| CPC B62M 6/55 (2013.01) [B62M 11/14 (2013.01)] | 10 Claims |

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1. An assistance device for a bike comprising:
a motor;
a reduction gear;
a freewheel; and
a shaft rotating solidly with a right crank and a left crank,
said motor transmitting an assistance torque to the shaft via the freewheel,
said device being configured to be housed inside a bottom bracket shell,
said shaft being mounted with the ability to rotate relative to said shell by virtue of two ball bearings,
said freewheel being made up of several components which are placed between the motor and the shaft,
wherein the device further comprises a torque transmission ring enabling one of the components of the free wheel to be secured to the shaft or to one of the cranks,
wherein said transmission ring is at least partially placed under one of the two ball bearings,
wherein the torque transmission ring creates a first mechanical connection with one of the components of the free wheel and a second mechanical connection with the shaft or with one of the cranks,
wherein at least one of the two mechanical connections can be disconnected in such a way as to remove the shaft, and
wherein the transmission ring is positioned in the vicinity of the right crank and the disconnectable mechanical connection is the one between the ring and one of the components of the free wheel.
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