Had a Talgo designed locomotive been pulliing the 501, might the operational mistake been lessened? If a Talgo designed locomotive been operated at the excessive speed, could it have remained railbound and given the passngers a very rough ride? Or, could a Talgo designed locomotive left the rail but the derailment would have seen the equipment coupled, derailed, upright and still within the right of way? Either way, fractures, bruises and lacerations preferable to death.
considering the severity of the overspeed, no the results wouldn't be much different.
Modeling the Cleveland and Pittsburgh during the PennCentral era starting on the Cleveland lakefront and ending in Mingo junction
SAMUEL C WALKERHad a Talgo designed locomotive been pulliing the 501, might the operational mistake been lessened?
The tilting systems are used for passenger comfort. The tipping speed is a lot higher then the for comfort restricted speed. The tilting lessens the lateral acceleration and force when entering a curve. That makes higher curve speeds possible without exceeding the passenger comfort limits.
Locomotives for tilting trains usually don't have a tilting mechanism (Acela Express) as the physics are not different and the locomotive engineer can stand the higher lateral acceleration.
Talgo says their system allows up to 25% higher curve speeds. That would have been 7.5 mph for Atk 501.
No, the train would have derailed anyway at 79 mph.Regards, Volker
SAMUEL C WALKER Had a Talgo designed locomotive been pulliing the 501, might the operational mistake been lessened? If a Talgo designed locomotive been operated at the excessive speed, could it have remained railbound and given the passngers a very rough ride? Or, could a Talgo designed locomotive left the rail but the derailment would have seen the equipment coupled, derailed, upright and still within the right of way? Either way, fractures, bruises and lacerations preferable to death.
An EMD F9 would have tipped at 68 MPH in the 8 degree part of the curve. And, of course, at higher speeds. I din't have a CG height for the derailed locomotive, so I could not calculate the tipping speed for that one.
If the center of gravity had been appropriately lower and possibly also shifted horizontally, the tipping speed could have been raised to 79 MPH.
These would be the "you can't go faster because you WILL tip" speeds. It does NOT mean that you won't tip at a slower.
Seems to me the derailment happened in the eased part of the curve. And it seems to me that then derailment wasn't caused solely by "tipping", but also by something that might be called "flange climbing".
Because the riding flange surface is never at 90 degrees to the centrifugal force as the curve happens, there will always be an upwards component of that force. Which will tend to lift the wheel and vehicle. And change to contact point to a different place on the flange (and rail).
It would be possible to have a derailment based on this flange lifting force EVEN IF THE CG WAS AT RAIL HEIGHT. A special case, indeed. But it illustrates the possibilty of flange climbing contributing to the derailment.
Ed
VOLKER LANDWEHR Talgo says their system allows up to 25% higher curve speeds.
Talgo says their system allows up to 25% higher curve speeds.
Than what?
If the locomotive had had a 25% increase in tipping speed:
1.25 x 68 = 85 MPH.
Looks like the "new improved" locomotive would not have tipped in the curve.
7j43kThan what? If the locomotive had had a 25% increase in tipping speed: 1.25 x 68 = 85 MPH.
The curve speed was restricted to 30 mph. So the speed restriction would have been 1.25 x 30 = 37.5 mph.
Only the carbody gets tilted to relieve the passengers. The wheel-track system doesn't change. So the tipping speed is unchanged.Regards, Volker
VOLKER LANDWEHR 7j43k Than what? If the locomotive had had a 25% increase in tipping speed: 1.25 x 68 = 85 MPH. The curve speed was restricted to 30 mph. So the speed restriction would have been 1.25 x 30 = 37.5 mph.
7j43k Than what? If the locomotive had had a 25% increase in tipping speed: 1.25 x 68 = 85 MPH.
The curve restriction would have been whatever management says it would be.
If you can have "25% higher curve speeds", you can go 25% faster. The absolute upper limit of speed through a curve is tipping speed.
If the fastest an F9 can go through a curve is 68 MPH, and the Talgo locomotive can go 25% faster, you get 85 MPH as a tipping point. The Talgo MIGHT have made the turn at 79 MPH. A train pulled by an locomotive with a CG height similar to the F9 would not.
