Electric Cooling Fan Reversal...

topcatcustom · Post by **topcatcustom** » Mon Feb 15, 2010 10:15 am

I bought a 16"cooling fan that is supposed to be reversable, when I got it through it became apparent that it is reversible- if you just swap the terminals around. The motor obviously works fine but as the fan blades are curved they are really only made for working one way and dont shift nearly as much air reversed.

I whipped the nut off and went to turn the fan round inside the case but doesn't fit inside reversed as the whole thing is slightly dish shaped. I really need it to be a pusher to go infront of the rad, if I have to get it behind the rad I will have to chop out some triangulation in the front panel which I dont really want to do.

Any thoughts or ideas?

Ian Anderson · Post by **Ian Anderson** » Mon Feb 15, 2010 10:19 am

Ask the supplier fro their input

They may say you have to remove a spacer from the shaft or something

Ian

topcatcustom · Post by **topcatcustom** » Tue Feb 16, 2010 8:58 am

Got a reply saying- "just reverse the polarity, thats what everyone else does".

How stupid can people be- the blades on the fan are all twisted/concave. This means they are made to run 1 way as they smoothly change the airflow 90degs. If you run it in reverse they just beat the sh1t out of the air and most of it gets pushed back out the front round the edge.

I wonder how people get away with it- maybe its because "it spins backwards without breaking"- thus it must be reversible.

Any thoughts on one like this? I'm not sure which way these banana shaped blades are supposed to run??
http://cgi.ebay.co.uk/UNIVERSAL-16-INCH ... 563973a6aa

ged · Post by **ged** » Tue Feb 16, 2010 9:42 am

Hi Tom,

I think your bolloxed mate because of the blade shape. I used a Mr Gasket reversible fan with straight blades from Real Steel. Even this if I remember correctly in the instructions said if you are to use it as a pusher it should be used in conjunction with a mechanical fan as it wouldn't be as efficient.

Looking at his add it does say reversible blades which it obviously isn't. I'd demand my money back!

Not much help to you I know.

Regards Ged.

topcatcustom · Post by **topcatcustom** » Tue Feb 16, 2010 10:12 am

I have just had a reply from the company selling the one in the link I posted with the properly bent blades saying that they ARE reversible so I think I will buy one.

I may also keep the other one as it will fit on my landy to replace the little 12" one from a fiesta! As it only cost me about £25 I think it will be more handy than waste of money- but you are right I would otherwise demand my money back!

At least in this one case being the buyer helps and you get to leave truthful feedback, its normally the otherway round!

Hopefully I wont be opening this thread again with the one I'm about to buy

ian.stewart · Post by **ian.stewart** » Tue Feb 16, 2010 2:28 pm

the only way it will be reversable is if the blades are straight, without a curved profile, thats designed to catch the air, and force it thru the fan, simple way to explain it is cup your hand and run it thru some water, then push your hand backwards with the same hand profile there will be less resistance, and the water will cavitate inside the cup of your hand,

DEVONMAN · Post by **DEVONMAN** » Tue Feb 16, 2010 3:27 pm

ian.stewart wrote:the only way it will be reversable is if the blades are straight, without a curved profile, thats designed to catch the air, and force it thru the fan, simple way to explain it is cup your hand and run it thru some water, then push your hand backwards with the same hand profile there will be less resistance, and the water will cavitate inside the cup of your hand,

Hi Ian. To use another method of explanation, imagine an aeroplane with a single prop on the nose and then the same plane with the same prop on it's tail. Both arrangements work the same and the blades are shaped. So, Provided the fan blades rotate in the same direction and the same edge faces forwards it will work on a car rad except for possibly slight loss in efficiency due to air blockage by the motor support frame.

When swopping a sucker to the front, the blades must be flipped on the spindle and the motor wired to to spin the blades in the same direction as before.

Some motors are not permanent magnet types and will only spin in one direction no matter which way you connect the wires.

Some later designs have shaped parts on the support frame to assist airflow and these are unlikely to be reversible

Cheers Den

topcatcustom · Post by **topcatcustom** » Tue Feb 16, 2010 3:37 pm

Yep you both got it, the seller doesn't have a clue (or he just wants to get shot of a load of fans) by saying reverse the polarity and it will be fine- each fan blade is a ) shape looking down the end, made to work efficiently one way. When reversed it just pushes most of the air round infront of it and doesn't push it out the front/back as it should. The electric motor spins both ways but there is not enough room in the fan case to turn the fan over as it is slightly dished.

Hopefully the new fan (one in link) will have enough room in the case to turn over as the seller has told me himself.

topcatcustom · Post by **topcatcustom** » Thu Feb 18, 2010 6:42 pm

Got the new fan today, absolutely perfect. The diameter is exactly the same height as the rad, but as the rad isn't square there is about 4" either side of the fan. It is a 2" thick ally rad, about 2' wide and 16" high so should provide sufficient cooling for the V8. The fan fits right up against the rad on the front as there is no room behind it due to the blower.

Question is- how should I mount the fan on the rad? It has 4 bolt holes at opposite corners, I need to tig on some mounting brackets for the rad mounting so should I at the same time weld on 2 thin bars down the front of the rad to bolt the fan to? Obviously they will block some flow but cant think of another option?!

mgbv8 · Post by **mgbv8** » Thu Feb 18, 2010 7:12 pm

As long as you seal the fan casing onto the fins of the rad you will have done the best you can Tom. I have read the above and as the guys say. Curved blades are made to be efficient in one direction only. And straight blades can be reversed. My gearbox oil cooler fan is one of those that runs the same way whichever way you connect the power.

topcatcustom · Post by **topcatcustom** » Thu Feb 18, 2010 9:25 pm

Is it ok to mount the fan to rad with cable ties through the fins then? Obviously if I'm careful! The fan doesn't weight much.

Ian Anderson · Post by **Ian Anderson** » Thu Feb 18, 2010 9:37 pm

There are fitting kits that work this way.

Instead of a normal cable tie it has a flat square end and a sponge "vibration"bit

I for mine from Car Builder Solutions
http://www.cbsonline.co.uk/fan-mount-ki ... -765-p.asp

IAn

topcatcustom · Post by **topcatcustom** » Thu Feb 18, 2010 9:42 pm

Cool, I will make up some with foam/rubber pads!

satancom · Post by **satancom** » Mon Feb 22, 2010 8:40 am

topcatproduction wrote:Is it ok to mount the fan to rad with cable ties through the fins then? Obviously if I'm careful! The fan doesn't weight much.

I fitted my fan this ay to my series land rover. A weekend off roading and uit had shaken loose and pulled a hole in the rad, which resulted in all the water escaping on the M6 and cooking my heads. I wouldn not use this method again.

Although to be faior I doub't this would be so much of an issue on a road car. I Used the old radiator as a template and made a bracket for the fan out os sheet steel. Much better now

topcatcustom · Post by **topcatcustom** » Mon Feb 22, 2010 8:46 am

I made up some 3mm rubber pads both sides and seems pretty secure- but you're right it could cause a big problem if goes wrong! Will have another look and tug with what I did and double check I'm happy!