Hello
Dieselboy and
ODK Members & Guests
Welcome first-time poster, long-time member.
Your first question on these forums is a vexed one, or at least contentious.
Nonetheless, a great and worthy question.
A simple answer to your blade disc question - about catching ability - would be
NO.
Both designs would fill the catcher 'efficiently' is my considered view.
This is a question of
historical worth and significance.
If you would like my thoughts on this interesting topic then read-on
-------------------------------------
A more complete answer will have to remain in the pipeline (at least for me) at this time.
In the meantime, I would like to make the following
observations & points:-[1] The British
Rotoscythe of 1932 recognised that if you were going to catch grass
on a rotary mower you would need an understanding of
aerodynamics. Their blade disc
had inbuilt fins for lifting the grass, but it did not have an efficient blade design.
[2] By the late 1950s, Australian rotaries were starting to use these ideas in blade disc
designs and blade designs.
[3] By the 1960s, there was clear recognition that grass catching ability also depended
on the grass discharge design of the
base itself. There is a clear progression of
base designs having no real skirt height, to
low-arch,
medium-arch, and then
high-arch designs. Many members will remember the famous Victa TV ads with the water truck, and
a high-arch VC Victa catching wet grass.
[4] By the late seventies a new consideration was taking shape. The advent of stricter
environmental laws meant that manufacturers were conscious as to how blade discs could
be designed to make lawnmowers quieter - to
lower aerodynamic noise. Here,
CSIRO's Engineering
Division (partly sponsored by Victa) developed what became known later as the
Victa Vortex.
That blade disc incorporated inbuilt fan flutes that enabled the mower to cut and catch
grass more efficiently at a lower engine RPM, also reducing noise.
[5] Also at about this time, there was increasing interest in so-called
mulching mowers.
Here, blade disc design was crucial (not just blades); with the recognition that fluted
discs could keep grass 'airborne' within the base longer, so that it could be chopped &
re-chopped, producing the
finer grass suitable for
mulch.
[6] In more recent times, with the advent of 'throw-away' entry-level lawnmowers, another
consideration has become
cost. What is the cheapest, most efficient, blade disc design
that can be made with a minimum number of production steps.
[7] I think the issue of grass catching cannot now be looked at in isolation; but factors
of mulching ability, noise, and cost of manufacture are all relevant. I might also add
that the issue of two or four blades is also a relevant factor here.
[8] The oval Victa disc is a clever design in that it provides efficient catching in a
cost-effective way. I might also point out that the oval shape may mean less material,
and lighter weight, but the design acts as a repelling device to foreign objects - the
shape 'pushes back' or 'repels' foreign objects.
[9] I think the main difference between the two disc types you refer to lies, not in their
catching ability, but in their contribution to
mulching capacity. [10]My final point is a fill-in; because I like my points lists to be in even numbers
All very interesting.
-----------------------------------
JACK.