We don't know what the design of the engine is/would be. We do know that Talgo moves parts of their cars around for the convenience of passengers. If they moved the CG of the locomotive inwards on the turn, it would raise the tipping speed.
7j43kThe curve restriction would have been whatever management says it would be.
The speed restrictions for passenger trains are set according physical requirements and passenger comfort design criteria(limit of lateral acelleration and force). In our case it is set to 30 mph according to comfort criteria.
If you are going faster the train exceeds the acelleration and force limits. To drive these speeds without exceeding these limits the carbody is tilted. It is a comfort system not a system to stretch the physis in the wheel-track plane.
The center of gravity is moved to the outside by the Talgo (passive/natural) tilting system. It tilts about 3.5°. To compensate this the carbody is suspended low between the wheels (indipendent suspension) with a lower CG than on conventional cars. Here is a broschure of the Talgo 8: web.talgoamerica.com/images/Amrak/Series_8_Brochure_sized_opt.pdfThe tipping speed doesn't get higher.
7j43kWe don't know what the design of the engine is/would be. We do know that Talgo moves parts of their cars around for the convenience of passengers. If they moved the CG of the locomotive inwards on the turn, it would raise the tipping speed.
As said above the CG moves to the outside of the curve. Natural or passive tilting means the tilting point has to be above the CG. Getting down the locomotive floor between the wheels seems impractical.
Talgo offers a locomotive: https://www.talgo.com/en/rolling-stock/locomotives/travca/
It doesn't tilt, the power car of the RENFE 130 neither.
In the above linked broschure is a picture showing the speed limit sign for passenger and Talgo trains: P-65, T-75. The derailment curve speed limit is posted as P-30 and T-30. That leeds to the conclusion that the tilting system is inactice at 30 mph. In European Talgo trains the tilting systems gets activated above 70 kph (44 mph)
In Europe active tilting trains are mostly DMUs and EMUs where the weight distribution allows tilting of the end cars.Regards, Volker
Right. 30 MPH curve. "If you are going faster the train exceeds the acelleration and force limits.". So, at 31 MPH, the train will derail?
I rather suspect the speed restrictions are set a good deal lower than estimated derailment speeds. Don't you?
Off and on, we have been speculating about how much slower the train would have had to have been going to have "made it". I have considered the "tipping" speed because it is an absolute. A vehicle CANNOT go through faster than that. It may or may not make it at a slower speed.
When a manufacturer says a locomotive can go through curves 25% faster (if they did say that) that should mean 25% faster at all speeds. Not just at 30 MPH.
If the upper limit for a "standard" locomotive through that curve is 68 MPH (the tipping speed), why would a 25% faster locomotive not be able to take that curve faster?
You could, and you may be doing so, argue the Talgo engine can crowd the tipping speed much closer than a "standard" engine. This may well be true. The lead engine surely looks like it derailed far ahead of the tightest part of the curve. In this case, the Talgo would have gone farther around the curve before derailing.
I speak of tipping speeds because they are relatively easy to calculate. And they concern such dramatic differences. And it is the absolute upper limit of speed on a curve. Derailments CAN happen at slower speeds. As in the case under discussion, I believe.
We are talking here about the locomotive, not the cars. I do not know HOW Talgo designed their locomotive to go "25% faster". I did speculate that they COULD have used active movement of CG, not that they did. The simpler would be to use passive (design the locomotive with a lower CG), and they perhaps did.
Or perhaps they used something subtler to gain their 25%. And this DID NOT raise their tipping speed. So then, they could crowd that speed, knowing that other derailment forces were kept under control.
VOLKER LANDWEHRThe derailment curve speed limit is posted as P-30 and T-30. That leads to the conclusion that the tilting system is inactive at 30 mph.
Leads to no such thing: it reflects the fact that the curve has a 'hard' 30mph speed limit for geometry reasons, as we have established, and anything going around it cannot exceed that speed. The tilt system may in fact be acting to reduce the perceived centrifugal force or discomfort; in fact, I would assume that it does (since it is passive tilt), albeit the effect is comparatively slight.
There is apparently one Talgo "locomotive" that has tilt, described as the Talgo BT (which I presume is a joint development with Bombardier from the name). I haven't seen technical material on it, so it may just be the 'driving trailer' from one of those four-car XXI sets (the one that looks like a power car but has only a single axle under the nose).
