Wednesday 26 September 2018

Kyeamba Creek Bridge - 2

I really do not know where my time goes.   Progress on the bridge has been glacially slow on the modelling front,  partially because some indecision on my behalf on the best way to proceed,  although I have been able to continue with some rollingstock acquisitions, a brass loco repair, and more research. 

8 car RUB set hauled by 3825 leaves Wagga in 1962.  Photo taken and kindly provided by Tony McIlwain. The train is passing the upper quadrant signal, which we now believe was to protect the Edward Street level crossing.  No, this picture  has nothing to do with the Kyeamba Creek bridge, but this image and others, are some of the reasons why time ran short on the Kyeamba creek model   

Now that I had a dimensioned sketch, (see part 1) the first part was to locate a suitable piece of pine.  My desire was to include both bridges on a single section of timber plank. Whilst I did have some chipboard, and some 9mm thick ply, these materials were either too heavy, or too bendy.  Sure the ply could have been re-inforced, but a trip to Bunnings located a 1 metre or so long pine plank, with enough width to fit the bridge wing abutments.  The width is also in keeping with my future plans to minimize the width of the upper deck benchwork.

Solid pine was used for the subroadbed “causeway” between the two bridges.  This also assists with stiffening the pine plank.

The two bridge openings were marked on the plank, and the pine subroadbed was glued between the 2 bridges. 3mm MDF board (also obtained from Bunnings), was cut according to the sketch, shaped, and glued into position for the Kyeamba creek bridge.  Gaps were filled with Aldi brand filling compound 

The Kyeamba Creek bridge opening is around 50cm wide.  It didn't come out too well in the picture, but I have penciled in the location of the creek, and the timber piers.  The pine "causeway" subroadbed extends to the unnamed creek, and I have left enough space for this bridge too on the plank.  Distance between the two bridges is the compromise.  The concrete abutments are 3mm MDF.  This gives a thickness close to the 1 foot estimate of the prototype abutments.  Note too that most of the abutment will be buried in scenery

The unnamed creek will have traditional timber supports.    One thing that I assumed, was that the water level in the unnamed creek, and Kyeamba creek would be the same, as the railway is fairly level between these 2 creeks (confirmed by looking at the railway gradient diagram), however, the water level for the unnamed creek is higher than Kyeamba creek by at least a metre, which might look a bit odd on the model.  To get around this, the unnamed creek may be modelled as a dry stream
Next step was to attack the Ironbark trestle bridge that I recovered from an earlier layout.  The only thing wrong with the trestle, was that the timber piers were the wrong height, so needed to be removed.  The bridge deck though was perfect for reuse, so I didn’t want to damage it.

My original trestle bridge segments

My glue of choice back when I constructed the trestle, was white glue.  White glue is normally not waterproof, and I hoped that this was the type I had used.  Carefully, I applied water to the joint, and waited, applying some more water as soon as the first lot disappeared into the wood.  After around 5 minutes, the glue started to “go white” at the join, and with some careful pressure, the piers separated from the bridge deck. 

2 timber piers removed.  The plastic squeeze tube was ideal to get the water exactly where it was needed

All timber piers separated from the bridge deck.  Now the construction can start

Ironbark Models suggested and provided plans for a jig to make up your own timber trestle piers. 

Nest stage is to complete modelling the concrete abutments, and this will also set the rail height.  The subroadbed will then be built up to this height, prior to fitting the unnamed stream timber abutments.  Once the first one is in, then I will know the positioning for the other timber abutment.
Hopefully my next post will show a lot more progress.   Happy modelling.

Wednesday 5 September 2018

Kyeamba Creek Bridge

The Kyeamba creek flows from the hills near the Hume Hwy south-west of Tarcutta, (near the Tumbarumba road intersection) for a distance of 66km before ending up in the Murrumbidgee River.  The Tumbarumba railway branchline crosses the creek just west of Ladysmith.

Kyeamba creek is but a muddy puddle in March 2017.  Whilst I was not able to actually measure the rail height above the water, I have estimated it at 21 feet.
Another shot of Kyeamba creek, photographed from the bridge, showing a typical creek bank, and vegetation

The Kyeamba Creek bridge is a 6 x 24’ span NSW timber trestle, with concrete abutments.  A small tributary of Kyeamba creek is crossed by a 3 x 24’ span trestle close by the main bridge.   

The last trains passed over the bridge in the late 1980s.  The bridge fell into disuse, although there was a later failed proposal from Tumba Rail to reopen this section for Trike rides.    It was last year, before I actually got to inspect these bridges.   My visit to the main bridge was unfortunately cut short, as I had disturbed a wasp nest, and they were not too pleased with the intruder, forcing me to make a tactical retreat.
Looking towards Ladysmith.  Checkrails are prominent., and also are spiked directly onto the sleepers, rather than on sleeper plates - similar to the Murrumbidgee River bridge.   The shed on the righthand side is part of the automatic water flow measuring system on Kyeamba Creek, used by the Bureau of Meteorology.

The first pier of the bridge holds the rail approximately 8 feet above the ground.  The ladder is part of the automatic water flow measuring system.  The wasp nest is hidden under the sleepers close to the ladder.  

The concrete abutment

The small tributary trestle was in far worse condition then the main bridge.  One of the embankments had been washed out in the big storms of 2016, and the rails had been left dangling in mid air.  But there was enough left to see what once was  present. 

The small 3 span trestle around 200 metres to the west of the main trestle.  This unnamed stream had caused a significant wash-a-way in the storms of 2016 

Closeup of the damage.  The main railway support piers survived but the embankment, and its supports had been washed away, leaving only the stumps.  The rail, and a few of the sleepers have been left suspended in mid air

The pair of intermediate piers are resting on concrete plinths, and these look in good condition

The timber abutment at the other end of the trestle is also collapsing, but 30 years since the last train, and probably over 40 years of no maintenance, this is understandable

Many years ago, I bought the Ironbark models NSW trestle kit and extension, and started construction of an eight span trestle bridge for a former layout.  I never finished this model, before a relocation forced me to tear the layout down.   However, I kept the part built kit.
My intention when designing the layout,  was to reuse, and complete the kit without modifications, as I like big spectacular bridges,  but the further I am heading up the prototypical accuracy modelling route, I realise that the bridge kit needs to be rebuilt.

2 spans and an abutment of the Ironbark models NSW Trestle kit that I built over 20 years ago.  I am hoping that I can use this section for the small tributary trestle, as the abutments look similar, and are the approximately the same height.  The longer pier will need to be replaced, rather than just cut down to size.  The reason for this is that the angled beams have been rebated into the round piers.  The other pier is really close to being right, but I will have to make a determination later

The Ironbark models kit has great diagrams to help with the construction of the trestle, but the Data Sheets (Sheet P4) is the reference for  the  24’ span NSWGR trestle bridge.  These plans contain all the bridge details I need, except the concrete abutments, and the height of the piers on the Kyeamba Creek bridge.  However, the end abutment drawing seems to be close to style found on the washed out tributary bridge. 
The first step was to draw up a diagram showing the concrete abutments, and pier heights. 

Sketch of the Kyeamba Creek trestle - showing details of the concrete abutments.  These sizes have been guestimated from photographs.

My next challenge will be to try and remove the trestle piers from the already constructed bridge deck, without doing too much damage to the deck, and construct the concrete abutments.
Until next time, happy modelling