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Andy,

 

Thanks for this, very interesting.  Both these bridges are on curves, although the rear one on the passenger line is a tighter curve.  The watercourse is not navigable but is tidal.  I'd envisaged something akin to a very short version of the old Barnstaple bridge, with a 4' (or so) deep I beam either side of a cross-span deck (at the bottom of the I beam) with the bridge spans being  3 x 20' with 2 piers (so 60' overall bridge length).  Must admit I've not even checked the span/depth ratio for these numbers they're just complete finger in the air jobs!

 

Cheers

 

CDG

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IIRC, and Andy will no doubt correct me if I'm wrong, depth:length for an I beam should be in the region of 1:10-12.  I believe the cross beams would sit on the bottom flange of the main beams and be riveted/bolted to them. 

 

Jim

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Where there is masonry in a viaduct or bridge there is proper support for an infil which can carry ballasted track. In fact masonary arches are best with a distributed load forcing the arch together.  Where the supporting structure is wood or iron/steel the ballast is unecessary weight and the the track is usually carried on bulks. These are my observations and there may well be exceptions

 

Don

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2 hours ago, Caley Jim said:

IIRC, and Andy will no doubt correct me if I'm wrong, depth:length for an I beam should be in the region of 1:10-12.  I believe the cross beams would sit on the bottom flange of the main beams and be riveted/bolted to them. 

 

Jim

 

Indeed Jim - that's a good rule of thumb for single span bridges. Where the main girders sit either side of the track, there are usually cross-girders which are as you describe (there are other types of bridge where the main girders sit more-or-less directly under the rails with a thinner deck).

 

There has been a recent thread in the Preservation section of RMweb (see below) which shows the type of bridge you mention being replaced on the North Yorkshire Moors Railway at Goathland (aka Aidensfield) and which has some useful photos on it. They got the bridge pretty-much finished before work had to cease due to the coronavirus, although there is only one track in place, and the signalling still needs reconnecting.

 

Andy

 

 

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1 hour ago, Donw said:

Where there is masonry in a viaduct or bridge there is proper support for an infil which can carry ballasted track. In fact masonary arches are best with a distributed load forcing the arch together.  Where the supporting structure is wood or iron/steel the ballast is unecessary weight and the the track is usually carried on bulks. These are my observations and there may well be exceptions

 

Don

 

Don - yes, arches work in compression. However, I'd certainly challenge the notion that the ballast is unnecessary weight on metallic bridges - it still forms an important function and most new bridges in the UK are designed where possible for ballasted track (apart from the ultra-high speed lines like HS1) as it's easier to maintain than longitudinal timbers and much more suitable for the higher speed and heavier trains that we run nowadays.

 

The design of older bridges varies enormously, and depends to a large extent on which railway built the bridge (or which engineer designed it). As I mentioned earlier, longitudinal timbers were generally used where there wasn't much headroom, or where it was important to keep the weight down - eg on bigger bridges.

 

Andy

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Posted (edited)
4 hours ago, CDGfife said:

Andy,

 

Thanks for this, very interesting.  Both these bridges are on curves, although the rear one on the passenger line is a tighter curve.  The watercourse is not navigable but is tidal.  I'd envisaged something akin to a very short version of the old Barnstaple bridge, with a 4' (or so) deep I beam either side of a cross-span deck (at the bottom of the I beam) with the bridge spans being  3 x 20' with 2 piers (so 60' overall bridge length).  Must admit I've not even checked the span/depth ratio for these numbers they're just complete finger in the air jobs!

 

Cheers

 

CDG

 

CDG,

 

Copying something like the Barnstaple bridge sounds the best approach, especially where there are lots of photos or the bridge still exists. David Eveleigh (link in the small suppliers section of the 2mm website) produces a couple of different sizes of etched bridge girders - I don't know if they might be useful (assuming they are the right size) - there are some photos of the larger bridge girders he designed here;

https://eveleighcreations.com/long-melford/

 

Andy

Edited by 2mm Andy
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2 different bridge designs might be interesting and appropriate. The siding could be an original, rickety wooden or iron bridge and the main line upgraded at some point to steel girders.

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Thanks folks for the info/comments/suggestions.

 

I like the idea of different bridges - will need to put my thinking cap on.  One of them will definitely be similar to the Barnstaple bridge, but I'm even wondering whether a stone/brick arch might do for the other one.  Some great photos on the NYMR thread.

