4 blade vs. 2 blade alum. fan

[MikeK]

Originally Posted by Utopia Texas

Call me crazy, but 32 years ago I took the four bladed fan from my 1931 late Slant Windshield 4 door sedan and welded the rivit heads to the blades, welded a bead where the blades Chris crossed and then welded a circular bead between the blades and the pulley. In effect this makes the fan all one piece. After reading all the comments above I now wonder why it has worked so long and on so many long tours. I am not a professional welder so some one clue me in if this was a stupid idea and I should switch to a different fan!

What you did created detrimental modifications in the grain structure of the rolled sheet used to produce the two overlapping blades. The welding added stress risers in the absolute wrong places. You now have a DANGEROUS fan.
Welding the four overlap joints of the two blades- two in front, two in the back, has made the fan far more prone to sudden blade loss than the riveted construction. You have concentrated the flexing directly across your weld beads. The grain structure in the steel sheet metal the blades are made from is refined, compressed, and stretched directionally during the rolling process. Essentially a type of forging. Your weld bead destroyed that. It annealed the metal and left a soft line with much less spring than the rest of the blade.

The fact that you now have many years of accumulated stress from dynamic flex on that fan makes it a real time bomb.

Didn't you post this under a different screen name 5 years & 11 months ago? My response was the same back then.