As mentioned, there is little point to tilting the locomotive unless the jacks are arranged to move the CG absolutely inward as the roll is applied. Even there, I suspect there is a limit on increased lateral force before flange contact and then flange climb start to make the gain not worth the risk. True HSR remains dramatically curve-limited, both in horizontal and vertical, no matter how good the transition spiraling can be.
It is not as difficult as you may think to lower a passenger locomotive: take the FM Speed Merchants or the LRC as a starting point, and those both used conventional diesel prime movers. The better question is the one you raised: is the gain from much lower CG worth all the packaging and fuel-bunkering compromises?
There may be another elephant in the room, which I expect to see emerge slowly from testing: is the current Siemens high-speed bogie design prone to quick derailing under 'abuse' conditions, leading to derailment before even conventional truck designs would show instability or high-siding? (This is not saying Siemens engineering is either incompetent or negligent; more that extremely-low-unsprung-mass designs might be less tolerant of lateral force imposition.) Don't these things have remarkably little cone in their wheeltread profiles?
Overmod There may be another elephant in the room, which I expect to see emerge slowly from testing: is the current Siemens high-speed bogie design prone to quick derailing under 'abuse' conditions, leading to derailment before even conventional truck designs would show instability or high-siding? (This is not saying Siemens engineering is either incompetent or negligent; more that extremely-low-unsprung-mass designs might be less tolerant of lateral force imposition.) Don't these things have remarkably little cone in their wheeltread profiles?
In motor vehicle suspensions, it has been held that lower unsprung weight allows for quicker reaction time by the suspension. Hence aluminum wheels, for example.
Less taper would lead to more hunting, and some consequent increased flange wear. I'm not seeing any other problem, though.
I certainly think that the full wheel tread profile (including flange) would be of interest here. Plus also the shape of the railhead.
I'm not finding an overhead view of the crash online, at this time. My recollection is that it looked as if the train derailed very early in the curve, appearing as if it just kept going straight. If my recollection is true, it seems very odd that it did that. Seems way too early. Considering that the curve was almost surely eased. If it was, then it had not hit the tightest part at 8 degrees.
I really wouldn't be surprised to find the derailment itself was caused by a problem in the truck/wheels.
That does NOT mean I think they would have made it--just derailed later in the turn. Perhaps with more damage/deaths.
7j43kRight. 30 MPH curve. "If you are going faster the train exceeds the acelleration and force limits.". So, at 31 MPH, the train will derail?
I said the speed limit was set according to passenger comfort requirements. In Germany this allowed lateral acelleration is 0.85 m/sec2.
If the acceleration gets higher the passengers feel less comfortable but the train doesn't derail.
7j43kI rather suspect the speed restrictions are set a good deal lower than estimated derailment speeds. Don't you?
Did I something different?
7j43kWhen a manufacturer says a locomotive can go through curves 25% faster (if they did say that) that should mean 25% faster at all speeds. Not just at 30 MPH.
Link to Talgo website: https://www.talgo.com/en/rolling-stock/technological-principles/
#2, at the end: For the passenger this equates to a much more pleasant ride, and for the operator it means an increased train speed, since Talgo trains can pass through curves at a 25% higher speed than equivalent vehicles from other manufacturers.
In this case 30 mph is already the fasted allowed (for above reasons) speed. Talgo says up to 25%.
7j43kIf the upper limit for a "standard" locomotive through that curve is 68 MPH (the tipping speed), why would a 25% faster locomotive not be able to take that curve faster?
Because the tilting takes place in the carbody only. The result is as if there were an additional super-elevation. But at the wheel-track plane there is no additional super-elevation. The tilting doesn't change the physics at the wheel-track plane.
7j43k I do not know HOW Talgo designed their locomotive to go "25% faster".
Talgo didn't design a tilting locomotive. The power cab of RENFE 130 was designed by Bombardier and doesn't tilt either. Regards, Volker
My guess is that it left the rails by where the investigators are standing.
VOLKER LANDWEHR The derailment curve speed limit is posted as P-30 and T-30. That leads to the conclusion that the tilting system is inactive at 30 mph.
