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posted: 6 Dec 2007 17:04 from: rodney_hills
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Hello, A recent item on http://www.mremag.com/ by Mark Damien (Australia) points at these two videos, which may be of interest to members of this Group: Track Video - http://www.handlaidtrack.com/nmra-online.php "Demystifying the NMRA Standards" Tilt Table Video - http://www.bronx-terminal.com/index.php?s=tilt+table They are by Tim Warris (Ontario, Canada) and there is further stuff at Fast Track site: http://www.handlaidtrack.com/documents.php Terminology is North American. Measurements are in thou/inches. Regards, Rodney Hills |
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posted: 6 Dec 2007 17:07 from: rodney_hills
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Hello again, Oops, forgot to clip the [00-SF] prefix from the subject line. Never mind, perhaps Martin could edit it please? Regards, Rodney |
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posted: 6 Dec 2007 17:20 from: rodney_hills
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The only mention of the first video I've found elsewhere is 3 postings on [handlaidtrack] back in March 2007: http://groups.yahoo.com/group/handlaidtrack/msearch?query=nmra-online.php&charset=utf-8 Regards, Rodney |
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posted: 6 Dec 2007 17:48 from: Martin Wynne
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rodney_hills wrote: Oops, forgot to clip the [00-SF] prefix from the subject line.Hi Rodney, Sure, it's done. (I wish Yahoo was so easy to tidy things up!) The Fast Tracks videos are quite well-known but I'm doubtful how much of the US practice is applicable to UK modelling. The idea of mixing copper-clad and wooden timbers in the same turnout seems very odd to me -- why not use copper-clad throughout? The "Demystifying the NMRA Standards" video seems to me to go all round the Wrekin to get not much further forward. Those expensive Fast Tracks assembly jigs are very popular in the US and aggressively marketed, but they do completely defeat the main advantage of hand built track, that you can design each formation to fit the site. For a good discussion of US trackwork you can't do better than Andy Reichert's site at http://www.proto87.com regards, Martin. |
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posted: 6 Dec 2007 22:14 from: Templot User
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----- from Andy Reichert ----- rodney_hills wrote: Track Video -The title is somewhat misleading as these are not produced nor endorsed in any way by the NMRA. The NMRA frog design explanation and recommendations are as published on their website http://www.nmra.org under the general standards section. In particular the NMRA does NOT specifically recommend (unprototypical) sharpening of the frog vee point, and especially not as a means of justifying the non-standard use of code 88 wheels. The NMRA is also neutral with the idea of including the very prototypical "filler" blocks that normally are fitted at various points in the flangeway. Most importantly, the NMRA does not recommend ANY gauge widening through the frog area of a turnout. Quite the reverse in fact. The latest review of the standards is emphasizing that the gauge tolerances should not be used within the turnout area, as the widening allowance was only ever intend for use at all on sharp plain track curves. Andy Deputy, NMRA Proto Standards group. |
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posted: 8 Dec 2007 17:03 from: Martin Wynne
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Andy Reichert wrote: Most importantly, the NMRA does not recommend ANY gauge widening through the frog area of a turnout. Quite the reverse in fact. The latest review of the standards is emphasizing that the gauge tolerances should not be used within the turnout area, as the widening allowance was only ever intend for use at all on sharp plain track curves.Hi Andy, What's the reasoning for this? Gauge-widening can be run through pointwork without any problems* providing you remember that the critical dimension is the check gauge, which should stay fixed. This is why it is always better to use a separate check gauge tool, rather than a combined roller gauge. What this means is that if you widen the track gauge by X, the check rail flangeway gap** must widen by X also. On the UK prototype widened check chairs are made for this very purpose. If it's done on the prototype it seems strange to argue against it on the model. Likewise Exactoscale make two widths of model 4mm check chair. If it's done in P4 it seems strange to argue against it in H0. *Except in rare cases where a wing rail acts as a check rail, for example in symmetrical 3-throw turnouts. (But it's very unlikely that such a condition would be constructed in track curved sharply enough to need gauge-widening.) **Guard rail gap. The crossing flangeway (frog) gap shouldn't be changed. regards, Martin. |
