Early vehicles

[DaleStan]

Later googling produced this page. 114 trailers.
.au laws apparently require that road trains not exceed 36.5 metres.

[jabberwalkee_]

Try to read the posts on the topic before hitting reply Wink

Sorry I thought my sarcasm was obvious.

.au laws apparently require that road trains not exceed 36.5 metres.

however...This can be got around by having a special vehicle licence with that particualar setup in mind....i believe some of the coal road trains in WA do that. They need an escort car though (with cool flashing lights) and they need to advise police when and where they are travelling.

Not that it matters.....there are so many roads in Australia that are really empty; some are even surfaced!

[Bjarni]

Later googling produced this page. 114 trailers.
.au laws apparently require that road trains not exceed 36.5 metres.

do anybody have a picture of this event? I would like to see it

Australia also have the record of the longest railroad (real railroad) without any curves at all. It's the Indian Pacific (Sidney-Perth) and it have a part of 459 km without a single curve at all. I looked for a picture of this railline, but I can't find any good ones online

[Celestar]

Bjarni:

I have a picture of this rail line somewhere in a book. I'll go looking for it.

Celestar

[jabberwalkee_]

We will also have the record for the most continuous peice of rail when the new line in the NT is laid. They have built a machine that lays the tracks molten and lets them dry as it goes to create one really long peice of metal. I believe its too avoid the linear expansion of the metal given heat. In the desert it can get above 50C and on the same night drop to a few degrees above zero.

[Prof. Frink]

I'd have thought that that would have the opposite effect of that intended. Normally a gap is left between rail segments to allow for this expansion.

[mdhowe]

I'd have thought that that would have the opposite effect of that intended. Normally a gap is left between rail segments to allow for this expansion.

The continuous line is to do with maintenance according to the document I read.

The following info about expansion is from here:

In order to balance the forces between those which want to buckle the track during high temperatures and those which want to pull the rails apart during cold temperatures the rail is laid at what is called the neutral temperature of 40 degrees Celsius. The range of rail temperature expected throughout the course of the year is approximately -10°C to +65°C.

On a railway the length of the Alice Springs to Darwin railway (1420km) this movement would be 16.3 metres for every degree of temperature change. It has been calculated that the rails are subjected to a temperature range of 45 degrees in Darwin and 74 degrees in Alice Springs. This would mean that the rails would expand and contract up to 1.2 km between the coldest night and hottest day during the year.

If the rail were free to move when heated or cooled it would expand or contract like all other steel. A small amount of the stress developed along the rail can be taken up with expansion across the rail. Its height and width expand due to their own dimension as well as some distributed stress from the longer length. The rail bulges slightly. As long as the column is prevented from moving sideways along its length it is very stable.

[Celestar]

You cannot afford to leave gaps between pieces of track on high speed rail. In Germany, most of the modern pieces of tracks are welded, and the tracks just have to deal with the temperature tension that arises. No problem for even pretty cheap steel.

Celestar

[jabberwalkee_]

Germany doesnt get real hot......that is when the problems arise with linear expansion of iron based metal (im lead to believe)

And you may use alloyed material to help combat etc. etc

[Celestar]

I think air temperatures of up to 40°C is pretty hot, and don't forget that we go down to -20°C as well, so you have around 60K span.

Celestar

[MT3269]

Australia also have the record of the longest railroad (real railroad) without any curves at all. It's the Indian Pacific (Sidney-Perth) and it have a part of 459 km without a single curve at all. I looked for a picture of this railline, but I can't find any good ones online [/quote]

478 to be precise, "the Nullabour". Not very ideal for breakdowns tho.

[jabberwalkee_]

however.....presssure/temperature/volume graphs tend not to be linear and i think the "knee" in the curve is around 50 - 60 degrees celcius. But anyway........It means less can go wrong with the track which is probably a little more important in the Australian outback than anywhere in Germany because of its vast tracts of nothing

[Celestar]

Er... in the temperature range we are talking about the thermal extension is linear (down to around 0.1% or less), and the coefficient is between 1e-5 and 1e-6 per Kelvin, for normal track steel I have to look it up.

But let's assume we're somewhere in the middle at 5e-5, that means on a 1000km long track, you get a elongation of 1,2 km if you have a temperature difference of 25°C (from the neutral temperature). However, if you put a gap every 100m, which is pretty often, you'd still have 12cm long gaps. This ain't very good.

On the other hand, if you just weld the tracks together, and force the elongation to Zero, you're up to around 250 MPa stress, which is quite a lot but can be dealt with even using the cheapest steel of all save one. Now if you have a single very slight turn, this will work in favour of you so that it reduces stress. Most tracks of 1000km length have more than a single curve.

Sum up: it's no problem nowadays to have a zero-elongation track.

Celestar