MTFCA Forum

Our 1915 runabout had the engine rebuilt in 2019 when I was restoring the car, and it easily starts by hand when set to the magneto. I'm currently in the process of putting back together the engine for the 1911 touring that I am restoring, and I also hope that it starts by hand cranking on the magneto.

Ideally it would be nice to know if the mag is working, and working well, before I try to start it for the first time. I picked up a replica St Louis magneto tester a couple of years ago, and one of the interesting things about it is that it shows if the magneto is functioning properly, almost independent of RPM. John Regan, who made the tester, told me that he thought that it would show if a flywheel/magnet/field coil is functioning properly even spinning the flywheel by hand. That makes sense, because obviously the magneto needs to be working well enough to start the car on magneto when hand cranking.

I decided to test it out on our runabout first. I had my wife handle the tester while I hand cranked it. Sure enough, it read about the same level it does when the engine is running. This week I got the flywheel assembly back together, height checked, and installed with the field coil while the block and crank were mounted on the engine stand. I was very glad to see that it did not take much of a spin for the tester to read about the same level, maybe even a bit higher, than our runabout does. What I noticed was that it was still showing a "good" magneto even when the magnet air gap was initially bigger than the max 0.040" called out in the Ford manual. I charged all the magnets enough that they can each hold a cast iron piston and pin (about 3 lb) so maybe the magnets being stronger than the minimum recommended 2 lb value helps. Anyway, for those that have access to one of these testers, it is a way that you can get a check on whether your magneto is functioning properly before the engine is back together and in the car.

Even though I used the method for letting the loose field coil stick to the flywheel and measuring the gap at the shim locations to allow measuring the resulting gap that can be used to determine the shim stack heights, I still ended up taking the flywheel off numerous times before getting the air gap that I was satisfied with. It was during that effort that I realized how much I like this Walden Worcester 3822 wrench. It, and a similar wrench made by Blackhawk, were specifically designed for this task and is well worth adding to your tool collection if major T engine work is in your future.

In my case when I put together the 21 Touring engine I restored I charged the magnets, I also bought a new magneto coil, and set the magnet gap for an average .020.
After everything was put together I started the car on battery and it ran fine. ( Making sure the magnets are charged is the most important part I think.)

THEN I switched to mag it it ran even better! I count myself lucky I guess but I did take my time on the wiring and the switch.

As far as your question I’m thinking Ford put the engines together, broke them in on an engine stand and found flaws but probably not many. That’s when they checked the mag output at that point but not before I don’t think.

I agree on both accounts Neil - I'm fortunate enough to own an original St. Louis tester and that Blackhawk flywheel wrench in the best available !

I also have one of those Blackhawk flywheel wrenches . They do work really well.

"...maybe the magnets being stronger than the minimum recommended 2 lb value helps..."

A minimum standard is just that, a minimum magnet strength at which Ford deteremined that good results could be expected with all other adjustments set properly. Stronger than minimum is better. Stronger magnets will give a stronger output under all conditions, which is especially useful under adverse conditions, such as cold weather starts and starting with the ignition system in less than a perfect state of tune. Magnets that are stronger initially can be expected to give longer service before becoming weak enough to affect starting and running the car. You could also expect the magneto to tolerate more thrust bearing wear before losing enough output to cause problems. Good magneto performance depends upon strong magnets.

Neal

I, too, use a St. Louis meter on assembled engines and spin by hand before rods are installed. It gives a certain and accurate result which you can take to the bank. It is a highly under-rated piece of equipment. Not that you can still buy them, but the St. Louis meter was fabulously reproduced by Fun Projects and works exactly like the original. If someone finds one at a swap meet, do not hesitate to buy it...it will pay for itself in short order.

I have a set of 3/8 dirve sockets with universals made by Bonney tools. They work great for the multiple times you need to lift the assembly to set clearance. I also have the Blackhawk tool for final tightening. They are similar to these. https://www.amazon.com/stores/TEKTON/Un ... 37C1C1C56E

Ron Patterson owns an "era" magnet charger - it's a monster ! I built mine (with help) from the David Gingery "how to" book - it will saturate a T magnet in 3 seconds to hold 4+ lbs. - it runs on 110 v. I used to use a cast iron piston w/pin - now I have a 4 lb. piece of square stock.

