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Driving around in poor weather conditions can be
hazardous. Perhaps the most challenging conditions are
caused by the various forms of water that fall from the
sky
and contaminate the surface of the road. Water between
a
car tire and the road surface reduces friction in many
ways
from
dissipating electrostatic interactions to forming a
complete interface layer that lubricates your tangental
path into a field.
Tire manufacturers have developed strategies to cope
with
this, largely by cutting/molding grooves into the surface.
The raised blocks create a smaller contact patch,
increasing pressure to channel flow between blocks.
That's
fine until water flow is insufficient, the car too fast, too
much water or the water is a solid.
Snow is particularly tricky, watching city dwellers
struggle
in snow* will highlight the problem: snow compacts into
the tire channels, lodges there and renders the tire
smooth. The typical countermeasure to this is to make
the
channels bigger and the rubber compound softer.
Softening
the rubber is partly a countermeasure against the
stiffening effect of low temperature, but also encourages
flex during loading and unloading as the tire rotates. This
movement helps shed compacted snow in the channels.
On
a larger scale, lowering tire pressure changes the whole
profile of the tire carcass for a similar effect. Sadly,
winter
tires are dreadful in the wrong environment, cars move
and weather changes rapidly. So an alternative solution
might be helpful.
Most people have had the opportunity to use one of the
Dyson air blade (TM) hand dryers. These use a wide, thin
stream of ~400mph air to remove the layer of water on
the
skin and distribute it to the general environment. Like all
products of the Dyson inventive process**, they work OK,
certainly 80%+ of the water is quickly and effectively
removed. Granted, the drying is less effective than paper
towels, dangerously loud and a microbiology nightmare,
but these drawbacks don't affect our application.
So, inside the wheel-well of the chosen vehicle, fitted to
to the suspension upright to maintain a constant distance
is
an air-knife nozzle. The best position is not obvious, but
the 4-5 o'clock zone is a good start. Here, the nozzle is
positioned at an acute angle to the surface, blowing
high-
speed air will dislodge water and act to encourage the
tangental separation naturally occurring because of the
tire rotation. The nozzle position means water is
separated
on the rear side of the tire and won't trouble that tire
again. Cooperation between car manufacturers and tire
makers is routine, here, the tire pattern and nozzle
configuration could be optimized to dislodge even the
most
recalcitrant crystalline water.
The source of air for each wheel will need to be fairly
robust. A Dyson hand dryer is 1.6kW, and this will only be
on in tricky conditions, this is easily doable with a 12V
centrifugal blower. However, we already have powerful
air
pumps in cars. Exhaust bleed could be used, A tap from
the
compressor side of now-universal turbochargers or, a
separate turbo re-purposed as a dedicated high-capacity
blower.
An extension of the idea would be to focus a high-
pressure
air jet right in front of the tire. Removing a substantial
percentage of the water would dramatically increase the
apparent capacity of the tire itself. Combining both
would
be a big help to trucks, and a possible advantage in
racing,
it's not obviously prohibited in the F1 rules for example.
*is an excellent hobby, find a bar with a big window
opposite a huge car park as a snowstorm rolls in on a
Friday night and enjoy.
**Browse through an industrial catalog, spot cyclonic dust
separator, add marketing, sell. Browse again, spot
compressed air powered mine ventilator, add marketing,
sell. Browse again, spot air-knife, add marketing, sell.
Dyson air blade
https://en.wikipedi...wiki/Dyson_Airblade [bs0u0155, Feb 13 2020]
[link]
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//~400mph air// Seriously??!! |
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<Starts calculating how many Dyson airblades would need to
be arranged in tight formation to make an indoor skydiving
rig> |
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This might actually be a jolly good idea. |
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Why not apply the jet to the contact surface rather than the wheel ? |
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//Why not apply the jet to the contact surface rather than
the wheel ?// I mentioned that in the last paragraph. |
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A sufficiently powerful jet will generate upthrust, diminishing grip. |
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A forward-facing jet will increase "drag". |
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So it needs to be aimed outwards from the wheel, close to parallel to the surface, in front of the contact point. |
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In that case, a blade isn't necessarily the best thing; a simple jet nozzle will do just as well. |
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Of course, any material blown owtwards may well impinge with considerable force on other vehicles, bits of street furniture and landscape, pedestrians and cyclists. Severe, painful injuries would result ... |
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This is reckelssly inconsiderate and blatantly antisocial, bad and wrong. Implementation must commence immediately. [+] |
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Actually, managing the airflow around rotating
wheels is desirable and tricky. An air curtain might
work nicely, reducing total drag might be enough to
offset the energetic cost. |
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[8th of 7] always finding the worst case and missing the obvious...
simply blast from the outside in (yes, the mounting will be a bit more
complicated...) so the 2 streams impact each other underneath the
vehicle. |
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[neut], you know better than to cross the streams, shirley ? |
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Er, yeah, didn't think of that.
Well, ending the universe WILL get rid of the crud in your tread... |
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Total Protonic Reversal seems a bit of a drastic way to improve traction ... |
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//drastic way to improve traction ...// Though not specifically prohibited by most motor racing regulations... |
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I see where this is going. Wheel reduction, more powerful thrusting blades, lighter passenger compartment. More trees, bushes and grass. |
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maybe I'm not seeing in the right direction? |
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Don't worry, [bs0u0155]. It will quite some time before the hot rodders overclock the air blades to get air fully flowing under the wheels. |
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An infinitely long time; air between the tyre and the road is the exact opposite of what's wanted. It would reduce friction. |
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[8th] You are usually good at quoting Blade runner. |
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Yes, but this smells of a set-up. |
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You could suggest it to [bs] as the basis for a title revision, though. |
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Suggest what as a title revision? I apologise, I'm
conferencing on the west coast, I think the sun is
making me a bit dim. |
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I wonder if manipulation of air in front of the tire
could lower air pressure? |
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// Suggest what as a title revision? // |
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The employment of "Blade Runner" memes, either in the title or the body. |
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"Apology accepted, Captain Needa... " |
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// think the sun is making me a bit dim. // |
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We hadn't noticed; you're no worse than usual. |
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// I wonder if manipulation of air in front of the tire could lower air pressure? // |
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It would have to work on the entire contact patch. Bernoulli's theorem indicates that a region of lower pressure could be generated but the energy cost would be high. |
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