Amtrak axle count discussion

[manchacrr]

I just travelled on the Capitol Ltd. Wednesday and Yesterday from WAS-CHI. Sounds like the SSL is coming off the consist and the diner will act like a CCC again with the cafe and flex - dining in the same car. After hearing this, I think it’s safe to assume this will also happen on the CONO which runs with a CCC and is flex - dining as well. Staff I talked to stated that the same was happening on that route. It would also be interesting to see if this would happen on the Eagle due to it running with a CCC, but also with a full dinner menu...

I doubt that they will remove any cars from the CONO, if simply because of the CN axle rule on that route that requires a train to have at least 30 axles. If they remove any cars off of the CONO, it will have less than 30 axles. Current Consist = ONE Engine + SEVEN Cars = 32 axles.

 

[Devil's Advocate]

I've been riding trains for most of my life but I've never understood the minimum axle rule. Is it a genuine issue or is it some sort of arbitrary host restriction? If it's a real problem what is the cause and how does the host handle smaller local run and maintenance vehicles?

 

[PeeweeTM]

I've been riding trains for most of my life but I've never understood the minimum axle rule. Is it a genuine issue or is it some sort of arbitrary host restriction? If it's a real problem what is the cause and how does the host handle smaller local run and maintenance vehicles?

Ahum, like the Corona virus, a (Amtrak) train more or less sticks on rails [@Moderators: I used the words 'Corona' and 'Amtrak', but I'm cheating a bit, sorry. [emoji6]].
Wheel and rail profile,
traction type (electric is better because of the return current burning through dirt between wheel and rail),
brake shoe type (cast iron cleans/rubs wheel surface),
type of trafic (mixed traffic makes for better contact),
connections between wheelsets and bogies and car/locomotive frame (so current can flow from railhead via all wheels to all wheels),
type of springs (cannot find the right word, but if the wheels cannot move freely in the bogie, they will rub extra over the rail surface for better contact)
and some more things on the rolling stock side influence the resistance for the current to transit from rail to rail via the train.
Below for clarification a picture of a funny kind of detection system. In this section there are two transmitters active. The train has to 'short' one signal below a threshold. At the left you see a four wheel diesel locomotive, red line is well below the threshold, but not zero. At the right you see an electric locomotive. the blue line is as a stable zero. Old systems need a certain current to pull relays, to activate railroad crossings etc. That's also a thing to think about, when you replace light bulbs with LED in some systems.

If you are not certain about the different values you need to have your system work properly, you just make the numbers count. With a lot of axles/wheels, you will usually be safe.
But I'm not an expert on this subject, only a reader.

 

[tricia]

Ahum, like the Corona virus, an (Amtrak) train more or less sticks on rails [@Moderators: I used the words Corona and Amtrak, but I'm cheating a bit, sorry. [emoji6]].
Wheel and rail profile,
traction type (electric is better because of the return current burning through dirt between wheel and rail),
brake shoe type (cast iron cleans/rubs wheel surface),
type of trafic (mixed traffic makes for better contact),
connections between wheelsets and bogies and car/locomotive frame (so current can flow from railhead via all wheels to all wheels),
type of springs (cannot find the right word, but if the wheels cannot move freely in the bogie, they will rub extra over the rail surface for better contact)
and some more things on the rolling stock side influence the resistance for the current to transit from rail to rail via the train.

If you are not certain about the different values, you just make the numbers count.

Huh? Would someone kindly connect the dots between this response and DA's question? Preferably in laymen's terms, please. How exactly do these things factor in to an axle-count rule?

 

[jebr]

I've been riding trains for most of my life but I've never understood the minimum axle rule. Is it a genuine issue or is it some sort of arbitrary host restriction? If it's a real problem what is the cause and how does the host handle smaller local run and maintenance vehicles?

I think (but am not sure) that it has something to do with certain signaling equipment not picking up shorter trains properly on some hosts. It could be a byproduct of an older era where it was a problem, or legacy equipment that just hasn't gotten around to being upgraded. But that's what I recall hearing being the reason for the axle count restriction.

 

[jis]

I think (but am not sure) that it has something to do with certain signaling equipment not picking up shorter trains properly on some hosts. It could be a byproduct of an older era where it was a problem, or legacy equipment that just hasn't gotten around to being upgraded. But that's what I recall hearing being the reason for the axle count restriction.

You are correct. Without diving into the weeds, in simple words....It is relevant only in areas where the signal system depends on track circuits to detect track occupancy. In order for a track circuit to be triggered by the presence of a train sufficient current must flow from one rail to the other through the wheels and axles of the train. If the track circuit system is obsolete or poorly maintained they require larger number of axles (i.e. wheels on rail) to ensure that a train is actually detected by the track circuit system,. And of course the way you ensure that there are larger number of axles is to hook on larger number of cars to a train irrespective of whether they are needed to carry merchandise or passengers.

