Hi guys, a question on the power required from the mag to power the coils effectively? I have a 1927 Aussie built tourer that is, currently, running on a distributor but I will be putting it back on to coils and 6V. Haven't got all the bits yet but almost.
Saturday I ran the car (on the distributor) and used that beautiful piece of equipment, the St Louis Mag Tester, I got a reading slightly below the 1913 level. Is this enough? Should I just use battery power for the time being?
Thanks in advance, Paul
Have the flywheel magnets been recharged recently?
An in car recharge might bring the reading on the St. Louis meter up.
To answer your question on how much power the coils need is not simple.
The coils are a current operated device (1.3 Amps RMS when operated on MAG).
Both voltage amplitude and frequency vary with engine speed (RPM's).
In a rough calculation by my estimation it is about 2.5 VA (Volt-Amps ... the AC version of Watts).
A good set of coils will run on 6 volt battery. So a good test of your magneto would be to install the coils and start it on battery, then switch to magneto and see how it runs. Since you do get a reading on your meter that would indicate the magneto is working. A weak magneto would run at higher speed but not idle on magneto. If so, you can try an in car charge. The other potential problem would be crankshaft endplay. A 26 has a 4 dip pan, so although difficult, the rear main cap can be removed in car and a little build up of babbit to the front side thrust surface would fix the endplay problem.
maybe this will help by recharging the magnets:
In the Vintage volume 42 number 2 is a fine article about the way to test a magneto.
If the output shows near 1913 levels it should run fine so long as the coils, coil box, timer and wiring are in decent shape. The magneto tester is a fine piece of equipment, much more sophisticated than one might suppose. Being made of wood and metal it will last many lifetimes.
The St. Louis Magneto tester is a fine vintage instrument but its ruggedness may not be as robust as some would suggest. The delicate mechanical meter movement is protected by thin glass window that can and will break under sufficient stress. Subsequent debris can destroy the delicate meter movement it protects rendering it useless and expensive to repair.
Fully solid state instruments offer distinct advantages in ruggedness, especially in automotive environments, with no moving parts to fail, fracture or wear out.
Hi guys, thank you for all the information. It has been brought to my attention that I got the reading wrong on the tester, it should have been "just below the 1914 mark". I was working from memory and, as often happens, my memory stuffed up!
Mike, my tester is brand new and in perfect condition and it was the first time used. It is a work of art and, even if it doesn't work, I love it and would be happy to have it in a display cabinet. I also have your "solid state" tester and love it as well. Both items have a valued place in my tool box.
Thanks again, Paul
Paul, my magneto output also registers just below the 1914 mark on the St. Louis Magneto tester scale and the car runs very well on magneto.
The St. Louis Magneto tester is a fine instrument as I stated. My comment regarding ruggedness was prompted by the comment being made of wood and metal it will last a lifetime. The same poster classified solid state test equipment as modern computerized plastic electronic crap that will eventually crumble and be of no use to anyone in a previous post. yet here, conveniently omits a key detail that a thin glass window is all that protects the delicate meter movement from damage or destruction; and it will last a lifetime.... So figured it a good opportunity to, again, correct misinformation.
No worries Mike. I sure don't want to, nor intend to, disparage either wonderful piece of equipment. Both are great in my eyes. Anything that simply tells me what I need to know gets my vote. You have both done great jobs with your respective equipment and I will continue to use both.
As to my mag, I'll use the "suck it and see" method once I have changed over to the coils. It'll either work or not, time will tell.
You certainly didn't Paul, nor did I intend to imply otherwise. Good luck with your Magneto, I believe it will function well based on the data you provided. Please report results when you have the opportunity to test it out.
For those not familiar with the St. Louis Magneto Meter.