Rail Physics & Track Class Science Discussion

Begging the forgiveness of the modertors (and everyone else)....

The following is posted "for the record" in the hope that should we need this data and information at a later date (especially in discussing Oil Trains!) it will be found useful:

Of particular note the described "Prud'homme Limit" discussing axle loadings and their importance to understand problems with track shift.

The initial study:

USDOT-FRA "Analyses of Track Shift Under High-Speed Vehicle-Track Interaction"

and the more recent followup:

USDOT-Volpe Center "New Track Shift Safety Limits for High Speed Rail Applications"

Also of note:

USDOT-RITA-VNTSC, "Examination of Vehicle Performance at High Speed and High Cant Deficiency"

[EDIT: Spelling]

gokeefe, if there's a "library" section of this site your recent posts should be copied over there. Truly excellent work, and I salute the memory of your grandfather.

gokeefe wrote:I'm quite sure that at current levels it wouldn't be necessary but I'm sure at some point, especially if the Downeaster goes north on a more frequent basis there could easily be a situation where it would make a lot of sense to send the train north of Portland via the MDOT/SLR instead of the rather crowded tracks through Deering to Royal Junction.

Maybe, but they'd need to build the new Union Branch (presumably along the reseved strip of ROW along I-295) almost entirely from scratch; the section from St. John St. to Forest Ave. hasn't seen traffic in (I believe) decades, the Forest Ave. grade crossing was removed, and they were discussing building out on the new ROW I mentioned anyway, so that part would be all new. One alternative, if added passing capacity is needed in the city, could be to restore the double-tracking from CPF 194 (just TT East of Allen Ave.) to just TT East of Forest Ave. at MP 195.02, a distance of c. 1.5 miles. That would avoid the high-density grade crossings in the Deering Highlands neighborhood between Brighton Ave. and Woodfords St. Also, it may be worth noting that, in the double track section between CPF 192 and CPF 194 (Riverside St. and Allen Ave.), only Track 1 got CWR; track 2 was untouched during the expansion project.

gokeefe-
So -- rail science is rocket science, just without as much verticality and hopefully none of the pyrotechnics. For us mere mortals (he asked non-seriously), is there a Track Science for Dummies available from Amazon?

gokeefe wrote:Also "in honor of":

I submit the following:

L/V=(tanδ-μ)/(1+μ.tanδ)

Described as the "Nadal Limit" in this paper, USDOT-RITA-VNTSC, "Application of Nadal Limit in the Prediction of Wheel Climb Derailment".

Of significance the paper simply says that using known variables of L, lateral load, V, vertical load and μ, where μ is the coefficient of friction (which is proportional to the "speed" or velocity of the object) then one can reliably predict at what point wheel climb will likely occur.

Theorems such as the above are the fundamental basis for the track class limits that we have in place (still) today. Q.E.D.

Your grandfather was an amazing individual!

LOL I stand corrected.

And while we're at it, anyone who has worked for NASA or any other space company is my hero.

EOT out of Dover NH at 10:52 today, and a bad photo of it.


http://www.n-scaler.com/gallery/albums/ ... re_287.jpg

Great info links on wheel/rail interface. it's troubling to me that the base posit was in 1892. At the risk of being tendentious, the variables in the various formulae tell me that oil trains can run faster. Also, won't the new tanks be a great application for e/p braking? The assigned power solves the power control issue. Perhaps clear thinkers will spend the few extra dollars to utilize radial trucks. I can see the state-of-the art running gear and train control dynamics letting these trains run at 40mph on 20mph track etc. Why is this important? Rail movement of Bakken/Alberta crude will improve our chances of becoming energy independent. ken patrick

KEN PATRICK wrote:Great info links on wheel/rail interface.

Thanks I appreciate that.

KEN PATRICK wrote:it's troubling to me that the base posit was in 1892.

I was watching for something like this in my skim. If you can refer to the exact sections that would be helpful and perhaps we can setup another thread somewhere else for further discussion.

KEN PATRICK wrote:At the risk of being tendentious, the variables in the various formulae tell me that oil trains can run faster.

There's no question of "can" it's merely that they establish a base threshold that then provides the desired margin of safety. Not sure if your "can" statement includes and assumes what you mentioned after that or you're referring to the oil trains "as is".

Regardless it seems we continue to return to capacity as one of the greater challenges that will be faced by PAR one way or another. I am also starting to wonder if we need to setup some kind of "capacity management" thread in the PAR forum for discussion of issues related to the physical plant. The MoW thread covers MoW activities quite well but I don't think it necessarily allows for the systematic discussions of system plant management that probably could be much broader.

Contraction of the present day system, which has been in progress basically since the 1950's (1930's if you really want to take the long view) has all been relatively simple. Just shutdown unproductive branch lines and focus on core business. This process then finally ended with shutdowns of redundant main lines as well. Expansion on the other hand is an entirely different issue that appears at some point to imply not just reconstruction of long sidings and even extended sections of double main line track but perhaps other options as well.

PAS or "District 3" seems to be a relatively simple proposition, however, I continue to assess that "District 1" is not as straightforward as we think it is, in large part due to the presence of substantial passenger operations, which at this point appear poised to grow, a lot, over the next 10-20 years.

Engineering student here...I haven't looked into track structure too much before but here's my best guess at how speeds are determined.

