The Stovebolt Site Forums The Shop Area General Truck Talk Fan Blade Balancing?

Saw an episode on youtube where a builder cut down his fan blades by an inch. He then mounted them in place and the motor ran smoothly. I was of the impression that once you removed metal from a fan blade it should be balanced. Seems strange.
Spoke to my neighbour who is an expert on everything and he said balancing was unnecessary. He is a nice guy but unless he knows the answer he will make up one. He also broke two crankshafts on his diesel Land Cruiser over the years. He is now on his fifth rebuild.

If you cut the same amount off of each blade, then there probably wouldn't be a need to rebalance it. The outer portion of the blade has the most effect on balance, and if it was OK beforehand, it'll probably be OK afterwards.
Now if you cut one blade out of 4, then it would definitely be unbalanced. I have a fan that one blade broke off and they cut the opposing blade off to get it back in balance.

It’s done fairly frequently in the hotrod world. They use a template and etch a fine line with a scratch awl. Cut a little short and sneak up on the line with a abrasive wheel. No issues.

Poured or hammered metal has inconsistencies, so nipping a little off the edges could throw it out of balance but we can’t be too certain how balanced it was from the factory. If you put it back on and hear vibration I guess you’ll know.

Most fans are pressed sheet metal and any inconsistencies in thickness would be pretty minor. Again as long as the same amount is cut from each blade, then no problems.

I won't even attempt to straighten a bent fan blade, let alone start whittling on one.
Jerry

The same thing happened years ago on the '46 truck my Dad had. Ran it for years with a 2 bladed fan.

I would have to agree with Jerry. Fan blades can come apart, and you don't want to be in the area when they do.
Jim

Yep, my in his 30's cousin did a total nut and bolt down to bare frame on a M38 Jeep. Built a nice Buick V6 for it and it was a nice rig. While leaning over the front and with a hand on the throttle linkage a fan blade came off. A few days later I was at his funeral.

RonR

Back in the 1950's it was common for the dirt track racers to shorten the fan blades on flathead Ford race engines. One night in Nashville a blade broke off as a driver revved his engine up. It hit a pit crew member in the sternum and pretty well destroyed his rib cage. He survived, but he was never able to work again.

If you want a small diameter fan, buy one.
Jerry

Had a fan blade come off my '60 way back in 1970's. It went down, put a small nick in the l.h. frame rail. Vibrate you off the road.

I had a flex fan ruin the hood on a freshly painted 57' Belair. No more flax fans...

Cutting blades shorter should have nothing to do with it coming apart. If it's coming apart, it will do it with longer blades due to the mass, short blades have less.
Use a lawn mower blade balancer once you start cutting them shorter.

Draw to an inside straight in a poker game- - - - -those odds are only 32:1 against you!
Jerry

Sedgewick In the olden days if you lost 1 blade you had to break off the opposite one just to get home,cause it shook so bad !

Had one come through the hood of my 69 (Not Chevy). I twisted that engine over 8K and it shot a blade right off the fan. Wish it would have gone down vs up, but it was a fun discussion every time.

I realize this is an old post but thought I would add to it In 1958 Chevrolet issued a "RED" memo warning not to rev the 348 with three dueces while sitting still for fear of a fan blade exploding. Since then I have seen two case of stove bolts launching fan blades thru the hood, both with no modifications. So it has been my practice to never stand in line with the fan when running an engine. Hope this keeps someone from getting hurt.

Works for aircraft propellers, too!

Ed