Who do you think made the best magnetos?

[Holtzer-Cabot]

I am learning a bit more about magnetos! Anyone ever seen a magneto like this? It doesn't seem to have gears at all, that is with teeth. The most unique magneto I have seen is a chain driven one, but not one like this.

[Jim Stettler]

I have been told that that style is called "friction drive". It makes sense to me.
Jim S.

[Holtzer-Cabot]

I have been told that that style is called "friction drive". It makes sense to me.
Jim S.

Yeah I have heard of 'friction drive' before too! I have never seen a magneto with such a system before though. I have only seen the regular gear driven magnetos, and one chain driven one.

[unbeldi]

I found a picture of the Alnico generator that Western Electric installed into the 331A telephone set.  This was made in 1963.

The switch assembly is different on this generator than the on the NE-41 by NECo, but other than that the construction appears the same.

[Holtzer-Cabot]

I found a picture of the Alnico generator that Western Electric installed into the 331A telephone set.  This was made in 1963.

The switch assembly is different on this generator than the on the NE-41 by NECo, but other than that the construction appears the same.

Wow thanks for sharing! I have never seen a WE version. It sure looks the same except for the points. I wonder why the points are different, unless they function the same, but are just a different design?

[unbeldi]

Wow thanks for sharing! I have never seen a WE version. It sure looks the same except for the points. I wonder why the points are different, unless they function the same, but are just a different design?

Well, the switch is a DPDT type, disconnecting both line conductors from the line and placing the generator across the line when activated. I suppose the normal switches on generator didn't do that.

Here is another one. This one was made in 1971.  The set had some water damage when found. I never assembled it again, actually.

[Holtzer-Cabot]

Well, the switch is a DPDT type, disconnecting both line conductors from the line and placing the generator across the line when activated. I suppose the normal switches on generator didn't do that.

Here is another one. This one was made in 1971.  The set had some water damage when found. I never assembled it again, actually.

Wow! Do you know when these stopped being made? What is the internal construction like of these smaller magnetos? Is it easy to disassemble them to clean them and re lubricate?

[Kenton K]

It should be noted that some magnets, like the ones in ringers and some magnetos, will demagnetize once taken out of the frame. The frame provides a 'flux' path so it stays magnetic. I believe they were magnetized in the frame. I know C series ringers were magnetized in the frame. I took one apart and completely destroyed the magnet. I've never disassembled a magneto for fear of ruining it.

[19and41]

Here is the magneto that was used in the TA-312/PT, the field telephone in use when I was in the Army.  It's about 3 1/2 inches in diameter and was a good performer.

[Ktownphoneco]

Kenton  ....    Actually not.   I've restored a lot of magnets over the years.     In order for magnets to retain their magnetic properties, they require a "keeper".      A keeper is a piece of ferrous metal (contains iron) which, when placed across the 2 poles of a magnet, help it retain it's magnetic properties.   The most destructive things which can destroy old magnets, are "heat", and "shock".
The frames of 48-A's, 47-A's and 22-A's for example do not provide any sort of path to keep magnets in good condition.     The pins that join the field coils of magnetos, are usually made of brass, which contain no iron, and therefore are not attracted to magnets in any way, therefore they do not act as "keepers".    Coincidentally, I had the round magnet out of a "C" series ringer today, in order to clean the frame.   It causes "zero" problems with the ringer.    If I removed it, and intended to use it 5 years from now, I'd have made a "keeper" for it, and left it that way until I was ready to re-use it.  The magnets in such things as 295-A subscriber sets are in the same situation.    It's a lack of a "keeper", and external effects like storing the sets in a very hot environment for prolonged periods of time that causes them to loose their magnetic properties.     A number of years ago, I made a magnet rejuvenator, creating 2 poles wound on two 1 inch round poles, and joined by a piece of iron square stock, 1" inch square.    I pulse current through the windings of each pole with a 12 volt DC battery charger / with a 70 AMP booster for starting cars.   It works quite well, and I'm able to restore the old telephone magnets without any difficulty.
If you destroyed the magnetic properties of a small round magnet in a C4 ringer, it was from something else, and not because you removed it from the ringer frame.

