Delft University of Technology
Faculty Mechanical, Maritime and Materials Engineering Transport Technology
C.A. Angevaren Ontwerp, simulatie en testen MTS-Safetrail.
Masters thesis, Report 97.3.TT.4939, Transport Engineering and Logistics.
By using longer trucks on public roads at night, a contribution can be made to solving the congestion in traffic during the day. In this way, the flexibility of road transport will be maintained without the need of building extra roads. The base of this study is the use of track-following multi-trailers for this transport. These trailer trains are used successfully at container terminals at a velocity of 30 [km/h] for twenty years now. If these multi-trailers are used over longer distance, their speed has to be increased to 50 [km/h], but then the track-following steering system can lead to an unstable road holding behaviour.
A new trailer coupling has been designed, which has a separated pull bar and steering rod. By adjusting the position of the steering rod of this so-called Safetrail coupling, the source of instabilities at high speed is removed. The lateral movement of consecutive trailers cannot exceed the movement of the truck at any time, so the driver remains in control of the whole vehicle.
Another change was made to the steering system of the trailer, because the magnitude of the transmission factor between pull bar and front axle reduces with greater steering angles. The rod mechanism is replaced by a cable and pulley system, with a different transmission ratio to allow the trailer to make sharper turns.
Both systems are applied in the MTS-Safetrail. The road-holding behaviour of this prototype was first compared to the behaviour of the conventional trailer by means of computer simulation. Then the prototype was tested in practice, performing the same tests. A comparison is then made between the tested behaviour with and without the new coupling system and the simulated behaviour.
The trailer coupling on the traction unit is placed further to the rear, imitating the behaviour of several coupled trailers. From the tests, the following can be concluded:
1. The adjustment of the trailer coupling has a clear positive influence on the stability of the combination. The road-holding behaviour is tested at a velocity of up to 75 [km/h], ensuring a safe use at velocities up to 50 [km/h].
2. In a final design, only two positions of the trailer coupling are necessary. Changing between positions should be triggered by the crossing of a limit value in the velocity.
3. With the cable transmission the combination can turn within a radius of 13 [m], whereas the conventional trailers are used at a radius of 19,5 [m]. 4. With simulation of the road-holding behaviour a good prediction of the actual behaviour can be made. In addition to that, simulation can be of good
use during the design of new constructions. Reports on Transport Engineering and Logistics (in Dutch)