Leads to no such thing: it reflects the fact that the curve has a 'hard' 30mph speed limit for geometry reasons, as we have established, and anything going around it cannot exceed that speed. Quote end
That is nonsense. The speed limits in curves are there to protect passengers and loading. This limiting lateral acceleration is much lower than that for tipping rolling stock. As someone, I think 7j43k, calculated an F9 would have tipped at 68 mph.
The Talgo tilt up to 3.5° I think. I have looked at the Bombardier data sheet of the Talgo XXI power car and found no mention of any tilting.
OvermodIt is not as difficult as you may think to lower a passenger locomotive: take the FM Speed Merchants or the LRC as a starting point, and those both used conventional diesel prime movers.
The LCR has a height of 12'-11'', the Siemens Charger a height of 12'-6''. You don't have to get the roof down. You have to get the CG down and means you have to lower the floor considerably so that it is far beneath the wheel tops.
When you look in the Cascade Talgo broschure there is a picture showing curve speed limits P-65 and T-75 for one curve. For 10 mph difference you don't need a tilting locomotive.Regards, Volker
I think you mistook what I said. The speed restriction at the point of derailment is dictated by track geometry: it is nominally fixed by rule at 30mph regardless of the type of train, perceived passenger comfort, or whatever. It has been mentioned that this is in part due to absence of superelevation, which is mandated by the few heavy military trains that still traverse the line. It may be important that the remainder of route past the reverse curves is also restricted by rule to 30mph, but in any case the rule, not some conception of acceptable discomfort, is what limits Talgo to the same speed as any other passenger consist at that point on the railroad.
I am well aware of the difference between low functional CG and low roofline or reduced frontal area. I do agree that either prototype I named could have had its CG reduced still further, probably at the cost of some additional sprung weight, were that desirable; perhaps a better example was the RP-210 with the Mekydro 'powered truck' which consciously put the components as low as possible.
At the risk of "drifting a topic", I wonder at the CG height for RDC's. The two engines were below floor level. And there wasn't much above.
OvermodI think you mistook what I said. The speed restriction at the point of derailment is dictated by track geometry: it is nominally fixed by rule at 30mph regardless of the type of train, perceived passenger comfort, or whatever.
Might be. Every curve speed restriction is dictated by track geometry. There is a speed at which the rolling stock will just stay on the track or just tip and there is the speed limit dictated by lateral acceleration limits to protect the load, passengers or freight. The latter is lower. And that is not different at that curve.
Even on a curve without super-elevation a tilt train can go faster than a conventional train. For me the same speed limit for conventional and tilting trains indicate that the tilting isn't activated at 30 mph. The following publiction shows on page 7, 3rd column at the top, that the tilting system is activated at 70 kph. Sorry it is in German. I didn't an English counterpart:www.talgo.de/download/SDNetzel.pdf
OvermodI do agree that either prototype I named could have had its CG reduced still further, probably at the cost of some additional sprung weight, were that desirable; perhaps a better example was the RP-210 with the Mekydro 'powered truck' which consciously put the components as low as possible.
I think it is a moot discussion. If you take a current locomotive like the quite low Siemens Charger you can be sure the designers tried to get the CG as low as suitable within the given specification.
Active tilting for DMUs (the whole train) with underfloor engines is an option and there are examples in Europe.Regard, Volker
difference in speed in a curve in the US is what unbalance elevation is used. The FRA 3" for passenger trains assumes a uniform center of gravity. Freight speeds dictate a lesser 1 3/4" to 2" because the centers of gravity are all over the place combined with spring trucks that are not as stiff under load as the passenger spring trucks are.
See FRA 49CFR213.57 (b) and (c)... The freight railroad ChE's had varied opinions on the unbalance elevations and how forgiving the curve surfacing conditions could be. ATSF was a lot more conservative than poky old BN.
VOLKER LANDWEHR For me the same speed limit for conventional and tilting trains indicate that the tilting isn't activated at 30 mph.
For me the same speed limit for conventional and tilting trains indicate that the tilting isn't activated at 30 mph.
I visited Talgo's website, and Talgo appears to say that the tilt is passive, rather than active. So the tilting would always be activated. Perhaps the effect is so little at 30 MPH that the potential increase in speed is too insignificant to make note of.
