The ventilation system
The ventilation system
Thirteen ventilation intakes are enough? It comes naturally to wonder when we have some helmets displaying at least a dozen more, so that the open surface is larger than the full one.
After many tests, carried out in the torrid heat that gripped our Country in the month of June, I can say that the air intakes are sufficient; and I one who chooses his helmet considering the presence of the front ventilation. It’s a long time, in fact, that I use for my rides a helmet with a particularly effective front intake.
Wearing this Manta helmet I feared I have suffered its lack. On the opposite, not at all. Sure, you pay for something, but much less than I imagined and then the gel pad really helps.
In the two subsequent pictures I highlighted the seven air intakes.
As you can see, they are large and well positioned; but the one I really wanted to test is the upper one, the one with the Venturi’s effect. Already present on the Met Strale but less refined because the conformation of the NACA entry is added. We look at a top range helmet and the Venturi intake manufacturing too follows the highest overall standard.
I am distinguishing between NACA and Venturi, even though they often coexist as in this case. With the NACA intake we mean the “shape” of the inlet duct, the path that the air flow must pass through and which is shaped to convey it, while ensuring a low aerodynamic resistance. With the Venturi’s effect we mean what happens in the air when it comes to circulation.
But what is the Venturi’s effect? I already wrote about it in a previous test. Rather than going crazy to find a different metaphor, I choose the easiest way: I copy here what I wrote in the Met Strale test 😀
“…it is a paradowx and explaining it is not easy for me, not one of the best physics’ student. I try.
In the most suffucating days, all of us go around the house, trying out different combinations of open and closed windows. Outside there is a little bit more than a light puff of wind, yet once we find the right combination we will be able to get a gentle refreshing breeze. This is because our timid puff of wind, once forced to pass through a narrow passage, that is the window, will increase its speed to keep its mass unchanged. However, if we move to a larger room, all of our beautiful breeze will disappear, even if the window’s curtains dashingly wave. In fact, by reaching it, we will recapture our providential cool and this because the breeze slowed down in the larger room; but near the second narrow passage, in our domestic example represented by the other open window, the mass build-up will result in a new increase in the outflowing speed. In practice, with the Venturi’s effect, we have a flux that, in normal conditions, we don’t even notice, but if we submit it to this paradox, we increase its effectiveness. The wind outside is exactly that, it does not increase if we open the windows. We do force it, opening, precisely, the windows.
All right, but how do we relate all this to our helmet? Having an air vent with the Venturi’s effect means that, in the theory, even at low speed, and therefore with a limited flux, thanks to it we have an increase of its effectiveness: cool head even if we go slowly.”
Our head is cool even if we go slowly? Yes, and the vent with the Venturi’s effect of this Manta helmet works better than that one on the Strale helmet, thanks also to the NACA intake shaped at the entrance.
In detail we can see the input intake, with a little focus the processing to split the flow, and at the end the hot air outlets with the wings that accelerate its evacuation.
Well, this Met Manta in our hands no longer has secrets. Let’s wear it and let’s start the test on the road.
Sono Fabio Sergio, giornalista, avvocato e autore.
Vivo e lavoro a Napoli e ho dato vita a questo blog per condividere la passione per la bici e la sua meccanica, senza dogmi e pregiudizi: solo la ricerca delle felicità sui pedali.
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