The Saga of the Lune Crossing
Posted: Mon Jul 31, 2017 9:51 pm
I wanted the bridge over the pond (I mean River!) to be of an open construction, to allow for the desired reflections of trains in the still waters of the Lune The first job, however, was to construct the piers on which it would sit.
To create the bridge piers, I was tempted to try a technique used in the construction of stage scenery, which involves applying a cement based render coat over polystyrene 'blockwork' applied to my foamboard piers. To put it mildly, I did not enjoy the process, which proved to be frustratingly slow, and in my opinion, not that successful either.
The fine summer conditions of late June 2016 resulted in a low flow for the river, making construction work easier (or I took some water out of the pond ) The buttresses/piers were the first order of work - the core is my favourite material - foamex board, which has the advantage of being tough and waterproof.
I had a rough sketch to work to, but needed to produce cardboard templates to accommodate the uneven lining to the pond. Once I had one of the piers as I wanted them, the other was produced in the same fashion, at a faster rate. Assembly was initially with superglue, but I reinforced all the joints with a high tack grab adhesive. Because of the curve leading into the crossing from the patio side, I had to make the 'throat' of the pier much wider than I originally intended to allow for swing on engines and stock.
I then proceeded to clad the foamex cores with foam to represent blockwork.
Mistake number 1 - I used open cell polyurethane foam, instead of closed cell. The main result here was that it didn't provide a rigid enough base for the applied cement render - but I didn't realise that then, so the render was applied. And re-applied, and re-applied. Well, you get the idea - no matter how many coats of render I applied, it just wasn't 'firming' up. It looked good, but was simply too prone to damage.
I was growing increasingly frustrated with it, and my enthusiasm for the technique really took a dive. I decided to try and stiffen the coating with PVA, and apply yet more cement render. The piers, together with several castings for various detailing items (causeway wall, other walling) were left in the garden under my gazebo overnight to dry.
On the morning of July 2nd I had to go out, returning about midday - to hear my wife calling urgently for help!
The gazebo had just gone walkabout - castings everywhere, table and chairs flying, and some damage to Burton station.(fortunately, the damage to the station area was minor and cosmetic, and easily repaired. However, my castings were trashed, apart from the wall section, where only a corner chipped off, so I will be able to use most of it, thank goodness. The gazebo had two broken legs, and one of the plastic feet had broken, but I think I was able to repair it sufficiently for 'light weather' use. Before leaving that morning, I had checked the tiedowns and pegs because the wind was gusting as showers came in. I thought, being as it's summer that it would be okay. Muppet! Thank goodness my wife was in, and sprang into action when she heard a crash - otherwise I've no idea where the gazebo would have landed!
The two bridge piers were the most annoying - one of them had the backing board broken in two places, and the stone effect had been scuffed off and through in several places on both. In the end I used the carcasses as a mould to make two piers from concrete, and then painted stonework on (though not very artistically). Whilst it's not as good as what I had hoped for from the rendered items, it is passable; and has proved to be durable in the 12 months since.
In the foreground of the above image are the components of the bridge deck. The main span is an old fluorescent light body, with two angle bars to provide rigidity. Once bolted together, the sleepers were bolted in place, with every third one being extra long to act as supports for the stanchions which would support the handrails. I made sure these were wide enough to clear the widest running stock I had, but - Mistake Number 2 - I forgot to allow for having to drill holes to support the stanchions This led to a rather tight clearance on my largest loco - a Ragleth...
To create the bridge piers, I was tempted to try a technique used in the construction of stage scenery, which involves applying a cement based render coat over polystyrene 'blockwork' applied to my foamboard piers. To put it mildly, I did not enjoy the process, which proved to be frustratingly slow, and in my opinion, not that successful either.
The fine summer conditions of late June 2016 resulted in a low flow for the river, making construction work easier (or I took some water out of the pond ) The buttresses/piers were the first order of work - the core is my favourite material - foamex board, which has the advantage of being tough and waterproof.
I had a rough sketch to work to, but needed to produce cardboard templates to accommodate the uneven lining to the pond. Once I had one of the piers as I wanted them, the other was produced in the same fashion, at a faster rate. Assembly was initially with superglue, but I reinforced all the joints with a high tack grab adhesive. Because of the curve leading into the crossing from the patio side, I had to make the 'throat' of the pier much wider than I originally intended to allow for swing on engines and stock.
I then proceeded to clad the foamex cores with foam to represent blockwork.
Mistake number 1 - I used open cell polyurethane foam, instead of closed cell. The main result here was that it didn't provide a rigid enough base for the applied cement render - but I didn't realise that then, so the render was applied. And re-applied, and re-applied. Well, you get the idea - no matter how many coats of render I applied, it just wasn't 'firming' up. It looked good, but was simply too prone to damage.
I was growing increasingly frustrated with it, and my enthusiasm for the technique really took a dive. I decided to try and stiffen the coating with PVA, and apply yet more cement render. The piers, together with several castings for various detailing items (causeway wall, other walling) were left in the garden under my gazebo overnight to dry.
On the morning of July 2nd I had to go out, returning about midday - to hear my wife calling urgently for help!
The gazebo had just gone walkabout - castings everywhere, table and chairs flying, and some damage to Burton station.(fortunately, the damage to the station area was minor and cosmetic, and easily repaired. However, my castings were trashed, apart from the wall section, where only a corner chipped off, so I will be able to use most of it, thank goodness. The gazebo had two broken legs, and one of the plastic feet had broken, but I think I was able to repair it sufficiently for 'light weather' use. Before leaving that morning, I had checked the tiedowns and pegs because the wind was gusting as showers came in. I thought, being as it's summer that it would be okay. Muppet! Thank goodness my wife was in, and sprang into action when she heard a crash - otherwise I've no idea where the gazebo would have landed!
The two bridge piers were the most annoying - one of them had the backing board broken in two places, and the stone effect had been scuffed off and through in several places on both. In the end I used the carcasses as a mould to make two piers from concrete, and then painted stonework on (though not very artistically). Whilst it's not as good as what I had hoped for from the rendered items, it is passable; and has proved to be durable in the 12 months since.
In the foreground of the above image are the components of the bridge deck. The main span is an old fluorescent light body, with two angle bars to provide rigidity. Once bolted together, the sleepers were bolted in place, with every third one being extra long to act as supports for the stanchions which would support the handrails. I made sure these were wide enough to clear the widest running stock I had, but - Mistake Number 2 - I forgot to allow for having to drill holes to support the stanchions This led to a rather tight clearance on my largest loco - a Ragleth...