Friday, 29 July 2011

Good news & Bad news

The good news is that I have done a lot more testing, run trains over the viaduct (on the final trackbed but with temporary track), and extended the trackbed up to the tunnel entrance.

One of the tests involved running a train up the steepest section, with increasing numbers of coaches, with and without a pilot. Without a pilot, the best it could do was 4 before it started losing traction on the rails.With a pilot, they managed 8, still with some slipping from Tangmere. I stopped at 8, when smoke started coming out of the pilot engine! (...and it wasn't the paintshop smoke seen in the pictures below.)

34067 "Tangmere" piloted by 2P 40579 (still in LMS livery) on a heavy cross-country train.

40579 and 34067 approach the viaduct, working hard up the gradient.
The troublesome increase in gradient can be seen between the green and red/cream coaches.

4F 44417 on the viaduct with an anachronistic ballast train.

View from a 00 microlight above the viaduct, looking along the trackbed towards the site of the tunnel mouth.
And the bad news? Well, the poor performance of the locos on the steepest gradient is the clue. I re-checked the gradient and found I had been somewhat over-optimistic in the measurements during construction, and instead of 1 in 50 with a short stretch of 1 in 40, I had about 2 metres of 1 in 40 with a short stretch of 1 in 33. This makes a big difference to the length of trains that can be handled.

What am I going to do about it? For now, I'll leave the track in place but won't extend it to double track. This will allow trains to be run and the weather-resistance of the track to be tested. Any new track further down-hill will have the trackbed raised so that eventually the existing track can be replaced with a maximum gradient of 1 in 50, as originally intended. The viaduct and the stretch up to the tunnel do not exceed 1 in 50.

Sunday, 24 July 2011

Tracklaying at last!

I spent this afternoon laying the first permanent track for the garden railway. The first three metres went well, then I found an uneven bit of trackbed and had to do some rework. Before locking up, I ran a couple of trial trains on the first three metres (gradient about 1 in 40). Note the prototypical superelevation on the curve.

Wednesday, 13 July 2011

A Railway in the Garden

After watching James May's second (this time successful) attempt at running a Hornby train to Barnstaple, the idea formed for a railway in the remoter parts of our garden. An initial survey showed that a gradient would be necessary, and after tests with several engines and up to 12 coaches, 1 in 50 was chosen as the ruling maximum, with short stretches of 1 in 40. The first picture shows the gradient trials under way, with a 9F pulling 8 coaches up 1 in 40.

It wasn't long before a brick embankment had appeared.  A removable section is required, in front of the gate, achieved with a plywood viaduct.

To check out the basic construction techniques, a short section of temporary track was laid.

... followed by a test with the part-completed viaduct, to assess whether a sound-deadening underlay is needed.