• Video- Kadee #708 Electromagnetic Uncoupler

    Today I decided to work on my Kadee #708 electromagnetic uncoupler. This device is made for HOn3 so it should work with n-scale. Having seen the video by Mr. Fifer about installing the uncoupler in Kato Unitrack I decided to give it a try in standard Atlas Code 80 sectional track.
    At first I just followed the Kadee instructions. I cut out the ties in a piece of 5 inch sectional track, attached the field plates to the electromagnetic coil and pushed the assembly up through the gap in the ties. Next I screwed on the center mounting piece to hold everything in place. No modification to the uncoupler at all. I made a little test track that followed the plan of the area on my layout where I want to use the uncoupler. It will be at the lead-in to the yard and the straight section is immediately after an 11" radius curve and is connected to the first turnout in the yard on the other side. I made the test section exactly that way.
    I put an Atlas GP7 and a couple of cars on the track and backed the cars over the uncoupler. Applying power resulted in a perfect uncoupling! I repeated the test several times and tried delayed coupling, pushing the uncoupled car off the uncoupler and over the turnout. Everything worked perfectly. Next I ran the loco over the uncoupler. I did this because I read an article online saying that the uncoupler assembled per the instructions would short out locos and required modification. In my case the loco ran over the uncoupler without problems. Next I put a Kato NW2 on the test track and repeated the tests without shorting out the loco. However when I tried my Bachmann Spectrum Heavy Mountain is shorted over the uncoupler on three consecutive tests. Clearly some modification was needed.
    I re-read the article about modifying the uncoupler and it seemed a lot of work, especially the part about bending the coupler pins on any rolling stock to be used over the uncoupler. I have a couple of regular magnet uncouplers on my layout and don't want to make my rolling stock unusable with them! I decided to try a different method.
    With the uncoupler assembled but not mounted in the piece of track and with the center mounting piece removed I used a huge pair of channel-lock pliers and gently bent the field plates in. I started at one end and bent it a bit, moved the pliers and bent again, moved the pliers, etc. until I had bent the entire length pretty evenly. I left the plastic spacer that fits between the field plates in place while I did this. (The plastic spacer is not the same as the center plastic mounting piece you see from the top.) How much did I bend them? I'm not sure, I just eye-balled the gap between the field plates and rails and stopped trying to bend them when the gap was about 1 to 1.5 millimeters.
    Once the field plates are bent the center mounting piece won't fit between them any more so that has to be filed down. I filed both sides, again just eye-balling it to make sure it was filed about the same amount on both sides. When it was sufficiently narrow to fit between the field plates I reassembled it in the track. I put it back in the test track and repeated my earlier tests. Still flawless uncoupling and no issues with my diesel locos. I put the steam loco on the track and voila!! It ran over the uncoupler perfectly without shorting.
    The entire modification took 30 or 40 minutes. I am now convinced this is the way I will go with all my uncouplers. I plan to purchase three or four more of these and do the same modification and get rid of my permanent magnet uncouplers.
    For the record I used a 12 volt, 12 amp DC power supply for all my testing. It is the same power supply that powers my turnouts and will also be powering my layout lighting. According to the Kadee instructions, using a 14V power supply you can activate the electromagnet for a couple minutes at a time without damaging it. In testing I never had it activated for more than a few seconds at a time. The 12V supply seems entirely adequate.
    Now I just have to cut the hole in my foam for the magnet, run the wires and add a momentary push button to my control panel. I guess I have a project for tomorrow!
    --Sherman

    [YOUTUBE]G1csEFIY6n8[/YOUTUBE]
    This article was originally published in forum thread: Video- Kadee #708 Electromagnetic Uncoupler started by Sherman View original post
    Comments 16 Comments
    1. Sleeper's Avatar
      Sleeper -
      I never could understand why manufactures have not come up with a flawless Electromagnetic Uncoupler. I was at a train show awhile back and they were selling Uncouplers. They said the HO was flawless, but not the N-scale. I can’t remember the name but, they said you had a 50/50 chance. Well that was it for me I decide at that point I would just use chop sticks.
      Now that I saw this video, I think I’m going to give it a try, Thanks
    1. Sherman's Avatar
      Sherman -
      I have wondered the same thing. Just a little modification on this one makes it work just fine, why can't a manufacturer just make one in n-scale that requires no modification? Maybe there's a business opportunity there.

      --Sherman
    1. Hoghead's Avatar
      Hoghead -
      Sherman,

      Now can you ballast over that and still have it work? I mean it looks like you've got it working slick but it would really stick out if you had one of these on every lead track to a yard unless there is some way to blend them into the scene. I could see how you could disguise it as a crossing at grade near an industry but what about a number of them in a yard?

      Scott
    1. Sherman's Avatar
      Sherman -
      Scott,

      It is possible to put some ballast on them in the middle and of course the sides. The two field plates sticking up will still be visible as will the ends of that center plastic piece. I have one I have disguised as a grade crossing and it looks OK I think. I may do another grade crossing but disguising the others will be tough. I'm just viewing it as a trade-off for reliable remote uncoupling.

      What I don't understand is why it isn't possible to make an electromagnet that goes completely under the track. Just cut a slot in the roadbed and put in the uncoupler then lay track over it. I suppose there is some technical reason. I purchased some magnet wire and am going to experiment with different configurations one of these days.

