Magnetic Uncoupling

Ok guys, I am still on the fence about these, so I haven't trimmed off any pins......yet. Just a couple of questions for the magnetic guys;

Randgust - what is RDA? And what do you mean by the trimming?

And as far as the magnets placement, I remember reading articles about burying them under the track, does this work?

Not having the trip pins would look more proto, nut then again it would also require a large investment in Z scale couplers if that is an issue.

And, lastly, how do you get rust colored paint to stick to these things?

 

As originally designed, there's a mild point on the inside 'finger' of the knuckle area, and an equally mild point on the inside of the grip on the opposing coupler; this is for molding purposes. Two couplers subjected to any real stress will move vertically up and down; one goes up, one goes down, and the one that goes down pushes the trip pin lower so that it snags on all kinds of things. Even if you set the trip pin clearance right, they still can snag and derail.

Micro-trains fixed this in 1996 by making the ">" to a "<" at the finger and calling it "reverse draft angle". So the harder you pull the more the couplers center with each other. Trip pins don't move and are no longer a problem. Jim Fitgerald of Ntrak discovered this and showed how to modify old couplers by trimming them lightly with an Xacto knife. Takes seconds with practice. I've had to do hundreds of cars. Get a really sharp #11 blade and work toward the center, takes two very light cuts.

http://home.earthlink.net/~bhender730/sitebuildercontent/sitebuilderfiles/rda_mt.jpg

If you've set the trip pin clearance to .010 with the gauge, and you're still getting snags and derailments, this is the problem, plain and simple, and it is easily fixed.

Brass-colored trip pins do look terrible, just paint them grimy black with a small brush and dab a touch on the brass at the top. Don't paint the knuckle. Again, seconds. They are supposed to look like air hoses. Something should be there, to me, grimy black trip pins look better than nothing under there that looks like an air hose, either.

MT did cast them in brown, at least for a while, and in some styles I think they are still available.

I've intermixed Z couplers with N couplers, rebent the trip pins so they reach down further, and everything still works fine, including delay uncoupling. I find myself using Z couplers a lot more on custom work and special cars.

You can also PAINT magnets, along with the short magnets I tend to paint my between-the-rails installations to match the ballast and ties and have even painted stripes on a couple to camouflage them better. But step one is to cut them far, far shorter.

I've never had any luck with under-the-track installations, too powerful, too much false uncoupling. I have one ultra-powerful electromagnet (an original Kadee) at the yard throat that will pull apart the stubbornest couplers and delay-set them if necessary but I don't use it all that much.

I tend to put 'standard debris' alongside the track to mark the magnets. I like to put a stained and weathered wooden tie beside the track to mark the spot where it is instead of some kind of sign. The overall result is that I try to not hear any compliment on 'gee, I like your magnets' because they are just not all that noticeable.

I have cut off trip pins on lead knuckles of some locomotives that rarely use them (F-units, steam pilots) but overall, I think the system works really well - the two biggest flaws are that the stock magnets are just way too long, and the longevity of older MTA cars without RDA causes all kinds of grief with trip-pin snags on longer trains.

 

Thanks for the link! That was very instructive, and answers some of the problems I have seen with some of my cars.

 

Rather than rewrite a bunch of stuff, I will just say Randy covered it all.

And he's right. The KEY is to cut the magnets shorter so the chance of slack occurring while couplers are over the magnets is much reduced. Like I said in my other post, some of mine are only about 3/8" long (OK, after measuring with a ruler, closer to 1/2"). But even just cutting them in half (about 1" long) works well.

I have painted some couplers with Floquil rust and it is still on them and doesn't affect operation.

I don't know why the other brands even bother with trip pins. They don't work.

My style of operation obviates some of the AD track/whole train movement to cut cars anyway. I usually just pull a train into the yard, shuffle car cards to make up a new train, and switch to get those cars out and into the train. I don't really adhere to prototype operations.

Doug

 

It has been a long discussion already, but I just wanted to point out that visibility of the uncoupling magnets should not be an issue anymore - Kadee has released under the track magnets long back, and S&L Enterprises released the completely hidden modular uncoupling solution using button earth magnets. I have been using them all along and they work perfectly.

However, the first and foremost thing about magnetic uncoupling is absolute straight track and perfect alignment at least over 1ft of track for the uncoupling to work reliably. For me they never did as in my track plan the uncoupling locations have curves in most cases. Additionally, in my experience MT/Delayed magnetic uncoupling is very unreliable in N scale if you are doing typical switching operations (like I do). This is what happens with me:

1. You have to replace most of the iron weights in your freight cars with non magnetic weights
2. If you use Metal wheels, you will ALWAYS have issues with magnetic uncoupling - I have seen this with top notch FVM and Inter Mountain wheels, as well as Bachmann wheels. This is the main reason why MT always supplies their truck with plastic wheels and recommends using plastic wheels
3. Small switchers like Kato NW2 and Atlas VO-1000 will go considerably slower all of a sudden when travelling over the magnet - this is not so apparent with heavier locos with more inertia, but is definitely visible for switchers
4. The fiddly/small couplers and it's pins will require periodic maintenance and realignment over continuous use - can't avoid it.
5. If you have a permanent magnet uncoupler on a main line/yeard lead, you are bound to have at least one accidental uncoupling in a one hour session!