The "Nadal Limit" was first proposed by Nadal in 1896. However, just because it's old doesn't mean it doesn't count...we haven't thrown out Newton after 400 years or Maxwell after 150, so as long as a new model hasn't been proven to supersede Nadal, there is no reason to discount the research based on its age. I would guess that the FRA calculates track classes based on formulas, such as Nadal's, combined with empirical tests done at Pueblo with a significant safety factor added on. Due to the safety factor, the theoretical maximum speed is always higher than the posted speed. So yes, you could go a little faster. Think of roads that are "good for 50" but are posted much lower. The reason for this is that if the science says you derail at 51 mph, if you post to 50 the error tolerance is much smaller. One mile per hour overspeed and you're theoretically on the ground. So you post for 40 so that in the case of a train going overspeed (human factors, runaways, etc), your likelihood of a derailment goes down.

Also, while I'd love to talk about railroad physics this really doesn't belong in the Oil Train thread. Can we move these posts to a new topic?

csor2010 wrote:Also, while I'd love to talk about railroad physics this really doesn't belong in the Oil Train thread. Can we move these posts to a new topic?

It should probably go in the General Discussion Board, Railroad Operations Forum.

I will start a new thread over there and see if we can get MEC407 to move some of the material over there.

ksmitty. Thanks for help in establishing this subject. I remain confused about the process in establishing track speeds. What i read actually is subjective. My experience, including placing one of my cars in the HAL consist at Pueblo, is that train safety is a complex relationship of many factors. lets start with the departed president of Pan Am who opined that '10 mph is a satisfactory objective for our railroad'. How about railroad management establishing 'safe speeds'. do they look at the 1892 formula by car? of course not. They simply re-affirm what was stated before hence historical in nature. The FRA car? I defy anyone to state that this car can validate speed windows. Perhaps all we have are railroad personnel remaining in a historical comfort zone. I think oil trains equipped with ep brakes and radial trucks can traverse PAR at 40 mph speeds. Ken Patrick

KEN PATRICK wrote:I remain confused about the process in establishing track speeds. What i read actually is subjective.

It's really simple. They took the old standards which were based against fatal accidents and other old operating data, tested them against multiple track profiles and derived mathematical representations of the safety margins that the "old" standards are providing. The research papers linked then show going forward that these older standards do in fact provide safety margins at the levels desired, but now do so from an objective basis grounded in math and not just from experience. Then they did research on high speed operations which have problems and challenges that Class V and lower operations don't. This required the development of a new set of operating specifications which took into account the unique challenges of dynamic forces produced by trains operating at speeds greater than 90 MPH. That's what I read in the material that I was able to find and post into this thread.

newpylong- My advocacy of ep braking is based on train handling, crew duties reductions, eot device elimination and brake rigging wear. It's not just on shorter stopping distances although a benefit. For example, setting retainer valves requires someone to walk the train flipping handles. Rear power to assist braking on downgrade moves. Costly events eliminated by ep braking. On the railroad/FRA side. A railroad decides to designate a section as , say class 4. The immediate benefit is improved system fluidity i.e. profits. When the FRA inspection car finally comes around- in 4 months or longer maybe and states that the track should be class 3 what happens? The railroad sets in motion a track improvement program? Probably lowers the speeds. But it has banked the fluidity savings in the interim. A simple judgment call has increased profits. Smart scenario? Increase speeds 5mph. Review results. Increase another 5mph. And so on untll some track work is necessary. Ken Patrick

KEN PATRICK wrote:newpylong- My advocacy of ep braking is based on train handling, crew duties reductions, eot device elimination and brake rigging wear. It's not just on shorter stopping distances although a benefit. For example, setting retainer valves requires someone to walk the train flipping handles. Rear power to assist braking on downgrade moves. Costly events eliminated by ep braking. On the railroad/FRA side. A railroad decides to designate a section as , say class 4. The immediate benefit is improved system fluidity i.e. profits. When the FRA inspection car finally comes around- in 4 months or longer maybe and states that the track should be class 3 what happens? The railroad sets in motion a track improvement program? Probably lowers the speeds. But it has banked the fluidity savings in the interim. A simple judgment call has increased profits. Smart scenario? Increase speeds 5mph. Review results. Increase another 5mph. And so on untll some track work is necessary. Ken Patrick

EP braking would not eliminate the need for an EOT device. The need for an EOT for trains is based upon factors such as grades, train length, weight, and track speed.
Even PASSENGER trains are required to have EOT devices in certain circumstances.

Additionally, a railroad must have an approved inspection plan in place before designating a class. It is not something that happens on a whim. Everything from rail heads, number of cross ties, the number of track inspections, the type of track inspections, curve banking, ballast requirements and even the number of required switch tests is tied to the class of track designation.

I posted the 423 page Track Safety Standards Compliance Manual on this board, but the link seems to have died. I did find a link for PART 213—TRACK SAFETY STANDARDS. It gives you the theory on the class of tracks and the different requirements of each. Although this is only 57 pages compared to the 423 monster I previously posted, it is still easy to see why railroads are reluctant to raise track speeds, especially if passenger trains ply your territory.

i believe eot's main function is to telegraph air pressure. Train line air degredation is a concern as is the delay in brake pipe adjustments. What was a leap forward by Westinghouse should no longer be viewed as satisfactory for today's train handling dynamics. Ep braking eliminates buff and slack damage. Also, i believe pueblo efforts are high speed related. I'm uncertain about the HAL consist. As to unloading -I suspect it is related to , among other issues, market demand. Since rail is 75% more expensive than pipelines, i can understand the push to build a pipeline at Casco Bay. My instincts would lead to dropping the price based on cost reductions arising from higher speeds so as to render the proposed pipeline uneconomic . When in the drivers seat, do not let any competitive alternative arise. Lastly, give Irving the option of building more storage in exchange for reduced transportation expense. Crude to end product is a complex process. I remain convinced that our society is best served by fair costing. Ken Patrick