BuslistFor hand calculations 4lb/ton is still a good # on flat, tangent track, figure 20#/ton/% on grades and for curves resistance is often considered to be 0.8-1.0 #/ton/degree (but very variable based on rail profile and lubrication environment). Hope this helpes.
Agree! Close enough nearly for most practical work.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
jrbernier You are asking how many tons of rolling stock a locomotive with 132,000 lbs of TE can pull? That will depend on a number of factors: Grades Curvature Short Time rating if this is a DC loco Most railroads have 'tonnage rating' tables for each division on the railroad.
You are asking how many tons of rolling stock a locomotive with 132,000 lbs of TE can pull? That will depend on a number of factors:
Most railroads have 'tonnage rating' tables for each division on the railroad.
An additional factor is the train's rolling resistance which can vary with outside temperature. Modern trains with roller bearing certainly require less TE to start moving compared to the trains used with steam power in the fifties.
CZ
Buslist Although 375 is the theoretical number to calculate TE from HP it doesn't take into account losses in the locomotive (air compressor etc) so 308 is often used for practical calculations. So the equation is 308 HP/V But this assumes that the wheel is able to transfer that force to the rail. So a second limiting factor is the coefficient of friction (often called adhesion in railroad circles). This is typically around .20 for DC diesel locomotives and around .40 for AC. Having a higher locomotive weight is beneficial here, hence heavier 6 axle locomotives.
Although 375 is the theoretical number to calculate TE from HP it doesn't take into account losses in the locomotive (air compressor etc) so 308 is often used for practical calculations. So the equation is 308 HP/V But this assumes that the wheel is able to transfer that force to the rail. So a second limiting factor is the coefficient of friction (often called adhesion in railroad circles). This is typically around .20 for DC diesel locomotives and around .40 for AC. Having a higher locomotive weight is beneficial here, hence heavier 6 axle locomotives.
My understanding is that in the U.S., the horsepower rating of a locomotive is net auxiliaries (radiator fans, traction motor blowers, air pumps) and prior to losses in the electrical transmission.
Ergo, a 4200 HP locomotive is rated at the shaft of the traction alternator, and the HP delivered to the wheels is that number multiplied by the efficiency of the alternator in combination with the traction motors. I have read that older DC traction motor drives were in the mid 80 percent efficient whereas AC drives are in the mid 90's.
With respect to a passenger locomotive such as the Amtrak Genesis, I think user "schlimm" had posted information that the P42 Genesis isn't "really" 4200 HP at the alternator shaft. This 4200 HP is 1) if the locomotive is not supplying HEP, the motive effort for which is also taken from the main engine shaft but 2) the locomotive is not in the HEP mode, where full engine RPM is not available.
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
timz JPS1 What is the relationship between horsepower and tractive effort? If you're measuring tractive effort at the wheel rim, and you're measuring horsepower there too, then the relationship is dead simple: horsepower equals TE (in pounds) times speed (in miles/hour) divided by 375. Next question: how much horsepower does a "4400 hp" diesel produce at its wheel rims, at a given speed. That's not so easy to answer.
JPS1 What is the relationship between horsepower and tractive effort?
If you're measuring tractive effort at the wheel rim, and you're measuring horsepower there too, then the relationship is dead simple: horsepower equals TE (in pounds) times speed (in miles/hour) divided by 375.
Next question: how much horsepower does a "4400 hp" diesel produce at its wheel rims, at a given speed. That's not so easy to answer.
On the pull back side the Davis equation is still often used (although there are arguments about aerodynamic issues especially with the large gaps on double stacks). Extensive tests were performed with large scale models in the Lockheed wind tunnel. These all of which produced more variability that folks wanted to deal with for hand calculations but were incorporated into modern simulation models like TOES (available to AAR members only due to misuse by the legal community). For hand calculations 4lb/ton is still a good # on flat, tangent track, figure 20#/ton/% on grades and for curves resistance is often considered to be 0.8-1.0 #/ton/degree (but very variable based on rail profile and lubrication environment). Hope this helpes.
JPS1What is the relationship between horsepower and tractive effort?
conrailfan2596if a locomotive can pull 132000 pound force how do you covert that to how much weight it can pull
conrailfan2596if a locomotive can pull 132000 pound force how do you convert that to how much weight it can pull
You don't. That 132K is STARTING tractive effort and it tells you how much pull the locomotive can exert against its drawbar. It's analogous to torque.
In order to figure out the tonnage of train it can pull, you need to know some other things, some of which are incorporated in 'car factor', compensated grades, etc. -- one good reference for some of the variables might be the Davis formula.
But starting TE won't tell you anything about 'how much weight the locomotive can pull AT SPEED. For that you need to know horsepower, which involves a time factor, and therefore invokes the idea of 'work'. TE is just a force, counteracted at the drawbar by train resistance, and F=MA at the moment of starting. But it takes more power to run the train faster -- look at the definition of horsepower for an idea about this if it isn't intuitive.
A diesel-electric locomotive with very high nominal starting TE will rapidly get to a speed where the effective 'tractive effort' is governed by the maximal horsepower that its prime mover can develop, and where the effective TE corresponding to this reaches the resistance of the train, you will be at the maximum speed that train can reach without external aid (gravity on a downgrade, tailwind, etc.)
JPS1What is the relationship between horsepower and tractive effort? Which is most important in determining how much power to assign to a train?
It depends on what you're trying to do. Tractive effort is how much a locomotive can pull. Horsepower is how fast it can pull a load. If you want it to just clear the ruling grade, simply assign enough tractive effort to get it over. If you want it fast, add more units for more horsepower.
What is the relationship between horsepower and tractive effort? Which is most important in determining how much power to assign to a train?
Rio Grande Valley, CFI,CFII
Modeling BNSF and Milwaukee Road in SW Wisconsin
if a locomotive can pull 132000 pound force how do you covert that to how much weight it can pull
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