Peter @tecko, Just an observation. The 'metal joiners' or splice collars would be a different elevations for one reason that comes to mind. The left side tower appears to be founded at a deeper depth than the right tower and since the wood columns are limited to a maximum length, between 9 and 12 meters , the joints will not match from left to right. From a purely engineering stand point this is not good practice, but it will work. The key is to make the cross brace truss sections be at or as close as possible to the same elevation. Attached are a few photos of what I do for work. I'm in the helicopter in the second photo, taking pictures from the air of the lift and setting of the structure.

2 attached images. Click to enlarge.

A truly fascinating build log.

James @jamesb, the Ghost and the Darkness is a strange movie. A pair of psychopathic serial killer lions working in pairs. Perhaps 'Legion' went into them like the 2,000 pigs of Gerasenes.

Anyway, the movie bridge, Kitulgala Bridge over Kelina River in Sri Lanka (Ceylon), was built in 1957. As the above photo shows, they used a cofferdam. The real bridge was not on the River Kwai but River Mae Klong in 1942-43. They did not use cofferdams. The piers were rammed into the base with a heavy weight. This weight was hoisted up by rope. The POWs had to pull up the weight and drop it on the pier. Then repeated this action all day, every day, for several months.

http://www.diggerhistory.info/pages-battles/ww2/kwai.htm

Thanks James @jamesb. Just to let you know, I won't show the collars on the model. Observers of the model would not know what they are. However I am tapering the main piers.

Below: Drilled holes for anchoring the uprights (piers). No cofferdams or pile driving here 🙂
Cut the 4 and 6 mm dowel with a Stanley Knife. I cut partly through and then break remaining fibres by slight repetitive bends. Top middle photo show a tapered 4 mm pier. It does not look like much. I believe that an overall build with tapered dowels will look more like tree trunks and more authentic.

No lathe here. Simple process of sanding the dowel down with coarse sandpaper. It really does not take long to sand one down. Though I have another 49 to go.

Looking superb so far. It’s the combination of engineering, modeling skill, veracity, and a desire to leave a legacy that teaches and enlightens - put together and we have a build for the ages, Peter. Enthralling.

James @jamesb, Here is a survivors artwork on how they pile drove the piers into ground.

Notice the POWs in background, all on a rope, hoisting the tree trunk. They used very primitive tools. The pulley is single.

Peter @tecko, Very cool find. Primitive indeed.

Excellent idea Peter.

I remember (not too long ago), watching a documentary where a Japanese soldier was calling out cadence (in Japanese of course) to the POW's as they were hoisting a large and heavy driver using ropes. As the soldier reached a certain number, the POW's let the weight fall, which in turn drove the pilings in deeper with each blow.

I will try to find a picture showing this method, and if I can find one, post it here for you if you like.

You also found some good pictures of what I think was called "Hellfire Pass" by the prisoners. Numerous persons died in this strip of the rail way. Your lighting idea will really help here.

On a lighter note, I like your humor, with the little figure in the saw dust...

Thanks for the updates.