Why isn't the DART Aerodynamic?

Thargor

Aside from being the ugliest trains probably on the planet didn't they stop building them like this 100 years ago or more because its a massive waste of energy to push a flat face like that along at high speeds? Has anyone ever seen anything written about this? Surely it wouldn't have cost much to put a pointed nose on them and would it have paid for itself seeing as they run for years and years? Even the LUAS is a bit streamlined and that doesn't go very fast.



Ugh, they're so horrible, I cringe when I see them pulling in. The interiors are even worse aswell. I think they must have cut the cleaning budget recently or something because they all stink of piss these days.

Judgement Day

The DART units don't get much opportunity to travel at high speed and the appearance is standard enough for commuter units. The pic you use is of the first, and by far the most pleasing, of the DART units to enter service back in 1984 - quality German engineering. As for all smelling of....I'll take your word for that but I haven't noticed.

DWCommuter

Judgement Day wrote: »

The DART units don't get much opportunity to travel at high speed and the appearance is standard enough for commuter units. The pic you use is of the first, and by far the most pleasing, of the DART units to enter service back in 1984 - quality German engineering. As for all smelling of....I'll take your word for that but I haven't noticed.

Please don't mention the Germans right now.:D

Daniel S

Probably because that would actually make sense. We can't have that now can we? :pac:

Opinicus

I was watching a docu about the famous steam trains like the flying scotsman and the mallard lately. There was an obsession with speed at the time because of competition between rail companies and this led to aerodynamic styling of the locomotive.

For setting records it proved useful but it was a pain in the arse to remove them when you wanted to service the boiler etc. After a while they were abandoned for practical reasons and they didn't really make much of a difference for day to day operation.

opinion guy

DART generally doesn't go fast enough for it to matter.

I actually like the look of the one in your picture. Very NY subway or something

chooochooo

beautiful chunky design. interior smart - travel everyday and never got any smell. thargor delusional.

TheUsual

Doesn't affect low speed DART's.
Aerodynamic is only used for high speed vehicles.

longhalloween

TheUsual wrote: »

Doesn't affect low speed DART's.
Aerodynamic is only used for high speed vehicles.

Most trucks on the roads have flat faces and they travel much faster than the DART.

dowlingm

Aerodynamic fairings decrease the useful length of the vehicle (because the driving cab has to be set back)

Cookie_Monster

because for trains under 90mph aerodynamics basically don't matter. Rolling resistance of the wheels and momentum is much more important.

I was reading a thread on this on ModelRailForum the other day* and that was basically the answer (was to do with HSTs running single power unit rather than both)

The "aero" shape of the Luas is for the crash structure at the ends as it runs on roads, rail vehicles don't need this cos a crash structure will do nothing against the momentum of a couple hundred tons of train.


* can't find it though
here it is http://www.modelrailforum.com/forums/index.php?showtopic=17600&st=0&start=0
post 9 onwards in particular is where it's mentioned

corktina

Opinicus wrote: »

I was watching a docu about the famous steam trains like the flying scotsman and the mallard lately. There was an obsession with speed at the time because of competition between rail companies and this led to aerodynamic styling of the locomotive.

For setting records it proved useful but it was a pain in the arse to remove them when you wanted to service the boiler etc. After a while they were abandoned for practical reasons and they didn't really make much of a difference for day to day operation.

it was mostly about styling rather han aerodynamics. Witness the post war
A1 pacifics which reverted to the standard classical layout.

(cue video of Tornado...any excuse)

http://www.youtube.com/watch?v=t0w06rSXTYg

Cookie_Monster

Opinicus wrote: »

I was watching a docu about the famous steam trains like the flying scotsman and the mallard lately. There was an obsession with speed at the time because of competition between rail companies and this led to aerodynamic styling of the locomotive.

that was streamlining to make it look stylish, not to make it go faster (well primarily for styling, it did of course make a small difference to overall efficiency and speed)


Also the flying Scotsman was never streamlined, other of the same class were however.

