I have always assumed (dangerous I know) that a fully loaded passenger train weighed considerably less than a freight train and is why larger diameter steam engine wheels could be used on passenger trains which proved unsuccessful in freight service. Does anyone know the weight of a fully sold out heavyweight and lightweight coach? Is there a known data source to compare HP, tractive effort, speed and other criteria between the two pasenger cars and a typical freight car? In other words how many freight cars = one passenger car in a train? Opinions are nice but I am not looking for opinions thank you. I am looking for facts. Don;t forget that speed of passenger trains equates to higher HP so a comparison at a slower speed is probably the kind of data I am looking for. Thanks
A HW passenger can weigh 80-85 tons(or more)
A streamline coach weighs about 62 tons
A streamline sleeper weighs about 70 tons
A streamline dome car weighs about 85 tons
A Superliner car can weigh anywhere from 70-85 tons loaded. I suspect the diners and sleepers weigh the most.
All of the above information is available on the Internet by searching on rail passenger car weight. The hard part of making a comparison is how well the car rolls. Passenger cars got roller bearings first as they have a lot of drag(the axle generators for car lighting). The current Heritage and Superliners do not use axle generators and roll quite well. The bottom line is that the HP/trailing ton is much higher on a passenger train! Freight trains on the CP & BNSF mainlines here in Minnesota run with anywhere from 1-2 hp/ton. Amtraks Empire Builder runs with about 8-10 hp/ton. You might want to read the following:
http://www.trainorders.com/discussion/read.php?4,1824865
Jim Bernier
HP, tractive effort, etc are characteristics of an engine, not of cars. An engine with a particular wheel arrangement, weight, driver size, piston stroke and boiler pressure will produce a particular tractive effort.
That’s fixed. It doesn’t matter whether its pulling passenger cars or freight cars, if the engine has 40,000 lbs. tractive effort then it has 40,000 lbs of tractive effort. Period.
For example a RDG I-8sb 2-8-0 and L-7sb 4-6-0 have the same boiler. The 2-8-0 has 54,000 lbs TE and the 4-6-0 has 38,000 lbs TE. One hauled primarily freight and the other hauled primarily passenger. But regardless of what they hauled, the TE was the same 54k or 38k. So the I-8 was rated for approximately 1100 tons and the L-7 for 800 tons. The engine doesn’t care whether its passenger cars or freight cars.
For more modern eras, some railroads used horsepower/trailing ton. Generall freight trains might have 1-2 hp/tt while expedited trains might have 4 hp/tt. Passenger trains might have 5-8 hp/tt.
I am not sure from your post what you are really looking for. Engines with larger diameter drivers have lower tractive effort.
I am trying to come up with a rule of thumb that a passenger train of X number of cars is equal to a freight train of Y number of cars at the same speed. The increased HP for passenger trains is no doubt arrived at due to the higher speeds involved as the torque curve drops off at speed.
There really isn’t a “rule of thumb” other than comparing the tonnage rating (and that’s a drag rating) and the tonnage of the trains. I came across a RDG passenger car chart and the baggage cars have capacities. All the heavyweight cars (all types) run in the 105,000-140,000 lb range. The baggage cars hav rated capacities of 50-70,000 lbs. So a “fully loaded” 70 ft baggage car with 6 axle trucks would have a weight of 203,0000 lbs, roughly 100 tons.
A typical 40 ft boxcar would weigh about 45-50,000 lbs and have a capacity of 100,000-110,000 lbs. So lets call it 150,000 lbs gross weight or 75 tons. So a passenger car equals 133% of a freight car in tonnage (at drag freight speeds).
The RDG tried running commuter trains with an NW2 1000 hp switcher. The NW2 could reach the speeds required and could pull the train (8 cars) but lacked the ability to accelerate quickly enough so could not maintain schedule.
Tonnage isn’t everything.
Everyone has given you good info here, let me try to pull some of it together.
Passenger cars are subject to a lot more rolling resistance than freight cars for a number of reasons - Diaphragms/buffer plates rubbing, axle driven generators and/or air conditioning in the steam era, 6 wheel trucks which have much greater friction in curves, poor aerodynamics with windows open, and longer length also adds more rolling resistance on curves than shorter cars.
Combine all this with their greater weight (again, I am using steam/transition era freight car weights) and the need to accelerate the train much more quickly, and/or be able to slow it dynamicly more quickly for smooth starts and stops, and you have a situation where a 15 car heavy weight trains needs as much power as a 70-100 car freight train.
So a given passenger train may only weight 1/4 of a given freight train, but actually have a similar rolling resistance and similar power requirement or greater power requirement to meet the schedule.
Sheldon
The size of the drivers was related more to speed, although you’re correct to the extent that a high-drivered steam engine would have a harder time starting a train than a small-drivered one…part of the reason 0-6-0 and 0-8-0 had such small drivers.
The rule of thumb was that 1"= 1 MPH; that is, a Pacific with 79" drivers should be able to go 79 MPH with ease, while a Mikado with 63" drivers would top out around 63 MPH. It’s a very rough guide but it does correctly show the idea that larger drivers allow for greater speed.As far as it goes, some “freight” engines could go very fast, and some “passenger” engines had considerable pulling power for freights when needed.
As far as a rule of thumb comparing passenger cars to freight cars, I don’t know if you could really come up with an easy comparison. A lot of things factor in, like steam being siphoned off the engine to be used to heat passenger cars and for cooking in the diner for example.
A UP 4-6-6-4 could haul a freight train a couple of miles long, but was sometimes used in passenger service. I can’t picture a passenger train a mile long (about 60-65 cars) let alone two miles.