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-   -   Active grill block idea (

holypaulie 06-27-2008 03:25 PM

Active grill block idea
What do you guys think about this automatic vent?
Link for more infoFind Black Plastic Auto Foundation Vent and other Home Ventilation at Aubuchon Hardware

tasdrouille 06-27-2008 03:36 PM

It works with a bimetal coil. That thing probably isn't strong enough to have the vent open/close at highway air pressure. It looks interesting though and could be a good base to use with a step motor in place of the coil.

Xringer 06-28-2008 10:44 AM

That wire mesh looks about like common window screen.
It might not work real well at highway speeds, due to surface turbulence on the mesh, slowing the air flow.
If it is indeed a small mesh, you could get an idea of how it might work by driving 65 mph while holding an 8"x16" screen (on a frame) outside the window.

justpassntime 06-30-2008 02:10 AM

Interesting idea...I think I have seen something like this on semi trucks. Would be nice to have this on the cooling fan switch and only have it open when the cooling fan came on. Obviously it would have to have a motor to operate it.

cfg83 06-30-2008 03:10 AM

justpassntime -

I'm not addressing automation, but I keep this idea floating around in my head :

Side View

*If* you had a flat nose on your car, and *if* you had the space for a cylinder, you could have a stepper motor control a pipe that has a cutaway view that looks like the picture above. The stepper motor would rotate the pipe closed or open.

I *think* it would be robust at wind speeds.

Maybe the best way to fight the wind velocity is to have a sliding grill. Maybe a grid of holes that lines up for ventilation and slides (horizontally?) to misalign the holes, closing the vent.


lunarhighway 06-30-2008 07:26 AM


Would be nice to have this on the cooling fan switch and only have it open when the cooling fan came on. Obviously it would have to have a motor to operate it.
that's exactly what i'm planning to build

@ cfg83 your idea might work too with my setup, although it's esentially the same as what's illustrated below; bur it might work for a multi door setup where all the "rollers" can simply be connected with a single belt... i emagine cutting a slot in some plastic tubeing could look great

here's what i plan to build for my'll go on the top grill but if it works successfull i might try the lower grill as well.

i'l not sure about the setup for the door yet, maybe a slider will work better, but the prinsyple remains the same.

i plan to use a small motor from either an old walkman or a computer fan, the walkman motor seems to have the most torque. old toys and machines seem to be a good source for little electro motors.

the hatch itself will press on a switch at either side of its travle to indicate it's position, if the hatch should move to any position in between the motor will take it to the appropriate position again. of course mechanicly it should be set up to prevent flutter, but the system should calibrate itself.

i don't know if this will prove workable in practice but in theory i think it's pretty sound

Keen 06-30-2008 09:19 AM

I love the idea.

Maybe you should have some sort of delay on there, so that the door stays open for a minute or so after the fan goes off. This may prevent the system from cycling over and over gain.

lunarhighway 06-30-2008 09:29 AM

that shouldn't be to difucult, with some sort of timer or even a capacitor that keeps up the right relays.

i hope i'll be able to get the mechanical part working reliable seen so i can see what the actual control needs are...

also i think the fan might already have some delay build in, wich is why i'd like to use it as a trigger rather than devise my own temperature measurement setup, useing existing car systems is more reliable and easier i think.

Keen 06-30-2008 10:02 AM

You might be right. The fan may already have a delay built in. I agree that it is wise to use the car's thermometer rather than hooking up your own.

dremd 06-30-2008 10:54 AM

Very cool

Some 20's cars had thermostatic grills that worked just like that vent. Anybody remember which ones? I thought the idea was cool, but dumb until just now; now I'm in the Awesome camp.

wizardwizard 06-30-2008 11:06 AM

i had an idea to get a more powerfull radiator fan and hook it to a tube like the air tube on a laundry dryer and put the end of it under the car, under or just past the dash board, to reduce drag. the tube from the dryer looks like an ok size tube to use, big enough to for large ammounts of air to pass thru and flexible enough to easilly route in the right direction,
by taking the hot radiator air and pushing it under the dash under the car, you stop it from ending up stuck under the hood like a parachute, also
it blows the hot air back onto to engine and by rerouting it under that stuff, the engine will end up running cooler without its own heat being sucked out and blown right back in its face, this could cause trouble if the hot air was to cause a fire under the vehicle or heat the gas tank, so, the air can be re routed all the way to the rear end by the mufler.
i think they use this to reduce drag in airplanes where the jet engine is in the back, it sucks air from the front to burn which reduces drag.
the idea is to counter the drag by manipulating the air flows, possibly to the extent that the drag is canceled out, its eazier and cheaper have a fan move the air for your car than for your car's front end to move the air