AngryLips

Maybe when Jackie Healy-Rae gets his way and the Dart is extended to Kerry IE will start considering a more streamlined design?

Gotta say it, I love the look of the Dart, especially the older units.

corktina

Cookie_Monster wrote: »

that was streamlining to make it look stylish, not to make it go faster (well primarily for styling, it did of course make a small difference to overall efficiency and speed)


Also the flying Scotsman was never streamlined, other of the same class were however.

no...A3s (and the Original A1s later classed as A10s) were never stremalined.Only the A4s, the W1 and a couple of B16s (i think its B16 cant be arrsed to check :-) )bore streamlining

the Cock o the North was sort of semi-streamlined.

http://www.google.co.uk/imgres?q=cock+of+the+north&um=1&hl=en&qscrl=1&nord=1&rlz=1T4GZAZ_enIE378IE378&biw=1015&bih=580&tbm=isch&tbnid=ExfE61AprwQp0M:&imgrefurl=http://www.lner.info/locos/P/p2.shtml&docid=uKstThWTfjT_QM&imgurl=http://d240vprofozpi.cloudfront.net/locos/P/p2_cockothenorth.gif&w=440&h=601&ei=mNi7Tr6QIoWZhQe7so3PBw&zoom=1

On The LMSR certain Princess Coronation classs locos were stream lined , this was subsequently removed but has been re-applied to Duchess of Hamilton recently

http://www.google.ie/imgres?q=duchess+streamlined&hl=en&sa=G&biw=1015&bih=580&gbv=2&tbm=isch&tbnid=zpcJs09JOQSwaM:&imgrefurl=http://www.flickr.com/photos/31339850%40N06/3541486389/&docid=WrdCcfXoHfjx1M&imgurl=http://farm3.static.flickr.com/2313/3541486389_ac4efa446f.jpg&w=500&h=335&ei=gde7TsfoJsmmhAeAhMimBw&zoom=1

On the GWR a King and a Castle were tarted up with psedo-streamlining

On the SR the West Country and Merchant Navy classes in their original form were termed as "air-smoothed".

corktina

AngryLips wrote: »

Maybe when Jackie Healy-Rae gets his way and the Dart is extended to Kerry IE will start considering a more streamlined design?

Gotta say it, I love the look of the Dart, especially the older units.

not all that bad an idea, the Kenmare line must have been spectacular!

Cookie_Monster

corktina wrote: »

no...A3s (and the Original A1s later classed as A10s) were never stremalined.

Indeed, I stand corrected. I had misread the paragraph, it had read "compared to the non streamlined A3 locomotives..." I had thought this meant some of the class were and some weren't...

dubhthach

Interesting thread but think Infrastructure forum isn't probably the most appropriate place, as the discussion is more on the train units themselves as oppose to the (fixed) infrastructure of the DART.

Niles

I remember seeing pictures on the web (probably on a now defunct fotopic site) of LHB built EMUs in I think Germany (but maybe somewhere in Eastern Europe, sorry, it's a long time since I saw it!) which were very similar to the 8100 DARTs. Maybe it was a standard design or something, modified for the Irish gauge. Have to say I like the look of them, though preferred it before they were modified - it looks more cluttered now, but that's a small price if any to pay considering the improvements made. Wouldn't call them ugly though, in fact I'd regard the 8520s are far more "ugly" looking. But then again I should remember that this is a public transport system, not an art exhibition!

The 8200s have a somewhat streamlined look about them, I like the look of them too, of course they'd look even better if they actually did anything!

dowlingm

The other thing is that DARTs are modular - they can be either single-unit trains or combined. It doesn't make sense to have aerodynamic cabs on trains which spend most of their time as combos. On the other hand if IE ever bought 8-car EMU sets it would probably make sense to have a slight nose at either end since the train would likely be a permanent consist like a 22000 class.