Jeff Lamb 

[Kenton K]

I've definitely destroyed some C ringers by disassembling them. They worked pre disassembling. Other people have had similar results as me.

http://www.vintagerotaryphones.com/cleaning-western-electric-ringers-be-careful/
http://www.classicrotaryphones.com/forum/index.php?topic=845.25


If you have a remagnitizer, I'm sure you could restore them though.

-KK

[unbeldi]

Kenton  ....    Actually not.   I've restored a lot of magnets over the years.     In order for magnets to retain their magnetic properties, they require a "keeper".      A keeper is a piece of ferrous metal (contains iron) which, when placed across the 2 poles of a magnet, help it retain it's magnetic properties.   The most destructive things which can destroy old magnets, are "heat", and "shock".
The frames of 48-A's, 47-A's and 22-A's for example do not provide any sort of path to keep magnets in good condition.     The pins that join the field coils of magnetos, are usually made of brass, which contain no iron, and therefore are not attracted to magnets in any way, therefore they do not act as "keepers".    Coincidentally, I had the round magnet out of a "C" series ringer today, in order to clean the frame.   It causes "zero" problems with the ringer.    If I removed it, and intended to use it 5 years from now, I'd have made a "keeper" for it, and left it that way until I was ready to re-use it.  The magnets in such things as 295-A subscriber sets are in the same situation.    It's a lack of a "keeper", and external effects like storing the sets in a very hot environment for prolonged periods of time that causes them to loose their magnetic properties.     A number of years ago, I made a magnet rejuvenator, creating 2 poles wound on two 1 inch round poles, and joined by a piece of iron square stock, 1" inch square.    I pulse current through the windings of each pole with a 12 volt DC battery charger / with a 70 AMP booster for starting cars.   It works quite well, and I'm able to restore the old telephone magnets without any difficulty.
If you destroyed the magnetic properties of a small round magnet in a C4 ringer, it was from something else, and not because you removed it from the ringer frame.

Jeff Lamb

I concur.
In general it should not be a great problem.  I certainly strongly disagree with the notion that this happens rapidly after the magnet is removed from its magnetic circuit. My experience also contradicts that, and theoretically it doesn't seem plausible. However, despite their high coercivity, even modern magnetic materials do loose magnetism to a very small degree, and so do the AL-Ni-Co materials, but this involves a lot of time and extra help.  Shock disturbs the magnetic domain structure of the material and heat disorders them too, especially when heated above the Curie temperature at which point the magnet is destroyed.

Some of the technical literature by ITT and perhaps others do state such problems, but it is not clear what the degree of the problem was.  We do know that the methods of tuning each ringer were quite elaborate,  perhaps the warnings are related to very specific performance issues.

I have not taken apart one of these Al-Ni-Co generators.
I do have some more Ericsson material that shows internal construction, I wanted post that still, but haven't got around to it.

[Jim Stettler]

I have heard that they can be re-magnitized  by a machine shop using a "growler".  I am not sure what this kind of a "growler" is.

Jim S.

In Colorado the growler's I am familiar with will  hold 64 oz. (to the brim) or are a 1/2 gallon jug (72 oz to the Brim) .

[Victor Laszlo]

The small cylindrical magnet from a C4A ringer was the magnet of choice on many a telephone man's refrigerator, and in many a tool box for picking up those tiny screws that always seem to get lost in the carpet when repairing a telephone in an office.  I have never had one fail after having been removed from its ringer.

[Holtzer-Cabot]

Interesting stuff here! I once took a few magnetos out of my SC 5 bar magneto, put them back in, and it is still going ever since, so I have never personally had a magnet lose it's magnetism just by being out of the magneto frame.