Successful Use of Electromagnets?

Discussion in 'FAQs' started by Gary S., Jan 15, 2007.

  1. Gary S.

    Gary S. Senior Member

    I'm experimenting on the test bench: My HO scale rollingstock is working great with Kadee's #308 under-the-track permanent magnet which will be used on my spurs. But now I am experimenting with the #307 electromagnet for use on the mainline. In my experiments, the magnet seems to be underpowered. I can get the cars to uncouple, but the couplers don't open far enough for the delayed action.

    Like I mentioned, the cars work well with the #308 so I don't think this is a rollingstock/coupler problem. I have a 7 amp DC supply that is adjustable from 8 volts up to 15 volts DC. I started out with 10 volts and gradually cranked it up to 15 volts, but the results were still not up acceptable. At 15 volts, the electromagnet was drawing about 1.5 amps, so this isn't a power supply problem.

    Is there anyone here who has actually successfully used the #307 electromagnet? I am looking for some first hand advice. Do they work without modification? Or did you make modifications? I have seen an article where more metal was added to the sideplates. Perhaps I can put more turns on the coil?

    Again, has anyone here successfully used these things without modification?
  2. YmeBP

    YmeBP Member

    I'm still curious as to how these things actually work ... i can't conceptualize how they function.
  3. Gary S.

    Gary S. Senior Member

    The uncoupler magnets work by attracting the coupler pin on the Kadee couplers to each side of the track. Check out the diagram below. When a car goes over the magnet, the trip pins of each car are pulled to opposite sides of the track. Once the cars are uncoupled, you can back up to the uncoupled car and push it to were you want to set it at a spur. When you pull away from the car, it won't be coupled up, it will stay where it you left it. This is the so-called "delayed action" of the Kadee uncoupling system.

    Attached Files:

  4. YmeBP

    YmeBP Member

    I got somehting that looks exactly like that in an ebay auction i won i wondered what it was ... there is no bed to it though i have to take a picture of it. Interesting .. wow the possibilities. So now i haev to convince the wife to let me buy a shnter train yard engine to move all my automatically uncouple cars around.
  5. Gary S.

    Gary S. Senior Member

    Okay, in my experiments, I came up with this. I took TWO electromagnet uncouplers and put BOTH of them together with a longer bolt. I used all of the steel side plates = 2 on each side. I wired the coils in parallel. Now we're talking! This thing is strong enough to seperate the couplers without even having to cut into the ties for the steel plates to stick through. It can be mounted completely under the ties like the #308 undertrack magnet.

    Now, the doubled up coils are drawing 2.5 amps at 12 volts. I have a 24 volt DC, 5 amp supply that I may try out, but I will wire the coils in series instead of parallel.

    Yeah, this will double the cost... each electromagnet is about 7 bucks, so $14 for the doubled unit. I have 4 places where I am thinking of using them, so the cost isn't that extravagent. I could get some electromagnet wire and build some stuff myself, but it will be simpler to just buy the Kadees and double up.

    Anybody see any problems or catastrophes brewing here?

    Attached Files:

  6. Gary S.

    Gary S. Senior Member

    One more thing: I know this topic is brought up on numerous occasions, and I have read the advice on other threads and on the 'net, so sorry for the redundancy. But, I just want to hear from someone who has actually made these things work as per Kadee's instructions.
  7. Ray Marinaccio

    Ray Marinaccio Active Member

    I helped a friend of mine install 3 of them on his layout.
    They are installed as per the directions and are powered by the ACC. terminals of his MRC power pack.
    They work flawlessly.
    The dual coil , under the tie set up sounds interesting though. Let me know how that works out when installed on the layout. I may try that. I would like to use hidden electromagnetic uncouplers on my layout.
  8. Nomad

    Nomad Active Member

    Gary, let me know how that works out to, will you. I am using the permanent magnets on my refrigarator. To many false uncouplings.

  9. Gary S.

    Gary S. Senior Member


    Glad to hear that you made them work on your friend's layout. Kadee's instructions say that the magnets will be a little weaker on AC, which makes me wonder what the heck the problem is with my experiments. I have a good DC source, my rollingstock works just fine with the undertrack permanant magnets, but they just don't want to work with the electromagnet when installed per Kadee's instructions.

