Hello all,
I don't see how
Sid Bowditch was involved with the 45 at all!
Sid retired in
1958; the 45 was released in late
1967.
Sid's last projects were the 30" Queen and the ill-fated second
version of the Spincut, the 18" (with twin height levers!).
The closest progenitor to the 45 is the
Bonmow 33, released in
1960,
also after Sid's retirement.
I don't think the frame issues on 45's can be attributed to a design defect.
The cracks are only showing up some 3 decades after manufacture, well after
the expected life cycle of a domestic lawnmower. In this light, the frame
is just plain worn out rather than suffering a premature fail.
It may be fair to say the single rail was a better design in not suffering,
or suffering less catastrophically, than the later twin rails in the way that
Grumpy described. I'd still have a twin rail machine any day - easier to clean
and inspect - particularly for cracks

- and nicer to look at (in my view).
Cheers.---------------------------
JACK