Fan Clutch

Topic: Fan Clutch (Read 10063 times) previous topic - next topic

Reply #15 – June 21, 2015, 01:47:08 AM

Lets pretend we have a single 17" fan blade. We only need the air to move about 25mph through the radiator to adequately cool it, in virtually any situation. A 10-15mph breeze isn't uncommon, and your car almost never sits. It really, really shouldn't use much of any power to cool down a stock setup.

I am really, really tempted to guy my taurus fan shroud, replace it with a $20 radio controlled brushless motor, throw a $15 controller at it, gut the thermal probe or find one with a 5v reference and then just hook that up to the "throttle" input to the speed control, throw a 16 or 17" prop on it and forget about it.

I understand what a peak load is, and i was actually really worried about being able to use a fan controller that would be adequate. I planned on sourcing a volvo relay setup but just couldn't find any right away and figured id try the $20 fan controller.

I can guarantee that the fan doesn't use anywhere near 100amp on start up. I tested it with a 160 amp peak, 120 amp continuous rated battery and a 100 amp volt/watt meter. It pulled 24 amps on high speed from a dead stop. If i ran the low speed first, it would hit 11, settle down to 8 amps, then when i switched it over to high speed it hit 16 amps.

If you really were getting 100 amp spikes every time you turned your fan on, it would chew up a 8 gauge wire. So why did ford use a 6 gauge wire on a 130 amp alt, then use 12 and 10 gauge wire for the fan motor?

My opinion, the guys volt meter in the video couldn't handle the instant load of the fan, mixed it out and then got an artificially high reading. Look at how ridiculously small that wire is. Looks like he pulled the end off of an alligator clip.

In my opinion, he is heating up the wire, increasing the resistance of the wire and raising both amp load and dropping voltage, which would cause a high spiked reading until the fan reached a certain speed, and then eventually dropping amprage as the fan started to run up to speed.

When i see a digital read out, which won't spike higher then the actual reading and at least a 10 gauge wire, then yeah, id say the guy was onto something.

Playing with just different sized extension cables that I've built for my model airplanes can more then double the amperage of the system when you go to an undersized cable. When you increase the size of the cable, your amp draw goes down, as do the peak loads and voltage drops. The ideal setup is when your voltage no longer sags any more then a smaller cable. Then you will see virtually no benefit from a larger sized wire.

One thing that is quite common on model airplanes is trying to hit the highest spiked reading so you can brag about how much power your system uses.

Fan Clutch

Reply #16 – June 21, 2015, 02:10:10 AM

That meter is doing exactly what it's supposed to..... Measure in-rush....

Fan Clutch

Reply #17 – June 21, 2015, 02:49:14 AM

And ill bet the voltage drops to near zero when it does so.

Lets pretend you have a 200 watt fan. Voltage x amperage= watts.
So 200 watts / 12 volts gives you 16.66 amps. Now lets say the fan is still drawing 200 watts and voltage drops to 6 volts, now your amprage is gonna be 33 amps. So now lets say voltage drops to 2 volts, now you have 100 amps, pegging the meter. As the fan spins up, your amprage drops and so your voltage raises, even though the fan is using about thru same amount of power.

The only way i can see getting an accurate reading with so small of a wire is if the shunt is running to the main power feed for the fan, and the tiny wire we see hitting the terminal is only tripping a relay. The starter on your car doesn't use 100 amps, why would a tiny fan that's barely moving air do the same?

Fan Clutch

Reply #18 – June 21, 2015, 03:05:45 AM

And ill bet the voltage drops to near zero when it does so.

Lets pretend you have a 200 watt fan. Voltage x amperage= watts.
So 200 watts / 12 volts gives you 16.66 amps. Now lets say the fan is still drawing 200 watts and voltage drops to 6 volts, now your amprage is gonna be 33 amps. So now lets say voltage drops to 2 volts, now you have 100 amps, pegging the meter. As the fan spins up, your amprage drops and so your voltage raises, even though the fan is using about thru same amount of power.

The only way i can see getting an accurate reading with so small of a wire is if the shut is running to the main power feed for the fan, and the tiny wire we see hitting the terminal is only tripping a relay. The starter on your car doesn't use 100 amps, why would a tiny fan that's barely moving air do the same?

