Templot Club Archive 2007-2020
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posted: 12 Aug 2013 12:01 from: LSWRArt
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What point blade movement should you allow for in 0 gauge? I am working to 0-MF with 31.75mm track gauge (31.5mm +0.25mm gauge widening as most of my turnouts and, indeed, most of the layout is on a curve). So with a back to back of 29mm and a tread thickness of (say) 1mm I worked out that the clearance from the closure rail to the back of the tip of the blade needs to be (31.75mm - 29 - 1mm =) 1.75mm, so I thought i should allow 2mm movement. The C&L slide chairs allow maximum 2.2 mm movement, so that tallied. Any comments, or should this work reliably? N.B. The GOG manual mentions 3mm, but that seems excessive. Thanks, Arthur |
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posted: 12 Aug 2013 12:25 from: Martin Wynne
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LSWRArt wrote: What point blade movement should you allow for in 0 gauge?Hi Arthur, The prototype movement is 4.25 inches at the tip, which scales to 2.5mm in 7mm scale. You should not use less than this, and you may need a bit more to ensure a 1.5mm flangeway clearance for 0-MF all along the back of the open switch blade. On the prototype it is very important that wheels don't contact the back of the open blade*. On a model it is not so important, but it will still cause rough running through the switch. *see the report into the Grayrigg accident in 2007: http://www.raib.gov.uk/cms_resources/081023_R202008_Grayrigg_v5.pdf regards, Martin. |
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posted: 12 Aug 2013 13:59 from: gsmorris click the date to link to this post click member name to view archived images |
LSWRArt wrote: What point blade movement should you allow for in 0 gauge?I use 2.0mm as standard and have no problems. one or two I actually only about 2.0mm! and I do not have any problem using most wheel sets and care with BB on some makes that have a slightly wider flange than is needed! GSMorris |
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posted: 12 Aug 2013 17:09 from: LSWRArt
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Thanks for the reply. The RAIB report makes fascinating reading and the underlying reasons for the accident (poor training; overstretched staff; inadequate fault reporting...). I was surprised to read about the Residual Switch opening. I had always thought the blade was more or less pressed against the stock rail - not that there was a deliberate gap. The analysis of why nuts loosen and the fact that the nut only had to turn 1/19 of a revolution to effectively be loose also showed that experience (it has worked OK for the last 50 years) is no substitute for engineering measurement. Thanks for all the info, Arthur |
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posted: 22 Aug 2013 01:23 from: Ian Allen
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I thought this item was interesting: "14 This situation arose at 2B points because of a combination of three factors. These were: • the failure of the bolted joint connecting the third permanent way stretcher bar to the right-hand switch rail; • incorrect set up of the points with excessive residual switch opening; and • the omission of the scheduled weekly inspection on 18 February 2008. All three were necessary for the accident to occur." Spot the mistake...which just goes to show even the RAIB should double check everything ;-) Ian |
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posted: 22 Aug 2013 15:57 from: LSWRArt
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IMHO, its them thaar time travellers what done it, mi-Lord Arthur |
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