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posted: 8 Dec 2007 22:04 from: Templot User
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----- from Andy Reichert ----- Martin Wynne wrote: Gauge-widening can be run through pointwork without any problems* providing you remember that the critical dimension is the check gauge, which should stay fixed.Martin, "Can be run" doesn't necessarily equal "runs well". You've quoted 00-SF as having "better running" than full gauge 00 many times. But the only difference is negative gauge widening thru turnouts. What's your reasoning on that? The NMRA gauge widening allowance is large compared to most. And I think far more so than for P4. It certainly was never intended ever to be merely the universal maximum gauge tolerance, although that condition was not very clearly published for many years. So for wheels that stray too far away from the Vee side, the wing rail instead catches them harder, not necessarily slightly at speed, adding to the bumping effect of that and the wrong end of the coning leaving the wing rail top earlier. Typical US H0 freight car trucks are very short wheelbase, so can skew across the track more when the gauge is wider, also making the bumping of any checking rails more more forceful, especially when pushing. Of course any random GW around the point tips (and in our case point heel hinges) just adds more complications with greater throw bar movement needed and even more places to possibly bump. Andy |
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posted: 9 Dec 2007 02:25 from: Jim Guthrie
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Templot User wrote: Can be run" doesn't necessarily equal "runs well". You've quoted 00-SF as having "better running" than full gauge 00 many times. But the only difference is negative gauge widening thru turnouts. What's your reasoning on that?Andy, I understood that the thought process behind reduced gauges like 00-SF was to get rid of the built in gauge widening - otherwise known as slop - in existing track and wheel standards. So you might argue that 00-SF has got it correct and you might want to add a bit of gauge widening through pointwork if the radius was sharp enough to merit it - watching the check gauge as Martin has noted. Jim. |
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posted: 9 Dec 2007 03:24 from: Martin Wynne
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Andy Reichert wrote: "Can be run" doesn't necessarily equal "runs well".Hi Andy, Sorry, my meaning lost overboard in mid-pond again. By "gauge-widening can be run through pointwork" I meant "can be continued through pointwork", I wasn't referring to the running qualities of rolling stock. In other words, if you have a sharp plain track curve with some gauge-widening, you can insert a crossing (frog) into that curve without having to remove the gauge-widening. Provided you use the proper check gauge, with the result that the check rail flangeway is widened too. So for wheels that stray too far away from the Vee side, the wing rail instead catches them harder, not necessarily slightly at speed, adding to the bumping effect of that and the wrong end of the coning leaving the wing rail top earlier.In the majority of cases the crossing (frog) will be in the outer rail on a sharp curve, so the wheels will be hard against that rail, and will interact with the check rail (guard rail) in the usual way, rather than with the wing rail. You've quoted 00-SF as having "better running" than full gauge 00 many times. But the only difference is negative gauge widening thru turnouts. What's your reasoning on that?Jim's explained this. We observe that 16.5mm works on curves down to train-set radii without any widening. So we conclude that 16.5mm already includes some gauge widening, and for better performance on gentler curves we remove that built-in widening. But the main performance improvement comes from reducing the crossing (frog) flangeway gap. To keep things symmetrical* we need to use a similar size for the check rail (guard rail) gap. Adding that to the check gauge (which needs to remain fixed to avoid changing the wheels B-B) we arrive at the track gauge. Happily these two approaches both arrive at the same track gauge -- 16.2mm. And when tried, it turns out to work beautifully. *Symmetry isn't essential to work, and is in fact lost where there is gauge-widening. But there are often places in complex formations where a wing rail is extended to form a check rail for the next crossing. Without symmetrical gaps, this would require a joggle in the check rail and cause rough running to any wheels being checked. regards, Martin. |
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