OT: Car radiator fans and HP

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On Wed, 27 Aug 2014 16:15:24 -0400, snipped-for-privacy@aol.com wrote:

Just about everything went electric when they went to front wheel drive. That was over 30 years ago.
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On Tuesday, September 2, 2014 5:42:28 PM UTC-4, Ashton Crusher wrote:

Just about everything still leaves a lot: BMW, MB, Volkswagen, Audi cars and the huge number of SUVs, vans, pickups, from all manufacturers. They mostly used mechanical fans well into the 2000's. Some of those only went to electric fans less than a decade ago. BMW with the very popular X5 for example, only went electric in 2006,
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On Wed, 27 Aug 2014 05:52:05 -0700 (PDT), trader_4

The typical fan-belt V-belt of years ago couldn't transmit 15HP in a fit, and it had to drive the water pump too! (The belt was only rated at about 1HP or so.)
Back in the 1960's my father used an un-guarded 4-bladed auto fan on an 1/3 HP electric motor to blow away cast iron dust on a head planer. The 1/3 HP motor had no trouble in driving the 4-bladed fan and it blew an absolute gale!
These sorts of silly ideas are un-stoppable. "Top Gear" has often demonstrated that an awful lot of "improvements" make the car perform worse, but it won't ever stop people thinking otherwise! :)
Ross
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Many lawn mowers rated for 20 hp or so seem to drive the mower or run the blades just fine. I don't knowhow much different they are than the car belt.
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On Wed, 27 Aug 2014 18:32:22 -0400, "Ralph Mowery"

That makes me wonder just how many HP that mower actually is. I think a belt can do more than 1HP but I also see real 5HP air compressors (240v 30a) with 2 belts.
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Probably less than those numbers. A while back some were called out for over rating the motors.
Air compressors are often started up under a load and take a lot of power to start turning due to the pressure in the tank. Lawn mowers and fans don't have that much of a problem getting going.
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I can't remember seeing a car with a belt driven fan (in recent years)! I h ave a 20yr old Saturn and a 13yr old Buick...they both have electric motors that are only on if the car idles for a long time. Personally, you are not the kind of person that can let things go...you like to beat it to death.. .you need another hobby or possibly a woman/man.
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wrote:

Back in trade school in the early seventies we had a dyno - at4500 RPM a Slant Six made 11 more HP to the rear wheels with the fan removed (and a big box fan providing wind-tunnel-like airflow to cool the rad)That was a rigid steel fan with something like 5 blades. What you need to remember about the belt is it just has to handle TORQUE. 15 ft lbs at 4000 rpm is 11.5 HP, and it is a VERY wimpy fan belt that will not transmit 15 ft lbs of torque. At 2000 RPM that is only 5.7 hp
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On Wednesday, August 27, 2014 9:35:09 PM UTC-4, snipped-for-privacy@snyder.on.ca wrote:

First question is, did that fan have a hydraulic clutch? If not, then it's forced to run a full engine speed, with no slip, which makes a huge difference.
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On Wed, 27 Aug 2014 21:35:09 -0400, snipped-for-privacy@snyder.on.ca wrote:

Just did a little bit of investigating, and assuming 4000 cfm (heavy duty cooling fans will often excede this), and 14" static head at 80% efficiency, the fan WILL draw 11 HP according to the calculator at http://www.freecalc.com/fansfram.htm
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On Wednesday, August 27, 2014 10:08:02 PM UTC-4, snipped-for-privacy@snyder.on.ca wrote:

Why 4000 CFM? The electric fans that the gear heads are using to replace mechanical fans are generally about half that. So, what basis is there to use 4000 CFM for a typical auto fan? Where did the 14" static pressure come from? Seems extremely high, probably an order of magnitude off for a fan/radiator combo. It's not driving air through some long duct work. And also at 60MPH, air is being rammed into the fan by the movement of the car, which would drastically reduce the HP required to turn it. As it would in your static car test.
Here is what a 5HP fan looks like:
http://www.grainger.com/product/DAYTON-Heavy-Duty-Fan-7M8F2?cm_mmc=PJX-_-GraingerBrand-_-43737-_-Generic
4 ft blades, moves 30,000 to 40,000 CFM. I don't see how you reconcile that to a small plastic car fan with a hydraulic clutch using 5 to 15hp.
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On Wed, 27 Aug 2014 19:58:28 -0400, "Ralph Mowery"

I am not talking about those homeowner models, I mean a real commercial air compressor. (hence saying 240v @ 30a )
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On Wed, 27 Aug 2014 21:30:49 GMT, snipped-for-privacy@invalid.invalid (RMD) wrote:

some info here.. http://www.flex-a-lite-blog.com/2010/02/27/which-is-better-an-electric-or-belt-driven-fan/
Also some interesting test results here http://www.carnut.com/ramblin/dyno.html
If I'm reading his write up correctly, at 4500 rpm a bolt on super HD mechanical fan can take 40 HP !!! A flex fan takes only 20 at 4500 rpm. On presumes that at slower rpm the HP drain is much less and goes down/up as the square of speed. So I'd presume at 2250 rpm the respective draws would be 10 hp and 5 hp, which seems in line with "normal" engine speeds and what people tend to think these fans draw in "typical" use.
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On Saturday, August 30, 2014 9:50:03 PM UTC-4, Ashton Crusher wrote:

