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MBB KOMET

the first high-speed maglev

Text by Kenji Eiler

The engineers at MBB were very successful developing the first manned maglev in the world. With the ‘’Prinzipträger’’ top speeds of 90 km/h could be reached at the short test track at their Ottobrunn facility. The next stage was to continue into the high-speed area. The Japanese state railway company (JR) had the world’s fastest train, the ‘’Shinkansen’’, in service, operating at more than 220 km/h. At the time, many experts thought that this speed was the maximum possible for an economical use of the wheel/rail technology. Increasing the speed to 400 km/h was inconceivable. Many critics believed that not even a maglev train could reach 400 km/h since growing eddy currents would induct a reverse magnetic field at high speeds. The controlling of the air gap combined with such a speed would require so much effort and energy, that a manned maglev was practically impossible to realize. But after months of calculations and studies, the engineers of MBB were sure it was possible. The next step was to start developing and building the world’s first high speed maglev demonstrator.

While the engineers where starting the development, a second team was responsible for construction of the test track. The double-‘’L’’ shaped track from the predecessor ‘’Prinzipträger’’ was the basic design, but a longer test track was inevitable. Plans to extend the existing 660 m long test track with another 300 meters and to upgrade it for a ‘’high-speed linear motor test stand’’, were cancelled. The location of the track, which was only designed for a maximum speed of 90 km/h, directly at the factory site was not suitable.

The MBB team was forced to look for a new location for their ‘’high-speed test facility’’. A 2.2 km long track was planned along an existing straight forest road and a high-voltage power line near Grasbrunn, southeast of Munich. The new track was designed to run elevated on 6 meter high concrete piles and should be dismantled after the completion of an even larger test track in Donauried. The application for the necessary permits made the plan public and several communities brought their objections. However, in the summer of 1973 the application was finally granted, but the lawsuits had delayed the realization of the test track. The MBB team therefore decided to simultaneously start planning for a second identical test site at their factory site in Lampoldshausen (near Heilbronn – today EADS Astrium). In Mai 1973 construction workers began with earthworks in Lampholdshausen. The completion of this track was planned for the end of the year but after a few weeks, the work had to be stopped.

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The KOMET test track, located 3km south of the Manching airbase

After an intensive search for an alternative area, the German armed forces allowed the use of their training grounds 3 km south of the airbase Manching (near Ingolstadt, today EADS Military). The construction works for the 1.300 meter long track started in the autumn of 1973 and only one year later, on 4th October 1974, the test track was officially opened by the German minister for science Hans Matthöfer. The efforts to build a test track as quickly as possible was justified because a consortium of Siemens, AEG and Brown-Boverie & Cie was also doing research for a competitive maglev system, called EDS with a pushing off magnetic field. The building of their circle test track in Erlangen began earlier in the beginning of 1973.

During this delay of over one and a half year, the MBB maglev team had time to update the measurement platform components with processed levitation technology and computers. This unmanned unpowered measurement platform was named officially ‘’Komponentenmessträger’’ – in short ‘’KOMET’’ and was 8.8 meter long with a weight of 8.5 ton. It was equipped with five levitation magnets and two guidance magnets on each side which were mounted on a frame. This frame was connected through hydraulic dampers to the vehicle. The power supplied through onboard batteries. If the totally independent working levitation or guidance system would fail, emergency skids would prevent damage to the KOMET. The onboard computer was working independently from the operating control center and received instructions through an antenna before and after the test run.

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The layout of the guideway track and the main components of KOMET

The unpowered KOMET had to be accelerated to the desired operating speed by a steam-water powered rocket sledge called ‘’Daniel’’. The sledge was manufactured at the ‘’Flugzeugwerke Emmen’’ company in Switzerland (today RUAG Aerospace) and weighted 8.5 ton (loaded). On the sledge were six thermally insulated cylindrical water tanks which could be filled with 800 l boiling water at a maximum steam pressure of 55 bar (5.500.000 Pa). Each tank was equipped with four steam nozzles with a mass flow adjustable valve. The propulsion sledge was measuring the actual speed and controlled the position of the valves to ensure the optimized thrust and acceleration curve which was programmed by the control tower before a test run was held. The thrust and the desired operating speed could be adjusted by the valves or by excluding a number of water tanks. With Daniel, a maximum thrust of 500 kN and an acceleration of 25m/s2 could be reached to run at the designed top speed of 400 km/h – most runs however were held in lower speed ranges.

Before every test run, the battery of the KOMET were charged and data was transferred to the on-board computer systems. Meanwhile the propulsion sledge Daniel was filled with boiling water. After a quick antenna communication test, the brakes were released and the vents of the nozzles were opened. After the desired operating speed was reached within the acceleration zone of 300 m length, an automatic coupler was unfastened and Daniel and KOMET were separated. Daniel was braking immediately with brake chocks while the KOMET was levitating independently away. If the brakes of Daniel should fail, it was in danger to clash with the KOMET, so a redundant braking system was installed. After standstill, the pressure vents were opened to ensure a complete relief of the pressure in the nozzles.

