Lets suppose that the promoters of the Texas ‘high speed’ rail link between Dallas and Houston scare up enough investors to make the project possible. Lets further suppose that they decided that they must run along existing track, with perhaps some straightening of the right-of-way and, furthermore, they cannot afford to electrify the line.
What is the top speed that they could hope for on first class track and roadbed, with a power car on both ends of the train, so that it would not have to be turned at the end points, pulling six cars? Keeping in mind that I am not an engineer, would it be diesel or gas turbine or could it be either?
I would think that 125 MPH would be possible. The Pioneer Zephyr exceeded 110 MPH with 600HP, though all it had was the locomotive and 2 cars. Main issue is that the axle mounted traction motors used on American locomotives would be hell on the track at 125 MPH.
The E units on one carrier I am familiar with were delivered with 120 MPH gearing in the 1940’s. I was in the cab of one and observed 118 being indicated. What modern power can be designed for is in the hand of the engineers.
The CB&Q ‘E’ unit fleet was geared for 117 mph(E5 & early E7 order), Following E7, E8 & E9’s were geared for 98 mph. I rode in the cab of these units several times. At speed, they were very smooth riding, I suspect good track, no freight slack action, and even acceleration reduces the ‘pounding’ from nose suspended traction motors. Keeping the HP to trailing tonnage high will reduce this issue. If your proposal is going to use exsisting trackage, or even new trackage laid next to an existing freight line - the grade crossings and curves are going to limit your speed. I sort of doubt an average speed of 125 mph. The engines should be able to peak out at 125 mph on short sprints if there is enough tangent trackage.
They have diesel-electric MU train sets in England that have no trouble at all with 125 mph.
I believe there is a spec out there for a 125 mph North American diesel locomotive. There was blurb on Progress Rail’s web site. It would have frame mounted traction motors.
I am an advocate of a cogent “engineering approximation”, but you may want to sharpen your pencil on that claim. Aerodynamic resistance is the dominant force at those speeds, and that force increases with the square of speed. Hoerner (1965, Fluid-Dynamic Drag, Hoerner, Brick Town, New Jersey) infers from drag data that there can be a cubic term relating to the swaying of the train cars but finds that effect only in freight trains.
Hoerner’s book is filled with practical applications regarding experiment and theory of drag for all modes of transportation – trains, planes, cars, boats. It was recommended to me by a mechanical engineering professor at Northwestern University, and I purchased it in the mid 1970’s by sending a check to Dr. Hoerner’s widow, who was filling orders. So if you want a copy, it may be as challenging to acquire as Waredale’s “Red Devil and Other Tales of the Age of Steam.”
So, a 20 percent increase in speed (from 125 to 150 MPH) increases the fuel consumption on a per-mile basis by the increase in drag force (“work” is force times distance) or 1.2-squared minus 1 or 44 percent. That increase in speed increases the HP requirement, which is the same as the fuel consumption per unit time by 73 percent. The fuel consumption per unit time is up 73 percent, but you are going 20 percent faster, so the net fuel consumption per mile is up only the 44 percent, which is a ways away from doubling.
If you are comparing 125 MPH to about 80 MPH (the 79 MPH speed limit for non-automatic train step territory), the gallons per mile increases by a factor 2.44 (144 percent increase, where a 100 percent increase is a factor of 2 or double).
The RTLIII Turboliners did 149 mph during acceptance testing. Key to high speed, other than horsepower is P2 forces which are directly related to unsprung weight. Diesel electrics with axel mounted motors tear up the right of way at speeds above 90 mph. The Turboliners with cardan shaft drive had very low P2 Forces. I co-aurhored a paaper on this amny yeas ago.
German ICE-TD DMU regularly touch 200kph (140 mph) between Hamburg and Luebeck on their way to Copenhagen.Those that start at Berlin Hbf would also hit 200 kph between Spandau and Hamburg, There is of course no reason why a diesel locomotive can’t use Quill Drive.
I think 200kph is the equivalent of 125mph (or near enough) rather than 140mph.
As mentioned earlier the Inter City 125s in the UK do what’s said on the tin, and have been doing so for over 35 years. Originally built with Paxman Valenta engines, now with more modern replacements. I haven’t got reference books to hand, but formation is two powers cars at c2,250 hp each with 7 or 8 coaches in between. Engines are less than 80 tones, coaches about 35 tonnes. They have not got a reputation for damaging the track.
The P2 forces would also be proportional to the square of the speed, with the forces at 125 MPH almost twice that at 90 MPH for the same unsprung weight.
One potential way of reducing unsprung weight is to use higher rotational speed AC motors, which should reduce the size an weight of the motor. A smaller motor would then allow the center of mass to be placed closed to the “nose” further reducing effective unsprung weight, This may be adequate for 125 MPH, any faster then either a Cardan or quill drive would be necessary.
Erik
P.S. Jerry, i had you in mind in my earlier comments about 125 MPH being impractical for American axle mounted traction motors.
Can’t believe I screwed up the speed conversion, thanks Eric.
There is a nice brochure on the Alstom website featuring the new AGV (produced as the Italo for NTV in Italy) page 11 of the brochure shows a power truck with frame mounted Permanent Magnet synchronous AC traction motors and a man with his hand on one of the motors. Power density is greater than 1kW/kg.
It would be nice to see 110-125 MPH speeds on the LOSSAN corridor, though 125 MPH would only be practical on the stretch through Pendelton. More time would be saved in reducing the number of miles where the trains are limited to 25-35MPH due to curvature and double tracking the line. One reason for the new interest in LOSSAN speeds is starting to commute between Solana Beach and Irvine.
The permag motors on the AGV are intriguing, and what I was thinking was pretty close to the motor mounting on the AGV. Especially intriguing was the 3.6kV bus on the inverter just about perfect for a recreation of the DL&W or Milw 3kV electrifications.
the milw. electrification started out at 3 \kv, but then they shimmed the motor-grnerator fields and operated at 3.3kv - except in Butte where they shared some \BA&P trackage at 2.4 kv, into the station, and the Tacoma roundhouse where they were run on and off the turntable using a 440 v jumper!.
