Jump to content


Google Ads are only seen by non-members of RMweb - Create an RMweb account and you'll only receive modelling ads.

Photo

Any Question Answered




  • Please log in to reply
1543 replies to this topic

#1526 chrisveitch

chrisveitch

    Registered Member


  • Members
  • Pip
  • 26 posts

Posted 16 October 2017 - 08:46

Permanent magnets need to be raised/lowered away from the un-coupling position so they act like electro-magnets . In the past I have used 1/4"/6mm ones sliding up/down in K&S tube, and worked by servos, an idea gleaned from Stuart Bailey. I think if I remember correctly that Ian Morgan uses a similar arrangement with the magnets on hinged flaps.

 

Here are acouple of shots of my arrangement. Lowered and raised. The magnets sit just under the sleepers with a thin layer of paper between- to hide them and allow for ballasting. All very crude as usual for me, but it works, which is all that is needed.

 

attachicon.gifRMweb 2mm 01.jpg

 

attachicon.gifRMweb 2mm 02.jpg

 

This particular one is for two magnets on adjacent tracks. I have arranged up to four across a baseboard - saves on servos.

 

hope it might give you some ideas

 

Izzy

 

 

Here is my arrangement under Freshwater. This one covers 3 parallel tracks. I drilled very small holes between the tracks so I could see where the magnets needed to go. The baseboard is something like 3mm MDF.

 

The servo arm rotates so it changes the axis of the magnets rather than just lowering them. The magnets need to move quite a long way away to ensure they do not cause unwanted uncoupling. In fact, I have since modified them so they rotate to nearly 90 degrees now. I have also replaced the Merg Servo4 modules with Merg CBus and CANSERVO8 modules, but that is another story.

 

I am sure these magnets would work through much thicker baseboards.

 

attachicon.gifmagnets_raised.jpg

attachicon.gifmagnets_lowered1.jpg

attachicon.gifmagnets_lowered2.jpg

 

 

Thanks for the suggestions guys - definitely food for thought. 



Google Ads are only seen by non-members of RMweb - Create an RMweb account and you'll only receive modelling ads.

#1527 2mmMark

2mmMark

    Member


  • Members
  • PipPip
  • 602 posts

Posted 16 October 2017 - 08:58

At the risk of being flamed for asking something that's been asked a dozen times before, can anyone point me in the direction of appropriate and up-to-date advice regarding suitable magnets for DG couplers?

 

I'm currently taking my first tentative steps and have assembled a small test rig with a couple of neodymium magnets and couplers on a couple of surplus Peco underframes but I can't seem to get the location of  the magnet right. It's on a bit of 6mm MDF and recessing one into the underside seems to be a bit hit-and-miss, whereas one positioned directly below the sleepers is far too powerful. Am I better off using electromagnets and winding the power down until it's just enough? Any help would be greatly appreciated. 

The 2mm Beginners Guide has a section on using neodymium magnets which slide underneath the track. I tink there are some photos of them in one of the thread here.  Might be in Jerry's Bath Queen Square or Highbury Colliery topics.

 

If you can can't  find them, I'll repost.

 

Mark



#1528 Kylestrome

Kylestrome

    Member


  • Members
  • PipPip
  • 349 posts
  • LocationEast of London and west of Berlin

Posted 16 October 2017 - 12:07

At the risk of being flamed for asking something that's been asked a dozen times before, can anyone point me in the direction of appropriate and up-to-date advice regarding suitable magnets for DG couplers?

 

Did someone mention magnets?  :scratchhead:

 

You could do worse than use the coils from 12V relays like these.

 

DSC_0037.jpg

 

The photo shows how I extend the pole piece to track level with a piece of 5mm diameter steel rod glued on with CA. These coils have the advantage that they do not run hot because they are designed to remain 'on' for extended periods

 

DSC_0040.jpg

 

Here's how it looks from above after installation. The reason the sleeper has a chunk cut out of it is because I forgot to drill holes before laying the track! 

:banghead:

 

David

 

PS. I also use these relays for changing points and crossing vee polarity, but that is another story.

 

DSC_0028.jpg


Edited by Kylestrome, 16 October 2017 - 12:10 .

  • Informative/Useful x 3

#1529 modfather

modfather

    Member


  • Members
  • PipPip
  • 726 posts
  • LocationAuckland

Posted 16 October 2017 - 23:43

Dec 1995 article

12.jpg

if you have not got a copy the back issues archive get one it is a goldmine of useful tips

Nick


I'm afraid all of mine have small parting stubs left behind. Maybe the design has been changed in the interim?

