I own two cheap pedestal fans - Big W $20 type - I've owned them for six or more years and they get a fair bit of use in summer as my house does not have air conditioning. They have done a fine job without issues for those years.
They had both become a little dirty on the fan blades and the areas where the wires are close near the centre of the fan guard, it must be three years since I cleaned them.
I took one fan apart, brushed the dirt from the guard and washed the propeller in warm soapy water, reassembled and all was good the fan was doing it's job.
That evening I checked fan number two and noticed that it wasn't as dirty as number one but seemed very inefficient in that at one metre distant I could not feel air flow from the fan. The next morning I checked number one and could easily feel airflow at three metres.
I did a strip and clean on number two, reassembled, and could now feel airflow at three metres and more.
What I'm guessing is happening: The fan propeller has three blades and each has a very sharp leading edge, if you tried really hard it would cut your finger, and I suspect that as dirt build up on the leading edge and blunts it then instead of slicing through the air the blunter edge is causing turbulence and preventing the blades getting hold of a solid column of air to push forwards.
So... if you're no longer a fan of your fan a good wash and brush up may give it a new lease of life.
MH
__________________
"I beseech you in the bowels of Christ think it possible you may be mistaken"
Oliver Cromwell, 3rd August 1650 - in a letter to the General Assembly of the Kirk of Scotland
Fan blades do not need a sharp leading edge, same as aeroplane propellors and also their wings and helicopter blades. Trailing edges are sharper than leading edges. It would be just the dust and fluff not being very slippery slowing the airflow down.
Fan blades do not need a sharp leading edge, same as aeroplane propellors and also their wings and helicopter blades. Trailing edges are sharper than leading edges. It would be just the dust and fluff not being very slippery slowing the airflow down.
I know nothing of fluid mechanics so my theory is very possibly incorrect.
But in regard to your comparison of fans and aircraft propellers... they need to push air in opposite directions I think - fans push it forward and aircraft push it backwards...?
__________________
"I beseech you in the bowels of Christ think it possible you may be mistaken"
Oliver Cromwell, 3rd August 1650 - in a letter to the General Assembly of the Kirk of Scotland
Fan blades do not need a sharp leading edge, same as aeroplane propellors and also their wings and helicopter blades. Trailing edges are sharper than leading edges. It would be just the dust and fluff not being very slippery slowing the airflow down.
I know nothing of fluid mechanics so my theory is very possibly incorrect.
But in regard to your comparison of fans and aircraft propellers... they need to push air in opposite directions I think - fans push it forward and aircraft push it backwards...?
Just stand on the other side.
__________________
"My mind is made up. Please don't confuse me with facts."
Fan blades do not need a sharp leading edge, same as aeroplane propellors and also their wings and helicopter blades. Trailing edges are sharper than leading edges. It would be just the dust and fluff not being very slippery slowing the airflow down.
Yes they do Diggerop, the sharper the better.
Aircraft size airscrews have issues with bugs, fatigue strength and icing, they are designed heavily toward the safety side of airflow, not efficiency.
Same as a boat propellor, your average tinny prop is quite blunt but a racing prop is very sharp and disturbingly thin-walled.
I've found that another reason the cheap fans slow with age is that the bearings at the front and rear of the motor start to run low on lubrication so when we annually clean the fan blades we apply a drop or two to the bearings. Bunnings had the fans for $10.40 the other day so we bought 4 of them to pack away for next year so we can dump the old ones as one of the fan blades has lost it's flexibility and is splitting. ...planned obsolescence!
