BaltACD Passengers care about the quality of their ride....286K load of coal doesn't.
Passengers care about the quality of their ride....286K load of coal doesn't.
There was an earlier post that went into that in more detail but that quote sums it up.
Also back then there were two different speed ratings for freight car trucks. The ancestors of today's 286K trucks used to have a max speed rating of 50 mph. Then there were high speed trucks rated for 70 mph. These were used on Express Reefers and Express Boxcars for head end service on passenger trains. Max speed ratings in those days were only vague suggestions.
On CP for instance freight car trucks had two springs per side and a wheelbase of 5'7". High Speed Trucks on the other hand had five springs per side, and a 7' wheelbase. There were three springs where you would normally see the two, and one more spring on each side of the three, mounted diagonally.
Bruce
So shovel the coal, let this rattler roll.
"A Train is a Place Going Somewhere" CP Rail Public Timetable
"O. S. Irricana"
. . . __ . ______
All the above reasons apply: rail weight, bridge capacity, ride quality, truck construction, etc.
I will now add 2 items.
Just measured a SU heavyweight coach (#1012) and SOU PS lightweight (#2004).
1. One theory I had was wheel diameter. However I found them the same at 32" diameter. Weight loading on rail today is limited by wheel diameter and 100 ton coal cars have at least 40" diameter wheels that allow increased loads on each axel. Someone have the figures both 1940s and today?
2. More importantly is almost all heavy weight cars were build before 1940 and had friction bearings. After WW 2 many were converted to roller bearings but kept the original 6 axel trucks. I have heard that the less weight on a friction bearing the better and if one bearing gave way the car could limp into a repair station (about 30 - 50 miles before 1950?)
3. The PS car had Hyatt roller bearings and the heavyweight had standard 4 x 8 friction bearings.
4. The construction of the 4 axel trucks were much more complicated than the friction bearing car!!!
BaltACD Passengers care about the quality of their ride....286K load of coal doesn't. In the day, there weren't any 286K loads either. The 286K and larger loads are a function of the very late 20th Century. Sawtooth500: timz: Sawtooth500: So how heavy were these things actually? I mean we've got 286,000 lb coal cars running around these days on 2 axle trucks... were those passenger cars even heavier than that? I'm guessing few six-axle passenger cars weighed more than 180,000 lb. Ok, but you have coal cars weighing 286,000 lb on 2 axle trucks, so why would a passenger car weighing 180,000 lb need a 3 axle truck then?
In the day, there weren't any 286K loads either. The 286K and larger loads are a function of the very late 20th Century.
Sawtooth500: timz: Sawtooth500: So how heavy were these things actually? I mean we've got 286,000 lb coal cars running around these days on 2 axle trucks... were those passenger cars even heavier than that? I'm guessing few six-axle passenger cars weighed more than 180,000 lb. Ok, but you have coal cars weighing 286,000 lb on 2 axle trucks, so why would a passenger car weighing 180,000 lb need a 3 axle truck then?
timz: Sawtooth500: So how heavy were these things actually? I mean we've got 286,000 lb coal cars running around these days on 2 axle trucks... were those passenger cars even heavier than that? I'm guessing few six-axle passenger cars weighed more than 180,000 lb.
Sawtooth500: So how heavy were these things actually? I mean we've got 286,000 lb coal cars running around these days on 2 axle trucks... were those passenger cars even heavier than that?
I'm guessing few six-axle passenger cars weighed more than 180,000 lb.
Ok, but you have coal cars weighing 286,000 lb on 2 axle trucks, so why would a passenger car weighing 180,000 lb need a 3 axle truck then?
There was still quite a bit of 90# (or less?) rail around for the first part of the 20th century, too.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
The MP ordered Budd built lightweight streamlined 10-6 sleeping cars that operated on 3 axle trucks due to the lightweight rail on a branchline they were ordered for.
Sawtooth500 timz: Sawtooth500: So how heavy were these things actually? I mean we've got 286,000 lb coal cars running around these days on 2 axle trucks... were those passenger cars even heavier than that? I'm guessing few six-axle passenger cars weighed more than 180,000 lb. Ok, but you have coal cars weighing 286,000 lb on 2 axle trucks, so why would a passenger car weighing 180,000 lb need a 3 axle truck then?
Never too old to have a happy childhood!
The reality is that car, train, and track dynamics have changed so much over the years; that construction, manufacturing, and materials have changed so much over the years. To understand this you must follow closely the history and evolution of railroads and trains. It appears that not only can't the younger generation fathom, nor understand how railroads used to operate, they can't grasp the equipment and facilities of the earlier times. Those not familiar with such are urged not to pick out individual items of operation or equipment but find the books and literature that explains the history, the evolution, and the operation of railroads in years gone by. It is difficult to wade through the nostalgia and the cold business of business in some tomes, but it is there. I have always found that articles in the early volumes of Trains and Railroad magazines to reveal more than history books, especially those magazines from the mid to late 30's into the mid 60"s. Articles also from the model magazines of the time period will delve into daily operations more. After that, study the books of rules and the employee timetables of the railroads in question. Times were different, rules were different, operations were different,, equipment was different, philosophies, were different, everything was different but understandable if you read and search through the materials.