#1530 nick_bastable

nick_bastable

    Member


  • Members
  • PipPip
  • 1,070 posts

Posted 17 October 2017 - 08:37

I'm afraid all of mine have small parting stubs left behind. Maybe the design has been changed in the interim?

designs change it happens apologies to all for leading up a blind alley

 

Nick


  • Friendly/Supportive x 1

#1531 modfather

modfather

    Member


  • Members
  • PipPip
  • 726 posts
  • LocationAuckland

Posted 17 October 2017 - 10:46

designs change it happens apologies to all for leading up a blind alley

Nick


Not complaining, just saving the next person the time spent trying.

Question 2 - are the jinty conversion roads designed to be used single thickness or laminated?

Kind regards, cautious of Auckland.

#1532 2mm Andy

2mm Andy

    Member


  • Members
  • PipPip
  • 739 posts

Posted 17 October 2017 - 13:15

Not complaining, just saving the next person the time spent trying.

Question 2 - are the jinty conversion roads designed to be used single thickness or laminated?

Kind regards, cautious of Auckland.

 

They should be laminated from two layers. A single layer would be very flimsy, especially with the fluting.

 

Andy



#1533 John57sharp

John57sharp

    Registered Member


  • Members
  • Pip
  • 24 posts

Posted 19 October 2017 - 13:43

Just to be sure before I cut metal, is it ok to slice off the shaft at the contacts end of the motor, and are there any measures I should take to protect the bearings etc? I plan to use a slitting disk.

TIA

John
Just to be sure before I cut metal, is it ok to slice off the shaft at the contacts end of the motor, and are there any measures I should take to protect the bearings etc? I plan to use a slitting disk.

TIA

John

Attached Thumbnails

  • IMG_4155.JPG


#1534 Ian Morgan

Ian Morgan

    Member


  • Members
  • PipPip
  • 262 posts
  • LocationHampshire

Posted 19 October 2017 - 15:02

  1. Wrap the motor in Sellotape to prevent filings getting inside it,
  2. Clamp end of shaft in a big vice, to act as a heat sink. Support motor in fingers.

 

Good Luck.



#1535 2mm Andy

2mm Andy

    Member


  • Members
  • PipPip
  • 739 posts

Posted 19 October 2017 - 15:33

 

  1. Wrap the motor in Sellotape to prevent filings getting inside it,
  2. Clamp end of shaft in a big vice, to act as a heat sink. Support motor in fingers.

 

Good Luck.

 

 

I'd add that it is critical that you don't let the motor shaft get too hot as the bearings are often plastic. As well as using the heat sink idea I've cut the shafts using a series of short sessions with the cutting disc allowing the shaft to cool between times instead of trying to go through it in one go.

 

Andy



#1536 John57sharp

John57sharp

    Registered Member


  • Members
  • Pip
  • 24 posts

Posted 19 October 2017 - 17:52

I'd add that it is critical that you don't let the motor shaft get too hot as the bearings are often plastic. As well as using the heat sink idea I've cut the shafts using a series of short sessions with the cutting disc allowing the shaft to cool between times instead of trying to go through it in one go.
 
Andy


Andy and Ian thank you both.

Done!

Phew.

#1537 DavidLong

DavidLong

    Member


  • Members
  • PipPip
  • 832 posts
  • LocationMostly Atherton. Sometimes Old Colwyn.

Posted 28 October 2017 - 19:09

Did someone mention magnets?  :scratchhead:

 

You could do worse than use the coils from 12V relays like these.

 

attachicon.gifDSC_0037.jpg

 

The photo shows how I extend the pole piece to track level with a piece of 5mm diameter steel rod glued on with CA. These coils have the advantage that they do not run hot because they are designed to remain 'on' for extended periods

 

attachicon.gifDSC_0040.jpg

 

Here's how it looks from above after installation. The reason the sleeper has a chunk cut out of it is because I forgot to drill holes before laying the track! 

:banghead:

 

David

 

PS. I also use these relays for changing points and crossing vee polarity, but that is another story.

 

attachicon.gifDSC_0028.jpg

 

David,

 

Thanks for the tip about the relays. I bought a pack of five on Ebay for £8.91 which, with a few pence for the steel rod extension, will make the uncouplers about £2 each. Considerably cheaper than the £7.50 for the Kerr type these days.

 

By the way, do you use AC or DC with them? I tried one with both today and couldn't see much difference in performance. I've found that the Kerr types seem to work much better with AC.

 

David



#1538 Kylestrome

Kylestrome

    Member


  • Members
  • PipPip
  • 349 posts
  • LocationEast of London and west of Berlin

Posted 28 October 2017 - 20:08

By the way, do you use AC or DC with them? I tried one with both today and couldn't see much difference in performance. I've found that the Kerr types seem to work much better with AC.