    But it is all a moot point now. This double coil system will enable me to avoid cutting the ties and installing all that other hardware and having it show on the layout.
  10. Gary S.

    Gary S. Senior Member

    Oh, one other thing: It will be awhile before I have these operating on the layout. At the moment, I am just now putting down the roadbed. But I will keep you posted on developments.
  11. MilesWestern

    MilesWestern Active Member

    ...just don't put any electonic device, like your DCC controller, camera or computer near that thing! :eek: you'll wipe the memory clean off it! :eek:
  12. Gary S.

    Gary S. Senior Member

    Ray and Loren:

    I've been playing with it for 20 minutes here on the bench, and so far it is working great.


    Maybe I should build a little metal box to contain the flux?:)
  13. Gary S.

    Gary S. Senior Member

    Now, the next plan is to build some controller circuits for these things. I'll use a momentary pushbutton, a relay, and a time delay relay to give the uncoupler a 5 second shot of juice, so I can use both hands on the controller during uncoupling.
  14. Nomad

    Nomad Active Member

    Gary, glad to hear your using a push button. I read somewhere that those things can overheat and catch fire if left on too long.

  15. tetters

    tetters Rail Spiking Fool!

    Any chance you could post up a step by step photo essay / tutorial on how you accomplish this project? I've been looking for something like this to build into my own layout when I start constructing it. The closest thing I've seen to your home build is on this website. Index Howard Construction Techniques However the site appears to be down and doesn't come up anymore. It was working last week though. Wierd. He talks about wiring up a red LED with a resistor to remind him if one is left on. If you're using a push button then I guess that point is moot.

    I like your build better though.
  16. Gary S.

    Gary S. Senior Member

    I would be happy to do a photo-tutorial of this project. Considering the number of questions I ask to The Gauge et al, and considering the amount of great information I receive from The Gauge members, I would be happy yo give something back that could be of help to someone.

    I will be gathering supplies over the next couple of days and then I'll get something put up.
  17. tetters

    tetters Rail Spiking Fool!

    Sweet. That would be awesome. I'm going to need a few of these puppies as well. :wave:
  18. Gary S.

    Gary S. Senior Member


    I just found out that Kadee makes both a "through-the-ties" electromagnet and an "under the ties electromagnetmagnet" for HO scale. One is the #307, the other is the #309. I have been experimenting with the under-the-tie version.

    The only difference I see between them is the under-the-tie version has twice as much steel to direct the flux... looks like they use the same coil. However, when I doubled up the metal plates with a single coil, it didn't make that much difference. Still, I doubt if the coils are wound any differently between the versions. The "through-the-tie" version is about 8 dollars, the "under-the-ties" version is around $15.

    I think I am still going to go with the double coil. There is an O scale version that comes with two coils and is about $11 but the steel lates are a bit different. I bought one and will experiment with it in the next few days.
  19. hooknlad

    hooknlad Member

    i got an idea folks --i believe that they want you to use AC instead of DC because electrically, when you Charge an iron or steel core, you align the electrons to create an electro magnet. We all realize this.

    With DC, every time you energize the coil, you consistently Align the electrons to Basically force them to have a North and South pole. So every time, you strengthen the magnetic field. Eventually the iron or steel core Will become a magnet, thusly having no ability to turn it on or off after awhile.

    With AC , the current flow goes from Positive to Negative 60 times a second. The electrons will not align in just one way and wipe its magnetic memory out. So every time you energize the coil, the core becomes a magnet and its magnetic memory goes away , allowing you to be able to control the magnet.

    Does this make any sense???
  20. Gary S.

    Gary S. Senior Member

    There may be a little residual magnetism in the iron after putting DC on it. But typically it is not enough to hurt anything. They use soft iron in electromagnets, and the molecules in soft iron will migrate back to a random pattern after you remove the magnetizing force. DC electromagnets are used in alot of applications: The field of both AC and DC generators, the rotor of 3 phase synchronous motors, DC relays, Electromagnetic cranes that pick up entire junk cars.

    From reading the instructions, Kadee intended these to be used with DC, but they put in a byline stating that AC can be used but you will have to increase the voltage.

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