one
First, find out what the appetite of our “locomotive” is. "Lada-Priora" on a good horizontal highway at a speed of 60 km / h is content with 4.7 liters of gasoline. At 90 km / h, she needs 0.6 liters more. (By the way, is this not a weighty argument in favor of a leisurely movement ?!)
Now that the control point has been defined, let's see what increment the “argument” will give the new “function” - the trailer. In the classic version, without an awning, an empty trailer at a speed of 60 km / h adds one liter per hundred to the Priora consumption, and one and a half at 90 km / h. This will be the second point that we focus on when estimating fuel consumption by our road train with different tents on the trailer. When driving even with an empty trailer, it is useful to set a low tent on it or remove the tailgate - save 0.5–1 l of fuel per 100 km.
LOW TENT
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Consumption against the non-tarred version is reduced by almost half a liter in any mode. Everything is logical: air, falling into an uncovered trailer, additionally “rests” on its rear wall, and behind it the vortices become more intense. The general whirlwind track behind the stern of the road train devours more energy - and slows it down more actively.
Hence the first conclusion: riding with bare sides, even if the trailer is not loaded, is irrational. However, in this case there is a hidden reserve of savings: if the trailer is empty, then its rear side can be removed and fixed on the floor or tied up in the open position parallel to the road. (Of course, the board should not close the lights and the license plate.) Measurements confirm that the appetite of a road train without a tailgate is even more modest than with a low tent!
However, we do not pretend to be a discovery - fuel consumption is proportional to the power expended on the movement, that is, aerodynamic drag, multiplied by speed. The longer (for example, with increasing speed) the loop of disturbed air behind the road train, the greater the loss. But these perturbations also depend on the size of the "outrage" - in this version, the rear side adds a lot. Without it, air flows off the trailer floor with less turbulence.
HIGH AWNING
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With it, fuel consumption increases by more than 2 liters. Recall that the tractor in our experiment was the Priora hatchback, a car with good aerodynamic qualities. If there was a large off-road vehicle in its place, our trailer would be completely in its aerodynamic shadow - in the "air bag" - and the dimensions of the tent would have little effect on the overall consumption.
HIGH AWNING WITH AERODYNAMIC CUT
four
If the transported cargo does not occupy the entire space under the awning, the aerodynamic awning is most beneficial. Its upper part is inclined to the front side. Measurements show: a sloping top saves up to a third of a liter. The effect is more noticeable, the greater the speed. Up to 60 km / h there is no sense in bevels. True, when the load is shifted backward, the stability of the road train deteriorates. But the awning racks are located symmetrically - nothing prevents the awning from being tilted back and the center of gravity of the load closer to the front side.
Well, how will this affect fuel consumption? It turned out nothing! Profitability is not worse at all than with the "branded" position of the awning. Again, we recall the laws of aerodynamics - the results obtained do not contradict them. If the trailer slanted forward, partially diving under the vortices of the tractor, then behind a huge rear section it generated its own, much more powerful ones. And the bevel directed back somewhat smoothed out the air disturbed by the road train. So, at the speeds we have adopted, both positions of the awning are equivalent in terms of gas mileage.
ECONOMY RESERVES
If the trailer is equipped with an aerodynamic awning, keep in mind that it can be installed backwards - it will not be worse. And when towing a car with a station wagon, a bevel backward is even preferable.
