Lotus Elan

Electric Fan runs Backwards!

PostPost by: vincereynard » Wed Jan 10, 2018 8:27 pm

I've been punting Toad around a bit with the bonnet off and before I put it back I thought it would be a good idea to check the fan worked.

I shorted across the radiator switch and was surprised (!) to feel the air being blown forward.

Taking the unit off and the intended direct of flow / fan rotation is clearly marked. Yet, which ever way it is connected, the fan runs anticlockwise and blows (feebly) towards the nose.

Now there's a funny thing!

screenshot-from-2018-01-10-20-15-42.png and
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PostPost by: JonB » Wed Jan 10, 2018 8:55 pm

As you probably know, a DC motor will rotate in a given direction dependant on the polarity of its input voltage.

That looks like a modern fan housing. Which manufacturer / model is it? I'd be surprised if it was a brushless AC or digital type motor. That's the only situation I know of that might possibly cause it to behave like this.

Let's assume it is a DC motor - I think this is most likely. What happens when you connect the battery directly to it? What happens when you switch the wires?
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PostPost by: nmauduit » Wed Jan 10, 2018 9:06 pm

vincereynard wrote:I've been punting Toad around a bit with the bonnet off and before I put it back I thought it would be a good idea to check the fan worked.

I shorted across the radiator switch and was surprised (!) to feel the air being blown forward.

Taking the unit off and the intended direct of flow / fan rotation is clearly marked. Yet, which ever way it is connected, the fan runs anticlockwise and blows (feebly) towards the nose.

Now there's a funny thing!

Screenshot from 2018-01-10 20-15-42.png


chances are you can take it apart and turn the actual propeller upside down, then mount the unit upside down and here you go : you've gained 1 horse power !
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PostPost by: vincereynard » Wed Jan 10, 2018 10:55 pm

JonB wrote:. What happens when you connect the battery directly to it? What happens when you switch the wires?


I was surprised as well. " Yet, which ever way it is connected, the fan runs anticlockwise and blows (feebly) towards the nose."

nmauduit wrote:chances are you can take it apart and turn the actual propeller upside down, then mount the unit upside down and here you go : you've gained 1 horse power !


I have considered that, but the plastic molding bits makes it look impractical. Why upside down?
(Not to mention I can get another on Ebay for about ?20! Whereas a replacement is ?70 + the usual.)

It must have been like this when it was built. Just as well it has a big new rad.
Last edited by vincereynard on Thu Jan 11, 2018 12:22 pm, edited 2 times in total.
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PostPost by: Craven » Wed Jan 10, 2018 11:01 pm

DC motors found in this type of application are mainly two types, early, have a wound stator and rotation direction is NOT polarity dependent, later type, have a permanent magnet stator and these ARE polarity dependent.
If your motor has wound field coils ( stator ) then you have two options using this type, mount the motor the other side of radiator or change the internal wiring to the field coils.
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PostPost by: ericbushby » Wed Jan 10, 2018 11:18 pm

Some time ago, when a manufacturer refused to supply me with motors running the way I wanted, I noticed that the assembly was basically symmetrical. My buying power was below their threshold of even being noticed.
By swapping the end caps so that the shaft stuck out at the other end I got what I wanted.
Is this possible in your case.
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PostPost by: Foxie » Thu Jan 11, 2018 12:44 am

nmauduit wrote:chances are you can take it apart and turn the actual propeller upside down, then mount the unit upside down and here you go : you've gained 1 horse power !


Actually , taking the fan (or 'propellor') off and fitting it in reverse will NOT change the direction of the air flow if the rotation is still in the same direction :shock:
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PostPost by: StressCraxx » Thu Jan 11, 2018 1:21 am

Best no cost option is to mount the fan on the other side of the radiator if it gives you sufficient cooling.

Try the fan with it removed from the car and determine if there is sufficient air flow first. If the flow is still feeble as you say, then a different fan is needed.
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PostPost by: john.p.clegg » Thu Jan 11, 2018 3:24 am

Vince
Thought I recognised that label...