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The coupling between KOMET and its propulsion sledge (left), the levitation coils and the brake chocks (center & rigth)

Meanwhile, the KOMET entered the 300 m long measurement zone. The sensors, controlling units and the data trackers were all powered by an onboard battery. After leaving this zone, the KOMET was stopped throgh conventional brake chocks. The deceleration in the 700 m long zone was lower than Daniel to prevent a collision of the both vehicles. After standstill the engineers was first inspecting both vehicles for any damages. After that, Daniel was dragged back to the starting point by a cable winch and after that on the same way the KOMET.

The result of the test runs with the KOMET was in many ways similar to the results the rival Krauss-Maffei made with their Transrapid 02 and 04. MBB had won experience with high speed maglevs and Krauss-Maffei had experience with curved tracks and active suspension of vehicles. Already in April 1974, MBB and  Krauss-Maffei began working together to develop control components. The joint venture group ‘’Transrapid E.M.S’’ was founded (E.M.S = Elektro-Magnetisches Schweben).

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The MBB logo at the left side

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After two field campaigns between 1975 and 1976, some intermediate data could be published. One of the insights was the need of movable levitation frames. The first generation of maglev trains as the KOMETs  predecessor Prinzipträger and the rival developments Transrapid 02 and 04 of Krauss-Maffei were all operated with unmovable and rigidly mounted levitation and guidance magnet systems. These magnets were mounted on each of the four corners of the vehicle. The KOMET was equipped with 5 rigidly mounted magnet systems on each side. In all developments, the magnet was controlled with a central control unit. This unit was alone responsible for the levitation, the conduct and the compensation of vibrations and characteristic frequencies. The test series of the KOMET showed no satisfactory results with this method. For reasons of weight, increasing the efficiency of the linear motor, the easier layout of the control system and profitability, a small gap between the vehicle and the track is desirable. In comparison, a bigger gap is advantageous to allow geometrical tolerances of the guide way and to compensate for the high inertia of the vehicle. The current configuration of the magnets and its control system had to accelerate higher masses, and in due to the greater gap, a higher power in the coils was needed. Another disadvantage was the need of a backup auxiliary control system for extra safety in case, the main system would fail. This doubles the weight and increases the cost.

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Guidance magnets: The difference between the KOMET (left) and the KOMET-M (right). The magnet coils are moutned moveable, so the air gap between the track and the coils decreases. This causes higher efficiency and better agility.

A new concept was tested with the upgrading of the KOMET to movable levitation frames. Every levitation and guidance magnet coil was mounted on a movable ‘’levitation frame’’. This allows higher geometric tolerances of the guide way and smaller curve radiuses. Instead of moving the whole vehicle to adapt it to the guide way, only the magnet coils had to be adapted. This agility allowed smaller levitation and guidance gaps. A new development was to give each magnet coil an own control unit, so if one of these units should fail, the other magnets could work without disturbance. Today, all Maglevs are using such levitation frames.

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Levitation magnets - the difference between KOMET (left) and KOMET-M (right). The magnet coils are mounted movable which increases the agility and allows smaller air gaps

In 1976, the onboard computer systems of the KOMET were upgraded and the whole bottom of the vehicle replaced. The previously five rigidly mounted magnet coils on each side had been replaced by six movable magnets. These coils was mounted spring-suspended on levitation frames which themselves were mounted spring-suspended on the vehicles chassis. Each coil had its own control unit for levitation and guidance, so a redundancy of the components was given. This reduced weight and allowed reducing the levitation gap from 14 to 8 mm. The upgraded vehicle was named ‘’KOMET-M” and made it first run at the end of December 1976. On February 19th 1976 a new world speed record could be set with 401.3 km/h.

Even if the KOMET was without any propulsion, the vehicle was the first High-Speed Maglev entering speed areas over 400 km/h. No wheel/rail based train could achieve this speed. Only the French air cushion vehicle ‘’Aérotrain’’ was able to run these speeds with a propeller fan. The experience of the test runs and the developments of new components and control units are used until today in the Transrapid maglev.

The 1,300 meter long test track in Manching was dismantled in 1978. Only the hangar and the control tower are left today. The road alongside the test track also remains. The ‘’KOMET-M’’ is stored today in Lathen – near the Transrapid test track. It is owned by the local community and can be visited with prior registration. The rocket sledge ‘’Daniel’’ has been returned 1979 to the manufacturer in Emmen (Switzerland).

MBB Komet & Komet M - Data

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Vehicle

KOMET

KOMET-M
Manufacturer: Messerschmidt-Bölkow-Blohm (1974)
length: 8.5 m 8.5 m
width: 2.5 m 2.5 m
height: 1.5 m 1.5 m
weight (empty): 8.5 t 8.8 t
maximum weight: 9.0 t 11.0 t
levitation gap: 14 mm 8 mm
operating speed: 400 km/h 400 km/h
maximum speed: 401,3 km/h



Propulsion sledge

Daniel

Manufacturer: Flugzeugwerke Emmen (Switzerland)
weight (empty): 5.4 t
propulsion: 6 Hot water rockets with 800 l water each, 5,500,000 Pa pressure
acceleration (max): 25 m/s2
propulsion force (max.): 500 kN



Track
Test track location: 3km south of Manching Airbase
length: 1.300 m
elevation: 1 m
max.gradient: 0 ‰
curve radius: ∞ m
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