samfp1943 [ BaltACD timz The cars are certainly not limited to 45 mph. What if they were limited to, say, 60 mph? How would the engineer be informed of that? If every car that ever ran on the railroad had its own limit, how would the engineer be told what speed his train was allowed? RR timetables have been known to limit certain specified cars to some speed, but usually the freight train speed limit is all the engineer has to worry about. If a train is otherwise allowed 70 mph, and a car is in the train, that car is almost always allowed 70 mph. If individual cars have specific maximum speeds - that is data that is contained in the car's UMLER (Universal Machine Language Equipment Register) record. All carriers in making their Train Documentation acess UMLER for specific aspects of data about each individual car in the train being documented. If there is a speed restriction for a individual car that fact will be represented and printed on the Train Documentation Report that both the Engineer and Conductor have in their posession and refer to for any restrictions that may be highlighted. Train Documents highlight such other things as Long Cars, High Cars, Short Cars, HAZMAT and a number of other data elements that will have a effect on how the train can be operated. Once one sets aside all the "regulations/rules,etc.". I would have to think that the most limiting factor of speed, would be the limit set on the next upcoming switch.
BaltACD timz The cars are certainly not limited to 45 mph. What if they were limited to, say, 60 mph? How would the engineer be informed of that? If every car that ever ran on the railroad had its own limit, how would the engineer be told what speed his train was allowed? RR timetables have been known to limit certain specified cars to some speed, but usually the freight train speed limit is all the engineer has to worry about. If a train is otherwise allowed 70 mph, and a car is in the train, that car is almost always allowed 70 mph. If individual cars have specific maximum speeds - that is data that is contained in the car's UMLER (Universal Machine Language Equipment Register) record. All carriers in making their Train Documentation acess UMLER for specific aspects of data about each individual car in the train being documented. If there is a speed restriction for a individual car that fact will be represented and printed on the Train Documentation Report that both the Engineer and Conductor have in their posession and refer to for any restrictions that may be highlighted. Train Documents highlight such other things as Long Cars, High Cars, Short Cars, HAZMAT and a number of other data elements that will have a effect on how the train can be operated.
timz The cars are certainly not limited to 45 mph. What if they were limited to, say, 60 mph? How would the engineer be informed of that? If every car that ever ran on the railroad had its own limit, how would the engineer be told what speed his train was allowed? RR timetables have been known to limit certain specified cars to some speed, but usually the freight train speed limit is all the engineer has to worry about. If a train is otherwise allowed 70 mph, and a car is in the train, that car is almost always allowed 70 mph.
RR timetables have been known to limit certain specified cars to some speed, but usually the freight train speed limit is all the engineer has to worry about. If a train is otherwise allowed 70 mph, and a car is in the train, that car is almost always allowed 70 mph.
If individual cars have specific maximum speeds - that is data that is contained in the car's UMLER (Universal Machine Language Equipment Register) record. All carriers in making their Train Documentation acess UMLER for specific aspects of data about each individual car in the train being documented. If there is a speed restriction for a individual car that fact will be represented and printed on the Train Documentation Report that both the Engineer and Conductor have in their posession and refer to for any restrictions that may be highlighted.
Train Documents highlight such other things as Long Cars, High Cars, Short Cars, HAZMAT and a number of other data elements that will have a effect on how the train can be operated.
Once one sets aside all the "regulations/rules,etc.". I would have to think that the most limiting factor of speed, would be the limit set on the next upcoming switch.
....and those higher speeds with tonnage are just fine if there aren't switches and turnout frog points getting the crap beat out of them. Your fuel savings are going to pay for additional welders and frog changeouts. [WA$H]....hope you don't have a crossing frog or two or three mixed-in there. (those are speed restricted)
It's a location and a local conditions balancing act.
Overmod oltmannd Speed kills. Conrail used to run unit coal at 40 mph. One such 'innovation' was reminiscent of the Carter story with thermostats in the Georgia governor's mansion in that a rigid speed limit spelled more fuel consumption ... there could be no faster running to get advantage on what had effectively been momentum grades. Whose thread brought this up?
oltmannd Speed kills. Conrail used to run unit coal at 40 mph.
One such 'innovation' was reminiscent of the Carter story with thermostats in the Georgia governor's mansion in that a rigid speed limit spelled more fuel consumption ... there could be no faster running to get advantage on what had effectively been momentum grades. Whose thread brought this up?
