Brunel Viaduct

[Moonraker]

I am just starting the construction of a Brunel wooden trestle viaduct on my railway. Does anyone know the best kind of wood strip to use in conditions of strong sunlight?

Peter

[cabbage]

Peter,

Several of my American friends have built trestles from Cedar -which is quite expensive here in the UK. This leaves the English hardwoods of Oak and Beech. I have used "Tanalised" timber to build bridges from but you require the special "Enseal" paint to paint over the newly cut surfaces. I normally used the green Enseal paint -which paints on blue(?) The stuff then dries to a dull brown colour and you can slop on something like  "5 Year Fencing Duck paint" for the next few days.

regards

ralph

[IanT]

Some more thoughts for you Peter - in terms of outside wooden structures generally - best to use well seasoned timber as it will be less liable to shrinkage/splitting. Also in terms of painting it - I would tend to use an oil based wood treatment (rather than a water based fence paint) as they tend to penetrate deeper into the wood. These are generally quite a bit more expensive - but then you are not actually going to paint fences with it.

If you can find an old table with a solid wooden top (most likely to be oak or beech) it will cut up into 'building' strips quite nicely. I have used this source for wagon frames. Pity really but good wooden furniture does not seem to be in fashion these days and can be quite cheap (look in charity shops!). Again remember that oak needs to be pinned together with wooden dowels (iron/steel will corrode if used) which makes it an awkward material with which to build this kind of structure, although it ages to a very realistic silvery colour if left untreated.

I'm not sure there is a real problem with using soft woods if they are well seasoned - but they will need much more regular protective treatment and would really be best if you can store them indoors during the worst of the winter weather.

[midnight miller]

Hello All

At the risk of being branded Irresponible , a luddite and worse by the P.C. brigade , And being wholley unrepentant . Good old fashioned cresote is still avalable from agricultural stockists .


                                                   John . T

[cabbage]

I am well aware of the fact -but you explain to my wife why her roses have died...

My sleepers are deep cooked in creosote and then sun dried -but prior to when they go down they are dipped in "duck" to seal them. When my son and nieces/nephews were smaller I used Tanalith treated timber entirely. This meant while it was edible -it did not taste very nice(!)

regards

ralph

[midnight miller]

Hello Ralph

Tell her the green fly got 'em

                                     Still unrepentent


                                              John . T

[Moonraker]

Thanks all.

I can get wood strip in Tasmanian oak so I will do that way and note the comments on coatings.

Peter

[Moonraker]

Just an update of my progress on this project. Three piers are up and five to go. It's a long job.

The design was complicated by the fact that the track needed to climb at one in fifty while the land below was at a variable gradient, averaging about one in twentyfive. This lead to some very tricky calculations of trestle sizes. In the end, I decided to play safe and cheat.

First I made a formwork mould for the concrete piers. When each pier was poured, I inserted two vertical treaded steel rods, on to which I was able to accurately locate the decking using supporting nuts. Using a laser beam, I was then able to adjust the decking up and down until it was level crosswise and at the correct gradient.

The decking consists of two thicknesses of Harditex BlueBoard, a cement sheet, sandwiched between two 12mm square strips of Tasmanian oak; all glued together with external Aquadhere.

Next came the trestles. I drew up two templates, one for the inner trestles and one for the outer. Again, 12mm square strips of Tasmanian oak were cut, pinned and glued to produce each trestle. They were pinned and glued into position in the gap set by the steel rods and cross bars were bolted in place each side. Finally all the woodwork was painted with decking preservative.

[Moonraker]

Sorry, the photo didn't work first time.

Peter

[IanT]

Brunel would have been proud of you Peter!