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electric and flex fans

Posted By: Matman

electric and flex fans - February 20th 2019 6:22 am

hi.......Its been a very long and very hot summer here down under, especially in Qld.
Now that my G10 Shorty is close to being back on the road I`d like to make sure it doesn`t have any overheating issues.
I have already fitted a new radiator, problem is the original fan sounds like a swamp boat propellor.
So I have been wondering ing .. should I fit a flex fan?
Also when the A/C is regassed and running maybe I should look at fitting a twin electrin fan setup, one to kick in for normal running and the second when the A/c is on.
Has anyone gone this route? I`d be interested to know if its worth doing
Posted By: shaggy

Re: electric and flex fans - February 20th 2019 11:01 am

I've done it but my reasons were to give me more access to the motor and to show off the shiny bits I've added. The old fan was working fine the new ones work well too. I don't drive it enough or in hot weather to tell you which works better.
Posted By: CatFish

Re: electric and flex fans - February 20th 2019 5:55 pm

Our old Ford has dual fans and they are great. The first is operated by a Flex-a-lite variable speed controller. The second comes on with a regular thermostat and/or AC override. Both can be turned on manually as well. I also run a "delay off" timer set for 15 seconds.
They are really, really great in the heat!!

Pic of the Flex-a-lite controller mounted on the front of my extra relay box:
[Linked Image]

To the right on the box are the bleed diodes for the fans.
I know ... overkill.
Posted By: Matman

Re: electric and flex fans - February 21st 2019 11:05 am

Thanks guys, yes I`ll be fitting the dual electric fans, if I get a positive vibe about the flex fans I`ll go that route as well. thanks again, much appreciated.
Posted By: tuner4life

Re: electric and flex fans - February 21st 2019 1:56 pm

x2 on that flex-a-lite controller Catfish mentioned. I got one by his recommendation and I love it. I was planning on having a manual override switch inside to turn the fans on in case the controller failed, but it has worked so well I never bothered. The soft start feature is great too! Keeps the strain off of the electrical system.
Posted By: Hasan Ben Sobar

Re: electric and flex fans - February 21st 2019 9:47 pm

Interesting to note that no vehicle comes from the factory with a "flex" fan. Take the hint.
Posted By: Wizard78

Re: electric and flex fans - February 21st 2019 10:08 pm

Please.... Never use a Flex Fan
Posted By: wrcsixeight

Re: electric and flex fans - February 22nd 2019 3:53 am

Looking at stock fan blades, there is no Foil, no thickness distribution, just bent and angled metal designed to pull and push air. it works, it is effective, yet it is hardly an Ideal method for moving air efficiently.

To say it would be ideal, would be akin to saying airplane wings could just be flat. Same thickness front to back with no foil, no shape, all they need to do is be angled upwards to give enough lift to keep the plane aloft.

Now is it worth the effort to engineer a fan blade with thickness flow, like an Airplane wing?

Well, they likely could get more airflow for less noise and power consumed, but it would be a lot of work, perhaps too much mass.

Enter the electric plastic bladed fan. The impeller blades on many are not simply angled, they have foils, thickness flow, and perhaps even a skythe style shape, to better grab onto the air, and either pull it through or push it through the resistance of the alternator, AC condenser, transmission cooler and then across the engine.

So which is more effective?

Well which could be much more effective, no doubt the well designed electrical fan with a tight fitting shroud so all the fans flow is sucked through or pushed through the radiator.

I am a Fan enthusiast. Look at the engineering which goes into some Computer Fans, Like Noctua's latest 120MM fan.

[Linked Image]

Look at all the little enhancements, like the 'flow aceleration channels' or stepped inlet design to make laminar flow into turbulent flow so the blades can grab more air effectively. Then there is the ultra tight fan tip to shroud clearance, or the inner surface microstructures, and the very mounting designed to cushion the whole thing in soft silicone to limit noise and vibration transmission.

This particualr fan is designed for both good airflow with little to no restriction, and also be quite effective when it is forcing air through a restriction, a pusher style fan. They have fans designed more for one or the other.

Do the radiator electric fans employ any design similarities as these Noctua's, I can't really say, I've yet to fondle one.

I do think the whole automotive engine fan design could be vasty improved upon.

With the computer fan comparison, I have many such fans. Some of them consume 2x as much electricity to move the same amount of air, with no restriction and 1/4 the air if there is a restriction and this is all accomplishe with better electric motor design and the shape of the fan blades. Surely there is a lot of cross over.

Each 25 amps an alternator has to make is said to consume 1 HP from the engine, so a high power electric fan told to be spinning fast, is still putting a load on the engine. As much as a metal fan attached to water pump through a viscous coupling? Likely not.

I've not really read good things about electric radiator fan longevity, which is one reason I have not pursued adding one, and I am also bit of an impeller design snob.

Moving air might be fine and dandy with an angled flat plans spinning on an axis, but I want a nicely shaped foil with an outline designed either to scavenge air in a puller scenario, or push it against resistance, and I do not think anyone has bothered refining designs to have excellent airflow characteristics for lesser amperage consumption at lesser RPMS and making less noise in the process. i think they just rely on availability of sheer RPM, and heck with efficiency of design.

So if it seems little more advanced than the stock flat metal angle bladed metal fan, devoid of an airfoil, I'll leave it stock. for now.
Posted By: shaggy

Re: electric and flex fans - February 22nd 2019 9:27 pm

I think they have made a bit of an effort to incorporate some of the things you mention. This is a typical modern electric radiator fan for automotive applications...

[Linked Image]
Posted By: wrcsixeight

Re: electric and flex fans - February 22nd 2019 10:28 pm

Still appears like many electric radiator fans are not really heavy into design of the impeller, and many of the Images of installations do not include a shroud on their puller fans, meaning much of the radiator is not getting air sucked through it.

My Computer fans are mainly to exchange air in my Van, outside air for inside air, and I want extremely powerful fans, with manual speed control. I can exchange the complete volume of air inside my van in about 60 seconds with all fans on high.

I bought one of the smaller Spal fans, and the noise and amp draw were out of control compared to high power brushless computer fan, and I sent it back. The computer fans obviously are not hardened against water intrusion and whatnot, but the design of their impellers and fan bodies is far ahead of anything I've seen for use as a radiator or transmission cooler fan.

Interior cabin air circulation is a different subject though.

However I would love to see some of the attention to detail of design exhibited in computer fans, on Radiator fans. If some company were to offer highly efficient electric puller fans with built in shroud to fit my radiator, I'd save up for it.
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