CSX had a 'hard' 40 MPH limit on coal trains system wide at one point in time. Atlanta Division officials, after much effort, were able to get a fuel consumption test between two coal trains with the same class power as well as the same train loading. One train observed the 'hard' 40 MPH limit and the other was allowed 50 MPH. The test was between Atlanta and Waycross which is a railroad with a undulating profile account the rolling hills of central Georgia. The 40 MPH train had to use brakes descending the hills to keep from exceeing 40 MPH. The 50 MPH train never had to use the brakes to control speed descending the hills. When fuel use was measured on the locomotives - the 50 MPH train used 150 gallons per unit less for the 278 miles from Atlanta to Waycross. The 50 MPH train was allowed to use the kinetic energy from descending hills as 'additional power' in the efforts to climb the next hill. The 40 MPH train wasted that energy by have to brake to keep from exceeding the 40 MPH limit.
Fuel Economy is not always enhanced by slowing down.
Never too old to have a happy childhood!
oltmanndrail. You can get "truck hunting" where the whole car yaws as each end of the car slaps back and forth.
To this is added problems of distortion and wear in the truck construction itself. I had a very interesting introduction to 'lozenging' (aka 'skew', where the truck itself experiences internal undamped oscillation). This was seen as such an issue that some truck frames were fitted with bracket pivots to allow an X-shaped light frame. To my knowledge better track standards and LWR combined with better wheel-profile maintenance, articulated and lighter cars, etc. was 'enough' of an answer at 286K ... but perhaps as with so much else, not enough at 315K...
jeffhergert Mechanical considerations do come into play. Our system special instructions allow empty hoppers with constant contact side bearings are allowed 60 mph. Empty hoppers not so equipped are limited to 50 mph. Jeff
Mechanical considerations do come into play. Our system special instructions allow empty hoppers with constant contact side bearings are allowed 60 mph. Empty hoppers not so equipped are limited to 50 mph.
Jeff
The two biggies that limit speed are braking and car ride dynamics.
You have to be able to stop trains per the signal system. You can have hopper cars without load/empty sensing brakes where the braking ratio is set to keep the wheels from sliding when empty. This leaves the car with really crappy braking when loaded (the main reason train stopping distances are so long). So, you might have to limit the max speed of a loaded hopper train so you don't go sailing past stop signals.
The car dynamics are governed by the stability of the wheel and rail. You can get "truck hunting" where the whole car yaws as each end of the car slaps back and forth. If it happens violently enough, the car can derail. Things the lower the hunting threshold speed are the car weight (low is bad), flange taper (higher taper is worse - worn wheels have higher effective taper), car length (shorter is worse).
Truck hunting stability is one of the things that new car designs have to demonstrate before they can be built. I think this requirment came about around 1980, so there are plenty of "bad" cars still on the road - shortish bulkhead flats, for example.
Constant contact side bearings are "meh" remedy to cars with truck hunting tendencies. They provide friction against truck rotation which raises the threshold speed. The friction isn't desirable when you are trying to move cars on curved industrial leads. Locomotives like GP60s often had truck yaw dampers (shock absorber) to stop hunting at speed.
Conrail once tried to move empty mill gons back west on the head end of an intermodal train. Really improved car utilization, but tore up the RR on day near Cleveland. Truck hunting at 60 mph was the cause.
It tends to occur on tangent stretches of welded rail. In the jointed rail days, the joints were enough of perturbance to stop the instability from getting going.
Further down the physics list, but higher up on the ledger is fuel consumption. Speed kills. Conrail used to run unit coal at 40 mph. Loaded because of braking distance, empty to save fuel.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
DR TORSTEN SOHNS Is the maximum permissible speed of a coal hopper exclusively a question of wagon technology?
Is the maximum permissible speed of a coal hopper exclusively a question of wagon technology?
No. Hoppers are constructed with the same technology as other cars. The biggest consideration the carriers apply is does increasing the speed of the commodities that hoppers carry bring more profits to the bottom line. That answer is no.
Each carrier has their own set of rules and recommendations on how they will handle bulk commodity unit trains.
If you are driving behind a truck with gravel, the wind can blow stones off the gravel and smash them into the windscreen of your car.