im not saying i think cars should have aero lift in them, but, it is about time that we had flying cars.
my car can go 200 miles on a tank an airplane can fly across the world, but, now even that number is not where it should be with all the rediculas engeneering flaws these things have. but we know the point is that the car can get better fuel economy and so can an airplane.

i had an idea to put an adjustable spoiler to add intense downforce during turns and add lift when accelerating, this could be worked into the gas pedal, when you hit the gas, it removes all downforce and maybe adds a bit of lift, when you take the foot off the gas, it pulls the spoiler back to heavy downforce mode for turning.... this wont work with the "hybrids", prius or with regenerative braking

i think that by trying to cancel the drag you could easily get +20% mpg

lunarhighway 06-30-2008 11:17 AM


some interesting ideas. i think some bmw have a duct behind the radiator that takes the radiator air out along a smooth path, some racecars also do think trough vents in the hood.

as for the lift-downforce spoiler... lift is generally not very good in cars... yes it virtually makes the car lighter, but the first effect of this is loss of traction... my car fequently spins its front wheels in the wet, when you have to merg into a bussy street from's never excessive but under these situations you want some grip as well for safety.

perhaps lift can work for dedicated hypermilers but in general it will make a car unsafe.
(and once you's ok with removeing some safety a light 80's style car without airbags and side impact beems will save more weight than the lift would compensate for)

so personally i'm not to fond of the idea. the theory is good, but there's side effects you don't want... perhaps it could have some use on tracked vehicles like trains..

i_am_socket 06-30-2008 12:02 PM

I like the active grill block ideas. I thought of a similar setup but using a spring and electromagnet for simplicity.

Re: flying cars - I know people who can't walk in a straight line, and I see a lot of drivers who can't handle traveling in 3 dimensions, let alone adding in a 4th; and let's not get into the care and maintenance of these vehicles. I'm rather happy that we don't have 85 year old cataract and arthritis patients going around in missiles. I'd much prefer to see less travel being necessary than giving people a much more efficient way to kill themselves.

Shawn D. 07-01-2008 01:29 PM

Active grille blocks have existed on big rigs for a while -- ever notice the venetian-blind-like things moving out front? ;)

A Walkman or computer fan motor will be way too weak for this purpose. I'd suggest finding a gearmotor or contacting a local robot hobby group to get some of their castoffs. In fact, they'd probably find the project intriguing and would help with the fabrication and control scheme.

Check out All Electronics for a good selection.

Cd 07-01-2008 10:08 PM

holyPaulie : I see youv'e posted to this forum too. ( and Gasavers )
I was hoping you would.
I think it's a fantastic idea.
The more people we can get to pitch in ideas like this the better.

Wizardwizard : I didn't read all of your post...but... it's really longwinded.

Maybe shorten it next time and ...stay on topic ? ;)

conradpdx 10-05-2008 02:36 AM


Originally Posted by Shawn D. (Post 40000)
Active grille blocks have existed on big rigs for a while -- ever notice the venetian-blind-like things moving out front.

I want a smaller one for my rig. I'm hoping to start modding my pickup this spring and have wanted to do a grill block. However, since I'm often moving 1/2 ton+ around I need some kind of manual override for opening the whole thing up when needed (Oregon if anything is hilly). I was thinking of giving up on grill blocks for me to begin with...perhaps a trip to freightliner is in order.

orange4boy 10-13-2008 02:17 AM

Heat actuated flaps
VW beetles and most of the air cooled VWs have a small bi-metal bellows which by way of a pushrod, open the flaps under the fan shroud. I kept a spare one for years hoping to use it somewhere. That could be set up for this kind of use with a long pushrod.

BTW VW beetles have no front grille but use belted fan to cool the engine. Tell that to anyone worried about grille blocks.

i_am_socket 10-13-2008 10:31 AM

OT: I love how the pic in the OP has changed to lumber. Sure makes a fine grill-block, but I don't know how active it will be ;)

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