Railroad Train Aerodynamics

[KamperBob]

Originally Posted by Piwoslaw

Piechna's book has a short chapter on train aerodynamics, so I though I'd add that info to this discussion.

Here is a simple comparison of how nose and tail cones effect the drag coefficient Cx.

This data comes from Wysocki's testing of train models ([1]), in this case a 250 km/h train.

[1] Wysocki Z., Badania aerodynamiczne zespołu trakcyjnego 4WE, Spr. Inst. Lot. nr 29/BA/76, 1976.

If available in English I'd love to read it.

The front-rear significance bears a striking resemblance to data from a Cycle Magazine article by Kevin Cooper of CNRC also 1976 mentioned here.

[wyatt]

Originally Posted by Bicycle Bob

As long as things are not going supersonic at the edges, there's no practical need for an extreme wedge front end. Those are for styling, at considerable cost to vision of the crew, especially when approaching a low sun. Not that vision will do those lads much good anyway. . . Maybe it is really for crush space.

The "old" bullet trains were designed with an aerodynamic front end, with no regard to boat tailing. The reason for having the engine on both ends was so they didn't have to try to turn around the train when stopped. The one with the extreme front end is likely being designed to make an effective boat tail also. Whether or not the air stays attached that long is another story, but that's my guess.

[Arragonis]

Not relevent I know, but I couldn't resist as this train is in a huge photo in my living room.

Mrs A challenged me to find a picture I really liked so I did I got this Including the 1940s "chap" in his hat having a "personal moment" contemplating the engineering miracle before him.



The train is called "Mallard" - LNER class A4 - and it holds the world record for speed for steam trains in 1938, 126 MPH. A record not bettered since, although I am sure someone in China is working on a better one as I tap. The record is not without challenge but it stands so far, designed by this other "chap", Sir Nigel Gresley - from the days when we in Blighty used to actually give honours to people who deserved them - unlike now where we hand them out to useless footballers for having a new hairstyle...



Sign on the tracks where it was done.



In ecomodder (rather the Colonel Blimp) mode I have wondered how much of this was just down to power and efficiency of the boilers vs actual aero. I did contemplate working out the front end pressure vs the old Flying Scotsman (below) but the sums hurt my head - I have, or had, a fairly massive spreadsheet with attempts.



There is a valid challenge from the Germans (of all people ) who did a 125.4 MPH run the year before. Of course that was done in darker days with a different leader, so we don't mention that one.

[euromodder]

Originally Posted by Cd

Also, this :

Graphs like these are usually biased by the fact that only 1 of them - the car - is used on an as-needed base.

The busses, trains, and aircraft mostly operate on schedule, and aren't always full. They often require pre-positioning as well, meaning more empty runs. These are usually not accounted for in these comparative graphs.

Matter of fact, off-peak our public transport often runs nearly empty and its passenger-miles are known to be very rough estimates based on unrealistic usage data.

Countless times when going to or coming from work, I've seen heavy trains go by transporting a mere 1 or 2 passengers.


Friends of mine went on a Boeing 737 with half a dozen passengers.
The CO2 output per passenger-mile on that flight would have been horrendous.

[wyatt]

Originally Posted by euromodder

Graphs like these are usually biased by the fact that only 1 of them - the car - is used on an as-needed base.

The busses, trains, and aircraft mostly operate on schedule, and aren't always full. They often require pre-positioning as well, meaning more empty runs. These are usually not accounted for in these comparative graphs.

Matter of fact, off-peak our public transport often runs nearly empty and its passenger-miles are known to be very rough estimates based on unrealistic usage data.

Countless times when going to or coming from work, I've seen heavy trains go by transporting a mere 1 or 2 passengers.

Friends of mine went on a Boeing 737 with half a dozen passengers.
The CO2 output per passenger-mile on that flight would have been horrendous.

What percentage of the time do you see mini vans with 7 passengers inside? (this goes for every car/truck/suv/van you see on the road). I can tell you the last time I had a passenger in my car, it was July of last year. My guess is the numbers that are quoted are for full vehicles, not for the average commuter.

[euromodder]

Originally Posted by wyatt

My guess is the numbers that are quoted are for full vehicles, not for the average commuter.

They're generally for passenger-mile or passenger-kilometre.

[aerohead]

Originally Posted by Cd

just look at this beauty :





Note the various nose designs :




These are just odd :


Also, this :

The 'nose' also serves as the boat-tail when running 'backwards'.
Japanese Railways had been experimenting with 50+ foot 'nose' extensions to help mitigate dramatic pressure spikes experienced when the trains entered or left tunnels.
I think the 'odd' noses are part of the stable of research items tested.
If anyone has had to do an emergency landing from high altitude with failing cabin pressure you're aware of the inner ear pain which one can experience for days afterwards.
I applaud their efforts to help with passenger comfort.

[basjoos]

Originally Posted by aerohead

Man,that put a smile on my face! A friend had just done a blog at EV World on a hybrid ship from around 1830,which combined steam-power and sails and I'd been seeing sails in my mind.---------------------- Good for those folks.Hope their profit curve looks just like the tether leading up to the sail.Thanks!

All of the early ocean going steamships were "hybrid" since the early steam engines were so inefficient (before they developed triple and quadruple expansion engines) that the ship couldn't carry enough coal to steam all of the way across the ocean. Steam was mainly used for getting out of and into harbors and for propulsion during windless conditions or when they had to travel directly into the wind. Of course the earlier sailing ships were also "hybrid", the alternate power source being human powered sweeps or oars.