ft and states the height as being 17ft 9". There is a sketch style side elevation in Chris Potts' book about the Windsor branch) Link to post Share on other sites More sharing options...
Lady_Ava_Hay Posted June 19, 2011 Author Share Posted June 19, 2011 Now the second bridge abutment is installed on the baseboard, i have been able to do some more careful measuring and ( back of envelope ) design work. Basically I need two brass arches 450 mm tip to tip with a 120mm rise from deck to top of arch and this curve is drawn on a 300mm radius and sits 20mm above the level deck at each end. The question is that my ability to cut even modellers brass to the sort of accuracy and finish I want is limited by....not having the tools to have the confidence to do it. I have a hacksaw and a mini drill with variety of cutting discs including some diamond tipped ones and I can acquire a jewellers snip. I have no real workshop tools to speak of and I can't afford to experiment. What would you good folks recommend? Link to post Share on other sites More sharing options...
Guest stuartp Posted June 19, 2011 Share Posted June 19, 2011 What would you good folks recommend? Styrene. The top girder on the two Paddington bridges is a box, i suspect yours is too - a curved box girder of 1mm/40 thou styrene will be more than strong enough to support itself over that length, and you can add all the twiddly lattice bits from Plastruct sections or similar. You can always overlay it with brass shim or even aluminium foil for the rivets. Link to post Share on other sites More sharing options...
Lady_Ava_Hay Posted July 10, 2011 Author Share Posted July 10, 2011 The bowstring truss was not viable. I had to glue together lengths of plastistruct square section and when stressed over a former, the internal section I had used, snapped. So I reverted to a box section truss and used lots of plasticard to embellish it and a blunted self tapper as a rivet gun. Now I need to start cutting ply to form the elevated deck.that is the reason for the retaining wall in the first place. There will be pics when mounted. Link to post Share on other sites More sharing options...
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