7j43kAt the risk of "drifting a topic", I wonder at the CG height for RDC's. The two engines were below floor level. And there wasn't much above.
Did not help much in the ATSF Redondo Beach incident that soured the railroad on any extensive use of RDCs (up to then I think they had been planning extensive adoption of the technology for a range of services).
It's not enough to have low CG, you also need enough total vehicle mass to keep the vehicle from tipover. The situation is different from road vehicles, which are limited by lateral adhesion, because sudden flange contact provides a hard fulcrum and even with low CG you can turn over quickly.
I suspect there may have been considerable mass (comparatively speaking) in the radiator structure and coolant high up in the roof, a long lever arm from flange contact.
7j43kI visited Talgo's website, and Talgo appears to say that the tilt is passive, rather than active. So the tilting would always be activated. Perhaps the effect is so little at 30 MPH that the potential increase in speed is too insignificant to make note of.
Quote from the German article I linked: Ab einer Geschwindigkeit von 70 km/h wird das Pendeln des Wagenkastens zugelassen.
Translation: Above a speed of 70 kph (44 mph) the tilting of the carbody is allowed.
The author is VP Marketing of Talgo Germany.
I know this is not proof but why should Talgo redesign the system.Regards, Volker
VOLKER LANDWEHR 7j43k I visited Talgo's website, and Talgo appears to say that the tilt is passive, rather than active. So the tilting would always be activated. Perhaps the effect is so little at 30 MPH that the potential increase in speed is too insignificant to make note of. Quote from the German article I linked: Ab einer Geschwindigkeit von 70 km/h wird das Pendeln des Wagenkastens zugelassen. Translation: Above a speed of 70 kph (44 mph) the tilting of the carbody is allowed. The author is VP Marketing of Talgo Germany. I know this is not proof but why should Talgo redesign the system.Regards, Volker
7j43k I visited Talgo's website, and Talgo appears to say that the tilt is passive, rather than active. So the tilting would always be activated. Perhaps the effect is so little at 30 MPH that the potential increase in speed is too insignificant to make note of.
This would imply that there was a locking mechanism to dis-allow body tilt. Until 44 MPH. Why do this? What benefit is there in locking at a lesser tilt angle?
I am not saying Talgo didn't add such a locking device, though I do question it. Even if a VP of Marketing says it.
I, as I said, ask: Why bother?
From the Talgo website:
"Talgo's system emulates the cant effect but without having to force the swaying motion.[implying, to me, a passive system]....This system is called tilting, and it is automatic: the faster the train runs, the more it tilts [also implying passive]..."
The train is claimed to tilt more when it goes faster. And yet, if it were locked up until 44 MPH, it could NOT tilt more when it goes faster if the speeds were below 44 MPH.
Talgo is describing a very linear passive system.
OvermodThere is apparently one Talgo "locomotive" that has tilt, described as the Talgo BT (which I presume is a joint development with Bombardier from the name).
The diesel-hydraulic power unit for the Talgo XXI was developed by Krauss-Maffei the electric power unit by Adtranz.
The European version has a front B-truck and shares a single wheelset with the first coach. A version for the American market has two B-trucks:https://web.archive.org/web/20080624062734/http://www.talgoamerica.com/talgo_xxi.asp
The German article I linked describes the Talgo XXI. When describing the coaches it mentions the tilting but not in the power unit description.
Here is the Bombardier data sheet of the 155mph RENFE 130 power unit:http://www.br146.de/revisionen_daten/S130_10293_LOC_Sept08_en.pdf
I think the Talgo Pendulum system won't work with B-trucks. The system depends on the common wheelset between two cars.Regards, Volker
Overmod 7j43k At the risk of "drifting a topic", I wonder at the CG height for RDC's. The two engines were below floor level. And there wasn't much above. Did not help much in the ATSF Redondo Beach incident that soured the railroad on any extensive use of RDCs (up to then I think they had been planning extensive adoption of the technology for a range of services).
7j43k At the risk of "drifting a topic", I wonder at the CG height for RDC's. The two engines were below floor level. And there wasn't much above.
Well, yes and no. They were going 69 MPH when they hit a 15 MPH curve. The equivalent for the Tacoma crash would be going twice that: 138 MPH into a 30 MPH curve.
