Hi Paul c and Jack,Vintage mowers home page (click on photos then click on Patrick's Mowers) has a clean image of the under base exhaust resonator (expansion Chamber).
Nice looking mower with a clean coat of paint.
I take it Whirlwind was the first Australian built rotary mower that came out with the recoil starter.
Lawn Boy and Masport had the under base resonator in the early days with the iron horse motor.
The first model has the Midget Mark 2 and the second Model has the Mark 3 Engine but I am not sure if the base castings are different because I have not seen the foot rest on the second model.
The casting must be slightly different because the second model does not have the exhaust hole in the base.
The first Whirlwind's base looks like it is shaped like a Simpsons-Sears mower base.
1953 Canadian Simpsons Sears made by RPM with iron horse engine.
![[Linked Image]](https://www.outdoorking-forum.com.au/forum/uploads/usergals/2017/03/full-9569-33396-whirlwind_18__1.jpg)
![[Linked Image]](https://www.outdoorking-forum.com.au/forum/uploads/usergals/2017/03/full-9569-33397-whirlwind_18.jpg)
![[Linked Image]](https://www.outdoorking-forum.com.au/forum/uploads/usergals/2017/03/full-9569-33398-masport.jpg)
![[Linked Image]](https://www.outdoorking-forum.com.au/forum/uploads/usergals/2017/03/full-9569-33399-foot_rest.jpg)
![[Linked Image]](https://www.outdoorking-forum.com.au/forum/uploads/usergals/2017/03/full-9569-33400-whirlwind_midget_mark_3.jpg)
Cheers Max.