Magneto

[Oldrusty26]

Another question for the team, when recharging the magnets on a magneto in the car, do you have to touch each magnet individually or just at the mag post? i’m working on a 1925. I have the hogs head off to inspect the coil rings. Everything looks good but the mags are weak. I was planning on doing the flash charge with a DC welder.
Thank you

[Rich P. Bingham]

Search this forum for the proper procedure for re-charging magnets in an assembled engine. It’s done through the block-mounted coil ring, the transmission cover needs to be on so a compass can be used to properly orient the flywheel. Many say the engine should be aligned with magnetic north, there will be advice on how to use a welder as a power source.

Good luck, and be careful ! (enjoy your T ! )

[John kuehn]

Here’s a good forum post about charging the Magneto in the car. http://www.mtfca.com/discus/messages/506218/528397.html

[Oldrusty26]

Thanks , hopefully it will be done today!!

[speedytinc]

The compass method assures that (A) a coil is centered over the magnet ends & (B) correct polarity.
Physically looking @ the position of the magnet keeper screws thru the inspection cover will, even more accurately cover (A).
Polarity is not important with a saturation re-charge. However if you dont believe the exhaustive testing Tom C. did in this regard, use you compass to confirm polarity after sighting the magnet keeper screws. Have the car pointing in an East/West direction.
Definitely read Tom C's posts. His method is proven, works great.

[Oldrusty26]

I set the chassis east and west , used a compass to determine north and south . Ended up using the 3 battery set up to flash with the positive on the solder button and striking ground to the engine block , it worked somewhat , but the magnets aren’t as strong as I feel they should be , but they’re stronger than they were if that makes sense .

[speedytinc]

Did you line up the magnet screws as I suggested? 3 batteries isnt enough for a saturation charge. A high output dc power source from a welder works best In my experience.

[Oldrusty26]

I’m going to try the welder tomorrow, I’ll post my results . Thanks !!

[Scott_Conger]

When you're done with the magnets, don't ignore the bands and band material which all look to need attention, as well as possible two-piece valves.

Be careful about stacking loose things around that abyss - it's no fun fishing parts out and even less fun starting the car up and finding out you should have spent more time fishing.

[Oldrusty26]

Very good advice !! I will definitely clean up the area before moving forward , I pulled this unit out of a barn quite a few years ago and am looking forward to getting it back together . They are the two piece valves , the whole thing needs cleaned up and out .

[Oldrusty26]

Tried the welder method @225 dc , flashed ground , no change , magnets will let the compass read north and south , but that’s all the magnetism I get ….

[speedytinc]

What are you using to determine how strong the magnets are before & after a recharge?

[Oldrusty26]

A socket to see if it sticks to the magnets , it does not . Magnets are very weak . Would rather not pull the flywheel and transmission assembly but I may have to.

[jab35]

Puzzling result for sure. Any chance mag stator coil ring is open/shorted? And have you minimized magnet to stator gap by pushing flywheel fully to front of engine? 36VDC from batteries should do that when you 'flash charge' the magneto. Seems likely to me there's a faut somewhere in the mag ring coils. Good luck, jb

[Oldrusty26]

I will try that next and report back. For checking the coil ring , just make sure there’s continuity between the coils and no short to ground correct ?

[TXGOAT2]

A socket may not give an accurate idea of magnet strength. Good sockets are hard forged chrome or vanadium alloy steel, which may not stick to a magnet as well as mild steel. Try using a piece of mild steel to test the magnets. The best test of a magneto is to start the engine and measure the output voltage with an AC voltmeter. The voltages that should be present at various speeds vary from 6 to 8 volts at slow idle to 30 volts or more at 1800 RPM.

[speedytinc]

I wonder if you could do a light bulbs test. See if you can light a 6v bulb with a vigorous spin of the crank.
That would test actual output.

[Dan Hatch]

Ok one more time.
Take a fish scale ( not the ones you remove from fish before cooking).
Bend a short piece of steel flat bar ( 1/2”wide x long enough to fit cross magnet ends)
Drill hole in middle, attach small eyebolt.
Place on end of magnet, hook scale to it and pull.
When bar pulls off magnet, record lbs of pull need.
That gives you good idea of magnet strength. Dan

[speedytinc]

Ok one more time.
Take a fish scale ( not the ones you remove from fish before cooking).
Bend a short piece of steel flat bar ( 1/2”wide x long enough to fit cross magnet ends)
Drill hole in middle, attach small eyebolt.
Place on end of magnet, hook scale to it and pull.
When bar pulls off magnet, record lbs of pull need.
That gives you good idea of magnet strength. Dan

