It occurred to me the other day that one might improve the ability of elderly magnetos to produce a spark by the use of a number of those very powerful (and very cheap!) disc shaped rare earth magnets used on tool boards etc. One might drill a series of holes into the bottom of each end of the horseshoe & set the magnets into the holes, either as an interference fit or with the assistance of a little Araldite.
Setting the new magnets into holes whould surely 'short circuit' them. I reckon you'd need to create a gap in the magnetic circuit by shaving material off the pole pieces or cutting a whole section out of the existing magnet so they could be put 'in series' with it (sorry about the electrical analogies - just what I feel comfortable with).
I had a go but being a lazy and tight *&^*%^ I used a couple of coils I had about me. Plenty of turns of nice thick wire but only room for 3/4" diameter cores. So, while I'm generating plenty of Ampere-turns, I fear I may be saturating the (mild steel) cores before reaching a high enough flux density to do the job. Any thoughts?
Also, I once had a mag remagnetised at EMI when I worked there. The 'charger' - which was about the size of a washing machine - didn't have coils and pole pieces as such but a stout copper rod around which one put the keepered magnet. Pressing the foot pedal a couple of times produced a satisfying thud and left the keeper feeling as if it had been welded on!
My thought was to drill right through the pole end and set the REM's in a row along the face. If positioned so that they were attracted to the pole piece, then the face they presented to the moving coil would be reversed from the original - not that it would make any difference, I suppose. However, the magnetism would be increased .
Perhaps I'll try a row of them on the outside of a pole to start with & see what happens - I have enough magnetos about in all conscience.
Yesterday while uncovering an engine for tomorrow's crank-up, I remembered that at cranking speed the Lucas mag (non-original fitment) had a weak spark, and this thread. I stripped and cleaned the mag earlier last year and once it is running its ok.
So today I experimented with the magnets that hold my engine info sheets. Using a compass to check polarities I put them on the sides of the mag....
...and it barked into life almost straight away. Took them off, no go. Back on, and away again. I took the plug out and turned the engine over and the spark had definately improved. Took them off, and back to weak spark. Going to the extreme, I reversed the magnets, and obviously no spark at all.
Question. Is it possible, within reason, to have too greater magnetism on a magneto?
I wasn't thinking about going quite as far as a couple of "Death Magnets", as at the bottom of :-
Depends on how much reason you still have. Not with just a few rare earths stuck in there though. Build something ridiculous and you could lock the magneto rotor into place well enough to make it difficult to turn over. One or two of them should be enough to saturate the existing polepieces, then there's no point (albeit no harm either) in adding more.
If you cut a gap across a horsehoe and insert the rare earths optimally, then you can sort a weak magneto with just one or two of them. Remember they're often free from old disk drives too.