Beginner question about fans
 

hey guys,

I am still trying to learn all about mopars and car basics to work on a 73 project I have. I was wondering if someone could explain or post a link to a good explanation for the difference between a belt driven fan and electric? How do the electric ones mount? are there ones worth getting on a budget? Thanks.

Electric fans run from a thermostat or switch.. belt driven fans run off the belt.

If you sit and idle a lot belt driven fans can struggle to keep things cool since they don't spin as fast and little air is moving through the radiator. You could run both, use an electric as a pusher on the front, if you'll be in traffic a lot. Electric fans sometimes mount through the radiator, sometimes to the surround, either way they're very simple.

I'm not sure if they make low budget electric setups that could keep things cool on their own.

belt driven is when the crank runs the fan.. electric has its own direct drive motor that runs the fan. they mount behind the radiator on the radiator suport. if its a pull style. push style mounts in front of the radiator. mounting them is by drilling hole to where ever you can run a bolt thru. id stick with a belt driven style. hope i helped a lil bit

defintely helped. I will stick with belt driven. Thanks!

1966sportfury - The electric fans can be mounted to the radiator whether it is a pull or push fan.

timmymacnj - Electric fans are far better than mechanical fans (belt driven fans) any day of the week. They can pull/push more air than a mechanical fan can and some even use less space.

On the vehicles that most of us drive on here, I would not mount a fan to the front of the radiator because as you are driving, the air that is being forced onto the fan will cause the fan blades to flatten out and not allow the fan to do it's job. Installing an electric fan should be done on the back side of the radiator (between the radiator and motor). This will allow you to mount a tranny cooler or A/C condensor infront of the radiator (where they belong). This will also allow the air that is being forced through the radiator to push the blades in a way that they pull more air through the radiator and over the motor dooing a much better job of cooling the motor.

Also, you can mount the fan right to the radiator itself with some some thin long screws, fender washers, and wingnuts (that is what I did when installing a 16" electric fan on my J10 and never had an issue). The only time that you would want to install an electric fan infront of a radiator is if you are building a four wheeling rig that will never see high speeds (abouve 10-15MPH).

Timmy -

IMHO, that's probably a good idea. Since you're on a budget, the KISS principle applies. A good high flow flex fan (with a good radiator, of course) will do the job simply and efficiently with minimal effort and expense. Just remember that fan spacing can mean the difference between a well cooled system and a so-so system. Mine is currently spaced about 1" away from the radiator (within the shroud).

Archer

Electric fans are the only way to go, cleans up the look of the engine, most cool better then the OE and 1 less thing the motor has to waste power turning - I like to mount them on the push side just for the fact going down the road at any speed will make it turn, you dont even have to switch it on unless your in traffic .... my 2 cents

scamp -

I'll add one more thing in addition to being one less thing for the motor to push. it's also one more thing that can fail. Bad switch/thermostat, faulty wire (any wire), failing or dead motor. With a good flex fan, sure you're loosing a little hp, but unless the belt blows, you're pretty safe. And frankly, I don't want to be bothered turning it on or off.

On a race car fine, on a street driven car - I'll pass.

We're talking about a new guy on a budget here.

Archer

[quote=SCAMP TRAMP I like to mount them on the push side just for the fact going down the road at any speed will make it turn, you dont even have to switch it on unless your in traffic .... my 2 cents[/quote]

like it says I never even have to turn it on it spins by it self lol so go with what works and that always has for me :)

scamp -

Sorry to belabor the point, but

If it spins by itself, then by a basic law of Physics, it's doing no more than the incoming air flow would do, meaning it doesn't even have to be there ... and when you're not moving, it's not moving fast enough to push enough air to matter ;)

Archer

That'd actually slow the flow a little bit, making things worse, wouldn't it?

Mount to the front for cars with lots of in-town driving, mount behind for highway drivers?

lol grab any fan and stick it out the window going down the road at any speed and tell me the pressure is the same behind that fan as the open wind, the curve in the blades make pressure, just like a prop plane that needs that air pressure to start the thing rolling to a point the flow of pressure over the wing causes lift - if fans had flat blades I would agree with the physics but they dont so.....

Next thing you'll try and tell me is I can't run the alternator off the drive shaft lmao

Alot to read here (too much science) so I wont say much but for my 2 cents I would go belt driven fan with a fan clutch. Assuming you got the room, cheapest, easiest, economical.

Scott-- (your friendly neighborhood sweeperking)

Hey nothing wrong with belt drive at all but like ya said some times space is a problem & some motors you just don't put an ugly fan on.....

http://i882.photobucket.com/albums/a...66/hemi540.jpg

scamp -

Your flight analogy is pretty far off base. The "prop" provides forward motion, the airfoil (wings) provide lift. That lift is cased by increased pressure below the wing AND decreased pressure above. The "prop" has minimal effect on that. Therefore your point should only refer to the wing and not the prop. In regards to the wing the same amount of air in front of the airfoil must be present behind it. The rates and pressures above and below are different - that's all.

In the case of a fan, you can't have more air blowing out than is coming in. Physically impossible. In effect, with regards to the speed of the fan, it really doesn't matter if the fan is moving the air or the air is moving the fan.

Back to the OP's question.

Electric fans have the benefits of not requiring direct engine HP, (however, electricity is still required to operate the fan, so in theory, the alternator is working harder ...) and that it can be operating at full speed even when the engine isn't.

The benefits to a belt driven fan are A. Cheaper. B. (a lot) fewer things to go wrong.

Archer

Hey not trying to call you wrong or anything, but the blades spinning via wind will reduce the air flow through your rad due to the conversion of forward energy into horizonal into the fans motor. Unless you've got a perfectly efficient and frictionless fan, in which case I'd take one for my perpetual motion machine...

The reason there is more force against a blade held out a window is because it's blocking more air, which is converted into that spin motion.

I'm very green with this hobby but not basic science.

All that said, I'm not knocking electric setups, mind you... And I mean no offense. As others said if you never turn it on it doesn't need to be there.

Well I guess my point is missed and its by prefrence what you run, but personally I have never had a problem and very rarely have to turn it on - I just go with what I have tried & tested over the years not with what Newton says on the matter, anyway the blower would inhale the fan off the front of the motor ..... and being as its winter in Toronto who needs a fan, hook the heater core back up lol !!!

lol, very true, it's still cold down here too, freeze notice tonight, in may...

be sure to start a build thread man, I can't wait to see your project come together, looks like a beast!

OP - sorry we are treading a little off topic ;)

lol will do .....

Think I have it narrowed down to this
http://cgi.ebay.com/ebaymotors/1968-...item1c12327e70

What do you guys think?

Very sweet set up you'll have no problem keeping the motor cool with that