C2 Project News

Easter 2020

Update from Easter 2020 – Working from home

We are now three weeks into the Covid-19 restrictions in the United Kingdom, and the workshops at Boston Lodge and indeed the railway as a whole remain closed. We have therefore been unable to carry on with our working parties as usual. However, there has been some work on going at home by various members of the project over the past few weeks. It is really amazing how much can be achieved at home, with a little thought.

Turbo Generator

At the last working party before the current travel restrictions, Erle, Andrew and Chris went though the box of parts that we have for our JWF-1Z steam turbo-generator. The governor valve had previously been removed and the parts kept in a box. It was obvious that there has previously been a failure and many of the parts are damaged. Although we had very little information, we laid out the parts on the bench and we were able to understand the basic mechanics of how the governor valve works. It appears to be a constant speed governor with the governor valve itself held open by a spring. Increasing the speed of the turbine shaft would cause a lever to act against the spring, thus closing in the valve. Two centrifugal weights spin out at speed compressing a spring this pushes what we think is a graphite bearing and carrier. This pivots on a yoke arm which in turn pushes in a sprung loaded piston which regulates the amount of steam entering.
By trawling the internet, it was possible to obtain a basic and un-dimensioned sectional drawing of the turbo-generator. Armed with this drawing and the parts he took home, Erle was able create a new sectional drawing with CAD for what we have. Unfortunately, some of the parts are badly damaged but there is sufficient information to establish their original shape. The spring to the bearing has broken into three pieces at some point. The Graphite bearing and its carrier have twisted down wards by 45° with metal to metal grinding and then failure of the carrier pivot points. It should be possible to repair this either with new castings or machining from solid. Without further information, it may be difficult to get the correct spring rating for the broken spring. It may be possible however to get an idea of the spring rate by measuring the wire diameter, the coil diameter, and trying to estimate the number of active coils. That may be accurate enough, given that there is some adjustment built into the system.
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New drawing of the turbo-generator by Erle.
The steam turbine has also suffered some damage, when the governor valve failed in service, some of the parts had evidently fallen into the bottom of the housing, but the machine had continued to operate. In the process, the governor parts had chewed their way in to some of the turbine blades. The blades are fitted tightly into the turbine disc and there are a lot of them! The damage looks mostly like a certain amount of peening over the middle of the blades. It quite soft material so it may be possible to use a Dremel and a thin polished rod and carefully dress them back. If this repair method is used, it will likely, of course, reduce efficiency as any small losses at the edge will have to be overcome with the governor valve applying a bit more steam. Alternatively we may be able to make and fit new blades if we can dismantle the turbine disc.
View of the turbine with blades visible round the edge.
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View of inside cover of the turbine. Part of the governor valve gear is visible as well as the exhaust steam pipe outlet at the bottom. At the top, the angled hole can be seen which directs the live steam onto the turbine blades.
Erle has also started drawings for some of the broken cast pieces. These have been fed over the internet to Erle’s son Ed who has converted them back into 3D drawings suitable for 3D printing. These have in turn been send back to Erle, who with help of another son Tom, have been able to produce some mock-ups of the replacement parts. These 3D models can later be used for printing patterns to allow us to cast the replacement parts. This is turning into a good family effort!
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Selection of 3D printed turbo-generator parts and how they fit by Erle, Ed and Tom. Obviously, these need casting for actual use! Thanks go to the Ford family.
Whilst buying old books from China as part of his historical research, Paul has also been able to acquire a few techincal manuals including one for a type JF-3 turbo-generator. While this is not the exact model that we have, it is very similar in design and contains some very useful information for us. With the manual being in Chinese, Andrew spent a few hours scanning in each of more than 80 pages and Paul has spent many more feeding in the scans into his OCR and translation software. The results have been remarkable and are a “gold mine” of information for us.
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Front cover of the JF-3 turbo generator manual.
Page 30 of the JF-3 Manual as scanned by Andrew
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The results of Paul’s efforts. Left is page 30 of the scanned JF-3 manual with OCR software and Right is after translation into English. This book is proving a “gold mine” of information.
Although most or all C2s were built with the JWF-1Z turbogenerator as we have, some were later retro-fitted with the JF-3 as described by the manual. These photos show a JF-3 mounted on a C2 originally built at Harbin in 1960, and which worked at Zhanhe Forestry Railway:
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Happily, the JF-3 manual describes the main differences between the two models of turbogenerator. These were mostly on the electrical side. The JF-3 is a clever brushless machine which uses direct current to energise a stationary magnetic field core which sits inside the rotor "claw". As the "claw" rotates around the stationary field core, it rotates the magnetic flux inside the outer stator winding. This has the advantage of not having any brushgear and therefore greatly reduces ongoing maintenance. However, the JWF-1Z as we have uses a more traditional design with brushes used to pass direct current to excite the rotor, spinning inside the stator winding.
The manual also gives us more details of the governor mechanism, and tells us the steam nozzle size for both models of turbogenerator (which was different between the two models). The JF-3 has a fabricated turbine wheel with 110 individual stainless steel blades. Although we initially thought that our turbine disc was cast in one piece, we now believe that the JWF-1Z is built in the same way as the JF-3.
The manual also gives instructions for the dismantling, repair, reassembly and testing of the turbogenerator, including illustrations of some of the special tools required, a fault-finding guide and a list of spare parts.
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Dismantling the JF-3

Vampires in North Wales

When we were last in Wales, Paul asked Alex (the Ffestiniog and Welsh Highland Railways' Chief Civil Engineer) about the curvature profile of the Ffestiniog Railway. Alex kindly dug out a report of a detailed survey which had been carried out back in 2014, and sent it to him.
Dave 1 has digitised the curve data, and put it into a spreadsheet. There were one or two values that were missing, but these could be estimated with reasonable accuracy using Google Earth. This has enabled him to generate profiles of track design curvature and installed cant, for the up and down lines (yes, we know most of it is single track, but there are loops at some of the stations). The data has been output in VAMPIRE format, so that it can be used to carry out dynamic computer simulations of the C2 running up and down the line.
Paul has been working on a "Track for Gauging" file applicable to the Ffestiniog Railway. "Track for Gauging" is a railway industry specification for defining track irregularities (roughness) applicable to a railway system, such that it is suitable for use as an input for gauging analysis. The track irregularity data should contain examples of all the features found on the line, which is a considerable task given the variety of track forms on the Ffestiniog Railway.
Once we have all the necessary files, we will be able to run a VAMPIRE model of the C2 up and down the line, calculating how much it sways and yaws. Then we can check that it will fit through Garnedd Tunnel!
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VAMPIRE plots of the FR track design curvature and cant, courtesy of Owen Evans.

More soon. Watch this space.....

We hope that you can see that work on the C2 is continuing apace, even if it is work from home and done remotely. We hope to be back in the C2 shed when it is safe to do so and the current restrictions are eased enough to allow it. Until then, we hope to keep publishing more updates about our homework C2 projects!
May 2020 
Suspension of Working Parties