WOW, thats a magnet charger.
Do you lock away your credit cards in a lead box inside the house & keep your mouth closed to not lose a filled tooth?

The book is for sale for only $3.97

http://gingerybookstore.com/product53.html

When i rebuilt my engine five years ago, I charged the magnets with house wiring and a 12 volt battery. 18 volt didn't improve results. Each picked up over 4 pounds.
Each dimension affecting the air gap was carefully measured. The theoretical shim thickness was calculated. After assembly, the air gap was at my desired.020 inch
This surprised me.
The engine starts on mag by hand crank or by battery
crank

Art Mirtes

Didn't lose any fillings John BUT my electrical engineer buddy that did the circuits & wiring told me to stand on a rubber mat to "smoke test" it, which I did but not clearing some hand wrenches off the bench top caused me to almost pee myself when everything in close proximity flew towards the charger ! No smoke though !

RajoRacer wrote: ↑

Fri Sep 23, 2022 5:30 pm

Didn't lose any fillings John BUT my electrical engineer buddy that did the circuits & wiring told me to stand on a rubber mat to "smoke test" it, which I did but not clearing some hand wrenches off the bench top caused me to almost pee myself when everything in close proximity flew towards the charger ! No smoke though !

RAJO. You hold the power on for 3 seconds. Do you think you get a stronger charge as opposed to 1 flash.

I did some experimenting using a starter cable ammeter to read magnetism. On different magnets, I tried 1 flash, multiple flashes & a hold on for 4-5 seconds. I could not read any difference between the 3 methods. The hold on method created heat in the coils.
I do 3 or 4 flashes typically. Even with evidence any more than 1 flash is unnecessary, I cant help myself.

That unit must create immediate saturation on a magnet.

I stand the T magnet on end for the first 3 second flash then lay it on it's side and slightly tap the horeshoe end with a brass hammer whilst holding the button down for another approx. 3 seconds. All the magnetism books I've read states that tapping while charging aligns the molecules more uniform for a stronger charge. I can do about 10-12 magnets before the coils get warm enough.

I believe that light tapping, about 3-4 taps with a brass hammer, while the magnetizing coils are energized might be helpful. Leave coils energized for a full second or two after the last tap. Do not bump the magnets around after magnetizing them. Warm (not hot) magnets might take a slightly better "charge" than cold ones.

This a follow up to my original post. This past week it was time to do the first start on the engine that I rebuilt for our 1911 T restoration project. After the engine was on the chassis, I used the St Louis tester to see if it would still show a "good magneto" while hand cranking the engine. Hand cranking a freshly rebuilt engine is harder initially, as anyone who's had the joy of doing that can attest to.

The test showed that I could still get it in the good range during a 1/4 turn crank. I still "cheated" and used a 6V hotshot battery arrangement to tickle the coils while I cranked until I got it going. Switching it to magneto showed that the engine ran even better than on the battery, as it should. After I shut it down I decided to see if I could start it on the MAG setting. The engine had lost some of its initial stiffness, and the engine started on the first crank with it set to magneto. I did several more starts on the MAG setting.

I cannot say enough good things about having access to a St Louis tester. Mine was built by John Regan, but hopefully they will be available again from Birdhaven, if they aren't available already.

My informal test also showed me at least, that there is no reason to charge your magnets to be any stronger than needed to hold up a cast iron piston and pin like Murray mentioned in his "Model T Ford Owners" book. In the article about magnet charging, he even points that out.

"My informal test also showed me at least, that there is no reason to charge your magnets to be any stronger than needed to hold up a cast iron piston and pin like Murray mentioned in his "Model T Ford Owners" book. In the article about magnet charging, he even points that out."

I hope this is the case, but you may find a slight loss in mag voltage a few years down the road. You might want to archive a current output voltage.
My "overcharged?" magnets hold a 4# sledge. Output was 35 volts initially. I think it's @ 30V after 6 or so years. I dont think a magnet saturation is a bad thing. I'm sure a 2# weight charge is adequate also.

This could be a good subject to debate.

The magnets will never be any stronger than when first charged. Over time, with use, they will slowly weaken, due to vibration, heat cycling, and perhaps other factors. Bearing thrust faces will wear. The stronger the magnets are initially, the longer they can be expected to provide good service, and the more reliably the car will start under adverse conditions.