 

My baseboard timber is due back tomorrow so I still have time to ditch the cork as per Nigel's comments .  I'm leaning towards doing so as it will only mean another print out of the Templot template, but before I bin the cork has anyone got any further thoughts on this?

 

Cheers

 

Chris

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1 hour ago, CDGfife said:

My baseboard timber is due back tomorrow so I still have time to ditch the cork as per Nigel's comments .  I'm leaning towards doing so as it will only mean another print out of the Templot template, but before I bin the cork has anyone got any further thoughts on this?

As I posted recently elsewhere, I used card under the main line and loop tracks on Kirkallanmuir, the stuff that costs £5.20 a sheet and comes as the backing of an envelope with a rather nice free magazine in it!  :D

 

I cut sections to the outline of the ballast shoulder, glued them down with a generous amount of PVA and then sealed it with a further coating of PVA before using the same glue to fix down the Templot print.  The sidings etc were laid straight on the baseboard to give that slight difference in height,Shaved down card and woodfiller being used to create the transitions between the two levels.  I had no problems when ballasting with a dry mix soaked with dilute PVA.

 

Jim

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As promised, back to the building build!

 

All my buildings start with TurboCAD drawing of the plan and elevations.  Each building face is made up of several layers starting from the outside:

  1. Matte paper (often with the building exterior printed on it)
  2. 1mm greyboard making up the structural wall
  3. 0.3mm brown card layer 1 for windows and doors
  4. Clear acrylic where the glazing panes are (actually from Farish stock packaging)
  5. 0.3mm brown card layer 2 for windows and doors
  6. Clear acrylic where the glazing panes are (actually from Farish stock packaging)
  7. An occasional third layer of 0.3mm brown card for door inlay panels

 

The Cad drawing has all these layers on it and all wall layers are usually the same shape and laminate together (more on this later).

The Cad for each layer (except the Matte Paper) is exported from TurboCad via dxf file to Lightburn which controls my mini lasercutter.  This has been a great investment at around £300 as it cuts way more accurately than I ever could with my scalpel and rule!  Here's a snap of both 0.3mm brown card layers for the single story part of the station just off the cutter:

273266897_Bosaleck05-09.jpg.0371cd33396f777e9d37e86b05f4209e.jpg

You can see from this shot why there are two layers of windows - it allows modelling of the two sashes one behind the other and that in turn allows some to be modelled open. Also on here are the roof sarking boards, which have been lightly marked with parallel lines (the lasercutter equivalent of half etch!) to aid the addition of tiles/slates.

 

The Matte Paper layer is printed out on a conventional inkjet and then a coat of matt varnish is added to protect the print.  Once dry and the outline shapes and window/door slits have been cut out, the next stage is to take the 1mm greyboard and glue on the matte paper.

The lower portion of brickwork is painted black so this was airbrushed with an ultramarine and Burnt Umber mix.  I rarely use black as I find it just sucks out the light!  For this building I needed a roughcast look so next I gave the light grey areas a coat of white acrylic and sprinkled in, whilst wet, some Attwood Aggregates Scenic Dust (no connection etc.).  The excess was blown off and left to dry.  Here's the kit of parts for the first two layers at that stage:

1159294217_Bosaleck05-10.jpg.a6ca72c8952f2c6e28ec55d2176f950b.jpg

Once the scenic dust had dried, I went over it with some white acrylic with a dash of Burnt Umber.  I keep a piece of 10thou plasticard and a clothes peg to use as a mask for this kind of spraying as it's much quicker (and less damaging to the faces) than masking up with tape:

983453008_Bosaleck05-11.jpg.42a52930b415c8d6d08de2b22745a50a.jpg

Following this the windows and doors were painted up on the brown card layers using white acrylic and some Precision SR green and cream.  So here's the full kit of parts ready for assembly:

2140141718_Bosaleck05-12.jpg.7d5b0a1598ad910ece8d0b97b81df635.jpg

It can be seen from this photo that I've designed in various slots and tabs to help with alignment during assembly.  Most of the buildings can stay together without any glue as a result, and I think it gives a nice strong result when glued.  Adhesive I am using throughout is glue n glaze (again no connection etc.), mainly as it is quite forgiving if it gets onto the window acrylic!

 

Thanks for looking

 

Cheers

 

Chris

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looks very good. Can you tell me who makes the mini laser cutter please.

 

Don 

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40 minutes ago, Donw said:

looks very good. Can you tell me who makes the mini laser cutter please.