There are other ways of detecting track occupancy, but most of the US railroad system was equipped before the other methods became widely available. So most of the US railroad systems use track circuits, and many railroads have allowed their systems to go to pot to save some money, figuratively speaking.

 

[west point]

Axel count routes ? The reason as posted on another site is that that the Amtrak wheel profile has been changed for better ride quality. Maybe new profile wheels are making less contact with rails ?

 

[jis]

Axel count routes ? The reason as posted on another site is that that the Amtrak wheel profile has been changed for better ride quality. Maybe new profile wheels are making less contact with rails ?

Clearly lower conductivity is happening or less sesitive detection circuits are around. Since this is happening on only on certain railroads and not on all of them, one is left wondering which of those two, or what combination of those two are found only on those railroads where this is a problem.

 

[niemi24s]

There are two types of simple electrical circuits, series and parallel. The total resistance of a series circuit is the sum of all the individual resistances. This means the total resistance in a series circuit increases as the number of individual resistances increases. This, however, is not the railroad signal sensing circuit type.

The railroad signal sensing circuit is a parallel circuit, in which the total resistance (between the rails) DEcreases as the number of individual resistances increases. Each of those individual resistances is the pair of wheels and axle in each cars truck - including the contact resistance between the wheels and rails.

So more axles means less total resistance (R) which by Ohm's Law (I = E ÷ R) means more current (I) to do the work of operating the signal system - whatever the voltage between the rails happens to be. Put another way, in a parallel railroad track signalling circuit, the total current between the rails is the sum of the individual currents through each individual axle.

These may be the weeds JIS referred to.

 

[John Santos]

Many commuter railroads run single or dual EMUs or DMUs. Is this not an issue there because those tracks use different detection or signalling systems or because the lines are better maintained or both?

Are the conditions requiring axle-count cars generally regarded as temporary ("we'll fix it when we get around to it, but it's low priority and might be several years"), or permanent, normal operating conditions?

If a rescue engine (sent out to a disabled train because its engine broke down) in danger while it traverses an area which requires axle-count cars because it might not trigger block signals or crossing gates and warning lights? If so, do they actually send a "rescue train", consisting of an engine plus sufficient cars? Plus (most likely), a 2nd engine because one engine might not be powerful enough to pull the disabled train plus all the extra cars?

 

[Skyline]

Many commuter railroads run single or dual EMUs or DMUs. Is this not an issue there because those tracks use different detection or signalling systems or because the lines are better maintained or both?

Are the conditions requiring axle-count cars generally regarded as temporary ("we'll fix it when we get around to it, but it's low priority and might be several years"), or permanent, normal operating conditions?

If a rescue engine (sent out to a disabled train because its engine broke down) in danger while it traverses an area which requires axle-count cars because it might not trigger block signals or crossing gates and warning lights? If so, do they actually send a "rescue train", consisting of an engine plus sufficient cars? Plus (most likely), a 2nd engine because one engine might not be powerful enough to pull the disabled train plus all the extra cars?

I've often wondered the same (about danger due to signal issues) when I've seen solo rail diesel cars operating in Canada, or a single locomotive deadheading through my hometown in Virginia. There must be a reasonable answer, but what I've described doesn't jive with the reasoning behind a 32-axle-count.

 

[Thirdrail7]

I've been riding trains for most of my life but I've never understood the minimum axle rule. Is it a genuine issue or is it some sort of arbitrary host restriction?

I suppose it is arbitrary, but it was driven by safety after previous crossing failures. Here is a brief quote from - a status letter CN sent after they imposed the restrictions:

We also are dealing with continuing issues related to what appears to be the failure
of Amtrak equipment to properly shunt crossings and CTC. After completing 95
percent of the upgrades to all the crossing activation equipment at CN's cost, we
have again experienced shunting failures in August 2010. These failures initially
resulted in a speed restriction to protect public safety, but CN has since required all
Amtrak trains operating on CN to operate with a minimum of 30 axles. This
requirement allows Amtrak trains to operate at their normal speeds because the
30 axles have been shown to eliminate the shunt failures. in recent days, we have
reviewed data which show that we will be able to reduce the minimum to 24 axles
on CN's Joliet, Elsdon, Holly, Shoreline, and South Bend Subs, where Amtrak has
short segments on CN and shunting has not been a problem when at least 24 axles
are present. The Amtrak and CM signal engineers are working with suppliers on
this issue."

If it's a real problem what is the cause and how does the host handle smaller local run and maintenance vehicles?

If a rescue engine (sent out to a disabled train because its engine broke down) in danger while it traverses an area which requires axle-count cars because it might not trigger block signals or crossing gates and warning lights? If so, do they actually send a "rescue train", consisting of an engine plus sufficient cars? Plus (most likely), a 2nd engine because one engine might not be powerful enough to pull the disabled train plus all the extra cars?

The reason why I say it is arbitrary is instead of imposing an axle count, CN could reinstitute slower speeds. Single units generally operate at lower speeds or have instructions to approach crossings prepared to stop and making sure the crossing protections are operating.

