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Re: electric fan question
[Re: 68 R/T]
#863366
11/26/10 01:07 AM
11/26/10 01:07 AM
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Joined: Apr 2010
Posts: 10,570
Sunny South Florida
Golden-Arm
I Live Here
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I Live Here
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Posts: 10,570
Sunny South Florida
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you cant "flip the blade over", as it will still be facing the same way.( if it pushes air spinning clockwise, flipping the blade will still push air, spinning clockwise) you can change the wires, and it will change direction. i just reversed the paired set of flex-a-lites on my truck, as they were pulling, and not pushing. drove 54 hours non stop, and had no issues. after talking to the flex-a-lite customer service guys, they said it's no problem. i cant imagine your fan, is any different. for $34.00, i'd try it. mine cost $400.00 and i took the gamble..... 
"When Tyranny Becomes Law, Rebellion Becomes Duty"
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Re: electric fan question
[Re: Golden-Arm]
#863368
11/26/10 01:37 AM
11/26/10 01:37 AM
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Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
70Cuda383
Too Many Posts
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Too Many Posts
Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
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Quote:
you cant "flip the blade over", as it will still be facing the same way.( if it pushes air spinning clockwise, flipping the blade will still push air, spinning clockwise) you can change the wires, and it will change direction. i just reversed the paired set of flex-a-lites on my truck, as they were pulling, and not pushing. drove 54 hours non stop, and had no issues. after talking to the flex-a-lite customer service guys, they said it's no problem. i cant imagine your fan, is any different. for $34.00, i'd try it. mine cost $400.00 and i took the gamble.....
not quite true. depends on the blade design.
if it's an S-curved blade, simply spinning it in reverse doesn't really do the same thing as flipping the blade over, due to pitch of the blade in relation to the curve of the blade.
now, if it's a straight bladed fan, sure, simply wiring it backwards will work fine.
**Photobucket sucks**
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Re: electric fan question
[Re: 70Cuda383]
#863369
11/26/10 02:03 AM
11/26/10 02:03 AM
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Joined: Oct 2010
Posts: 606
Montana
Yancy Derringer
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mopar
Joined: Oct 2010
Posts: 606
Montana
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Quote:
If it's an S-curved blade,...............
now, if it's a straight bladed fan, sure, simply wiring it backwards will work fine.
This is not true, either. Most fan blades I've seen were only designed for one direction. If you look at them, they should be "cupped" sorta like a scoop Pushing air off the backside, or convex side, will result in much less air.
I used to service HVAC................
Here's an example:
See the cup of the uppermost blade? This blade is ONLY designed to go ccw as in this picture, to suck air back. If you were to rotate that blade in the opposite direction, it would move little air. Now maybe if you could remove the blade and physically turn it around.....
http://www.truckinweb.com/tech/engine/0809tr_ford_f150_radiator_fan_install/photo_16.html
Last edited by Yancy Derringer; 11/26/10 02:10 AM.
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Re: electric fan question
[Re: 70Cuda383]
#863370
11/26/10 02:10 AM
11/26/10 02:10 AM
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Joined: Apr 2010
Posts: 10,570
Sunny South Florida
Golden-Arm
I Live Here
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I Live Here
Joined: Apr 2010
Posts: 10,570
Sunny South Florida
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these fans, regardless of which way they are facing (front side up, or back side up) move the air, in the same direction, when spun in the same direction. they wont mount reversed, due to the mounting parts, cast into the blades, but they will flip over, and can be spun. being dc motors, i can reverse the flow of current in them (2 wire set up) and change directions. these blades seem to look like "S" shaped blades, but the air moves the same way, using same rotation. even though they are "S" shaped, they still have a leading edge, a pitch, and a trailing edge, and reversing the physical orientation of the fan itself, still produces the leading edge and trailing edge, in the same orientation. (on this fan, anyways)here's the fan unit, and then the fan blade, removed (yeah, i was bored, and pulled my fan apart) if you look closely at the fanblade, and imagine it rotating clockwise, it will move the air off the desk, and towards the camera. in the second pic of the fanblade, the fan is flipped over, and the "S" is reversed. but looking at the blades, and imagine it spinning clockwise, it will still lift air from the desk, and move it towrds the camera. the leading/trailing edges, dont change orientation, even though the entire fan has.   
"When Tyranny Becomes Law, Rebellion Becomes Duty"
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Re: electric fan question
[Re: Golden-Arm]
#863373
11/26/10 06:15 PM
11/26/10 06:15 PM
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Joined: Oct 2010
Posts: 606
Montana
Yancy Derringer
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Montana
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Quote:
if you look. at the fanblade, ... rotating clockwise, it will move the air off the desk,...
in the second pic of the fanblade, the fan is flipped over, .. spinning clockwise, it will still lift air from the desk,
This was an EXCELLENT dissertation on HOW FAN BLADES DO NOT WORK
If you look at the top blade, spinning cw the CONVEX side of the blade is pushing the pair off the desk and this is VERY inefficient, and the blade will move very LITTLE air
If you look at the bottom blade, flipped over, spinning CW, you will see that the CONCAVE side of the fan is biting in, throwing air up and out just like quickly moving a curved snow shovel. THIS IS IN THE ONLY CONDITION this blade is made to be operated.
