While working on a friends motor, I had the opportunity to inspect some unrelated items. I found what looks like a crack in a magneto magnet. All the prior cracks that I have seen have been across the rectangular section of the magnet and near the crotch of the Vee, not along the length of the magnet. I can see this line on the inside of the Vee and is through the length of the magnet. I can not see the outside part of the magnet since it is next to another magnet. I can pick at it and there is a definite catch to it. But is it a crack or just a line or a ditch in the magnet? I can also see the line across the ends of the magnet I thought of taking a small burr and slightly grinding into the crack to see if it is just on the surface. Any ideas? I'm not all that anxious to pull the transmission apart. Mike
You could sprinkle some magnaflux powder on the area and see what it does. Or some wet solution, but you would need a UV lamp to view the solution.
Well, well.....well, it's a crack, and before I broke it, this magnet would ring true like a bell. The magnet was placed in a vise and hit with a small hammer. The magnet split longitudinally and broke off at the crotch.
So, it pays to do the ring test, BUT... also do a good visual inspection and suspect anything. Mike
Wow, glad you went through the extra effort and caught it before it failed!
That is one peculiar crack !!!
Your telling me! I never seen a crack like this one. To top it off, after cleaning the other magnets another magnet had a similar crack. Could this be a 100 year old forging flaw? Mike
Mike, I would expect that the magnets are made from rectangular bar stock which was hot rolled rather than forged. Each magnet length appears to have been sheared, going by the appearance of the ends. On bending, the bend itself then appears to have been 'squashed' to flatten the area under the bolt and washer.
Perhaps there was a variation in heat in the stock being rolled to make the bar at the end of a run or some such!
Allan from down under.
Allan, I'm only an amateur metal worker. I believe I read that the magnets were forged, but I can be wrong. This failure doesn't appear to be the result of the bending process or any bolt tightening. This could have been from the making of the material or during the forming of the rectangular shape. This crack could have survived 100 years of service and may have lasted even longer if we would have not seen it this time. I have assumed that all cracks were rough. Looking at this closely, the cracked surface is very smooth. Working in the power plant, you would see all kinds of metal failures and they all had rough surfaces where they failed. Fun to think about but this one is odd. Mike