      --Sherman
    1. Hoghead's Avatar
      Hoghead -
      I thought that Kadee made an under the track electromagnetic uncoupler. I went to their website and sure enough they do, however it is for HO scale. Looking at the pictures though it seems that the HO under track electromagnetic and the HOn3/N electromagnetic are very similar. I wonder if the HOn3/N uncoupler would work under the track. Here is a couple of pictures. The one on the left is the HOn3/N scale uncoupler and the two on the right are the HO under the tracks uncoupler. They look the same other than the middle piece on the N scale one is screwed to the magnet with the track in between and the on for HO the middle piece is screwed to directly to the magnet and the whole assembly screwed to the bottom of the track. I'll bet if you screw the middle piece of the HOn3/N uncoupler to the magnet and the whole assembly to the bottom of the track, it would probably work like the HO one. Things that make you go Hummmmm...

      Scott

      Attachment 6304Attachment 6305Attachment 6306
    1. Sherman's Avatar
      Sherman -
      Scott,

      Thanks for posting that. I have an uncoupler that isn't mounted in the track yet. I could probably just screw the middle piece underneath as you mention and give it a try. Maybe I'll get a chance to do that in the next week or so. If it works that way then I don't think any modification would be required except to mount it underneath. Plus it would be very easy to mount into existing track, just make a hole underneath large enought to slide it up.

      --Sherman
    1. Hoghead's Avatar
      Hoghead -
      Sherman,

      Additionally I think you would then be able to ballast over it at least lightly to disguise it. Keep us posted with what you find out.

      Scott
    1. Jason Smith's Avatar
      Jason Smith -
      Suscribed, though I will most likely cheap out and go with regular magnetic uncouplers under the track.
    1. nycrr1's Avatar
      nycrr1 -
      Thanks for posting the video -- I have been searching for video of n scale uncoupling for a while! Much appreciated (along with the finishing tips!)
    1. Sherman's Avatar
      Sherman -
      OK, I did a quick fit test to see if I could mount a #708 completely below the ties. Unfortunately I don't have pics. When mounted normally the electro-magnet assembly with coil and field plates is normally held in position by the center piece which actually slips between the field plates. You control the height the field plates stick up by using two washers between the magnet assembly and the center plastic piece. The center plastic piece then screws into the flat piece of plastic that is glued to the bottom of the ties.

      To mount the assembly completely below the ties you attach the center piece to the magnet assembly. You then glue the flat plastic piece to the bottom of the ties. Now screw the center piece/magnet assembly to the flat plastic piece. The only catch here is that the screws have to be installed from underneath as they don't grip the center piece, only the flat plastic piece. Anyway, once that is done the screws can be tightened to bring the field plates in contact with the underside of the ties. Where the screws stick up through the ties or between the ties they should be snipped off.

      So it is possible to mount the whole shebang under the track with almost nothing visible from up top. However there are two issues, one minor, one maybe not so minor. First the minor issue. Ballast will fall through the ties and onto the center piece and magnet assembly. That is easily rectified by putting a piece of paper or masking tape on the bottom of the ties before gluing on the flat plate. The paper or masking tape will seal the gaps and prevent any ballast from falling through.

      The second issue could be more difficult to deal with. In normal mounting the field plates of the magnet project up through the track to (in my case) just below the level of the top of the rails. This results in a gap of just a hair over the normal gap between the uncoupling pin and the rail height. Which I think MT says should be 0.01", so call the total gap 0.015" or 0.02". Mounting the assembly below the track results in a much bigger gap between the uncoupling pins and the field plates. The gap is now the height of the rail plus the thickness of the ties plus the thickness of the paper or masking tape. The total gap could be 1/8". This could be large enough to affect the ability of the magnet to move the coupler pins.

      I didn't have time to do a thorough test and will try to do one later. In a quick check some of my couplers seemed to work normally and some hardly moved at all when power was applied to the magnet. I was using a smaller power supply for the test than I have on my layout (same voltage- 12VDC but less available current, 600mA vs. 12 amps) so I'm sure that has some effect. Only a more complete test with the actual power supply will tell for certain if this method of mounting will work reliably.

      If anyone else wants to give it a try I'd be interested in their results!

      --Sherman
    1. Hoghead's Avatar
      Hoghead -
      Thanks for the update Sherman,

      Keep us posted I'm interested in how this will all shake out.

      Scott
    1. MooseID's Avatar
      MooseID -
      If the magnetic field continues to be too weak to pull the couplers, try adding some turns to the field coil.

      I would try ten turns to start and adjust from there. You can get coil wire from Radio Shack and other sources.

      You do not have to change the power supply to do this.

      However, an increase in voltage will increase the current in the coil and the magnetic field. Be careful with this to prevent overheating the coil.
    1. Sherman's Avatar
      Sherman -
      Moose,

      The coil is already wound though I suppose I could unwind it and splice on some magnet wire, revarnish the splice and add turns that way. I already have some magnet wire.

      I just don't know if it would prove to be a real problem or not until I actually put it to the test. I was simply holding a car on a cut off section of flex track over the magnet in my "test". I need to assemble a length of track and make a test bed before deciding the magnet isn't powerful enough. Just looking at it the size of the coil in the Kadee unit actually seems like overkill for moving those tiny couplers.

      --Sherman
    1. Bryan's Avatar
      Bryan -
      If you are marginal on your magnetic field, make sure all your couplers are as free moving as possible, to make the magnets task easier... lube them with graphite powder.
    1. Sherman's Avatar
      Sherman -
      I bought an MT 'coupler kit' and it included some graphite powder. I haven't used it yet. I assume I just turn the coupler upside down, let a little drop in and then move it by hand to make sure it spreads around. Is there a better method of application?

      --Sherman
    1. Bryan's Avatar
      Bryan -
      For a pre-assembled coupler, that should do it... I drop a little in the coupler box during assembly, squeeze everything together tight (by hand), and burnish the parts together... when the pressure is released, the parts move very freely.