Reversing it as you described in the upper picture results in MUCH less airflow.
One last time----I used to service HVAC, and I used to know a little about airflow and blowers
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Re: electric fan question
[Re: jcastle1]
#863375
11/27/10 12:50 AM
11/27/10 12:50 AM
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Joined: Jan 2003
Posts: 28,071
Irving, TX
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Senior Management
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Senior Management
Joined: Jan 2003
Posts: 28,071
Irving, TX
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Let's look at the fan in question.  Rated at 1250cfm CFM: Pull-1900-2300 Dimensions: 14" x 17.7" x 3.2" Amps: 5.5 - 6.5 Volts: 12 The fan has blades that are essentially flat, not scooped like the S-blade fans. It's built to be reversible. It will blow equally well in either direction. It has a 7 amp draw. THAT is the concern. It has no power. See the 1250 cfm rating? Feel free to laugh. It will move all kinds of air until you put a radiator on one side. That's a big restriction for the dinky fan motor to overcome. Will it help cool in low speed traffic or at a stop? Maybe. If your current fan draws more air than this thing, you will not see much of a change. In fact, it could hurt the air flow if you're moving a lot more air. Should your cooling system not draw that much air it will help until the fan reaches it's capacity. If you leave it on when cruising down the highway, it will most certainly cause higher temps. That motor will not be able to keep up with 60 mph air flow. That means it will become an obstruction and essentially a wind powered generator. You're looking at a $20 fan. Don't expect $200 fan performance. It's effectiveness will be directly related to the amount of air your system currently moves.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon
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Re: electric fan question
[Re: jcastle1]
#863376
11/27/10 12:53 AM
11/27/10 12:53 AM
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Joined: Oct 2010
Posts: 606
Montana
Yancy Derringer
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Montana
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Quote:
so now I'm totally confused.
Can i use the Mancini fan as a pusher or not?
If so,what do I need to do?
Car runs around 190 and will creep up to 195-200 if waiting in traffic for a while.
John
My answer is, "post a picture" (or link) to the exact fan. Unless the blades are shaped like a slab of wood (no "airplane wing" shape) you cannot reverse them without a loss of airflow.
So you need to be able to physically remount the blade on the motor, and the motor needs to be reversible.
To sum this all up, if the fan is designed to be mounted behind the rad, the fan blade must be in the same respective orientation in front of the rad as it was in the rear (physically flipped) and the motor running in the opposite direction.
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Re: electric fan question
[Re: Yancy Derringer]
#863377
11/27/10 01:47 AM
11/27/10 01:47 AM
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Joined: Apr 2010
Posts: 10,570
Sunny South Florida
Golden-Arm
I Live Here
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I Live Here
Joined: Apr 2010
Posts: 10,570
Sunny South Florida
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yeah, i guess youre right. silly me, taking the words of the american made manufacturer, regarding the reversibility of their product. i'll be sure to note them, on monday, and inform them of your advice. (somehow, i imagined the company that designs, and manufactures their products, might actually be knowledgeable about them...)
"When Tyranny Becomes Law, Rebellion Becomes Duty"
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Re: electric fan question
[Re: Golden-Arm]
#863378
11/27/10 02:26 AM
11/27/10 02:26 AM
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Joined: Oct 2010
Posts: 606
Montana
Yancy Derringer
mopar
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mopar
Joined: Oct 2010
Posts: 606
Montana
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Quote:
yeah, i guess youre right. silly me, taking the words of the american made manufacturer, regarding the reversibility of their product. i'll be sure to note them, on monday, and inform them of your advice. (somehow, i imagined the company that designs, and manufactures their products, might actually be knowledgeable about them...)
I actually went to the flex-a-lite website and downloaded a couple of their instruction booklets.
The two that I happened to pick (marked reversible) SHOW in the instructions that you must PHYSICALLY turn the blades around. Interestingly enough, they do NOT show that you must also reverse the motor.
So NOW what do ya think of "those who make them?"
Someone above mentioned a fan with "flat" blades. These are the ONLY blade designs that are reversible in this sense, and I can guarantee you that they are a pretty poor design.
There is no easy way out of this. REAL fans that move REAL air draw a lot of current, and use a lot of horsepower. There is a REASON that belt driven fans used to be big, have lots of blades, and use up horsepower.
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Re: electric fan question
[Re: Yancy Derringer]
#863379
11/27/10 02:56 AM
11/27/10 02:56 AM
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Joined: Jan 2003
Posts: 28,071
Irving, TX
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Senior Management
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Irving, TX
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I've been down this road and I agree with Yancy 100%.
All you have to do is look at the stinkin thing and do a wee bit of thinking.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon
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