Fan Clutch

Reply #19 – June 21, 2015, 03:09:34 AM

Im an idiot, he is triggering it with the ac, through a relay.

I still have a hard time believing it could actually pull 100 amps, but then again, my constant load numbers are half on my double speed what his are and i still burned up a 35 amp controller, without burning up either 20 amp fuse on high and low sides.

Fan Clutch

Reply #20 – June 21, 2015, 08:45:24 AM

car makers use an insulation rated for temps in Celsius pulled from tables that I have not ever seen.
they are not req'd to follow any NFPA standards so who knows.
using the 90degC table as a ref, the 6awg is good up to 105Amps,, #10 is good to 55amps.
using multiple thin hairs of copper called "flex" or "FX" can get you even more amperage vs solid think strands twisted around in one jacket called "stranded" or "STR". OEM alternator wiring is STR wiring including the big yellow or browns entering the ignition switch. the battery cable + or - side would be considered FX wiring.

one day I would like to see the same test done on the brushless motors you mention,, that would be interesting to compare. Tests like these seem like there isn't any way around using buttstuffog equipment though and that stuff is getting harder and harder to find each and everyday.

if they had to follow nfpa, then they would have to follow ambient temperature correction factors.
example, an Electrician must de-rate a wires capability by 58% if it is going to be inside a space that it is known that space will be from 141-158degF.

Fan Clutch

Reply #21 – June 21, 2015, 05:12:56 PM

Quote from: jcassity;449065

one day I would like to see the same test done on the brushless motors you mention,, that would be interesting to compare. Tests like these seem like there isn't any way around using buttstuffog equipment though and that stuff is getting harder and harder to find each and everyday.

THIS.

I need to find what Ford rates the stock fan in my Mustang at. The stock cooling system is up to the task of the blower and other mods I've done in 100 degree heat while driving. I do wonder how much faster it would bring temps down between runs at the track if at all by installing the '13-14 GT500 fan and rad......

Fan Clutch

Reply #22 – June 21, 2015, 08:08:34 PM

I've been doing some thinking on this, and i forgot that most model airplane speed controls have a soft start function it is designed specifically to prevent in rush. It can be disable or programmed out, but it cm cause other problems, like the instant torque and rotational forces on the small air frame.

http://www.youtube.com/watch?v=cPttIgvW1tw&feature=youtube_gdata_player

This is one of my videos from an argument i had with someone on a model airplane forum about if a plane could fly with the prop on backwards.

The digital display reads voltage, voltage drop, amprage peaks, mah used (1000mah = 1 amp hour) as well as wattage and instant wattage. This video is my smallest model airplane, it is rated at 240 watts and 19 amps maximum power. I have several others that run on higher then 3 cells (12.6 charged, 11.1 volts nominal) and have one that puts out about 11lbs of thrust and weighs 3.5 pounds with a peak level of 836 watts.

The rating of the batteries, size of prop, style of speed control, humidity and altitude will all effect numbers. Generally for an actually laboratory test, you would also have one measurement of thrust, which is usually just a fish scale that you hand to motor or plane off of. Due to my elevation (4500ft or so) , my numbers are lower then most other peoples due to a lower air density. I also have a habit of way overpowering my stuff and using the maximum or over maximum recommended parts.

That little yellow airplane weighs about 16 oz and produces about 38oz of thrust with a pitch speed (prop air speed) of about 57mph, when the prop is on the right way.

Fan Clutch

Reply #23 – June 21, 2015, 09:13:45 PM

well,, all I know is work is work and watts is watts... till the magic cure is found then at the end of the day spec sheets can be swagged one way or the other to suit whom it benefits.

Fan Clutch

Reply #24 – June 23, 2015, 12:21:28 PM

Quote from: softtouch;449029

The load is moved to the alternator. Nothing is free.

True, but overall, the electric fan is more efficient.

A clutch fan is near 100% efficient when clutched, but not nearly as much when it's decoupled since there are a lot of losses from the fluid being sheared to make the blades move (think torque converter).
An electric fan is probably somewhere around 45% efficient, assuming 50% alternator and 90% motor efficiencies.

However, an electric fan only runs when needed (at extended idle, etc) whereas the clutch fan is always moving air and using energy.

Quote from: V8Demon;449043

FWIW -- I've often wondered if there was any standardization in the testing done to get the rated CFM of these fans.

