Abstract: A transmission assembly comprising coaxial input and output shafts. A drive sprocket wheel carrying member is secured to and extends radially from the input shaft. A first sprocket wheel is co-axially mounted on the output shaft and a second sprocket wheel is rotatably mounted on the output shaft. A drive sprocket wheel assembly is rotatably mounted on the sprocket wheel carrying member, and each drive sprocket wheel assembly includes a primary and secondary sprocket wheel. For each drive sprocket wheel assembly, a chain extends about the primary sprocket wheel and the first sprocket wheel and a further chain extends about the second sprocket wheel and the second sprocket wheel. The speed of the rotation of the second sprocket wheel is controlled to control the speed of rotation of the output shaft.