Some solutions that I have thought of (to be used in my next layout) -

1. use one magnet for each of your yard tracks, and/or industry, placed in the exact place where you want to uncouple, with one car clearance so that you can push the car back when coupling
2. As others have mentioned earlier - use as small magnets as possible, preferably use S&L Enterprises Hidden Earth Magnets.
3. At least 6" of straight track on either side of the magnet - a big aesthetic issue for people like me who prefer curved tracks and switching actions in tight space
4. Remove all magnetic metal weights - alternatives are marble dust, sand, non magnetic metal.
5. And last but not the least - servo driven, under the table magnetic plates that come up when you want to uncouple with a flip of a switch, and goes down when you are done, and stays down when you don't need them at all. This one technique can solve most of the magnetic uncoupling issues and can enable mainline/yard lead uncoupling with no accidental uncoupling issues.

 

One thing that hasn't been mentioned - I have much better luck with truck mounts than body mounts, for several reasons:

Vertical height on the coupler pin to wheel tread platform is constant. On a body mount, any vertical curve at all over the carbody changes the trip pin alignment.

Horizontal alignment of the trip pin to the track centerline is much better with a truck mount; if you think coupling up on a curve with body mounts can be interesting, the uncoupling is far worse. I have successfully placed my tiny cut-down in-track magnets on curves as tight as 9 3/4 and reliably uncoupled, but only with truck mounts, and not with delay.

Truck mounts that are pre-assembled tend to be more reliable than home-assembled body-mounts, at least the way I work. I also find that the body-mounts do take a lot more maintenance from the screws loosening, boxes twisting, etc.

So if your priorities are on reliable coupling and uncoupling, that's a good reason to use truck mounts as well. I'm fully aware that's absolutely against conventional wisdom and trends, can't help that, can only tell you what works. I have many of the old Quality-craft 25' cast metal log buggies; about half had the coupler support ends cut off and have truck-mount archbars, the other half have sill-mounted 1024's. Even on cars that short, the differences are painfully obvious - the truck-mounts work better even if the body-mounts look better. I'm converting a lot of the body-mounts on those cars over to link and pin anyway (with Z's on the ends) as they run in blocks, that's one sure way to prevent false uncoupling!!

I do use very small sections of magnets on spurs with clearance just beyond them to push back and recouple in many locations. A truly tiny magnet may only have enough power to pop the knuckle open without throwing the entire head over to the delay position, but in exchange for that your likelihood of false uncoupling is minimal.

I've been using more and more metal wheels and I haven't noticed any increased problem with my smaller in-track magnets. I have seen chassis designs with the motor right down on the rails get reasonably impacted; my electromagnet at the yard throat could absolutely dead-stop an old Rivarossi SW1500 with the motor barely over top of the railhead. Most aren't quite that bad.

 

About parasite uncoupling over magnets, as said before I just recommand NOT to put any permanent magnet on a mainline or even on a siding. Permanent magnets should only be put on spurs where cars are pushed to place.

For mainlines or siding I strongly recommand to use electromagnets (or hinged permanent magnets that can be remotely side swinged, as said earlier). Myself I'm modelling Z scale (1:220) but physics are the same whichever the scale. For that purpose I'm using Kadee #309 electromagnets, made for "Horribly Oversized" (HO ). I just omit to put most external steel plates in order to "concentrate" magnetic field, to have a better match with my beloved small scale. I guess that should work for slightly broader N scale.

Will try to remember to set a few pics of my uncouplers here when I work with my main computer...

Dom

 

Knew I had one somewhere. This is a demo of one of my custom-build Climax models, but at the end of this video I'm repeatedly stopping, uncoupling, recoupling, and uncoupling on my 'main line' with one of my tiny little between-the-rails magnets. The Climax has a Z coupler, the boxcar behind it has a regular one. As you can see, even with only two cars behind the locomotive, it doesn't false uncouple, and I can still back it up and easily uncouple.

https://youtu.be/hjlvj7f_rBA

I'm just trying to prove a couple points here; just how small my magnets really are, the combination of N and Z working, and how I mark my magnet locations. On the adjacent piggyback spur I have another 'cut' small magnet, that lets me drop a car and push it clear behind the magnet, note the tie marking the spot.

For the record, the coupler on the pilot of the locomotive is a dummy, I did not cut the pin off!

Here's another one of me switching with my micro-sized GE 25-tonner, and delay-uncoupling and dropping to my fuel distributor. No stickers. And I'm moving one car back and forth over the shortened magnet with no false uncoupling, the only uncoupler in the area is the one right near the pile of rail.

https://youtu.be/-KYPCfBCJcU

My 25-tonner is barely controllable, it's a little rocket sled, so yeah.... if that was LPG gas in those cars there'd likely be an explosion!

 

Everyone has their druthers. I druther be able to uncouple a car an inch before or after where a magnet may be. I like backing in an industry and spotting a car at the exact place it should be dropped. With the newer slow speed/scale speed motors...I like the feeling that I wont get unwanted uncouplings anywhere on the layout. Like I said...its a matter of 'Druthers". Its all good

 

and some of our [ www.nscalekits.com ] 25' log spine cars - beautifully made up, if I may be so bold. A great consist.

Peter

Peter Harris
N Scale Kits
www.nscalekits.com

 

I want to modify my statement, above, about trip pins on brands other than MT. Accumates actually work pretty well with uncoupling magnets.

Doug