 

Don 

 

Thanks Don,

 

Laser cutter/mini CNC was from Amazon here:

https://www.amazon.co.uk/dp/B07ZS9KYG1/ref=pe_3187911_185740111_TE_item

 

Took around 3 hours total to assemble and I downloaded Lightburn rather than use the supplied GRBL software.

 

The bed will take an A4 sheet but the realistic cutting area given the bearings on the screw shafts is actually around 175mm deep by 250mm wide.  I've also installed an extractor fan and eventually built a mountboard enclosure, but I use it in my office not outside so if you're going to use it in the garage say you may not need to factor that in.

 

Cheers

 

Chris

 

 

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5 hours ago, CDGfife said:

 

Thanks Don,

 

Laser cutter/mini CNC was from Amazon here:

https://www.amazon.co.uk/dp/B07ZS9KYG1/ref=pe_3187911_185740111_TE_item

 

Took around 3 hours total to assemble and I downloaded Lightburn rather than use the supplied GRBL software.

 

The bed will take an A4 sheet but the realistic cutting area given the bearings on the screw shafts is actually around 175mm deep by 250mm wide.  I've also installed an extractor fan and eventually built a mountboard enclosure, but I use it in my office not outside so if you're going to use it in the garage say you may not need to factor that in.

 

Cheers

 

Chris

 

 

 

 

Interesting machine. I shall have to think about this.

Don

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Don - it's not the most powerful laser you'll ever see - I can just about cut through 5mm ply with it but it takes several passes, but for card it's really accurate and having the z axis control allows a very precise focus to get the cut as thin as possible using Lightburn's nifty focus check.  Instead of focusing the laser every time I change material thickness, I now have a table of heights for each material so I just have to remember to adjust the z height in Lightburn when I switch materials.  I don't know if most of the cheap Co2 lasers have this facility. 

 

I've only used the cnc motor a couple of times as I now have the laser finely tuned so I don't want to mess with that but it worked fine also.

 

HTH

 

CDG

 

 

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First job of assembly is to build up the laminated layers of the walls.  Here's the rear long elevation of the single story building in it's three layers ready for assembly.  The acrylic clear glazing has been added and also the door panels have been glued on the back of the door.

1781437256_Bosaleck05-13.jpg.2fcb2a5335ffd51f2be49a6db15876a1.jpg

 

Here's the rear 2 layers assembled, showing door with frame and window gone together

151048597_Bosaleck05-14.jpg.17b42c576933ebe6a8718b986a49f7f2.jpg

 

Finally the front layer (1mm greyboard plus matte printed paper and render finish as discussed last time) is added to the rear two.  This elevation is now ready for the building

2027056235_Bosaleck05-15.jpg.3790d7faa0b4b93512117efe9657f800.jpg

 

Here's a shot of the gable end pre-assembly showing the way the door panels are done. From the left: Front wall finish & reveal, door frame, door leaf framing, inlay panel.

606356601_Bosaleck05-16.jpg.646ec35379e0a926eb8e0b8fc439d56f.jpg

 

Finally with all the elevations assembled, here's all the bits ready for the building to be built!

742838046_Bosaleck05-17.jpg.7acfd02e6bcb57d764add88f8be1a1e8.jpg

 

In other Bosaleck news the baseboard timber arrived back from the grown up laser cutter this morning and the board is gluing up as we speak, so Bosaleck could, well start coming to life shortly.  I did take some pics and will share them tomorrow.

 

Thanks for looking

 

Cheers

 

Chris

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So tomorrow rolled into Sunday, but at least there has been progress.

 

The timber arrived back on Friday from my friendly Laser cutter and here's the pile of parts for Bosaleck's 1200x750 baseboard:

594776021_Bosaleck05-18.jpg.29bcb882c664a1d8a1ab1e45cf57eed3.jpg

In 10 minutes I had it dry assembled

1935501418_Bosaleck05-19.jpg.1f2cf245c4bdeec1395cdb0d682e27c2.jpg

And after a further 35 minutes it was all glued up (ends excepted):

1928862139_Bosaleck05-20.jpg.dd82e7f26dd1190a63522b82d72ba878.jpg

The following morning (having glued on the ends) the (now redundant) cork with track plot on it was used to mock up where it will go.

1239696607_Bosaleck05-21.jpg.44ca236dd1472e552af0ad6fe927f496.jpg

1580888855_Bosaleck05-22.jpg.5f80494dbe172babdb6aac018dff1daa.jpg

 

I think it's going to be ok.....

 

More on the station build to come next time.

