Gradually the number of these double-ended engines (known as Double Fairlies) grew to 10, and came to include the B class of 1874. There was still a need for orthodox engines with Fairlie manoeuvrability. The Avonside Engine Company of Bristol, England solved the problem by providing both the R and S classes of Single Fairlie engines; 18 of the former in 1878-79 and 7 of the latter in 1880-81.
The number of double-ended engines (known as Double Fairlies) increased gradually to 10, encompassing the B class of 1874.  There was still a demand for conventional engines with Fairlie maneuverability. The Avonside Engine Company of Bristol, England addressed this by offering both the R and S classes of Single Fairlie engines; 18 of the former in 1878-79 and 7 of the latter in 1880-81.