DDD SYSTEMS & Dr. Dan Diaper. Cricket Writings - The Hover-Roller and Additional Hover-Cover Functionality.
The Hover-Roller and Additional Hover-Cover
Functionality.
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It was during
commentary of the
There was a little
hilarity in the commentary box. I
doodled in my mind how a hover-roller might work. The commentators mentioned it a few hours
later and, a couple of days later, in the final session of Day 3 (Tuesday, 26th.
May), the hover-roller got a third mention.
Gentlemen,
I’ve been amused by your discussion
of a Hover-Roller.
This might just be a heavy
hovercraft which would press down evenly across it’s footprint.
But what would it do to the wicket?
1
It would clean all dust and debris;
2
While pressing the wicket it would erode any cracks;
3
It would dry the wicket.
Excellent digressions during your
commentary. Thank you.
Dr. Dan <>
Read out on the radio
almost immediately, I was just pleased I managed not to get too technical,
proudly avoiding mentioning plenum pressure (the plenum is the space between a
hovercraft’s body and the surface on which it rides). Reading Science Fiction (SF), I’ve several
times noted that how hovercrafts work isn’t always well understood. Hovercraft are actually one of two types of
GEMs (Ground Effect Machines), the other is an ekranoplan.
To be clear, a hover-roller would not work because it
would have to be extraordinarily extremely heavy as a hovercraft distributes
its weight fairly evenly over its ground footprint. In contrast, a traditional
roller does just the opposite, it concentrates its weight onto the very small
surface area in contact with the ground.
Between first and third
mentions of the hover-roller concept on the radio, my mind had turned to more
practical things, not about rollers but about hover-covers. At present, the hover-covers I’ve seen are
single units a bit bigger than a wicket.
The are pulled out on ground effect and then the engine is turned off
and the cover lands. The critical point
is that it is not operating for very long as a hovercraft when over the
wicket. Thus, while a hover-cover will
blow around dust and light debris, on the other two numbered points in my
email, there will not be time for crack erosion or wicket drying to take place.
Bingo! A practical idea, i.e. one that is
engineering feasible in terms of both functionality (what it usefully does) and
at minimal cost. Working entirely from
theory, hovercraft must dry the solid ground surface below them. This is so because a lot of air escapes the
plenum chamber and moving air will pick up a lot of water; a good drying day
for one’s washing is one that is windy, even if not sunny.
An important part of
design is requirements analysis, identifying what is needed, and often a
creative part of this is recognising real problems. Here’s a real cricketing problem:
After
a rain interval it is often the case that, even with extensive covers on the
outfield, that areas are damp and, most worryingly when this is so in the areas
of the bowlers’ run-ups.
Why not use a hover-cover’s hair-dryer effect to dry the
outfield,
or at least parts of it? The ground
staff’s procedure would be to remove the covers and then start up the
hover-cover as usual, but instead of just taking the hover-cover off they
manoeuvre it around the outfield, either in a set pattern or concentrating on
areas of greater dampness. They should,
of course, keep it off the wicket to avoid the undesirable effects numbered in
my email.
What’s the
alternative? Up to now it’s involved
passing a rope over the outfield grass, which will spring water droplets into
the air, dispersing them as smaller ones which will evaporate much more rapidly
(evaporation depends on surface area and drops of smaller volume have much
bigger surface areas relative to their volume – it’s a non-linear or power
function to the mathematically literate).
I’ve never been impressed with this rope trick and I’ve heard plenty of
cricket commentators sound equally dubious over the years, even if they aren’t
really sure of the basic physics.
Being long and thin,
and heavy, a full wicket hover-cover will not be that easy to manoeuvre. Again SF is useful as the proper concept is
not weight but mass, which is a problem for spaceships trying to change
direction in the frictionless environment of interstellar space. A hover-cover has low friction, it glides
across the ground and, once in motion, it will go a long way as there is little
ground braking effect (which is another way to say “low friction”). Thus it is difficult to manoeuvre because
nearly as much energy is needed to stop it in any direction it is first moved
(see
As I usually do with my
engineering designs, I see in my mind’s eye, just as I watch cricket on the
radio, here a team of husky groundsmen hauling the hover-cover around the
outfield. In dryer mode, the hover-cover
would be moved sideways (long axis going forward), slowly, in straight
lines. Steering is done by spinning it
only when it is stationary as hovercraft are notoriously difficult to steer.
Hover-covers are
expensive bits of kit. Finding a
desirable, additional, practical use for something that costs so much must be a
good thing.
Finally, if I were to
design future hover-covers, I’d consider a two unit system. Two separate hover-covers only half the
length of a wicket would be much easier to manoeuvre when used to dry the
outfield because their individual mass would be less (but more than half) of
the existing single wicket sized hover-covers.
It was an excellent
cricket match with an excellent, entertaining and enjoyable commentary, as I’d
said in an email to the commentary team.
Just as might mighty oaks from little acorns grow, so a little slip of
the tongue has produce a useful, practical idea, if not an oak of a one. Unfortunately, I can see no way to make money
from the idea, which will disappoint the beautiful Japanese wife, so I offer it
free on the internet.
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