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Corrosion . . . A Vacuum Generated Unintended Consequence
a) WHAT IS VACUUM?
Vacuum
– the “parasitic evil” in aerodynamics – in a race car driver’s term, is simply the terminology
used from a driver to describe that his race car is producing a suction behind it
enabling the other driver to draft him – This draft will enable the driver behind to gain speed (because of lesser frontal
air drag) thereby gaining momentum and passing the car in front of him (even if both cars are absolutely identical, with the
same horsepower, the same frontal surface and the same weight). . . The second driver basically took advantage of the vacuum
created by the first driver – the "frontal surface" ahead of him.
In simplified terms, aerodynamics is a science producing
two forces:
- Displacement of air – because of the object’s speed (Velocity)
- Vacuum – because of the object’s size (Frontal
Surface).
In physics, vacuum is “a space in which the pressure is significantly lower than atmospheric pressure”.
Because of their large size, our Industry’s van style trucks and tractor trailer rigs, driving at highway speed, are
producing a partial vacuum (referenced to units of pressure as Pascal, abbreviated
to Pa).
Our atmosphere pressure is 101.3 kPa – A good vacuum cleaner is approximately 80 kPa. . .
For simplification, a point can be made that a van style truck traveling at highway speed is producing a vacuum (suction
action) similar to a vacuum cleaner behind it, just much more massive. . . It is this suction
action which causes unintended consequences to our equipment addressed in this technical bulletin.
b) HOW CAN WE MANAGE
VACUUM?
This bulletin is to detail the benefits our product, the “Airglide” air deflector,
can offer to any van truck and tractor trailer operator as a fuel saving device in general, with the functional benefits of
managing the air flow on a truck in a unique and efficient way, assisting in reducing corrosion causing road spray and other
unintended consequences produced by vacuum.
Generally speaking, most people look at
an aerodynamic improvement towards the shape of a racing car or an airplane. In our Industry, this is not
necessary; we are not driving fast enough. Our tools, regardless
if truck or tractor trailer, are large structures with a known given frontal surface i.e. height and width and a known legislated
maximum speed. As this structure is traveling through the air, it has to displace the air in its path and
the various aerodynamic shapes, now incorporated in our modern trucks/ tractors, will assist us in displacing that air. Keep in mind that the air you are displacing at highway speed will produce about hurricane
#1 forces and the drag reduction achieved by utilizing aero-aids is the reason why an aero-aid becomes a fuel saving device i.e. lesser drag will require
lesser horsepower to push our large object through the air, which will result in lesser fuel required to produce this horsepower.
However, Aerodynamics
is a double edge sword science – First, you have displacement which is obvious and most visible but as this vehicle
is increasing its speed driving through the air, it will produce a partial vacuum behind it. . . Any increase in frontal surface
(and speed) will produce more vacuum and it is the negative forces generated by vacuum which, in our experience and observations,
are producing a number of unintended consequences to our trucks, specifically to the back of the cab (and all accessories
attached to it) and further on to the actual front of the van body or trailer unit (and all accessories attached to it).
Vacuum produces a “suction action” easiest explained by comparing its forces to a vacuum cleaner however, much more massive and lesser directional in its velocity because of wind buffeting and
unequal flow separation from the various leading edges of the cab. This
“suction action” is strong enough (keep in mind we are producing hurricane #1 wind speeds) to re-direct dirty
road spray into the space which is producing the vacuum and strong enough to carry even heavier “muddy” road dirt
as well into that space, depositing all that contamination onto all surfaces in that space. In areas
utilizing magnesium chloride in winter months, this road spray will consist of an acidy mixture of magnesium chloride and
water which will be sucked up from the road and carried by vacuum up into the gap between the tractor and the trailer’s
front wall; on regular LCF trucks, vacuum will carry that road spray up into the gap between the truck cab and the van body.
Also, the existence of vacuum will trap engine and exhaust aftertreatment equipment
heat at the same locations and if the operator is utilizing a reefer unit, the reefer will have to get its own air supply
from a contaminated environment – therefore its own apparatus will be affected by dirty air and/or road spray.
The “Airglide” is managing vacuum in a unique way. . . Its shape and mounting position are providing
for a specific sized “path” at the bottom leading edge of the air deflector and the cab roof which is allowing
for a pre-determined amount of air to rush through at speed immediately behind the air deflector and tractor cab; because
of the back pressure provided by the front wall of the van box or trailer unit, this high velocity air flow will change into
a low velocity pressure bubble, continuously regenerated as long as a rig is at highway speed (Ram Air Effect).
The escaping air is of low speed, slightly pressurized and is replacing any possible vacuum with a pressurized zone
eliminating unintended consequences produced by vacuum. . . To the contrary, because
of the existence of pressure, the exhausting flow of air will reduce road spray from penetrating into the gap, will assist
heat to dissipate and will provide ample air to the reefer unit if so equipped. It will also produce a
cleaner air flow to air vents installed on truck or trailer van bodies (a major concern on roof fairing equipped LCF bakery
trucks utilizing van bodies with front air vents).
It is important to note that with the “Airglide”, the day-to-day
maintenance requirement and/or mechanical maintenance functions will remain the same;
you’re still going to wash the truck but there will be lesser corrosive residue or road dirt to be washed away. You
will still need the various fluid filters, the air filters, brakes, transmission and any other mileage generated service on
the big trucks as is. You will still need to service a reefer as you always did but there will be lesser
contamination because of the more efficient air flow provided by the “Airglide” (most bugs and large airborne
road dirt will have been deflected away) however, since you cannot eliminate all contamination, you will still have to clean
the refer apparatus at regular intervals . . . (again, the improvements here would be as
above in the reduction of dirt build-up and the build-up will be more diluted, lesser severe in its acidity).
Let me refer to a recent trip to
Canada – 1,447 miles one way . . . Driving up, we had generally good weather, killed millions of bugs on the way and
the first function we performed was washing the truck on arrival. Coming back, we had continuous rain,
there wasn’t a single bug however, our first function the next day was again washing the truck – The contamination
on the vehicle was different, nevertheless it needed the same service function i.e. a thorough wash (and an oil change performed
every 3,000 miles). If our truck would have had an air deflector installed on it, the same maintenance functions would have
had to take place, i.e. washing the truck and making the oil change!
IN
SUMMARY:
The air management function accomplished by the “Airglide” unit is producing a cleaner environment and
lesser environmentally produced contamination which can cause short term, but more
likely long term maintenance concerns (mostly corrosion and paint deterioration, but also heat and its destructive force possibly
affecting maintenance and premature systems aging); basically, our Aero-Aid is providing a more “user-friendly” climatic
condition behind the truck/tractor cab and is saving fuel by efficiently deflecting the air away from the front of
the van body behind it, without any vacuum generated unintended consequences.
FOR FURTHER INFORMATION, PLEASE CALL TRUCKAID LLC
Toll Free 1-866-844-8292
e-mail:
truckaid@usa.com
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