The risk of the wind blowing the load away depends on the size and weight of the particles and the wind speed, the latter being largely determined by the speed of the freight vehicle. In addition - for example, if the track is not optimally positioned - there could be rocking movements of the wagon, which have higher kinetic energy at higher speeds than at lower speeds. These rocking movements can further intensify the effects of the airstream on the coal.
I could well imagine that for coal there could be a critical speed of 40 to 60 mph depending on its particle size.
A colleague of my father's was stuck in a traffic jam under a railroad bridge in the late 1960s / early 70s. His car was severely damaged by falling briquettes when a freight train loaded with coal crossed the bridge.
In the early 70's Chessie System restricted any open top load to 40mph. Once when I was a brakeman an engineer who liked to run fast stopped at a spur to set out the one loaded coal hopper in our train, saying it had some defect. He wanted to be able to run faster. We probably lost more time setting it out than we gained by running faster. The maximum speed allowed on the trip was 50mph. Of course he always ran at least 5mph over the limit.
Any empty car except intermodal was restricted to 50mph on CSX.
Mark Vinski
SD60MAC9500 Hopefully Mr. Hergert will chime in on this, and correct me if I'm wrong. If I remember correctly at one time in the past UP was running loaded coal trains at 60 on it's Kearny Sub.
Hopefully Mr. Hergert will chime in on this, and correct me if I'm wrong. If I remember correctly at one time in the past UP was running loaded coal trains at 60 on it's Kearny Sub.
I think at one time that was the case. Now any car loaded with coal is restricted to 50mph. For awhile all bulk commodity trains, loaded or empty, were restricted to 50mph. Even though some coal hoppers/gondolas are good for 60mph. Now the empties can do the maximum speed for the car type.
The fastest allowed speed of the train is governed by the car with the slowest allowed speed. As pointed out, we receive a train list that lists the maximum speeds for cars. However, there is still Tons per Operative Brakes and any other specific subdivision or service unit (Divisions on other RRs) that may be in place. If no train list is available, the system special instructions has allowable speeds for car types.
Trains received from foriegn connections that don't meet UP system car placement instructions can be handled without correction at 45mph to the first location it can be fixed. That is, the first place it's due to work. It can pass umpteen yards, as long as it doesn't do work it's good to go.
caldreamerThe BNSF System Special Instructions have specific speed limites for all types of freight cars based upon the mark and/or number(s) or aar class or both.
And I suspect BNSF Train Documents highlight all those restrictions that are identified in System Special Instruction as they pertain to individual cars that are in trains.
With the voluminous size of Special Instructions and the various Train Handling Rules - highlighting cars that are identified in all those 'rules' on the Train Documents that apply to the train they are actually handling enhances the crews ability to comply with the required restrictions.
The BNSF System Special Instructions have specific speed limites for all types of freight cars based upon the mark and/or number(s) or aar class or both.
The cars are certainly not limited to 45 mph. What if they were limited to, say, 60 mph? How would the engineer be informed of that? If every car that ever ran on the railroad had its own limit, how would the engineer be told what speed his train was allowed?
Speed restricted cars are identified in the train journal, which a crew must have before departing.
Some coal cars are restricted to 50 mph, and centrebeam flatcars without constant contact side bearings are restricted to 45 mph.
This is because they are unstable at high speeds, and some older freight car truck designs are prone to hunting above 50 mph.
On many runs it is a moot point, between slow track speeds, underpowered trains, and throttle restrictions you can't get over 50 anyway, unless you are going downhill.
Greetings from Alberta
-an Articulate Malcontent
timzThe cars are certainly not limited to 45 mph. What if they were limited to, say, 60 mph? How would the engineer be informed of that? If every car that ever ran on the railroad had its own limit, how would the engineer be told what speed his train was allowed? RR timetables have been known to limit certain specified cars to some speed, but usually the freight train speed limit is all the engineer has to worry about. If a train is otherwise allowed 70 mph, and a car is in the train, that car is almost always allowed 70 mph.
Operating rule.
Freight coal cars loaded - keep 'em under 45, empty is a different story. Think brakes and how fast can you stop 110 cars, all exceeding 100 tons per car. Where is your center of gravity?
Coal cars can do 100+ MPH, but they might encounter things called curves (and centripital force).....seen the aftermath of that.
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