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daveklepper A lot also has to do with track structure. All steel heavyweight railroad business ("private") cars had six-wheel trucks, with one exception. That exception was (pardon me, IS) PRR 120, no owned by Juniata Equipment, along with the restored PRR E8s. This was a rebuild of a P70, but was as heavy as many of the other office cars, but the PRR had the track structure to support a heavy car on 4-wheel trucks. But their parlors were Pullman operated and were part of the Pullman parlor car pool, so they had six-wheel trucks to be able to operate on "foreign" railroads.
A lot also has to do with track structure. All steel heavyweight railroad business ("private") cars had six-wheel trucks, with one exception. That exception was (pardon me, IS) PRR 120, no owned by Juniata Equipment, along with the restored PRR E8s. This was a rebuild of a P70, but was as heavy as many of the other office cars, but the PRR had the track structure to support a heavy car on 4-wheel trucks. But their parlors were Pullman operated and were part of the Pullman parlor car pool, so they had six-wheel trucks to be able to operate on "foreign" railroads.
So really it was never about the ability of two axle trucks to support the car, but more about the fact that on lighter track a 2 axle truck would put to much strain on the track, whereas a 3 axle truck distributed the weight more, correct?
In today's railroads that may be true, but that is after a great deal of upgrading. In the heyday of passenger trains most freight equipment was limited to 50 to 70 tons of load, not 110 tons. The fixed plant reflected this, especially bridges, and working timetables often had a list of restrictions prohibiting certain classes of locomotives or weights of cars from certain lines. While this type of restriction was mostly on secondary and branch lines, they still had passenger service with coaches and/or sleepers running through.
John
timz Sawtooth500: So how heavy were these things actually? I mean we've got 286,000 lb coal cars running around these days on 2 axle trucks... were those passenger cars even heavier than that? I'm guessing few six-axle passenger cars weighed more than 180,000 lb.
Sawtooth500So how heavy were these things actually? I mean we've got 286,000 lb coal cars running around these days on 2 axle trucks... were those passenger cars even heavier than that?
Paul of Covington Wouldn't the increase in freight car weights with the concurrent increase in the rail load- carrying capacity have made the six-wheel trucks unnecessary even if the passenger car weights remained the same? By the way, I have long been interested in the suspension on those trucks; they were pretty complicated. I have studied some on display cars and tried to sketch out the "layers" of springing and equalization. Does anyone know of any diagrams or other literature that would show these details?
Wouldn't the increase in freight car weights with the concurrent increase in the rail load- carrying capacity have made the six-wheel trucks unnecessary even if the passenger car weights remained the same?
By the way, I have long been interested in the suspension on those trucks; they were pretty complicated. I have studied some on display cars and tried to sketch out the "layers" of springing and equalization. Does anyone know of any diagrams or other literature that would show these details?
I would bet a new built passenger car could be constructed on 2 axle trucks. Freight cars do use a different kind of truck however...
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So how heavy were these things actually? I mean we've got 286,000 lb coal cars running around these days on 2 axle trucks... were those passenger cars even heavier than that?
Believe it or not, it WAS the weight. To reduce vertical jarring, many heavyweight cars were built with concrete floors!
Since that time, many advances have been made - like adding shock absorbers to trucks and laying continuous welded rail, and the need for sheer mass to resist vertical acceleration has gone away. So has te need for three axle trucks.
Chuck
And it was not just the weight but also a matter of smoothing out the ride. Heavy weight cars were loaded with all kinds of accutriments and appliances, thus the six weels offered a cushioned existance while the patron got a more cusioned ride.
Heavier passenger cars required 6-wheel trucks to carry the weight. In the streamline era, most of the full-length dome cars rode on 6-wheel trucks and Santa Fe's hi-level dining cars for the "El Capitan" also rode on 6-wheel trucks. There may be others.
The heavyweight era was a different story. Almost all sleeping cars and dining cars rode on 6-wheel trucks, again because of their weight. As I mentioned in another post, South Shore Line had two dining cars and two parlor cars on six-wheel trucks.
Currently, all amtrak cars have 2 axled trucks. However, the circus train article in the latest Trains mag brought to my attention that back in the day certain passenger cars were build with 3 axle trucks. What was the point of this? Clearly passenger cars do not need the traction nor does their weight mandate 3 axle trucks. So why were those cars built like that?
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