Southern Railway's Class Ms-2 was a type of experimental steam locomotive.

Beginning in 1915, the Southern had the unique idea to fit "tractor engines" underneath the tender.

[2] They did not produce good enough results, and the tractor units were removed from the Mikados in 1923, and from #5046 in 1926,[2] and were replaced by standard tenders.

An obvious problem with this arrangement is that, similar to the Garratt locomotive and the Triplex, as the tender coal and water ran out, the traction decreased.

Additionally, the tender engines were too large for the steam generating capacity of the locomotive's boiler.