Jo-Jo

3. 250 km/h above a motorway?

A publication from the Swedish Transport Administration states that a Swedish motorway, with a good standard and with a maximum speed of 110 kilometers per hour, must have a minimum horizontal curve radius of 1,200 meters. For the Jo-Jo train and shuttles, the maximum speed is 250 kilometers per hour. With a 200 millimeter cant (dosage, skew) we get a minimum curve radius of 1,800 meters. This applies provided that we have a lateral acceleration of less than 1.5 m/s2 and that we use anti-roll suspension. More lateral acceleration means that passengers cannot move freely on the train. Anti-roll suspension is a well-established technology that prevents the side acceleration from tilting the vehicle. The suspension in the outer curve is made stiffer. The vehicle is straight on the track. If we also use active basket inclination, we can drive 15% faster in the curve without the side acceleration increasing (gives the same effect as a larger dosage). With basket inclination, we get the Jo-Jo train's smallest curve radius down to 1,320 meters. Very close to the smallest curve radius on the highway. To cope with even smaller curve radii, eg the 1,200 meters, we can take a short cut in the curve. How much we can do this depends on the length of the curve. If the turn is less than 25 degrees, we can stay over the motorway itself (normal width 21.5 meters). The motorway corridor is 70 meters wide. If we use that entire width to obstruct the radius of the 1,200 meter curve, we can manage a turn of 65 degrees. Should we occasionally have sharper curves than that, well then the Jo-Jo train speed must be reduced below 250 kilometers per hour or the dosage be more than 200 millimeter.

Vertical curves. The Swedish Transport Administration states that for motorways, a convex curve (hilltop) may have a vertical minimum radius of 16,000 meters and a concave curve (valley) of at least 5,500 meters. For railway vehicles, a vertical acceleration of a maximum of 0.3 m/s2 is specified. The convex curve can handle the Jo-Jo train at 250 kilometers per hour, but to cope with the concave curve, the pillars of the bridge deck must be made higher to increase the radius of curvature (reduce the valley). It increases the cost, but only marginally. The combination of deep valley and narrow curve is not technically insoluble, but entails higher costs. The lateral forces at high track and sharp turns require stronger pillars under the bridge.

4. ERTMS European Rail Trafic System

ERTMS is available in different basic versions 1, 2 and 3. Sweden has chosen version 2. Version 2 is more expensive to install and maintain than version 3. But version 2 has been in more extensive practical operation. Cut out from Wikipedia: "Version 3 includes features for higher capacity, including more frequent train operations and the possibility of another radio system instead of GSM-R." Version 3 thus allows us to, for example, use 5G for communication between the Power Shuttle, command center and other shuttles on the track. Of course, it is especially valuable with fast communication in connection with docking, and shuttle entry on the main line. When platooning (driving with a truck convoy) you use wi-fi and the same technology should also be applicable for the Jo-Jo train.

GSM-R is already developed throughout Sweden and coverage is ensured by the system working even if every second base station were knocked out. 

So-called Eurobalises are deployed on the track. These have fixed information, for example about their location, about the track's properties later on. The balises get their energy from the train that passes over it and then it responds by transmitting the information to the train that sends information on to the command center. The Swedish ATC2 system also has similar balises. However, they have a fairly limited memory capacity. The Eurobalises also have plenty of capacity available for future development - such as Jo-Jo trains.

ERTMS version 3 provides the opportunity to run the trains closely in succession. The so-called block section is not a fixed installation in the track, but an adjustable electronic quantity that surrounds the train. It provides the opportunity for linear docking.

5. Distance between rails

Normal track gauge is measured as the distance between rails. They are measured 14 mm below the top edge of the rails (Rail top). The standard value is 1435 mm, but it is allowed to be down to 1430 mm and up to 1470 mm before it needs to be adjusted. In simpler terms, the center distance between rails is 1.5 meters. The railway wheel has a flat roller path and on the inside of the rails the wheel has a flange. The transition between the flat roller path and the flange is not sharp, but is curved with a slow transition between roller path and flange. The finesse of this is that if the railway vehicle tends to move e.g. to the right of the track, the wheels on the right side with their curved surface will start to "climb" up on the rails. There on the curved surface, the circumference of the wheel is larger and the wheel thus automatically steers the railway vehicle back towards the middle between the rails. This function is independent of the track gauge. If you increase the track width while maintaining the distance between the wheels, the impact effect will not be so strong. There is a discussion about increasing the nominal dimension 1435 to 1437 millimeters. The advantage would then be that at high speeds the so-called sinus movement would be smaller on long straight stretches of the track.

Risc to turn over. Railway vehicles have a so-called load profile. It indicates e.g. the maximum height and width of the vehicle. In Sweden, we have a load profile: A 3,40 m wide and 4,65 m high, B 3,40 m wide and 4,30 m high and C 3,60 m wide and 4,83 m high. Or simpler, generalized; 3,5 m width and 4,5 m height. To get a low center of gravity, the ratio of height over width should be as small as possible 4,5 / 3,5 about 1,3 (This is a simplified way of looking at the matter, of course knowledge of the actual central of gravity above the base surface is preferable, but it is not readily available). In order to have a stable function, the support surface must be as wide as possible, the ratio of vehicle width relative to track gauge must be as small as possible 3,5 / 1,5 gives approximately 2,3. The product between the relative height of the center of gravity 1,3 and the relative value of the support surface 2,3 then becomes a typical roll risk value of 3. Let us compare with a passenger car. We then choose an SUV that is significantly more prone to overturning than a sports car. Values ​​for the Volvo XC90, height width ratio = relative center of gravity height 0,92 and the relative support value of the support surface close to 1 (the wheels placed as far to the side as possible). The inherent risc to overturn is three times larger for the train. If we made the comparison with a race car, the difference would obviously be even worse for the railway vehicle. Vehicles that stay on the "right keel" in an accident cause considerably less damage to their passengers, so low center of gravity and wide base are always preferable.

The reason for the large load profile is of course the desire for the opportunity to take large loads. The gauge was early so-called narrow gauge (narrow gauge is less expensive to build). As the state took over the railway in the Sweden, we now have a normal width of 1.5 m (Exception of Stockholm's local traffic operated Roslagsbana with just under 0.9 m between rails). Changing the existing railway network to something more technically sensible is not economically reasonable. Not only tracks but also the fleet must be changed.

A larger track gauge is safer.  For a completely separate new railway, which requires vehicles with extra wheel axles for the gear unit without moving parts, the situation is different. Here we have the chance to develop technology that is significantly safer than what we have today. As for the car, we can choose a track gauge that corresponds more close to the vehicle width, e.g. for railway vehicles 3 meters between rails instead of 1,5 meters. The risk of overturning is minimized. We can choose an optimal load profile. And not least valuable, the technology for suspension will be simpler, cheaper and more robust. Finally, we can have a larger cant elevation in horizontal curves. We can easily drive on a bridge over a motorway, probably without active tilting. Note in particular that on Jo-Jo-han all trains run on the main track constantly with a very small speed variation, only +-5 km/h. We get a smooth flow and the track can be optimized for the speed of 245 km/h. Optimal and unbeatable comfort for the traveler.