What's a good # to see when testing the pull on an assembled flywheel?
I have charged loose magnets to a 4# pull. After installing into a complete flywheel Magnetism was noticeably less.
My imagination or is there a scientific explanation?
Magneto puts out 33 VAC measured.(that's what magnet saturation will give you)

[TXGOAT2]

Magnets mounted in place on the flywheel will probably behave differently than loose magnets. Most alloy steels, such as sockets and other tools, contain non-ferrous metals and are less attracted to magnets than mild steel or soft iron. You need to connect an AC voltmeter to the mag post and crank the engine with the plugs out and ignition off. A meter with a 0 to 50 AC volt scale should work. Don't start the engine with the hogshead off or the access cover off the hogshead. Oil will go everywhere if you do. Spinning the engine with the hand crank ought to show 8 to 10 volts on an AC meter connected to the mag post and to a good ground.

[Mike Silbert]

Even if you hand crank the engine quickly enough to get a magneto reading it will be dumping the oil.
If you do the hand crank magneto test with the hoggs head removed, drain out the oil.
And DO NOT start it without it being fully assembled, sealed and full of oil.
I have dumped lots of oil on the garage floor thinking it can't leak that much.....

Mike

[Oldrusty26]

Ok , so , checked coil ring continuity , not open , however checked the solder blob ( hogshead is off ) and have continuity to ground , ensured that the flywheel magnets were as close as they could be to the coils , flashed again , nothing , compass reads north and south poles and with a small piece of steel strap , very little magnetic pull , as in practically none , not even enough to read on the pull gauge . So am I right to believe this one needs to have the magnets either replaced or sent out for recharging ?

[TXGOAT2]

If you mean the steel strapping as used on boxes and crates, it may not be ideal, either. What you need is mild, soft steel. I don't think you can get a meaningful magnet test with the magnets assembled to the fly wheel except by rotating the flywheel and checking voltage. I'd drain the oil as suggested above and get hold of an analog AC voltmeter with a 0-50 range. You can buy an inexpensive multi-meter at Wal Mart or most any auto parts store that will do the job. They are handy to have on hand for general use.

[Oldrusty26]

Strap was cold roll steel about 1/8” thick and 4” long , not sticking anywhere , but has some draw to the magnets , hand cranking ( hogshead is off and oil drained ) 0.7 vac on a fluke multi meter ( not analog )

[speedytinc]

NO.
You don't know that the field coil is not grounded @ the first coil from a continuity test.
If the coil was out, you could put power to it & check each coil for alternating magnetism.
When you flashed the coil, you should have heard/felt a healthy thump from the coil pulling in the flywheel.
Are you sure your welder is DC?
Magnets, generally don't go "bad", they need replacing if cracked.
A saturation charge in car is not any better than a saturation charge done individually.
In fact, in reassembling individual magnets, they can lose some charge from hitting to reset magnet heights.

.7 is no good. You don't need to use an analog meter if buzzing coils are not involved.
So your description says the magnets are not adequately charged. I think that can be concluded, but not necessarily the fitness of your field coil.

[Mike Silbert]

To check for magneto ring coil shorts or opens:
1) Line up the magnets to the coils like you are charging it. Skip this if it is a loose ring coil bench test.
2) Hook up a 6V battery or 6V charger to the ring coil like you are charging the magnets. Don't leave it hooked up long as it will heat up parts.
3) Go around the the coils and see if a big wrench "sticks" to the coils.
Most importantly check the last one in line that is on the generator side of the engine next to the post.

I have seen ground shorts between and in the coils (taking some of the coils out), bad connections, bad ground rivets, and windings shorted between the layers before.
If you suspect there is a problem with the ring coil it is an easy test.
Mike

[Scott_Conger]

Fluke DVM will all but certainly give erroneous readings regardless of health of the mag coil, and without a small load such as a light bulb during cranking, you will not get a real meaningful reading with an analogue meter, either. A St. Louis Magneto tester is best, but this test in this link is darn near equivalent and a whole lot cheaper: https://www.mtfca.com/discus/messages/7 ... 760271.pdf

You need help - the kind that means someone is standing next to you that has experience trouble shooting this sort of thing. I am with others who suspect your coil ring, but on the other hand, don't believe that your test methods are adequate, either. You may have a shorted mag ring, or quite possibly simply have a worn out 3rd main bearing allowing the magnets to sit too far away from the coils to properly charge (or subsequently provide adequate voltage to work the coils). Dealing with well-meaning respondents is no substitute for thorough checking with adequate methods and equipment along with immediate advice from someone working with you who has experience with this sort of thing.

Unfortunately, you are delving into one of the more potentially confounding issues that a T can have, thus my admonition to do your very best to enlist experienced help.

If I were you, I'd start a thread asking for local help with Magneto Troubles

good luck