PART SIX - The Record Today - & My Thoughts
The Mohall was never a prototype for a lawnmower.
The Rotomo prototype was a deliberate proof of concept.
The Rotomo production machine is the clue to Hall's contribution!
When Lawrence Hall mounted one of his marine engines in a vertical shaft
configuration onto an old plough disc he did something different in Australia.
The design was not inspired by originality; but by necessity. He took an
existing idea and applied it to what he had ... his own small marine engine
and what was laying around at his factory. We know Hall was 'reconditioning'
comb sets for agricultural harvesters, so it is no stretch of the imagination
that he would have had plough discs readily at hand or available to him.
By this time, the rotary lawnmower was not a new concept at all.
Though the petrol-powered British Rotoscythe first sold here in the
interwar years, it was most certainly sold in Sydney from ... 1948.
The Australian-made rotary lawnmower appeared in ... 1948.
I have written at length on these forums - and another forum - at
length on this. The electric Tecnico was our first rotary lawnmower.
Post-WWII the rotary lawnmower form was well-established by 1952.
Lawrence Hall took 'prior knowledge' and applied it for a specific
purpose out of necessity. He thought it a good idea to cut his mum's
yard with one of these new rotaries- that could handle higher grasses -
and he could do it on the cheap ... perhaps a reconditioned Hall marine
engine mounted to a primitive chassis, and using an inverted
agricultural plough disc. A bit heavy? Well, yes!
This is John Mason's account of Merv's use of the 'plough-disc' design:-
THE PEACH TIN MOWER
So ... on this momentous Saturday afternoon he made a 'skeleton' frame of
flat wrought iron bar material to which he assembled two mild steel round
rods as axles, front and rear, and to which he attached four cast iron
billy-cart wheels. A piece of flat steel bar was bent like an inverted 'U'
and attached to the skeleton frame to serve as a handle.
On the skeleton frame, he mounted one of his Villiers mower engines in a
vertical position - the crankshaft was vertical with the flywheel magneto
and pulley (for the starting cord) uppermost. But it was the lower end of
the crankshaft which was to be the 'business' end of the experimental
machine. Here he attached a flat steel bar sharpened on the leading
edges and fixed by a heavy nut and washer to the lower end of the
crankshaft.
To provide the engine with a fuel supply of the petrol/oil 2-stroke
mixture he mounted a peach tin to which he fitted a small tap and a
piece of plastic tubing which connected to the carburettor.
It was this peach tin which gave the experimental model its name.
Having filled the peach tin with fuel he wound the cord onto the
pulley and gave it a pull and the engine burst into life under
control from the throttle lever mounted on the handle.
Merv pushed the mower into some long grass and it disappeared -
the grass not the mower, and after a few minutes doing the same
thing he saw that with some modifications here was the basis of
a new style mower/grass cutter.
He was ecstatic and called his wife to watch his demonstration -
the first demonstration of countless thousands by a Victa
Rotary Mower.
Amongst other things which Merv Richardson saw was that, in its
present skeletal form, the mower was potentially dangerous; because
stones and other objects could be thrown out at speed and likely to
injure the operator or bystanders. So it was back to the drawing board,
though I suspect the plans for the Peach Tin mower were just a few
rough sketches.
Quite early in his re-consideration of the design was the decision
to determine the width of cut at 18 inches (45cms) which was to be
10cms wider than the standard domestic reel type mower.
His next decision was that a firm base or chassis was needed on
which the engine could be mounted and for the attachment of the
handle, height adjustment mechanism and front and rear axle
brackets. The ideal base would be in the form of a round steel
plate with turned down edges to provide greater safety for
operator and onlooker.
Merv Richardson's engineering knowledge told him the only way
he could have a circular steel base was to have it spun to shape.
To make a die for a base-plate to be pressed out of sheet metal
would cost a lot of money, and before indulging in such
manufacturing luxury, lots of trial and error testing would be
necessary, leading to further modifications.
Spinning the base-plates was a one-off operation and Merv had a
few of them spun, and he set about making and assembling the
hand-made parts for his second and more advanced model.
The results were amazingly successful and this became the
base model for limited production of the Victa Rotomo.
TO BE CONTINUED ...
