How many layers are there in a Lionel ZW transformer laminated core?

@dennish posted:

I was examining several ZW's in the shop.  One had a tremendous hum to it.  I pulled out the core and counted 94 layers making up the core?  Another core, which was much quieter, had 104 layers.  It got me thinking: could you simply add more layers to a core that was loose and vibrated loudly to get it tighter and quieter?  Would that change anything about the transformer - volts, watts, safety, etc.

I also noticed that the layers were not always alternating.  There were several wider gaps on one end where their was clearly 2-4 layers, which are shaped like a "C", inserted from one side consecutively.  Should the layers be alternating at all times?

I've never had to take one apart, so I have no answer to your direct question, but as a general matter, electrical devices tend to "hum" only when some metallic part is free to move under the effect of a magnetic field.

ISTM that if your "humming" transformer has fewer core layers than others of the same model, and the orientation of some of those seems to have been disturbed, my guess is that someone has had the core apart, and didn't reassemble all the original parts. IOW, omitting some of the layers might have left some gaps or room for the remaining layers to vibrate, producing the enhanced "hum" you hear. I doubt the orientation would have much of an effect unless that helped produce a gap, but any visible space between the layers would likely be a "smoking gun" as to the source of the hum. Filling in the space(s) left open would reduce/eliminate the hum if my hypothesis is correct, not because of some magical number of layers required, but rather by simply restoring the original solid core by filling those gaps.  Good luck!

The amount of layers is not the cause of the hum.  It more depends on if the core was riveted together.  The plates which make up the core will hum if they get loose.  Riveted cores tend to be quieter because they do not loosen over time.  Non riveted cores tend to loosen over time which will cause a louder hum.  This is why some shops, when doing a ZW rebuild, will dip the core in a solution which will solidify the core to stop the hum.

At work we  apply a chemical made by one of Loctite or Permatex onto laminations, then cure it in an oven.  Some have windings (stator), some do not (rotor). Its mostly to keep them from rusting. Can look them up if you want. One of the chemicals is like 100 feet from my desk.

I understand where the hum comes from and the difference in riveted cores versus loose plates in the cores.  What I was wondering was if you could add more plates to the core to tighten it up and would that affect any aspect of the transformer, such as output voltage, etc.  I also toyed with running a screw or rivet through the four corners of the plates to make a riveted core.

The laminations have to be insulated from each other. If you drill the core and rivet them together, that may short them all together. They will cause heating and low efficiency.  

@David Johnston   Any ideas on what was used to insulated the laminations?  A special lacquer?  I would think aluminum rivets or screws might work in keeping the layers isolated?

Have you checked to see if the winding, as an assembly, is loose on the core?  I have had to use wood wedges to tighten some up on larger transformers I have dealt with because the hum was really coming from the looseness of the winding, which are usually wound around a waxed cardboard sheet which is first thing on the core to prevent the core edges from cutting the enamel insulation of the wire.

I reexpoxyed the core of my ZW type R and now its very quiet. Getting core out was tough but with a little muscle it came out. For the other type of ZW I have used the wood wedge method to help quiet the buzz with some success.

This how it sounded when I got it.

I did not know what Lionel specified to insulate there laminations. Today most everything is insulated with inorganic coatings, maybe sodium silicate?  Modern epoxies and other two component insulating dips are so hard to remove that most cores are burned out prior to rewinding. The insulating material has to be able to survive the burnout without loosing its insulating properties. Aluminum is a good conductor. I think it would do a good job of shorting the laminations. I use to work with transit cars that had reactors that would get noisy over time. We would send them to a motor shop for VPI, a recoating process, to quiet them down.    Those people on this thread who talk about sealing the laminations up with various adhesives and epoxies I think are on the right track.  

I have a noisy ZW and have just been living with it.  Never thought about a chemical sealant.  Is there any concern about breathing the vapors if the epoxy / sealant gets hot, or there's a meltdown?