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Author Topic: Magnetic uncoupling  (Read 384 times)

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Offline Jonathan Prince

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Magnetic uncoupling
« on: May 14, 2018, 12:52:29 pm »
Just done a bit of research into the whole uncoupling business and I've discovered a few things I hadn't realised (being a complete novice...)

Originally I planned to make little mechanical ramps, but seeing how accurately you have to position them has put me off that idea a bit. However I've realised that the magical art of magnetic uncoupling isn't as complex/expensive as I'd thought. I hadn't realised you could get N gauge versions of the little metal coupling arms to attach to the couplings that easily (Peco NR103 or Gm EM2).

However, I've heard they don't work with 'sprung' couplings. A brief inspection of my stock has revealed that there's a fairly even split between the normal 'unsprung' couplings, 'sprung' couplings and some unsprung couplings attached with a "wiggly" piece of plastic to allow it to flex up and down (anyone heard of these?)

Of the sprung couplings, nearly all my locos have them covered inside the chassis so I'd assume they'd work OK with the magnets? However my Farish coaches do indeed have uncovered springs in the bottom. Is there any solution for this - perhaps attaching a small cover to the bottom to hold the spring in, or can I take the springs out completely (or will the couplings then 'droop'?)

I'm thinking of making mechanically controlled magnets which move up and down. Would a normal moderately strong magnet manage to uncouple from below 9mm plywood, or do I need to drill some holes to allow them to move up closer to the track?

Thanks in advance!

Jonathan

Offline Trev

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Re: Magnetic uncoupling
« Reply #1 on: May 14, 2018, 01:02:43 pm »
Hi Jonathan,
I've operated a few layouts at exhibitions where the stock has been fitted with the Peco metal lift arms and they work surprisingly well.

In terms of stock with sprung couplings, you don't need to put these lift arms on all your stock. For example, if a loco has a sprung coupling, put the lift arm on the first wagon or coach that will be connected to it and that will work fine.  Depending how you arrange your stock into trains, you should be able to do as much uncoupling as you wish.

As for a mechanically controlled magnet to move up and down, yes this can work.  Another member posted instructions a while ago as to how he had done this.  If you do a search for couplings, you should find it.
Whenever I write a letter to someone, I add a footnote briefly explaining Ohm's law. It's my P.S. de resistance.

Offline Jonathan Prince

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Re: Magnetic uncoupling
« Reply #2 on: May 14, 2018, 01:57:53 pm »
Hi Jonathan,
I've operated a few layouts at exhibitions where the stock has been fitted with the Peco metal lift arms and they work surprisingly well.

In terms of stock with sprung couplings, you don't need to put these lift arms on all your stock. For example, if a loco has a sprung coupling, put the lift arm on the first wagon or coach that will be connected to it and that will work fine.  Depending how you arrange your stock into trains, you should be able to do as much uncoupling as you wish.

As for a mechanically controlled magnet to move up and down, yes this can work.  Another member posted instructions a while ago as to how he had done this.  If you do a search for couplings, you should find it.
Thanks for the reply! Your logic does make sense, although in my case the locos will have the lift arms and the coaches won't. I've heard that the Gm EM2 ones work better (as they have a larger metal surface) but if the peco ones are fine then I'll get those as they're 2/3 the price.

I searched for couplings but unfortunately couldn't find the post you were talking about - maybe I'm not looking hard enough...

Offline TrevL

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Re: Magnetic uncoupling
« Reply #3 on: May 14, 2018, 06:12:32 pm »
Hi Jonathan,
I've operated a few layouts at exhibitions where the stock has been fitted with the Peco metal lift arms and they work surprisingly well.

In terms of stock with sprung couplings, you don't need to put these lift arms on all your stock. For example, if a loco has a sprung coupling, put the lift arm on the first wagon or coach that will be connected to it and that will work fine.  Depending how you arrange your stock into trains, you should be able to do as much uncoupling as you wish.

As for a mechanically controlled magnet to move up and down, yes this can work.  Another member posted instructions a while ago as to how he had done this.  If you do a search for couplings, you should find it.

