32 as shown in the lower half of fig2 is in the left position in contact with the flank 59 of the output side central wheel 54 in this position the control hub 32 simultaneously covers a section of the gear toothing 53 of the control wheel 52 and a toothed section 60 on the output side central wheel 54 which is formed on a collar 61 of the central wheel 54 projecting in the direction of the electric motor 10 the position of the control hub 32 and the coupling of the toothed sections 60 and 53 causes the speed of the central wheel 54 to be transmitted to the control wheel 52 and therefore to the gear shaft 34 in contrast to this as has already been set out above in the normal gear position the control hub 32 engages with the gear toothing 39 of the drive side central wheel 37 and the toothing 53 of the control wheel 52 in such a way that the gear shaft rotates at the same speed as the torsion rod 24 of the frequency converter motor 10 the starting gear position brought about by the two gear toothed wheel gear mechanism is only initiated if a breakaway effect is to be achieved with the frequency converter motor 10 and the chain drive 50 in order to start the loaded chain scraper conveyor or to release the plough as shown schematically in the diagram in fig3 in the starting gear position the motor torque m d brought about on the output side by the combination of frequency converter motor 10 and toothed wheel gear mechanism 33 and or.