Santa Fe may not have expanded useage of RDC's, but I don't see why the incredible overspeed on a curve would have affected their decision. And note than they DID put them back into service. So I don't see them being that concerned.
For railroad tipover, the total mass is irrelevant. The tipover speed for a 300 pound motor car is the same as a 300,000 pound locomotive. If the CG height is the same. Otherwise, for the motor car, which is ENORMOUSLY lighter (1000 times), they would have to get off and push the thing through the curve.
That certainly would appear to be the case. Which, of course, would raise the CG back up a certain amount. But a radiator has no need to be heavy. It's got lotsa fins (thin), and some tubing (hollow), and coolant (not a lot). So, while that neat looking bump is visually massive, it's not that heavy. Consider that on most diesel locomotives, the designers are not shy about placing their own radiators about as high as they can go. They are clearly not terribly concerned about a raised CG. The same is true of the dynamic brake system.
7j43kThis would imply that there was a locking mechanism to dis-allow body tilt. Until 44 MPH. Why do this? What benefit is there in locking at a lesser tilt angle?
With a Google search I found the following publication: In Pursuit of Speed: New Options for Intercity Passenger Transport, Issue 233 On page 28 is stated:
The Talgo Pendular has a passive tilt mechanism that is allowed to function when speeds exceed 43 mph and the radius of curvature is less than 5,000 feet.
https://books.google.de/books?id=Ar4vLYagxtMC&pg=PA28&lpg=PA28&dq=talgo+pendular+tilting&source=bl&ots=jJTooWWw1V&sig=D-bev0u-jjDuiJ_NKkWOFyToSwY&hl=de&sa=X&ved=0ahUKEwjWz8X7hMTYAhUKiLwKHc4eBdEQ6AEIsAEwFA#v=onepage&q=talgo%20pendular%20tilting&f=false
Why it is this way I don't know.Regards, Volker
Then it's really semi-passive. Or maybe semi-active.
I do wonder at the why's and the details.
7j43kI do wonder at the why's and the details.
Perhaps a Talgo patent published in 1979 contains some information:https://www.google.com.pg/patents/US4041878
In this patent the use of adjustable diaphragm air springs is described.
Quote: In this particular case, and following the normal layout, each spring has a level adjustment valve maintaining the spring height. The operation outlined herein is for a straight track. When negotiating a curve, the valves close and the springs are distorted vertically until the torque produced by centrifugal force is balanced, thus resulting in the tilting of the coach. When travelling around wide curves as well as at low speed which has little effect on the tilt of the coach, the operating conditions are the same as for straight-line travel.
Closure of the valves can be effected by electro-magnetic means controlled by equipment which senses whether or not the curve radius is smaller than the predetermined limit and whether or not the speed is in excess predetermined limit which are the conditions to be met for the valves to close. These simple means are described in greater detail at a later stage........
Speed can be determined by any known means, such as by an electrical generator 6 located on a wheel shaft, to produce a signal (voltage) proportional to the speed. On reaching a given voltage level, a relay 7 closes a switch 13 in the control circuit, which remains activated in the event that the train reaches a curve having a suitable radius.
The curve radius is detected by the relative angle between coaches as they enter a curve for instance, using the relative displacement of adjacent coach front ends. On reaching a minimum stipulated movement corresponding to a particular degree of curve radius, one of a number of switches 8 in respective curve sensors 10, 10' closes, and remains closed providing the relative longitudinal movement does not drop below a given predetermined minimum value................ End of quote
I think that answers the questions.Regards, Volker
Thank you, Volker, for posting that description. It does give a decent description of how the tilting mechanism in the Talgo cars appears to work.
JL ChicagoI recall that Talgo designed the tilt to be locked out at low speeds because the pendulum effect when going over numerous crossovers in station approaches caused nausea in passengers.
Something else I dimly remember from a different context is that 'coordinated' forced tilt arrangements that are curve-derived produce entirely the wrong cant-deficiency 'correction' if the train is standing on a superelevated curve. I did not observe this with the passive pendulum suspension on the Turbotrain (which I think passively settled nearer objective level in equilibrium) but I would defer to those with more specific knowledge of the suspension action.
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