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I Forge Iron

champion 40 blower

mike muzzarelli

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Mike, We can't see what you describe because there are no pics. I assume the missing portion includes part of the center of the fan assembly, the hub. The blades being individual paddles attached to a central hub and the hub itself being mounted on the end of a shaft.
Is part of the hub gone? i.e. perhaps one arm? or is there a portion of the affected blade remaining and a fully intact hub still there unaffected?
If the damage extends into the hub then follow DenK's advice and remove the opposite blade and hub arm. File to true it up so each side matches. This should give you a fan now in balance, albeit missing two blades but still a serviceable fan that will work just fine with no wobble or loping trouble and a blower which works fine, giving you plenty of air.
If you have a portion of arm remaining then it is worth it to repair the the affected arm so the whole of the hub is restored to the original. If you are a welder you can figure this out and do it. Where the slot is cn be filled with a piece of copper (nonferrous) as a blank to define the space as you weld, fold copper flashing to the thickness you need to fill the slot and weld, then pull it out which leaves the slot there.
These hand cranked blowers are not machines made up of precision tolerances. When in good running order they do perform very well, very smoothe but tight tolerances are not critical.
When I was in the Marine Corps I worked on Huey and Cobra helicopters. For the balance on the main rotorheads we would go to the pistol range and dig up .45 slugs to balance the heads with. This was actually called for in the maintenance manuals. There is a little cup atop the head on each side with a cap screw over it. Into this goes a slug ot two, precise weight being achieved by filing the last slug until balance is achieved. They are just dumped in there loose and the cap screw replaced and safety wired.
Later I attended the Riverside School of Aeronautics in Utica N.Y. and while covering wooden propellers (yes, they're still used) we went very in depth on balancing. On a stand a prop is placed and balance is noted. It is manipulated by holes drilled near the hub into which lead is inserted.
This is all very critical and precise.
A handcranked blacksmithing blower has a lot of "slop", leeway in it so precise balance is not so critical. It will not tear itself up if things are a little off like high rpm aircraft components, it will work just fine indefinetly. If you really wanted to get into balance to the nth degree on one of these fans it could be done like an aircraft propeller on a stand with weight added by mig welding a lump on there and filing in degrees to achieve total balance.

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I've had several blowers with weights added to the fans so it must have been common practice at the factory. Never paid much attention but IIRC, all were small solid rivets made from what looked like lead or maybe tin. Perhaps they used rotary balancers or something similar to set the fan and shaft to detect the out of balance side.

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