Numerous reports for the Taurus fan claim 3000 cfm and 4000cfm or mor for the Mark VIII fan. I'v also seen reports that debunk those numbers and claim much less (although there are far fewer of these).

The reason I ask is due to this:

This is the stock unit that Ford installs in the 2013-14 GT500. Note the CFM rating, which one can guess comes straight from Ford. It's a drop in replacement on all S197 chassis Mustangs.
Ford engineered this thing and figured it to flow well enough on a car with 660+ crank HP that they KNEW people were going to upgrade.

I wonder how large the shroud is on this in relation to the Taurus and Mark VIII setups?

Fan cfm is pretty much related to blade diameter and power. Since area is related to radius^2, larger diameter fans will easily outflow smaller one given the same power.

For the fan you've referenced, what is the fan blade diameter and how many amps does it pull. That will give you the best idea of how it compares with the MN-12/Mark VIII and Taurus fan.

Most non OEM fan companies vastly overrate their fans. The 'Black Magic' fan was one of the most popular ones for Mustangs. A 15" fan that pulls 18A and claims 3300 cfm? lol. Unpossible.
Look at Spal's website if you want to see realistic cfm numbers. They also chart cfm vs pressure, where the blade design really comes into play. https://webstore.spalusa.com/en-us/productlist/0118/products/fans/fans+-+high+performance.aspx
One example, they have a 16" fan that pulls 3300 cfm @26A. https://webstore.spalusa.com/content/files/content/PDF/30102803_SPEC.pdf

Delta Current Control old website has a great page showing how to calculate fan cfm. https://web.archive.org/web/20061212052018/http://www.dccontrol.com/ (Click the right arrow until it gets to "Fan Selection")
Getting the actual plugin to work can be a pain, but you can manually create a spreadsheet if you want to calculate it yourself.

Also, high quality fans such as the Taurus and MN-12 fan have an inrush current that is 3X-4X greater than the continuous current. So, you can have a 100A inrush for the Taurus/MN-12 fans. It doesn't fry wiring because it is a very short transient. The A/C compressor for my house has a LRA (Locked Rotor Amps) of >100, but a continuous rating of ~25A. The wiring is sized for the continuous rating.

Fan Clutch

Reply #25 – June 23, 2015, 04:01:33 PM

There are too many variables in fan design to have any idea how many cfm they might be able to flow, and each one would flow differently installed.

How many blades are there? How fast does it spin? How wide are the fan blades, and what shape is the air foil of the blade?

Air does some very interesting things when you cram it in little box.

One reason why i brought up the blade size and shape is because a different brand propellerwith the same size and pitch might be very, very different as far s efficiencies, thrust and air speed goes.

Fan Clutch

Reply #26 – June 23, 2015, 04:45:05 PM

Blade efficiency will vary, but not by a massive amount. Since you are already have blade diameter and power usage, the only other variable is blade efficiency, which is wrapped up by rpm, # of blades, blade design, etc.

Look at spal.com and you'll see how well you can predict flow given blade diameter and power, at least at 0" H2O.

Fan Clutch

Reply #27 – June 23, 2015, 07:49:41 PM

I decided to check the inrush with my electric fan. On high speed, i got 36.6amps and 24 amp on high. Low speed was actually 16 amps and 11 amps after it settled.

My fan controller was also rated for 40 amps and did not blow either 20 amp fuse on high or low side. However, i was running the fan at 24 amps continuous, where i remembered it being lower.

Fan Clutch

Reply #28 – June 23, 2015, 08:00:32 PM

Quote from: Haystack;449133

I decided to check the inrush with my electric fan. On high speed, i got 36.6amps and 24 amp on high. Low speed was actually 16 amps and 11 amps after it settled.

What are you using to measure in-rush current? What is the refresh rate on it?

What fan are you measuring?

Fan Clutch

Reply #29 – June 23, 2015, 08:35:18 PM

A digital watt meter, no idea the refresh rate, but it stores all peak values and you can view them individually. I can guarantee the refresh rate is faster then the 100-60 amp drop in the earlier video. It must be pretty fast, because on my model airplanes i can see wattage peaks in real time, as fast as i can move the sticks on my transmitter

I am measuring a dual speed fan off of a ford taurus. When i bought if, my research showed that this was a better fan then the single speed/ mark7 fan.