| 摘要 |
The present invention relates to a power transmission device which enables a user to use a traditional wheel hub and a wheel smaller than the length of a pedal, by installing a chain ring on an underframe to be chain-coupled with a single-free member of a main wheel, and which includes: a hub installed with the single-free member on the main wheel; and an underframe installed with a chain ring, and chain-coupled with the single-free member to transmit power. The hub comprises a hub body formed with bolts and nuts in order for the single-free members to be installed on both sides of the hub. The underframe comprises a pair of upper and rear frames respectively formed on the top and the rear side around the hub. The end portions of the upper and rear frames are fixed with a crank shaft holder, in order to form the underframe having a triangular shape and in order to install the chain ring. |
