Monday 13 February 2017

Building a bridge

The G scale layout itself has existed for just over 3 years (as far as i can tell) and yet in that time it has probably only had about 6 months of running on it total spread over those three years. The culprit for this quite terrible performance is the long curved trestle bridge at the far end of the railway. This bridge was designed to be the feature point and as such has different height bents on a constant curve into a short straight, the bents were constructed from hardwood on a jig i made on some plywood and have survived the weather quite well being completely unprotected. The deck was the major weakness of the design being made from marine plywood which after a year managed to get moisture in it even though it had been coated quite a few times. it was so bad every time the Aristo C16 drove over it you could watch the deck deflect by over 5mm! I really should have screwed the deck to each bent which would have held it together but for all of the reasons the bridge was never very good

Mark II bridge

Due to the aforementioned problems with the wood decks i had the idea of using plastic garden edging for rails and recycled plastic garden stakes as uprights to make a kind of plate girder bridge. Unfortunately the girders cracked as soon as i tried bending it despite trying to build it with a curve in it! As mark two never got beyond construction i dont have any photos of it

Mark III
Mark 3 is a bit of a blend, the best of both worlds if you like. It uses the recycled plastic tomato stakes as uprights with a wooden deck screwed on using brackets. this has been by far the most successful iteration of the bridge requiring no maintenance in the four months of continuous operation (trains running every day!) this bridge is due for some aesthetic upgrading at some point as I loath the "railway on stilts look"

 Test fitting the bridge deck before painting (note one of the original trestle bents reused on the new bridge)
Completed bridge with a visiting lyn from the eltham south electric tramway

 Painted bridge
Train dashing across