 

Thanks for looking 

 

Cheers

 

Chris

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Onwards with the station build.

 

Assembly of the building could now begin.  I picked up these little magnetic right angle clamps from Smart Models at Glasgow this year.  Although the tabs mean that once you have two sides fitted onto the floor they do tend to sit correctly, it still helps to be able to leave things to set whilst the right angles are assured.

1709436535_Bosaleck05-23.jpg.90d0dab564fdccac5adf28b5bc96f0df.jpg

 

Here's all the sides (except the recessed back wall) now fitted

1368522505_Bosaleck05-24.jpg.5d83d13dffcb96aa0eac3b8163b3e83a.jpg

 

Next the recess back wall and the roof support panels were fitted.  The roof supports stop the (0.3mm) roof sarking from sagging.  They have tangs 0.7mm wide (that's the laser cutter target cut - which comes out at just about 0.65mm once the cut thickness has been taken into account) which represent the rafters that poke out through similar (0.6mm cut target) slots in the top of the walls.

2087930798_Bosaleck05-25.jpg.70610e6694596a0b4d91f6b15a4f8fb5.jpg

 

The recessed area would probably have had a ceiling, but I wanted to try modelling some truss-rafters.  The lavatory would need them at the other end of the station anyway so I thought I'd learn here, where mistakes could be covered by a ceiling.  The (half) rafters were cut from the 0.3mm brown card and once painted could be fitted into the slots in the wall plate of the front wall beam and at the top of the recess back wall.  Here's the first one fixed:

2074053294_Bosaleck05-26.jpg.57b53afd44892d55cf4567f8567a4abf.jpg

 

And here's the rest now fitted.  I was not unhappy with the look so I decided to leave them on show (albeit only to a 2mm scale person!!) rather than cover them with a ceiling.  You see - you deviate from prototype by painting a door panel the wrong colour and look where it leads!!!

1524950379_Bosaleck05-27.jpg.8f4b07de0a0d7a09a156c0b60a00b459.jpg

 

So that's this wing pretty much ready for attaching to the main building and also the rear porch, so that's what will follow.

 

Thanks for looking

 

Cheers

 

Chris

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The porch was made up in the same way as described above

509490512_Bosaleck05-28.jpg.47a375c8f83d9a9faba5ff4710518398.jpg

 

Next it was time to fit this carcass to the rest of the main building

778675466_Bosaleck05-29.jpg.787afaad330e27c9be05a468592d369e.jpg

It's almost a shame to cover up the truss-rafters!!  Still I know they are there.

 

1846304152_Bosaleck05-30.jpg.374566a65998a041c7752c626f9438fa.jpg

 

Time for some slating.  The sarking boards had been drawn up in CAD with the rest of the building and also cut out on the laser cutter with parallel guide line for the slates "etched" on.  Here's the front elevation placed to test the fit.

2127495700_Bosaleck05-31.jpg.28ccb179bcf973a988ce3c34231364a1.jpg

 

For the slates I'm using 80GSM Kraft adhesive label paper in an A4 sheet.  I've found the brown coloured stuff has a pleasing texture to the surface when painted.  A bit of experimentation with the laser cutter found the settings cut just the label and leave the backing as one piece.  I drew the sheet of slates up and included some random corner knocks and uneven spaces just to break up the monotonous patterns.  The slates come off the backing in strips:

104816819_Bosaleck05-32.jpg.4cb423b269380c5d6169577bcc308802.jpg

 

These were then stuck onto the sarking boards.  I've found that if gently offered to the sarking card they stick enough to assess but are easily adjusted to get them straight and then a firm press bonds the adhesive.

556207600_Bosaleck05-33.jpg.557fba6137491fca8e1df3ef1aac7a07.jpg

 

I've been pleased to work out how to cut the slates as it opens the possibility for sheets of lots of different sizes/shapes of tile/slate with just a one-off drawing effort for each.  The only draw back is each A4 sheet takes around an hour to cut!!!

 

Next it was time for paint and that will follow next time.

 

Thanks for looking

 

Cheers

 

CDG

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Quick instalment this morning whilst I have some coffee!

