On 12 April 1962, the original propeller was removed and replaced by a fine and faster propeller in order to remove a gear train.
Pierre Jean Cavey left the BEST April 30, 1960 to take charge of the factory Flambo at Nogent-le-Roi but he continued to visit the station from time to time to meet with his successor Mark Léguillette. We have no written documentation or photographs of this period and must therefore rely on my father' memory.
The year of the change of the propeller, during a test, one blade was broken by mechanical fatigue as a result of self-sustained vibrations. Luckily the wind was oriented so that the blade detached went to mow a nearby field causing no casualties.
This type of accident is fairly standard in the history of high-power wind turbines. The first propeller had a linear speed nominal at the blade tip area of Mach 0.3. The following propeller reached Mach 0.45. At this speed the major risk is that the propeller resonates. The only emergency solution is a shutdown of the machine provided we have time. Tests of variable pitch propellers, more fragile, have all resulted in a loss of blade and the destruction of the wind turbine.
According to Lucien Romani, the reasonable limit of speed at the blade tip is about 100 m/s or 360 km/h (Mach 0.3).
Meunier tu dors
(Miller you sleep,
But the wind turbine of Nogent-le-Roi was robust. While the loss of a blade on a moving propeller had everywhere else, caused the destruction of the turbine because of damage to the generator as well as the superstructure, that of Nogent held on.
Both BEST and EDF studied the possibility of returning to service. In the magazine « Les Cahiers de l'Iroise » published by Yves Peslin, André Argand says: « I even bought for Electricite de France, 4 acres near Trémazan (in Landunvez) for the purpose of transporting a huge test windmill, directly debiting electricity in the general network, previously installed near Chartres ». But the project was quickly abandoned. The very low cost oil gave, at the time, an undeniable economic superiority upon the renewable energies. Nuclear power was beginning to emerge and mobilized all minds to the Direction des Etudes et Recherches of EDF especially since COGEMA close to Limoges operated a uranium deposit which seemed to promise an indigenous resource and a significant reduction in the cost of energy imports. Pierre Ailleret was about to retire and his successor had a little passion for wind ressources.
However, he was matter of dismantling the turbine and to reinstall it at St. Pierre et Miquelon. This new life would had no follow up because of the distance between the Overseas Territories and the metropolis that excluded any regular monitoring both by EDF as the BEST.
Remained abandoned for three years, in spring 1966, the wind turbine was finally delivered to metal scrap and the field returned to its owner, the farmer Vaubrun.
The photographs below were taken by Pierre Jean Cavey May 21, 1966. On some of them one can see on-board equipment in the nacelle and the pivot.
(Click on the pictures to see their actual size).