MTFCA Forum

The following is a sharing of my current methods for a best magnet recharge method. I strive for the best possible repair/restoration methods available. I am open minded to any better way.

There are 2 recharging methods. In car & disassembled motor. Using a large DC arc welder has given a 25-30V mag output in car. Best output I know of.

A field coil can be similarly used laying on a disassembled transmission flywheel's magnets. I would expect as good or better output with direct magnet/field coil contact.
BUT if apart, why? Go the extra mile & do the magnets OFF individually.(to insure all magnets are good. crack free & otherwise)

Remove & clean the magnets. Hit them looking for them to show a break. Additionally hang via a string & ring test. You should hear a continuous long ring like a tuning fork. If you get no long ring replace it.
Get out a compass & mark each with its polarity. I also measure & mark the magnets thickness on the ends to make setting the heights when assembling easier. Note the magnet box has an old ring gear as a "keeper" built in. The recharging coils fit over each magnet. Polarity observed. Power source was a 12V battery from my truck. Running @ 14V. I have used a 12V battery & 100 amp battery charger. Striking once some times didnt give a maximum charge. 4-5 quick hits is the norm. Maximum magnet charge seems to be achieved. Saturation.
This method I used on my '14. It puts out 35V @ speed. Starts easily on 1/4 crank.

This was night 1.

Day 2
I am wondering about the tool that has the coils fixed to the cores & is walked around a flywheel or individual magnets that magnetize by contacting magnet ends.
Is it as effective? Lets test! Night 2

Using a magnet as a fixed core in my 2 coils, I placed another magnet against the ends for re magnetizing. Simulating that other type charging unit.
The result was an inferior charge. Would not hold the 4# sledge. Tried several recharges, but never got enough charge. In case the problem is the magnet, I placed the new magnet in the coils as with the other magnets for charge & got a good full charge.
My conclusion: the charging tool that contacts magnet ends does an inferior job. In addition. 1 of the magnets in the pile didnt pass the ring test. Thud. I beat on it & it wouldnt break. I noticed it was rougher & thinner like not enough material when it was rolled out. Gave it a charge. It would not take a "full" charge. It would not hold the 4# sledge & gave a similar meter read as #3 magnet above. Defective. It will not be used.

John: In the second photo "coils over each magnet" how many turns of wire in each coil and what wire gage was used? And you use one fully charged 12V automotive battery for the current source, correct?

Have you ever placed an iron bar, a keeper across the ends of the magnet when you recharged it with the above method? Obviously, if you are getting 4 lb lift the method needs no further 'improvements', but in light of a recent post on the subject I'm curious what effect this might have. Thanks, jb

The coils are made from 2 delco starter solenoids per a tinkering tip article. It was built years ago. I dont know how many turns of wire were used - all the wire in the solenoid.
Current source: 12v truck battery, running. 14V indicated. The idea was to insure no weak voltage for the last magnets done. Continuous battery recharging.
The charged magnets are on a keeper throughout the process until the flywheel is installed. A used ring gear as a keeper. Its in the base of the wooden form & will be placed on top of the magnet shoes after the flywheel is reassembled.

Here's another method of charging magnets - like John, each magnet needs to be checked for cracks or defects - a defective magnet usually won't hold a charge overnight. I built my 110 v. charger from the plans in David Gingery's book probably 20 + years ago with the help of an electrical engineer who was employed by Boeing Aircraft Co. - he wired up the control box for me. I purchased a good sized spool of coated wire (can't recall what size but you can see it was substantial) and another machinist friend milled the pole pieces. I verify N or S and charge accordingly - I hold down the contact button for approx. 3 seconds whilst gently tapping the magnet with a brass bar which according to several books on magnetism, assists in aligning the molecules or electrons or something to that effect, remove the charged magnet while attaching a sized bar so as to not interfere with the flywheel mounting process and let sit overnight - any magnet not holding a charge strong enough to hold a Model T cast iron piston w/wrist pin gets tossed in the scrap bucket. I have a hand held Gauss meter and after mounting the magnets onto the flywheel, I go around and check each pair, N & S and my meter will register right around 30 + units.

...my meter will register right around 30 + units.

How does that translate into weight held by each magnet? Two pounds? Three pounds? Four pounds? More?

I believe a stock early c.i. piston & pin weigh in around 3+ lbs. - I'll go weigh it today.

 
 
I use a cast iron piston with wrist pin and a few washers on the wrist pin to make three pounds.