I'll add some more data to this not-very-structured history. We know that the Rotoscythe may have pioneered the rotary mower both globally, and specifically in the UK. We know that in 1950, Briggs and Stratton began making a vertical crankshaft engine specifically for rotary mowers. I have found some material intended to expand on the development of rotary mowers in the US, prior to (and perhaps leading to) that Briggs product introduction.
It is a very long and detailed history of Goodall, a pioneering firm in the field of vertical crankshaft rotary mowers in the US. The history was produced by the State Historical Society of Missouri:
http://www.gasenginemagazine.com/fa...tor-leonard-b-goodall.aspx#axzz2mdj9PZjuThe article shows a very early production version of Goodall's mower, probably much the same as one featured but not photographed in a newspaper article from 1939. This apparently used a Maytag washing machine engine:
![[Linked Image]](https://www.outdoorking-forum.com.au/forum/uploads/usergals/2013/12/full-2772-13490-goodall_first_model_1939.png)
It also includes a reproduction of a March, 1947 advertisement for Goodall's product:
![[Linked Image]](https://www.outdoorking-forum.com.au/forum/uploads/usergals/2013/12/full-2772-13489-goodall_mower_advertisement_1947.png)
Just after the war Goodall negotiated with both Briggs and Lauson to have them make vertical crankshaft engines for him. The outcome was a 5 year agreement for Lauson to make vertical crankshaft engines exclusively for Goodall. I think that is probably the engine on the mower in the 1947 advertisement. Meanwhile I note that the Clinton engine company claimed to have produced the "first mass produced vertical-shaft engines for rotary lawnmowers", though it doesn't say in what year this happened:
http://www.clintonengines.us/Clinton_Open_House.pdf