Thanks for the reply! Your logic does make sense, although in my case the locos will have the lift arms and the coaches won't. I've heard that the Gm EM2 ones work better (as they have a larger metal surface) but if the peco ones are fine then I'll get those as they're 2/3 the price.

I searched for couplings but unfortunately couldn't find the post you were talking about - maybe I'm not looking hard enough...


You need to look at Jon's thread @PostModN66  http://www.ngaugeforum.co.uk/SMFN/index.php?topic=14792.30, it is post 42, and gives the lowdown on how it's done,  He also has a very good Youtube channel where you can see it operating faultlessly.
« Last Edit: May 14, 2018, 06:17:21 pm by TrevL »
Cheers, Trev.


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Offline Jonathan Prince

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Re: Magnetic uncoupling
« Reply #4 on: May 14, 2018, 06:43:02 pm »
You need to look at Jon's thread @PostModN66  http://www.ngaugeforum.co.uk/SMFN/index.php?topic=14792.30, it is post 42, and gives the lowdown on how it's done,  He also has a very good Youtube channel where you can see it operating faultlessly.

Ah thanks! I had actually come across that video whilst looking around, but didn't realise there was a post here explaining it! Very useful explanation - I will try something along those lines

Offline Jonathan Prince

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Re: Magnetic uncoupling
« Reply #5 on: May 15, 2018, 06:34:57 pm »
In terms of stock with sprung couplings, you don't need to put these lift arms on all your stock. For example, if a loco has a sprung coupling, put the lift arm on the first wagon or coach that will be connected to it and that will work fine.  Depending how you arrange your stock into trains, you should be able to do as much uncoupling as you wish.
Sorry to reawaken the thread again, but I've just remembered another thought I had: isn't the problem with the sprung couplings that the magnet will pull the spring out from underneath?
In this case, even though the magnet will be attracting the lift arm of the other coupling, won't it accidentally pull out the springs as well? Or should I just be extra careful lining up the trains with the magnets so the magnet is never on/raised when the sprung coupling is too close?

I don't really have much idea of the relative strengths/distances of the magnets, lift arms and springs, so maybe I'm overthinking it...

Offline PLD

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Re: Magnetic uncoupling
« Reply #6 on: May 15, 2018, 07:31:32 pm »
However, I've heard they don't work with 'sprung' couplings.
The issue with sprung couplings is whether the pull of the magnet is sufficient to overcome the tension of the spring. A stronger magnet often isn't the solution due to the lightness of the rolling stock meaning it can pull down the entire wagon! the solution is to reduce the strength of the spring by removing a couple of coils.

Of the sprung couplings, nearly all my locos have them covered inside the chassis so I'd assume they'd work OK with the magnets? However my Farish coaches do indeed have uncovered springs in the bottom. Is there any solution for this - perhaps attaching a small cover to the bottom to hold the spring in, or can I take the springs out completely (or will the couplings then 'droop'?)
Not sure how you think having the spring enclosed makes a difference - it doesn't... removing the springs and the couplings will droop rendering them non-functional as couplings...

isn't the problem with the sprung couplings that the magnet will pull the spring out from underneath?
In this case, even though the magnet will be attracting the lift arm of the other coupling, won't it accidentally pull out the springs as well?
Nope... Coupling springs are generally brass so are not attracted to the magnets.


Offline Jonathan Prince

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Re: Magnetic uncoupling
« Reply #7 on: May 15, 2018, 08:09:06 pm »
Nope... Coupling springs are generally brass so are not attracted to the magnets.
Aha! I had got the wrong end of the stick - I thought the issue was the springs being pulled out by the magnets! It didn't occur to me the springs would be strong enough to stop the magnet pulling the lift arm down. Thanks for explaining this to me - I thought I'd have little springs pinging out and getting lost all around the layout!  :D

Offline Paul-H

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Re: Magnetic uncoupling
« Reply #8 on: May 15, 2018, 10:40:18 pm »
Springs being pulled out of the coupling by the magnet can and does happen to the Dapol Magnetic couplers though, a totally different system though so not really relevant here.

Paul

 

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