Ballancing a fan

I have a 38 inch belt drive whole house fan mounted in the ceiling of my attached porch.
This thing will move some air. Guessing 6000 CFM range.
It has to be around 50 years old as I got it out of a house built in the mid 60's to very early 70's.


Runs great but vibrates.
It has vibrated since I got it so it is not a bearing going bad.
I have even checked it by trying to wobble the fan to see if bearings were loose.
I had used it as a shop fan so the vibration did not bother me.
Now that I mounted it in my ceiling I want to try and fix the vibration as it shakes my whole house.

I was going to take the fan blade off and try and balance it but each blade is individually mounted to a 13 inch cast wheel that the belt drives. Taking the cast wheel off will involve getting into the bearings so I was trying to avoid that.

So my question is....
Is there a way to balance a fan without taking it out of the frame??

I would think it could be done if you can set it on side and see where it rolls too.

There may be another consideration. Is the fan frame mounted to a structural part of the house such as a joist, stud, purlin ,or other member? do all blades have the same pitch? Are the blades free of insect nests,or other foreign matter? I remember years ago some of my friends would attempt balancing tires by marking where the wheel would stop in spinning the tire;this would indicate a heavy spot. I do not know how precise it was but poor boys had to be frugal. I would think equal pitch to all blades would be more critical than weight of the individual bledes

trial and error tape a small weight to one of the blades a car tire wheel weight see if is better or worse if worse move it 180 degrees to the other side when you get where you want it go to the tire store and get some tape on weights that wont fly off that are the same as your test weight

(quoted from post at 17:17:50 09/01/18) I would think it could be done if you can set it on side and see where it rolls too.

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And take the belt off. See if the same blade always ends up on the bottom.
Could be a wore out belt.

Same as the others are saying. First pop the belt off. Very slowly turn the blades and keep your head steady in the same place. See if any are bent. They will need to be convinced back into a common path. Next gets a bit more trouble. The fan must be vertical. You are going to see when you can get all of the blades to stop where YOU put them and they don't creep away. As said use stick on weights and take a marker and draw around them and their position and weight for future reference. Lastly....after you get everything mounted and back together. Go to an HVAC supply house and pick up a fractional Horse Power belt. Has little notches on the inside of the belt. Very flexable. You can also use some rubber isolation mounts. Every little thing will help.

How about a lawn mower blade balancing tool. Pretty simple accurate way to balance any thing with a round hole in it. Just a balance tool, pretty fool proof.

Also one of those old time wheel bubble balance things from some old
tire shop. The prosedure with it sitting vertically should do it. He
needs to be very patient. The finner tuned the better. Try doing a
bicycle wheel some time. Use those splitshot fishing weights. Did it
when I was in my teens. When the speedo on the handle bars was at
40mph and there was almost no vibration, that was a head rush!

If the fan turns really free with the belt off and the heavy spot goes to the bottom each time I would braze a spot on the top til it was heavy then grind it off til it is in balance. Did this on a big vacuum fan and was really easy..

If the blades are bolted on you could mark where each one is located. Then weigh each blade. Find a way to make them all the same. Like someone said. Braze on a spot, go to tire shop and buy a few stick on weights. They are easy to cut. Piece of double faced tape and a cut up piece of aluminum if you don't need much. Add some solder, glue on part or all of a penny. If bolted, che the weight of the bolts too. The farther out from center the more it will shake. The weights don't always need to be at the end of the blade. Balanced a ceiling fan an the weight was put in the middle of the blade. Just kept moving it around with a piece of tape till I found the sweet spot.

John, got some good info here. Growing up, Dad used the trial-and-error method on ceiling fans. He'd start with a cent and tape it on using masking tape, then turn the fan on low. If the fan wobbled worse, then try a different blade. First, as someone else mentioned, make sure all blades are clean and dry, and mounted tightly.

Once he tuned the coin on the correct blade, he'd then move the coin from side-to-side on the blade until finding the sweet spot. I remember one fan (el-cheapo with hardboard blades) took a quarter and another coin on one blade, plus another cent or dime or something on a blade next to it. Thought that was gonna drive him insane! *lol* After that, he only bought Hunter ceiling fans.

Another trick you can do initially is to get a fairly thin piece of cardboard about a foot long. Turn your fan on low. Then, carefully move the piece of cardboard to the face of the spinning blade and see if they all seem to be in alignment. Then do the same for the back face, and again for the ends. That will quickly tell you if the blades are at same pitch, length and plane. When doing this, make certain the piece is not able to catch on a blade edge. Doing so would result in a projectile.

Be careful. We don't wanna have to start calling you Stubby. *lol*

I have seen the fan and motor frames suspended by four springs, rather than secured directly to the ceiling joists. Springs absorb much of the vibration and shake. just an idea. gobble

My guess is that big pulley is causing most of the vibration along with the belt. To start with I would put on a new link belt. I put one on my Delta table saw and it made a world of difference. The better woodworking supply houses will have the good ones.

Ezee Pezee, Just take out the extra "L" in the word "ballancing" and I bet the vibration goes away. :lol:

Since the blades are bolted to the hub, mark where each is on the hub, and take them off.
Then stack them all on top of each other into one pile, if they do not nest together nicely, one or more need to be tweaked back into conformity.
One or more might have a twist or bend, etc. effecting pitch and creating the vibe. The leading and trailing edges might also not be the same, stacking them will show that too.
Make sure no blade holes are elongated and that when assembled the tips of the blades are all the same distance apart when mounted.

I found out it is not just the balance of the blades but the pitch of the blades matter too. One wrong angle screws up the whole fan.