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
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.
Ed
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
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.
[quote]
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.
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.
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.
Ed
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 close
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.
Ed
I 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. And apparently for those already standing for their stop a tumble or two.
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.
Posted speed limits will be very conservative, rather than a theoretical maximum. In the real world the track curvature will have minor variations, the cross-level (superelevation) will vary somewhat, rail and wheel profile will have an influence, as well as the truck behaviour. At least center of gravity is fairly predictable for passenger trains. Freshly rehabilitated track is quite likely to have some imperfections through settlement. While trains and freight cars running away on steep downgrades have successfully negotiated some sharp curves at surprisingly high speeds, that just proves there is a comfortable factor of safety used.
On the highways we see advisory speeds for curves, which for the most part are also very conservative under good driving conditions. Of course speeds grossly in excess of that suggested will similarly have bad results.
John