In Toronto the existing T & H series subway trains are 6 car consists of 3 x 2 units and the guard stands in the cab of a mid-train driving trailer,



but the new units are 6 car units and have driving cabs only in front and rear so have a shallow nose.

CIE

Thargor wrote: »

Aside from being the ugliest trains probably on the planet didn't they stop building them like this 100 years ago or more because its a massive waste of energy to push a flat face like that along at high speeds? Has anyone ever seen anything written about this? Surely it wouldn't have cost much to put a pointed nose on them and would it have paid for itself seeing as they run for years and years? Even the LUAS is a bit streamlined and that doesn't go very fast.

Ugh, they're so horrible, I cringe when I see them pulling in. The interiors are even worse as well. blah blah blah

Since when does the DART travel at anything resembling "high speeds"...? The top speed is 62 mph and the average speed is somewhere in the 25-mph range. The energy required to overcome air drag is very minimal.

And if you want to talk about practical front-end aerodynamics at high speeds, that's mostly to prevent front-end lift more than worrying about energy to overcome air drag.

Thargor

I think aerodynamics do make a difference at low speeds, if I wear normal clothes on my roadbike to get to work I feel like I have a parachute on my back slowing me down compared to wearing my proper gear.

Cookie_Monster

Thargor wrote: »

I think aerodynamics do make a difference at low speeds, if I wear normal clothes on my roadbike to get to work I feel like I have a parachute on my back slowing me down compared to wearing my proper gear.

that's because your front section compared to total mass is quite large, your weight and power and momentum is also very low.

For a train weighing hundreds of tonnes with basically unlimited power (for the purposes of argument) aero resistance does not matter at all at low speed.

parsi

Thargor wrote: »

I think aerodynamics do make a difference at low speeds, if I wear normal clothes on my roadbike to get to work I feel like I have a parachute on my back slowing me down compared to wearing my proper gear.

The DART is wearing skintight clothes - no flapping bits...

dermo88

Aerodynamics only matter at speeds greater than 80mph (130kph), and DART does not need to go that fast. What DART and Commuter trains on that kind of stop-start every 2km or so pattern is acceleration.

There is a rationale in a way to the opening argument on aerodynamic styling. It is from the perspective of public relations and branding. Take the new 22K DMU's. They are the best looking train to appear in Ireland for many years.

As for anyone saying "DART" is ugly. Its not meant to be pretty, its meant to do a job, one which it does quite well. Thats an inherent beauty in its own right. Noone can conceive of life in Dublin without DART. But I remember when the original units arrived in 1983, and they were the coolest thing since sliced bread compared to virtually everything on Irish tracks at that time (mind, I had a soft spot for the NIR Enterprise in those days...nicknamed the Beller)

lord lucan

The original LHB units were and still are fantastic looking units. Whilst EMU/DMU's are not my thing i have a soft spot for the originals(not the Spanish & Jap ones since though).

I particularly loved when they sported briefly the Red & White buffer.

Thargor

But it runs on electricity, would there not be a direct measurable effect of having it cut through the air a bit that would add up as it ran for years and years? I go out to Bray all the time and it runs for long distances there at high speeds. Also if you mention a train please post a pic of it!

Actually now that I think of it the electricity bit makes no sense, you could measure any kind of fuel for an effect, but my other point about it adding up over the years stands.

PseudoFamous

Thargor wrote: »

I go out to Bray all the time and it runs for long distances there at high speeds.

40km/h isn't a high speed. That's roughly what they do between Shankill and Bray. They barely move between Greystones and Bray, due to the fact the cliffs are literally all of about 25cm from the tracks in places, now.

As an aside, IR should really, really reline that section of rail along Bray Head soon, a bit of steady, hard rain would seriously compromise the safety of commuters..

