details in connection with the installation of a pod unit may thus be eliminated while the costs are reduced in order to obtain a suitable rotational speed of the gear ring a transmission unit should however be provided between the outlet axis of the electric motor and the gear ring suitably a gear transmission is used the invention is not limited to the above description but may be varied within the scope of the accompanying patent claims for instance it should be understood that the driving of the electric motor fig6 7 also may be applied in connection with a conventional installation of a pod unit and that it will be possible to gain great advantages also when a conventional installation is concerned further it is realized that it is not necessary to use an intermediate mounting flange 16 to utilize the advantages according to the invention as also with a conventional installation i e with the bearing socket 19 for the gear ring 14 connected directly to the base 15 many advantages according to the invention are obtained the advantages according to the invention are also obtained even with a seating having another exterior cross section than a rectangular e g an oval or a cylindrical one the cooling elements may in certain cases especially if the plate 6 f is the floor board advantageously be located at the air inlet 22 to the seating 6 in order to keep the temperature of the plate 6 f down for comfort reasons insulation may however be.