THREAD: going on a Big Adventure today, couldn't start at a more modest station. Selfie game still terrible

@andyg831977 @chriswilson_cw It's macaroni cheese, right? I can feel my arteries hardening

Clamp, link, pulley: the 3 headspan genders (a #railwaysExplained thread)

A few of the #OLEbook images are a bit meh. So yesterday I went out on a trip to West Ealing to pick up some better ones. In this case, headspan supports.

But 1st, a refresher on along-track movement

1/ All OLE systems have to deal with the phenomenon of along-track movement - the amount of expansion and contraction the wires experience as wire temperature varies, due to ambient heating/cooling from solar gain and wind, and also current heating due to electrical load

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@alanlmsca @poggs @partialcontent @WillDeakin1 @petemashmorgan @jamesjefferies Lets look at that idea.

RTC were very good at learning from R&D done in other sectors. e.g. the APT having a body structure derived from aircraft design.

1/ @alanlmsca @poggs @partialcontent @WillDeakin1 @petemashmorgan @jamesjefferies In this case they'd be looking at the work done by the automotive sector on EVs. Automotive has far larger buying power than rail.

With all of that R&D effort over the last 10 years, they have managed to create batteries with an energy density of ~1/5 that of diesel fuel

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THREAD: A few of you requested a #railwaysExplained thread Return Conductors (RCs) and Auto Transformer Feeders (ATFs). As part of that I'll be attempting to explain how immunisation works. HEALTH WARNING: this will involve electromagnetism. Apologies in advance!

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Lets start with the very basics: overhead line forms part of an electrical circuit. Just like all circuits, the electricity flows out from a supply (the feeder station) to the load (the train) and then flows back to the supply. The OLE forms the outward leg of the circuit

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THREAD: some of you might be wondering what the hell this train is. I'll try to explain that, while touching on some of the wider requirements for testing new #OLE for entry into service #railwaysExplained

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https://twitter.com/TonyP146/status/1195062897329737730?s=19

This is an OLE test train that's been put together by the @networkrailwest electrification project team. The train is intended to undertake mechanical and electrical testing of the OLE between Bristol and Cardiff in advance of entry into service

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THREAD: Every so often during a discussion about electrification at bridges, the subject of COASTING comes up. I denigrate the idea without explaining why, then move on. I've been meaning to do better than that for a while: so here it is, buckle up!

1/ Let's start by defining coasting as follows:

Coasting is when an electric train passes through a section of railway without taking power, using only its own inertia to make it through the gap.

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THREAD: recently @EurostarJustinp and @EurostarGeorge mentioned windspeeds in relation to #OLE design. In response I promised them a thread on #wind.

No sniggering. Yes, you at the back. I saw you. STOP IT

This is that thread.

1/ OLE is exposed to a number of enviro factors, and wind is one that we spend most time worrying about. It's common for industry types to jokingly refer to OLE as "the wind-blown wobbly wire" - and there is some truth in that.

But wind affects a lot more than just the wire...

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THREAD: Nice sunny day, so off to the garden centre. What's that you say? The UK's only open air section of Rigid Overhead Conductor Bar is just down the road, between Patchway Old and Short Tunnels? Oh go on then. You might be wondering why it has been done like this. Both tunnels are too low / arch too cramped to fit conventional OLE, So ROCS is used instead. Normally you would transition back to conventional OLE outside the portal. But here the distance between portals is too short.

A thread about OLE systems, steelwork sizes and the general perception that we've got it wrong...

Ever wondered why so many different systems worldwide? After all there are only a handful of track forms.

Unlike track, OLE has two wobbly things interacting - the wire and the pan Getting that interaction right is critical - if you don't, the necessarily lightweight (read: fragile) pan will be damaged - or worse, the OLE will

The interaction is largely a function of two things: the speed you want to go, and the number and spacing of pans on each train