Electromagnetic Uncoupling That Works!

[Gary S]

Gary, I like you uncoupling magnet design. I'm curious, do you use Athearn cars with steel weights or Athearn cabooses with steel ladders?

Russ, all my cars are weighted with lead - because the magnets absolutely will drag a steel-weighted car around. But on that note, so will a Kadee 308 under-the-ties permanent magnet. I do weight my cars a little bit heavier than NMRA standards because it helps keep the slack out of the cars when going over permanent magnets at the spurs. I know that everyone likes to have "super-free-rolling" cars, but really they are the bane of magnetic uncoupling. It is best to have cars with just a pinch of drag in them.

I do have Athearn cabooses (with lead weights). From memory, I didn't have any issues with the ladders. I think they are small enough and high enough to not make the car roll to the magnet. >>>>> okay, I just got back from the train room. Took an Athearn caboose. The magnet had little to no effect on it. I tried it in various positions, then activated the magnet. Out of about 10 tries, there was one time when the caboose moved maybe 1/8 of an inch.

I'm asking because I saw a similar product at a train show recently. I can't remember what it was called, and the guy making them out of his garage doesn't have a web site, just an email address. I took his brochure with me and after reading it over, I found that he did not recommend any steel be in rolling stock. None of the Athearn steel weights or Tichy's use of 1/2 inch steel nuts for weights or Athearn's steel ladders on cabooses.

Sounds right as mentioned above. No steel weights!

but he advised that the magnets are strong enough that they might derail cars if there is steel in them other than the Kaddee trip pin.

I don't see how it would derail a car, but the e-magnet will definitely make a car roll toward it. But again, so will a Kadee 308. The e-mag will also attract steel axles. I use Intermountain wheelsets for the most part, which are ~almost~ totally non-magnetic - not enough to be attracted to the magnet with a weighted car.

Also another question about the Kaddee O-scale coils. Will they stand a short period of time energized, or are they a momentary type that will burn out if energized for more than a few seconds? One reason that I haven't considered using Kaddee Ho-scale electromagnets on a module is that when we set up at shows anyone in the club can operate on anyone's module, so I try to avoid any momentary contact components.

I mentioned some of this in my reply to Jack above, but first, the Kadee O scale coils are the exact same thing as the HO scale coil, you just get two of them.

Using some basic electrical math, the series twin coils at 24 volts are 33 percent stronger than a single coil at 16 volts, yet they draw only .75 the current of the single at 16 volts. Therefore, they can remain on longer without frying. I do use an automatic time delay circuit to control the magnets - push and release the button, and the magnet turns on and then turns off after five seconds (this is adjustable, but 5 seconds seems to work for uncoupling). The time delay isn't so much for protection as it is to allow both hands on the throttle.

One other thing - the twin coils could be wired in parallel and operated from a 12 volt supply.... or if a person wanted a REALLY strong uncoupler, put 16 or 18 volts on the parallel coils!

Now, with my circuit, if the button was just held down continuously, the magnet would turn right back on after the 5 second delay, so it is not FooL prOOf. But a circuit could certainly be designed to keep the magnet off for a period of time between energizations. I didn't do that because I have control over who will operate on my layout.[/quote]