 

Once the slating was completed for each sarking board the slate strips (which had been left over long) were cut to size and then a couple of coats of acrylic paint were added.  A mix of Ultramarine and Burnt Umber plus a bit of White and some thinner gives a good coverage down into the cracks and nooks.  It's darker than the eventual colour I want.  Here's one coat:

1662542843_Bosaleck05-34.jpg.13e123137443643c25f7c5979586f298.jpg

 

And here is the whole lot of roof after two coats:

988924719_Bosaleck05-35.jpg.aa11e4af10a149f45313cffb26073008.jpg

 

An extremely dry brushing of white then brings out the texture of the brown paper and to my eye brings it to life:

575199834_Bosaleck05-36.jpg.3fcf8aae410579490a563b1b9dd9521e.jpg

 

I suspect this is all very over-scale (if you take the actual slate sizes and scale, there would be no visible gaps/steps at all) but the eventual effect is to me quite suitable as the viewing eye seems to adjust for what it is seeing.  Either way I'm pretty pleased with the finished effect I've been getting once it's been weathered. 

 

Next the roofs are added and guttering, sills etc.

 

Thanks for looking

 

Cheers

 

Chris

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The white does make a real difference. It always seems to me that because we expect to see gaps and texture the eye/brain accept it although it might not be visible at the scale distance. In fact you could find the lack of it dissapointing. My thoughs are that if you have scribed brickwork, stonework etc. on the buildings at the front of a layout but use flat brickpaper etc. for the ones at the rear the eye accepts this and gains an impression of distance accross the baseboard because that is what you get full size the texture of any surface becomes less visible the further away you are. If you are looking at a foot away from an 18inch baseboard the rear buildings etc should look about 200ft  further way than the ones at the front.

 

Don

 

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I think those slates are as good as any I've seen in any scale and as Don says, the white really helps with the texture - I wonder if a very similar consistency of an olive might give a good impression of moss/lichen in the relevant dark/damp corners?

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Don - thanks for the comments - I agree entirely.  In my view the detail (particularly relief) should get less the further back as we're trying to deceive the brain into thinking in metres rather than millimetres.  That said as always there's a balance to be struck!

 

dseagull - thanks for your comment.  I'm looking forward to other buildings and varying the patterns/sizes so it does not look all the same through the town.  The olive (and a bit of brown) will come with the weathering, which will not happen until the roofs are in place so position of things like drains and sills can be assessed and incorporated.  You are right though it does add to the overall when it's done.

 

Cheers

 

CDG

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Final assembly of the Station building .

The sarking boards with slates trimmed were added to the roof sections and some initial weathering using brown and green acrylics dry brushed on.  Then a bit more laser cutting, this time in 0.5mm greyboard gave me gutters, sills and chimney cope plates, again with dims taken from the CAD plan.  Here's the guttering - the tangs fit in between the rafter ends that stick out from the wall plate and glue to the bottom edge of the sarking board.  The green part is to indicate the guttering.  Once painted and separated from the "fret" of card I ran a black line using an ink pen along the top surface to simulate the trough

493798579_Bosaleck05-37.jpg.278729f6b6a748a704a3dc64f5af9e10.jpg

 

These were then added to the building along with the sills and chimney copes.  Down pipes were fabricated from 0.4mm nickel silver with the header tanks just a blob of solder filed to shape.  Here's the front elevation:

1580516021_Bosaleck05-38.jpg.f79a58658142cc7d5f48dd22a0c7918f.jpg

 

Right hand end showing down pipes and guttering plus a bit of weathering water marks on the single pitch roof where the downpipe from the main roof empties:

2142484854_Bosaleck05-39.jpg.86d992087b25ac13c69e15db1f519b8c.jpg

 

Rear elevation with downpipe right in the corner.

900338857_Bosaleck05-40.jpg.ac067f3eb086e9d8fe7354dad85f41c9.jpg

 

Still a bit more weathering of the roofs to do and also some on the walls (around the sills for instance).  Here's how it will sit in the layout.  Chimney pots have also been added and are just visible here in front of the workshop clutter!

782868864_Bosaleck05-41.jpg.8292441a9ca989063c0d0247f197670d.jpg

 

So that's it for the station (apart from the weathering and some detailing benches/fences bedding in etc).  Next up the platform and some other bits and bobs before we hopefully get some track down soon!!

 

Thanks for looking

 

Cheers

 

CDG

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You really don’t waste any time do you? Probably would have taken me 6 months at least to get here.

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Thanks Gareth,

 

I work on the 10 minutes a day principle, as expounded by the much missed Richard Chown. It almost always ends up being a bit longer than 10 mins, but for me the key is the discipline of always trying to sit down and do at least that every day.  It's amazing what can then be achieved and also I find that the progress becomes self-fulfilling.  That said everyone has their own pace and it's a hobby for enjoyment after all.

 

Cheers

 

CDG

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