2017_0316lminor0010.jpg and


Twin fans on the M***** M**** , and they are " sucking"

Fit them in front of the radiator.....

John :wink:
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PostPost by: RichC » Thu Jan 11, 2018 8:16 am

this might support the argument that you could get away without these fans , especially this time of year .......

I have a wide radiator with just the original two blade pump mounted mechanical fan and was very anxious when stuck in M25/ M4 bank holiday traffic jam last spring with temperature in mid 30's and idling / crawling for 3hours in bright sunshine over a 20 mile stretch .
We were on our way to castle combe lotus meeting .
The temperature dial did rise but never got to the red !
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PostPost by: JonB » Thu Jan 11, 2018 8:34 am

If it came from Spyder, have you asked them for advice?
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PostPost by: oldelanman » Thu Jan 11, 2018 9:20 am

Foxie wrote:
nmauduit wrote:chances are you can take it apart and turn the actual propeller upside down, then mount the unit upside down and here you go : you've gained 1 horse power !


Actually , taking the fan (or 'propellor') off and fitting it in reverse will NOT change the direction of the air flow if the rotation is still in the same direction :shock:


That's true ... but it will affect the efficiency if the blades are profiled. The OE Kenlowe plastic fan is marked to show correct orientation but it's easy to get it back to front if you are not aware. Might be why some have cooling issues with the original set-up and others not so much.
cooling-fan-006.jpg and
cooling-fan-005.jpg and
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PostPost by: nmauduit » Thu Jan 11, 2018 9:58 am

Foxie wrote:
nmauduit wrote:chances are you can take it apart and turn the actual propeller upside down, then mount the unit upside down and here you go : you've gained 1 horse power !


Actually , taking the fan (or 'propellor') off and fitting it in reverse will NOT change the direction of the air flow if the rotation is still in the same direction :shock:


sorry, I meant upside down with respect to the radiator, i.e. not rotated 180 degrees along the rotation axis (less confusing when the radiator is out of the car and flat on an horizontal table... )

you also would have to mount the unit in reverse (many casings were reversible, so that the same part could be used for "push through" and for "pull through" blowers) - the fan profile not always being symmetrical

oldelanman wrote:That's true ... but it will affect the efficiency if the blades are profiled. The OE Kenlowe plastic fan is marked to show correct orientation but it's easy to get it back to front if you are not aware. Might be why some have cooling issues with the original set-up and others not so much.

yes, actually the most efficient fans are not reversible (like a wing profile, they have a roundish leading edge and a sharper trailing edge and specific entering/exiting angle for the air to be moved), the fan being design either to pull or to push air - cheap far east units are offered as fitting both uses, but one can also have somehow mistakenly reassembled his one way unit wrong
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PostPost by: vincereynard » Thu Jan 11, 2018 10:55 am

Note the pretty curved blades and the B. Presumably for Blow. The other side of the fan has an S, presumably for Suck. Changing the fan around makes it much more efficient at blowing forward!
screenshot-from-2018-01-11-10-32-01.png and


As Foxie (?) states, neither way will blow through the rad unless the direction of spin is changed.

RichC wrote:this might support the argument that you could get away without these fans , especially this time of year

As the present arrangement would have a negative effect, it would appear so!

john.p.clegg wrote:
Twin fans on the M***** M**** , and they are " sucking"

Fit them in front of the radiator.....
John :wink:


It is fitted in front and it does suck (to use present Yoof vernacular.)

Where did you get you fans John? I would like to keep the same as the rad is make to accept them.

JonB wrote:If it came from Spyder, have you asked them for advice?

I'll PM you.

....................

On the plus side Toad is starting, running and performing as it should have a year ago! Roll on Summer.
Last edited by vincereynard on Thu Jan 11, 2018 11:16 am, edited 1 time in total.
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PostPost by: john.p.clegg » Thu Jan 11, 2018 10:59 am

Vince
Sorry but they were a chance purchase off Fleabay...
Will they not fit on the other side of the rad....or is there no space??

John :wink:
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