 

[MARC Rider]

Clearly lower conductivity is happening or less sesitive detection circuits are around. Since this is happening on only on certain railroads and not on all of them, one is left wondering which of those two, or what combination of those two are found only on those railroads where this is a problem.

In my youth, the Paoli Local on the Pennsylvania RR ran perfectly well with 2-car EMU trains during the non rush hours. For all I know, SEPTA still tuns shorter trains off-hours, too. I think they used electric signals, and I don't think the laws of Physics have changed since the 1960s.

 

[jis]

In my youth, the Paoli Local on the Pennsylvania RR ran perfectly well with 2-car EMU trains during the non rush hours. For all I know, SEPTA still tuns shorter trains off-hours, too. I think they used electric signals, and I don't think the laws of Physics have changed since the 1960s.

I was being diplomatic about the answer that stares one in the face. Laws of Physics have not changed and the entire world is somehow able to run pretty short trains on track circuit protected tracks.

Yeah they do have problem detecting very light weight track maintenance equipment. They have to be moved under special orders.

 

[John Santos]

[...]
If a rescue engine [...] in danger while it traverses an area which requires axle-count cars because it might not trigger block signals or crossing gates and warning lights?

Ugh. That was supposed to be a question: "IS a rescue engine in danger...?"

 

[iplaybass]

In my youth, the Paoli Local on the Pennsylvania RR ran perfectly well with 2-car EMU trains during the non rush hours. For all I know, SEPTA still tuns shorter trains off-hours, too. I think they used electric signals, and I don't think the laws of Physics have changed since the 1960s.

Been on 2 car Chestnut Hill locals that got up to 75 on the mainline between North Philadelphia and 30th street many times. I don't think SEPTA cuts its trains now, since the PRR and Reading were connected. They just close the extra cars to passengers.

 

[amtrakpass]

For a single engine I think many railroads have a speed restriction or if not, might require absolute block for a following train in case the engine bouncing around as it goes down the track at track speed doesn't shunt the circuit for split second. But what these particular companies require for axel count is super excessive and I can't see any valid reason except making life difficult for Amtrak and passenger service in general.

 

[Siegmund]

It would also not be shocking if a railroad required additional safety precautions when passengers are involved vs. when it is operating a light engine or a very short freight train. (Perhaps the track circuit does indeed work 99.8% of the time with the light engine, but 99.99% of the time with 30 axles.)

I've not seen any formal analysis of what the minimum axle requirement should be - can only observe that it is a new thing, and only on a few roads, which suggests to me that its origin is an overabundance of caution on those roads' legal departments, rather than a purely physics-driven thing.

 

[Ryan]

can only observe that it is a new thing

I'm not sure on what timscale this is new, but it's been around for quite a few years.

 

[chakk]

Many commuter railroads run single or dual EMUs or DMUs. Is this not an issue there because those tracks use different detection or signalling systems or because the lines are better maintained or both?

Are the conditions requiring axle-count cars generally regarded as temporary ("we'll fix it when we get around to it, but it's low priority and might be several years"), or permanent, normal operating conditions?

If a rescue engine (sent out to a disabled train because its engine broke down) in danger while it traverses an area which requires axle-count cars because it might not trigger block signals or crossing gates and warning lights? If so, do they actually send a "rescue train", consisting of an engine plus sufficient cars? Plus (most likely), a 2nd engine because one engine might not be powerful enough to pull the disabled train plus all the extra cars?

Rescue engines would be treated as light engine movements and would be restricted to the applicable speed limits in the employee timetable for that division of the railroad. On the U.P. Nebraska Division in 1948, my employee timetable says the speed limit for streamliners with diesel-electric locomotives and all roller bearing cars was 90 mph. Speed limit for light engine movements was 45 mph.

 

[Ryan]

I'm not sure on what timscale this is new, but it's been around for quite a few years.

Digging through the archives, it looks like this may have started in 2009. Jay would have been in a position to know back then. Anyone know how he's doing? It's been a while...

https://www.amtraktrains.com/threads/cn-puts-restriction-on-city-of-new-orleans.27558/

 

[Devil's Advocate]

Just wanted to thank everyone who replied to this thread. Your explanations helped me understand where this requirement came from, why it was deemed necessary for Amtrak, and why it persists to this day.

🗣

 

[Steve4031]

I enjoyed this thread. Never really understood how this worked. My question: Do the signals use the same system to determine if a train is operating within a block? If so, why does the axle room apply only to situations involving grade crossings?

 

[west point]

It may be that crossing signals use a different system than the block signals. It might be you can look and see if there is code line signaling systems. Then see if the code lines are connected to all crossing signals. We can find that any route may have several different signal systems and made by different builders. Compatibility problems are and can be heavy.

 

[OldCond]

Where I used to work, a single engine without cars was restricted to 30 mph. Two or more engines or an engine with one or more cars could run at track speed.