Cookie_Monster

Thargor wrote: »

But it runs on electricity, would there not be a direct measurable effect of having it cut through the air a bit that would add up as it ran for years and years? I go out to Bray all the time and it runs for long distances there at high speeds.

I'm sure there is but it's so small that it makes no difference. And again to clarify the DART doesn't run at high speed

Also if you mention a train please post a pic of it!

why, if you don't know what it is google it. Most people here know what the unit mentioned are already, no point posting pictures for no reason

Actually now that I think of it the electricity bit makes no sense, you could measure any kind of fuel for an effect, but my other point about it adding up over the years stands.

Why don't you go and ask IE or Siemens why ther is no need for areo since you won't believe what anybody here has to say on it.

Aero is insignificant for trains at low speeds. Their narrow face combined with their sheer weight overcomes any small areo drag.
Why not question why buses and (most) trucks aren't? much more relevant to them as their faces are much bigger in comparison to overall volume and power.

AngryLips

They should also make the Dublin Bus fleet aerodynamic ...and all the trucks on the roads.

The original Dart carriages remind me a bit of the old Berlin U-bahn, two of the nicest metro designs around.

Cookie_Monster

AngryLips wrote: »

They should also make the Dublin Bus fleet aerodynamic ...and all the trucks on the roads.

how do you propose they do that then?

(aside from minor improvements like the cab top deflectors and streamlined trailers, both which are already common)

Niles

Niles wrote: »

I remember seeing pictures on the web (probably on a now defunct fotopic site) of LHB built EMUs in I think Germany (but maybe somewhere in Eastern Europe, sorry, it's a long time since I saw it!) which were very similar to the 8100 DARTs. Maybe it was a standard design or something, modified for the Irish gauge.

I think this is the foreign unit I referred to earlier, not quite the same but there does seem to be some family resemblance between it and our own 8100s. It's from the same era (1982/3) and seems slightly narrower, but that could be attributed to CIÉ having a wider gauge.

Then there's these units,which were built about ten years later, they seem slightly curvier at the front. You can still see the resemblance to the 8100s though.

PseudoFamous

Cookie_Monster wrote: »

how do you propose they do that then?

Install snowplows on every bus. It'll solve our problem of snow, and keep self important audi drivers out of the buslane, too

Cookie_Monster

Niles wrote: »

I think this is the foreign unit I referred to earlier, not quite the same but there does seem to be some family resemblance between it and our own 8100s. It's from the same era (1982/3) and seems slightly narrower, but that could be attributed to CIÉ having a wider gauge.

what happened to the right hand rail just in front of the unit?

It can't be actively operating that close to missing track can it?

Victor

Photos http://irishrail.ie/fleet_information/commuter_and_dart_fleet.asp

Class No. in Service Horsepower (HP) Date Built Manufacturer
8100/8300 Class 38x2 (originally 40x2) 690 1983 GEC and Linke-Hofmann-Busch (now Siemens)
8200/8400 Class 5x2 690 2000 Alstom
8500 Class 4x4 690 2001 Tokyu Car Corporation
8510 Class 3x4 690 2003 Tokyu Car Corporation
8520 Class 10x4 690 2004/2005 Tokyu Car Corporation

Much of the air resistence on a train is to the sides - surface area, open windows, fittings, panel joints, the gap between carriages - not the front.

As mentioned, DART is modular, so if you put a point end on every carraige, the train would experience more substantial air resistence every carriage / every second carriage.

A greater efficiency would probably come from reducing the number of end cars from about 78% to about 50% and using the current cab space for passengers.

Niles

Cookie_Monster wrote: »

what happened to the right hand rail just in front of the unit?

It can't be actively operating that close to missing track can it?

Not sure myself. Looking closely the rails seen in the foreground seem to be slightly higher than the rail near the unit, my guess is that these are checkrails or something similar, and the actual running rail is obscured from view by the platform edge? If you look closely you can just make out the chairs for the right hand rail along the platform edge.

