Aerodynamics

Is the typical, asthetically unappealing 2 p42's + baggage car + superliners or amfleet combination aerodynamically inefficient? Or does Amtrak not go fast enough to cause the effect? Would making this combination more aerodynamic make trains more fuel efficient than they already are and save money?

The Genesis is clearly more streamlined than the prior F40s. And today's Acela and HHP8s more so than the AEM7s and GG1s.

R36 Combine Coach wrote:The Genesis is clearly more streamlined than the prior F40s. And today's Acela and HHP8s more so than the AEM7s and GG1s.

OP is also taking into account the rest of the consist, not just the power.

From Marriott Fairfield Marion IL--(home tomorrow)

Likely the blunt "face" is the Superliners is less than ideal.

I'm not sure if aesthetics or fuel efficiency was Santa Fe's objectivew in adding to Bagg-Dorms assigned to the El Cap, but those cars had a "deflector' added to their roof line.

The motive was likely aesthetics; Diesel fuel during 1956 was maybe $.10/ga (ten cents a gallon).

addendum: photo of the car in question has been added to the discussion by another member.

Autos and trains travel within the same range - 0-80 mph. Automakers tend to spend lots of money on aerodynamics, so I would assume there is an effect within that speed. Whether the automakers' spending on aerodynamics is for noise reduction, stability, or efficiency is a good question though. Obviously the train is heavy enough that stability is not an issue, as it would be with a 3300# Audi TT (true story - that's why the TT has a little lip spoiler). Noise can be an issue, that's why Lexus is so proud of the Cd of .27 and .28 on their high-end cars. Less whistling and wind noise. But it's also known to be a performance issue, and thus likely a factor in train performance as well. You'll notice sports cars and electric cars have low drag coefficients to help with efficient use of the power available. I can only imagine that with the proliferation of ancillary devices on a locomotive, the Cd is quite high - the horn, the coupler, the brake hoses, snowplow... And we know the coupler shroud went away with the EMD E7 and will not return for maintenance reasons.

I have the feeling the speed would have to be much higher for aerodynamic R&D on a P42 to be effective with regard to efficiency. If you look at the Acela, aerodynamic aids are in use - the pans, in lowered position, are shrouded from wind. The coupler is also shrouded, and there are few ancillary devices out in the open.

One other effect that I've heard of: Car and Driver once found that the longer wheelbase version of a Jaguar XJ6 had a 6mph higher top speed and they though it was due to the shape - the same but with a 6" longer passenger compartment. Is the same effect enjoyed by a longer train? Probably not, because a longer train is also ~ 100,000# heavier per car.

I'm not an engineer, so I'm open to comments and criticism on this analysis and the relation to one of my other hobbies, fast cars.

well on a motorbike , you put your head down behind the fairing and the speed increases 5 - 10 mph without increasing the throttle . you also notice when you pull up behind vechicles how much "dirty air" there is behind them . it is amazing the difference and its not always to do with the size of the vechicle .
Whats at the back of a vechicle is just as important as whats in the front , probably why fish and birds dont have a fat arse . crude but if you want to talk areodynamics , the animals already have it sussed .
Working with wind turbines , whats behind / 2 the sides , underneath is just as important as whats in front of the turbine . someone actually worked out having the turbine blade downstream of the pole / turbine body was more efficent than the way they are designed now . (blade in front ) .
a few issues of trains ago , there was a picture of a bnsf loco with a wind turbine strapped to the front , to test aerodynamics , it could just as well be on the back . last issue , they were talking about empty coal hoppers using as much energy to move as full ones

http://en.wikipedia.org/wiki/Drag_equation
http://en.wikipedia.org/wiki/Drag_coefficient
http://en.wikipedia.org/wiki/Reynolds_number

I'd assume that the most aerodynamically efficient train on this continent would either be the Acela due to its streamlining, or the Auto Train due to its extreme length. The longer the object passing through a fluid compared to its width, the larger its Reynolds number and the more easily boundary-layer airflow will become turbulent over its surface, leading to lower friction. Ore freighters are more hydrodynamically efficient than a sailboat because they're so long compared to their width, even though their bows are often nearly flat. The most important part for them is to have a clean, uninterrupted hull line, with no barnacles (or grab bars, mirrors or radiator fans on passenger locomotives) that reach out of the boundary layer.

