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rail expansion

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duncan webster08/07/2018 16:53:33
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We've been having trouble with our signals in this recent hot weather. The one which kept on having intermittent fault is the one exposed to full sun from about 1:00pm. Of course this doesn't happen when I'm there, so I have to rely on verbal reports. Why can't people write it down with all relevant info when it happens? Come Wednesday I check the gaps in the track circuiting, a bit small but definately there. Just to be safe I ran a saw down the gaps. We measured the temperature inside the signal box itself. Over 50C. This is pretty warm so I made a sunshade (baco foil and plywood as a trial). Signal now much cooler, but as soon as the sun came round, the problem came back. The gaps had closed up again, it looks as if that whole section of track is somehow ratcheting itself down the hill.

Has anyone else come across this, if so how did you cure it? We are going to experiment with insulation between the rail ends, and perhaps some kind of link between the rail and the bolted down sleepers to stop it moving at that one point.

Edited By duncan webster on 08/07/2018 16:54:18

Brian Baker 108/07/2018 17:01:18
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Greetings,

I have seen this rail movement happening before, but mostly with wooden sleepers, where the heat dries out the wood which seems to slacken the grip on fixing screws. We use to get this happening a lot at Parklands Railway, but now we are all plastic sleepers, it seems to have stopped happening, presumably because the screws in plastic do not "dry out". Once set up the gaps remain constant. we tend to use a double width sleeper (100 mm instead of the normal 50 mm wide) to support the rail joints, and reduce end droop of the aluminium rail we use.

regards

Brian

Neil Wyatt08/07/2018 18:16:38
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At IMLEC they have been suffering with the track closing up all its expansion joints. In winter it shrank enough to damage the sleepers!

duncan webster08/07/2018 18:57:13
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1631 forum posts
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We are on plastic sleepers. Using a thermocouple on the rails you can tell when the sun goes behind a cloud. Today was quite windy, but rail temp was ~38C, we've measured 50+ on windless days.

Brian Baker 109/07/2018 08:06:45
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74 forum posts
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Greetings,

In the case you mention then Duncan, I think "Tee" shaped plastic inserts should solve the problem, but perhaps it needs a slightly larger expansion gap. One club had a supply laser cut in plastic to the same profile as the rail.

Over here in Norfolk, the heat has stopped the full sized rail swing bridges opening, because rail expansion has jammed them shut.

Regards

Brian

duncan webster12/07/2018 14:50:01
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1631 forum posts
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img_3315 (small).jpgFollowing Brian's advice we've fitted fibreglass board spacer between ends of rails on worst affected spot, will keep an eye and do any more if successful. I've also made a sunhat for the signal which gets full sun, that was getting up to 50C+ as well. Note after you've cut the SS sheet with an angle grinder, wearing safety boots, overalls, goggles, gloves and making sure it's clamped down, don't then pick up the cut off pieces with bare hands, not unless you want a trip to A&Eimg_3314 (small).jpg

Tim Stevens12/07/2018 18:22:07
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907 forum posts

At last, a mystery object I can identify. It is a manually operated finger, developed in prehistoric times for indicating directions, and subsequently used for related (and other) purposes. The wrapping is rather later, in fact probably quite recent.

Tim

SillyOldDuffer12/07/2018 19:14:56
3193 forum posts
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Posted by Tim Stevens on 12/07/2018 18:22:07:

At last, a mystery object I can identify. It is a manually operated finger, developed in prehistoric times for indicating directions, and subsequently used for related (and other) purposes. The wrapping is rather later, in fact probably quite recent.

Tim

Thank god it was only his finger...

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