Magnets For Aligning a Lift Out/Lift Gate: Problems?

[Capt. Grimek]

I was at a train show a week ago and one of the display layouts used an old speaker magnet to hold down and align a lift out or lift gate. I would have thought that a magnet of any appreciable size would "freak out" a locomotive's motor or reverse the polarity or have some other issues, but their locos seemed to run fine over the magnets. I didn't realize until I'd gotten home though if they were running a DC powered layout or DCC. Would that make any difference? I liked the ease of aligning tracks on the lift out with the approach tracks. Tolerances didn't have to be as designed into the benchwork as usual. Made for a quick release and replacement method too. Are there any potential problems with this use of magnets and locos? (Especially steam) Thanks.

[Phoebe Vet]

I've never used anything as large as a speaker magnet, and my swing gate uses a mechanical latch, but I use magnets to hold scenery against the back wall, and have not had any problems.  My minature world is DCC powered and trains run within a few inches of the magnets with no problems.

[retsignalmtr]

think of all the kaydee uncoupler magnets on layouts and all the loco motors that have permanent magnets in their motors and you'll see there isn't any problem with them. using a magnet to align tracks at a lift out cannot be dependant only on them. there is probably some side to side alignment that the magnats alone will not provide and requires a tighter tollerance for rail alignment. i like the idea of the magnets to hold the liftout down but there has to be another thing to keep the rails in line at the joints. my club is looking to build a lift out or lift up for our show layout and i saw many at springfield from very simple to very elaborate.

[Capt. Grimek]

Thanks for your responses guys. This particular layout used ONLY magnets to align the tracks. The magnet was large/powerful enough to be very steady, yet still allow a last second adjustment in seconds if someone passed through the opening. That was the appeal. Isn't it possible to reverse the polarity on motor wire coil windings if a magnet is passed over it? I thought I'd remembered a H.S. science experiment/demonstration that did that, hence my concern. However it has been 40+ yrs. so I may not remember that correctly. Using magnets to attatch and detatch scenery to the wall is a cool idea that would never have occured to me.

[tomikawaTT]

The key magnets in our model motors are permanent magnets, mostly rare earth types that have to be allowed to solidify from the molten state in a powerful magnetic field to magnetize them in the first place.  Nothing short of the magnets in a linear particle accelerator is likely to have much effect on them.

The windings in our motors reverse their polarity once every revolution.  That's what makes them turn.  Since they are literally wrapped in the field of the motor's permanent magnet, outside magnets won't influence them at all.

Chuck (Modeling Central Japan in September, 1964)

[Phoebe Vet]

Capt. Grimek

Using magnets to attatch and detatch scenery to the wall is a cool idea that would never have occured to me.

I fasten a can lid retrieved from the recycle bin and pounded flat to eliminate can opener damage and ridges on the wall, and embed a cheap Radio Shack magnet in the terrain or building.  It holds tight in place and is easily removed if needed.  The can lid is large enough that only minimal care is required in alignment.

 

[Capt. Grimek]

Thanks Chuck. I appreciate the explanation. Just a very brief follow up question-does some of this differ from the earlier box frame motors of my youth like the Mantua, Athearn stuff? Has this changed with the advent of can motors? Are permanent magnets a more recent development than say, the 1960's in HO locomotives? I thought it was a concern with earlier motors but as I said, maybe (probably) remembering that incorrectly. (I was a teenage then.) Thanks. By the way, can you tell me where I can find a gallery of your Japan(ese) based layout pics? Phoebe Vet, thanks for the details. I think this will come in very handy.

[tomikawaTT]

Capt. Grimek

Thanks Chuck. I appreciate the explanation. Just a very brief follow up question-does some of this differ from the earlier box frame motors of my youth like the Mantua, Athearn stuff? Has this changed with the advent of can motors?

The main difference is in the strength of the rare-earth magnets (much stronger than the alnico magnets which were state of the art in 1950) and the design of modern can motors which wraps the magnet around the coils rather than relying on iron 'legs' to crate a field at the armature.  The end result is a lot more torque for the amount of current applied.

 Are permanent magnets a more recent development than say, the 1960's in HO locomotives? I thought it was a concern with earlier motors but as I said, maybe (probably) remembering that incorrectly. (I was a teenage then.)

The old Pittman motors with their narrow field legs were permag motors, which had pretty much become the standard when I started modeling HO with a DC power pack in 1948.  Lionel used wound-field motors, which are necessary for AC operation.  Those early motors had relatively weak field magnets which could be overridden by more powerful magnets - especially since the rotating coils were 'bare' over a large percentage of their diameter.  They have been much improved - but I have my very first motor (in a Mantua 0-4-0) and it still works.

 Thanks. By the way, can you tell me where I can find a gallery of your Japan(ese) based layout pics? 

At present there is no gallery - only a couple of shots (not on the internet) of some of my hand-laid specialwork at locations deep in the netherworld.  My layout strongly resembles the 'under construction' phase of Disney World's 'Himalayan Adventure' thrill ride - raw steel framework, with a rollercoaster of track running through it seemingly at random.  I have yet to lay a millimeter of rail that will be on the daylight side of the tunnel portals leading to, 'The rest of Japan.'

Chuck (Modeling Central Japan in September, 1964 - eventually)