79 mph travel does exert a fair amount of drag on a train, but not nearly as much as the 110-125 mph on the Corridor. Besides, most passenger trains spend a comparatively small amount of time even at 79. Once we get sustained 125 mph travel around the country, we can discuss aerodynamics more complex than simply keeping trains clean and smooth-sided.

I always wondered if the Acelas and HHP-8's were quieter in the cab than AEM-7's and other less aerodynamic locomotives.

When I traveled aboard the cab car on a Keystone in push mode, I was struck by the amount of wind noise at 100+ mph. I recorded a short video clip to try to capture the noise:

http://www.youtube.com/watch?v=yGbU4QR146o

I would guess that either the Acela or my avatar are (were?) the most aerodynamically optimized trainsets run by Amtrak. As David Benton correctly points out, the tail end is even more important to streamline than the nose.

~~Ken.

rohr turbo wrote:I would guess that either the Acela or my avatar are (were?) the most aerodynamically optimized trainsets run by Amtrak. As David Benton correctly points out, the tail end is even more important to streamline than the nose.

~~Ken.

Well , i would say as important , not more important .
To be amtrak specific , i would say alot of what the hhp8 front end gains in aerodynamics is lost between the back end of it and the first carriage . then of course , the rear of all regional trains , which spend a fair time at 125 mph , is a slab end .
the superliner front , well thats a sail into the wind , begging for a deflector on the baggagge car in front . is it significant at 79 mph ? , well , it would be interesting for someone to work out the payback period .
Not just in money , but in energy use / carbon emissions , as i believe one day Amtrak is going to have to stand up and be counted on that one . As things stand at the moment , i don't think it will get a glowing report card .

Matt Johnson wrote:I always wondered if the Acelas and HHP-8's were quieter in the cab than AEM-7's and other less aerodynamic locomotives.

When I traveled aboard the cab car on a Keystone in push mode, I was struck by the amount of wind noise at 100+ mph. I recorded a short video clip to try to capture the noise:

http://www.youtube.com/watch?v=yGbU4QR146o

I can attest that the cab cars and even the cabs on the AEM7's are quite noisy. The HST and HHP, the cab is extremly quite...It could be aerodynamics, but also everything seems tighter in those cabs since they are still considered "new". Also on the AEM7s you get alot of noise near the cab doors but the HST and HHPs have the cab doors behind the cab. the cabs are seperated.Some AEM7s have been getting newer doors which are thicker and are tighter when they are closed, and this has reduced noise in the cab very much...

Budd built RDC-9s with about 1/2 the horsepower of a RDC-1 or 2 because less horsepower was required for the trailing cars since the first car broke the air. The SPV had two noses, a blunt one for 100 mph gearing and a more aerodynamic nose for 120mph gearing. Automobiles at 50 mph spend almost 1/2 required horsepower to overcome drag.

typesix wrote:The SPV had two noses, a blunt one for 100 mph gearing and a more aerodynamic nose for 120mph gearing.

Shame it never saw production...it looked pretty cool!

http://www.northeast.railfan.net/images/spv2000a.jpg

Matt Johnson wrote:

typesix wrote:The SPV had two noses, a blunt one for 100 mph gearing and a more aerodynamic nose for 120mph gearing.

Shame it never saw production...it looked pretty cool!

http://www.northeast.railfan.net/images/spv2000a.jpg

looks like something out of the jetsons

The High speed nose was just a bolt on Fiberglass cone, Engineers setup was same at both ends.
It was more fake than a foamrubber boob.