OT: What is this?

[no_spam]

Found near the route of a dismantled railway, what is it?

[Tim+]

Spring clip that holds the rail in the "chair" which is bolted to the sleeper.

[Tim+]

[Andy Cap]

down the page on the right.

[no_spam]

Excellent service! Thanks Tim and AndyC

[Andy Burns]

Chair fixing clip, pre-runner of a pandrol clip

[DerbyBorn]

Andy Burns wrote in news: [e-mail]:

I can never understand why rail joints are not supported by a extra wide chair. They are cantlevered and rely on a bolted tie.

[polygonum]

Not sure I am fully getting what you mean.

There are really not that many rail joints of the traditional type. Continuous welded track has special expansion joints rather than old-style fishplates - like:

A lot of track is flat-bottomed which rather changes the approach from bullhead on full chair.

Perhaps I am totally missing your point?

[Tim+]

I've seen plenty of square-cut butt jointed rails where the join lies between chairs and the only thing preventing sag is the bolted on tie. Seems like poor engineering.

Tim

[DerbyBorn]

Yes - seen on preserved lines. There is no support under the bolted tie which seems poor design.

[The Natural Philosopher]

well that's cos you ain't an engineer.

The ties are more about preventing lateral than vertical movement.

The stresses on sleeper supported rails are broadly cantilever type stresses anyway.

[DerbyBorn]

The Natural Philosopher wrote in news:nc3gdq$bvt$7 @news.albasani.net:

I was an engineer - On the running track the cantilevered load is taken to to the adjacent chair - but at a rail end it is not - it is only partially passed to the next chair by an often loose bolted tie. Therefore it is a true cantilever rather than a beam.

[The Natural Philosopher]

that's why I said 'broadly'

It's not a beam either, because the ends are pinned.

[DerbyBorn]

Thinking further, the stresses on a rail supported by two chairs are compressive on the top surface and tensile on the bottom whe n under point load. Beyond the last chair the situation is reversed and the top of the rail is under tension and the bottom under compression. I am assuming the tie to have no role and is only there for lateral support.

[Harry Bloomfield]

polygonum a écrit :

Thanks, I did wonder how the allowed for the expansion on welded track.

[polygonum]

A large part of the "allowing" is actually putting the rail into tension (at lower temperatures). Much of the expansion simply reduces that tension - with the precise temperature at which there is zero tension being chosen to (hopefully) avoid unacceptably high tension at the lowest temperature the track will experience, without allowing the expansion at the highest expected temperature to be unmanageably high.

[RayL12]

Wow. In spite of following rail tracks for miles as a kid, this is an eye opener. :-)

[newshound]

So how frequent are these joints? I always thought that CW rails were tensioned when laid so that even at the max temperature they would remain in tension and thus have no tendency to buckle. The tensile loads being maintained by friction between the rail and the chair, under the load imposed by the clip. I've seen calcs in the past showing that the axial load per chair associated with typical temperature changes is not really all that large.

[The Natural Philosopher]

Well that clip is from yonks ago when bullhead rails with fishplates were the order of the day.

IIRC CW rail - flat bottomed - came into play in the 1960s.

And they used a sort of spring clip on concrete sleepers, and thats about all I can recall. Haven't been on a train for a long time

[Chris J Dixon]

Do you have evidence for that?

Chris