48" drum fan question

[subarub4]

I have a Air King belt driven fan and I was curious if this was for all drum fans but if you stand 8 ft away from the fan in the middle you hardly have any airflow at all but all the airflow seems to be from around the outer areas of the fan blades.

I'm just saying because of it's size it seems pretty weak on airflow, I ended up changing the angle on the blades a little and it helped a bit more but I can't see how this thing pushes 10,000 cfm on high.

 

[aka Larry]

Mine is not that brand, but I believe it's about the same size. I agree for it's size it doesn't seem to move that much air.

 

[subarub4]

Not complaining because the fan was free but I would never pay the amount for it as I see how the air flow is..

I guess that's why they never demo the fans.

 

[aka Larry]

Mine was free also (garage warming present from a friend) so like you I can't complain too much.

 

[LS6 Tommy]

That's pretty much how any single-pitch axial fan is because of the velocity difference from the hub to the tip of the blade. I wouldn't increase the blade pitch too much. You could overload the motor. Keep in mind, CFM is volume, not velocity. You can move a lot of air at a relatively low velocity, so 10,000 CFM at a low velocity may not feel real strong. How "fast" the wind is blowing against you feels can be misleading as compared to how "much" air is blowing against you.

Tommy

 

[subarub4]

But the fact that most of the air is on the outer parts of the fan and little to nothing at the middle part and none as you near the hub.

 

[LS6 Tommy]

But the fact that most of the air is on the outer parts of the fan and little to nothing at the middle part and none as you near the hub.

That's right. It's normal for that type of fan.

Tommy

 

[gzuckier]

Btw, this is why large fans at low rpm move more air than smaller fans at high rpm; it's the ends of the blades doing all the work.

 

[Vegaman_Dan]

If you really want to feel the air flowing from that large of a fan, you'll have to fabricate a cowl on the output to direct the air flow. Try it out with some cardboard to see if that really is the effect you want or not.

 

[Tweeker]

Notice the blades are not in the center. Try the same bs sience on a smaller scale/smaller fan its the same story.