That was a good find. It's the first actual real test data that I've seen. Some observations:
The HP required actually varies by the cube of the speed, not the square. So how fast the fan is actually spinning is critical. From what there is in the test description, it appears that only one of the fans had a clutch. He describes it as a Yearwood 9189N thermo clutch, I couldn't find anything on that. So, we don't know is it a relatively recent hydraulic clutch or an old design? I would think newer clutches might attempt to limit the top speed of the fan? He also says it was behaving erratically, IDK what effect that had on the test. But you can see the effect a clutch and what it does can have on the results. The clutch reduced the HP used when cold to 19hp from 35hp when it was hot and presumably fully locked up. If a more modern, better clutch also limited the high end, so the fan can't run full speed at 4500, that would make a big difference. I haven't seen anything definitive on what clutches used in later year cars actually do, if anything to limit speed. Everyone seems to agree that they have a lot of slip when cold, less slip when hot. How they perform versus speed, I couldn't find anything.
Also a major difference in this test versus the real world, is this was stationary. A car doing 2500 RPMs would typically be cruising at highway speeds. In that case, air is being forced into the fan. I would think it would act like a windmill. Windmills don't need power to run, they generate power.
I still don't know what to make of this. Most of us have an idea of what 20 or 40hp is, what a motor that size is, what it can do, etc. It just doesn't compute to me that it could take anywhere near that much to run an auto fan with a decent hydraulic clutch. It also doesn't compute that auto makers have been struggling for decades to get mileage up to meet CAFE standards and to make their cars more competitive. Switching to an electric fan is almost trivial. It's hard to believe that you had this huge, low hanging fruit there and it's only in the last decade or so that you've seen a big move to electric fans. Case in point, the discussion that involved this was BMW X5s, they used a mechanical plastic fan with a hydraulic clutch until 2008.
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On 8/31/2014 9:01 AM, trader_4 wrote:

Doubt automakers are doing much research on better fan clutches. Aside from your example, mot are using electric for the past 30 years. Every car with FWD and transverse mounted engine uses electric. I had an '83 Mercedes 300D and it had electric.
If a fan can use 40 hp, it is no wonder the used air cooling for the 36 HP Volkswagen. Oh, wait, it had a blower whee.l
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On Sunday, August 31, 2014 9:45:38 AM UTC-4, Ed Pawlowski wrote:

I doubt they are today either. But you would think in the 80's through 2000 when they were still widely used, if the fan was using 20 -40hp, they would have. And it's still an issue today, some SUVs, many pickup trucks apparently still use them.
This 20/40hp thing is just astonishing. The HP to keep a car or SUV going at 55MPH is what? Maybe 50hp? I just find it impossible to believe that those fans were/are sucking up 10/20/40 hp. If they were you could have gotten ~2x increase in fuel economy in 1980 by going to electric. That's HUGE. Instead the transition took decades, while they were squeezing .1mpg out of small stuff, desperately shaving a pound off here and there?
Aside

You recollection is different than mine. I recall cars replacing mechanical fans with electric during the 90s. With many cars, those probably not the majority, still using them in the early 2000s.
Every

You might want to check your memory on that....
http://www.autopartswarehouse.com/search/?searchType=global&N=0&Ntt n+Clutch&tahsearch=1&tahgroup=UGS&tahrank355930&tahscore=5.50773
They list a fan clutch for the 83 300D. Are you confusing the auxilliary electric fan with the mechanical one? That car had both.
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On 8/31/2014 12:26 PM, trader_4 wrote:

What memory? I remembered the electric since it had to be replaced.
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On Sunday, August 31, 2014 5:23:59 PM UTC-4, Ed Pawlowski wrote:

OK, let's start with the basics. There is no 1983 Mercedes 300. They only made the 300 series in diesels, they were the 300D, 300CD, 300SD, 300TD. Which car did you have? And all of those used the same 5 cyl diesel engine with a mechanical fan and hydraulic clutch. Did you look at the parts link? I ask again, are you confusing the auxilliary elec fan with the primary mechanical cooling fan? Those cars had both.
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Talking about air cooling - the fan on a Corvair, which is actually a centrifugal blower, not a fan, consumes 14 HP at 4000 RPM pushing about 1450CFM at 7" water pressure through the cooling fins. The horsepower goes up significantly when the speed is increased to 4800 RPM and higher.
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On 8/31/2014 3:42 PM, snipped-for-privacy@snyder.on.ca wrote:

I had a '62 Corvir Monza and it would have been nice to have that 14 HP at times. Fun car to drive though.
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