1. Fitting the iron rim on the wooden wheel:
The iron ring is always made slightly lesser in diameter than that of the wooden wheel. Therefore, the iron ring cannot easily slip onto the rim of the wooden wheel.
Wooden (Cart) wheel with an iron rod
Now the iron ring is heated to a higher temperature, it results in the expansion in the size of the ring, and the hot ring is then easily slipped onto the wooden wheel's rim. Coldwater is poured on the iron ring to contract in size and hold the wooden wheel tightly.
The iron ring fitted on the wooden wheel