I think what happens with a pusher is that the air backs up and goes around the edges of the blades instead of through the radiator. Obviously it's going to take the path of least resistance. A puller by virtue of the location I believe to be more efficient and all the testing that I've done with cars over the years...granted it wasn't very scientific...but by observation I always ran cooler with a puller. You can use either one...if the pusher works for you that's great, but I've always been on the hairy edge with my drag cars and always had to use the puller.
Oh and Simon...the air is always going the same direction with the blades. It doesn't make them turn backwards. The blades may slow the air going through the radiator down at speed, but more likely the air will speed up the fan instead. I used to have an led hooked up to one of my fans years ago and when I was traveling at speed with the fan off the light would light up as the fan was creating electricity by spinning.
But the air will hit the same obstruction on the other side of the radiator causing it to back up or at least slow down.
Hmm...it's actually creating a vacuum in front of the fan between the radiator and the fan blades. To equalize that vacuum pulls through the radiator. When pushing it just piles up and bleeds out the edges. I understand it's 6 of one and half a dozen of another, but even the manufacturers of the fans state that it's more efficient to pull the air through.
great conversation and even better pro's/con's. Its fun to have a nice debate on a topic without all the mud slinging. Thanks its been fun reading.
OK. but if mounted in front, its building up pressure between the fan blades and radiator pushing the air through. I dont see it piling up because there is no obstructions once it leaves the blades.
what i meant was the shape of the blades... you get one either as a pusher or a puller, because of the "airfoil" of the blade... it is simple aerodynamics of airfoils.. let me explain. when the air hits the "outside" of the blade and if it is shaped as a PUSHER, the air flow will help the blade turn, if you take a PULLER and put it as a PUSHER, the shape of the blade is the other way, so if you put it as a PUSHER, the air pushing against the "air foil" will cause the blade to have resistance, and therefore wont be as efficient.. it is the same principle in aircraft engines.. you CANNOT take a pusher propeller and use it as a puller.. the airfoil is made directly into the airfoil of the blade for its intended purpose.. yes a puller will work as a pusher ( when talking about radiator fans), but if you read my post i said it wont be as efficient i hope this clarifies a little.. i should have stated this before.. sorry for not being as detailed as i should have been
There are some factory pushers fans out there. The first that come to mind are some GM front wheel drive cars - think of the GM fans that don't have a shroud.
I know you made your choice already but here is an article about finding a electric puller fan in a junk yard. http://www.fordmuscle.com/archives/2003/02/electricfan/index.php I hope it helps. I just bought one last week end and will be putting it in my car in a month or two. Joe
Hey Mavaholic, the entire surface of the radiator is an obstruction. All of the fins create restriction. Either way, like I said originally...whatever works in your particular application. I'm just throwing out my empirical data and the experiences I've had. The theories are just my thoughts on why it works that way.
Hey Simon, you're absolutely right about the shape of the airfoil. The way I read your post it sounded like the blades would try and reverse direction. That's what I was referring to.
Not true. First of all most airplane props are pullers. I've been flying RC model airplanes since the 70s and have built several rear mounted engine pushers. All you have to do is mount the prop backwards and it works great.