Victor

Cookie_Monster wrote: »

what happened to the right hand rail just in front of the unit?

It can't be actively operating that close to missing track can it?

Hover trains. :cool:

Unusual rail type. Might it be third rail power and this is the boundary between two circuits? Actually, given that it is a terminus, I wonder if it is some sort of deliberate de-railing arrangement. The view seems to be within this train hall. http://maps.google.ie/maps?q=warschauer+strasse+s-bahn&hl=en&ll=52.506531,13.449476&spn=0.005485,0.027466&sll=53.401034,-8.307638&sspn=5.766735,19.753418&vpsrc=6&hq=warschauer+strasse+s-bahn&radius=15000&t=m&z=16&layer=c&cbll=52.505459,13.448795&panoid=_g68WPPg2tqC2arD_zpgbw&cbp=12,152.02,,0,-4.29

It is an unusual U-bahn set up. The station entrance is nominally at ground level, but the ground to the north is lower for S-bahn tracks and while it falls away steeply to the south to the river bank, meaning the first section of the U-bahn is actually elevated.

http://en.wikipedia.org/wiki/File:Ubahn_oberbaum.gif

CIE

PseudoFamous wrote: »

Install snowplows on every bus. It'll solve our problem of snow, and keep self important audi drivers out of the buslane, too

That's nice. Where will they store the salt for melting the snow and ice?

corktina

whereas you will no doubt save minute amounts of energy over many years by streamlining the DORT, the advantage of this is lost by losing probably 4 seats behind each driving cab. The overall most efficent configuration for a suburban train in terms of energy per passenger is therefore a flat front.

steamengine

OP has a point ok. The DART presents a flat surface to the oncoming air, so using the drag coefficient of 1.2 for this type of surface give a resistance of approx 190 lbs at 30mph. This increases to 750 lbs at 60 mph - figures based on an estimated frontal area of 64 sq.ft. The reason for the increase is that the resistance is proportional to the square of the speed. That is double the speed equals 4 times the resistance. In terms of power these figures equate to 120 horse power or 90 kw absorbed to overcome this resistance at 60 mph.

However the total drag coefficient for this type of train may be as high as 1.8,- still reading up on it. Some figures for streamlined trains may be as low as 0.2, so one can see how power could be saved by having a more aerodynamic shaped cab front.

Estimating an average speed of 30 mph for a DART equates to a 30 hp or 22.5 kw loss based on a drag coefficient of 1.2. - hardly significant in the scheme of things.

PS - I like the look of the original DARTs - heading for iconic status just like the 071's !

CIE

The DART presents a flat surface to the oncoming air

Actually, it's not flat. The outer thirds are slightly convex. Also, some extra bits were added; the new lamp assemblies with the rebuild feature some new interesting-looking external fascia.

I'd say the parts that cause the most turbulence are the doors that hang on the outside. Never understood that design; it's not even like a plug door design.

monument

In the event the reasoned answers to date are not good enough...

Stopping drag? How about maglev, fully in tunnels?

CIE

monument wrote: »

In the event the reasoned answers to date are not good enough...

Stopping drag? How about maglev, fully in tunnels?

I presume you mean the "vactrain"? Good for a laugh, that is, especially at the recent estimate of over €2 billion per mile for its infrastructure. Maybe when they get "cold fusion" to power it and what does this really have to do with DART anyhow?

monument

The op had a reasonable question but reasonable answers have already been given.

CIE

monument wrote: »

The op had a reasonable question but reasonable answers have already been given.

As far as the "vactrain" goes though, it could be any shape you want on the front and back, since there's no air to resist its forward motion. One estimate for average speeds was 2,250 mph, so you can go from Dublin to Cork in about 4.5 minutes

corktina

i can only hold my breath for three minutes...:(

Wild Bill

For what it's worth - I think the DART trains look very handsome.

The Luas also looks good; but would look a bit daft on a heavy rail commuter line.

Horses for courses.