perforated grill block?

[Who]

Originally Posted by Peter7307

Some trucks achieve a similar result by using a thermostat to control the opening of the grille slats ahead of the radiator.

I remember being in stop and go traffic beside a large Autocar truck and its grill opened and closed with it's throttle. Every time pulling up 15 - 20' it opened, then closed while slowing or idling. Seemed pretty clever and this was even pre-internet.

[cfg83]

Frank -

Originally Posted by Frank Lee

Perforated screens are velocity sensitive; at low speeds they let in about what you'd expect- say, a 30% open screen will let in 30% of what an unobstructed vent would- and at higher speeds they "close up" to the oncoming flow and appear to the air to be more "solid".

This is cool because I think you may end up creating an "aesthetic" that is also MPG efficient. Aaaaaaaaand ..... it's a passive design. No moving parts means uber-reliability and cheap to make.

CarloSW2

[Frank Lee]

I made this thought experiment to visualize it: imagine a pail with a 30% open screen covering it. Let a small stream of water flow onto it; all the water easily goes through the screen and into the bucket. Turn a deluge of water onto it and most of the water flies off all around the bucket, yet some gets through, but probably not a whole lot more than the small stream.

[DifferentPointofView]

Has anyone noticed that the newer vehicles are using honeycomb grills that imitate a perforated grille? I've noticed this on newer dodge trucks and dodge vehicles.

Some trucks achieve a similar result by using a thermostat to control the opening of the grille slats ahead of the radiator.
At low temperatures the grill opening is small and at higher temperatures the opening change to allow more airflow.

This is the stuff auto manufacturers need to start doing and shutting their mouths about the 35mpg fleet average they have to meet. Couldn't they just make one that is controlled by air so the electrical system doesn't have to work so much? it's open whenever your at low speeds, but go fast enough and the flaps are caused to lift up from the force of air and cover the grille openings.

Basically, there are flaps that lay down on the front bumper on hinges, and is bent at the tip at an angle. At slow speeds, they stay down, but when you go fast enough air is forced under the flaps because the bend at the tip is at an upward angle. The air being forced under it lifts the flap into the air, and is pressed up against the grille opening until you have to stop, where they fall back down onto the front bumper.

Maybe not the best idea, but it's a start.

[Peter7307]

There was a Ford car from the 70's which had a normal grille with horizontal slats which achieved the same result with no moving parts.

The slats were shaped like an aerofoil / teardrop shape in profile. At slow speeds the air went through the openings but at higher speeds the shape sent air over the grille slats and over the bonnet / hood.

The material was a simple injection molded plastic and at a quick glance it wasn't even visible but the shape could clearly be felt with your fingers.

Pete.

[Frank Lee]

That would be the early '80's Tempo.

[cfg83]

DifferentPointofView -

Originally Posted by DifferentPointofView

...

Basically, there are flaps that lay down on the front bumper on hinges, and is bent at the tip at an angle. At slow speeds, they stay down, but when you go fast enough air is forced under the flaps because the bend at the tip is at an upward angle. The air being forced under it lifts the flap into the air, and is pressed up against the grille opening until you have to stop, where they fall back down onto the front bumper.

Maybe not the best idea, but it's a start.

I like it. I was thinking the same thing but I was being more complex because I was thinking of a flap that was hinged at the top and "pushed" by the air in a similar way. But, a flap that just falls back down is nicer because gravity helps out (mine would have needed a spring). That sounds really easy to do. Hinge some plastic and put little bumpers to raise the flap :



CarloSW2

[Frank Lee]

Mine would be iced up half the year. The other half, it would pound against the stops, one way or the other, because of the strong gusty winds and every passing semi.

[diesel_john]

my take on the perforated sheet metal grill is yes it will work but round holes are a very inefficient way to duct in air.
We might pushing a lot of air around all the time when we don't need it.
If we divert all the air with a smooth airfoil and then have an NACA intake duct that opens only as much as we need, it would only induce extra drag when we need lots of air instead of all the time. does that make sense.
note the shape of the intakes on the hood of this red car.

[DifferentPointofView]

It is a Ferrari, 0.0 F40 at that, So I'm not surprised on the smart design :thumbsup: why don't we just do full grille blocks and have intake ducts like that? one of those things that could benefit more vehicles out there.