 

David

 

I use 12V AC which makes the couplings vibrate a bit and 'un-sticks' any that are reluctant to uncouple. 

 

There is a theory that using AC avoids magnetising the DG steel dropper wires, but I don't know how much truth there is in it.

 

David

 

PS. I'm pleased someone finds my posts useful.  :)


Edited by Kylestrome, 28 October 2017 - 20:10 .

  • Thanks x 1

#1539 Nigelcliffe

Nigelcliffe

    Member


  • Members
  • PipPip
  • 3,138 posts

Posted 29 October 2017 - 16:20

David,

 

Thanks for the tip about the relays. I bought a pack of five on Ebay for £8.91 which, with a few pence for the steel rod extension, will make the uncouplers about £2 each. Considerably cheaper than the £7.50 for the Kerr type these days.

 

By the way, do you use AC or DC with them? I tried one with both today and couldn't see much difference in performance. I've found that the Kerr types seem to work much better with AC.

 

David

 

Is anyone still buying the PK electromagnets ?  They're a terrible design.    The somewhat similar outside, but considerably better inside alternative is the Seep badged electromagnet.   The Seep delivers a decent field strength and works on a fraction of an amp.  Unlike the PK, which seems to be designed to dim your house lights when operated.  

 

Or, there's "chop up a relay".  Or move rare-earth magnets under the baseboard as alternatives. 

 

- Nigel


  • Agree x 1

#1540 Donw

Donw

    Member


  • Members
  • PipPip
  • 6,928 posts
  • LocationMinehead

Posted 29 October 2017 - 19:46

Or wind your own as Julia Adams did for Highclere details here http://www.rmweb.co....tracted-to-you/

 

Don



#1541 2mmMark

2mmMark

    Member


  • Members
  • PipPip
  • 602 posts

Posted 29 October 2017 - 20:43

Is anyone still buying the PK electromagnets ?  They're a terrible design.    The somewhat similar outside, but considerably better inside alternative is the Seep badged electromagnet.   The Seep delivers a decent field strength and works on a fraction of an amp.  Unlike the PK, which seems to be designed to dim your house lights when operated.  

 

Or, there's "chop up a relay".  Or move rare-earth magnets under the baseboard as alternatives. 

 

- Nigel

 

I don't know if the design has changed but the batch I bought directly from Phil Kerr have been tough and reliable over many years usage. They do need an appropriate transformer and a button capable of carrying the current.

 

Nowadays, I think my preference for the type of layout I build is for rare earth magnets moved mechanically under the baseboard.

 

On the first layout Richard Wilson and I jointly built, we used a Post Office 3000 relay coil. Fortunately we had room under the baseboard as it is not a compact design.

 

Mark



#1542 Kylestrome

Kylestrome

    Member


  • Members
  • PipPip
  • 349 posts
  • LocationEast of London and west of Berlin

Posted 29 October 2017 - 21:16

Or wind your own as Julia Adams did for Highclere details here http://www.rmweb.co....tracted-to-you/

 

Don

 

I've done that in the past. They worked very well but very nearly burnt a hole in the baseboard when a push button switch got stuck 'on', hence my preference now for ex-relay coils and spring loaded toggle switches.

 

David


Edited by Kylestrome, 29 October 2017 - 21:17 .


#1543 DavidLong

DavidLong

    Member


  • Members
  • PipPip
  • 832 posts
  • LocationMostly Atherton. Sometimes Old Colwyn.

Posted 29 October 2017 - 22:09

I've used the Kerr magnets with ordinary Maplin push buttons for years and have never had any trouble with them. They have worked everytime and no burnouts on switches or coils. What on earth to people do with them to have these sort of results? My main objection is that they have got rather expensive and as for Seep coils they cost even more! I have better things to do with my life than wind my own coils and, although ingenious, I'm really not sold on sliding magnets.

Hence the appeal of David's idea which, with a bit of modification work, gives a working magnet for a couple of quid. Excellent!  :yes:

 

David



#1544 Donw

Donw

    Member


  • Members
  • PipPip
  • 6,928 posts
  • LocationMinehead

Posted 29 October 2017 - 23:09

Probably academic if you get get suitable onnes for about £2  but if needed a coil shouldn't need to get to hot. The Magnetic flux is proportional to the ampere-turns if it is to hot increase the turns (and possible decrease the wire size) so the ampere turns remains the same but the current is lower. I used to juggle with things like this to ensure ampliances would not overheat when stalled (or a solenoid jammed). The other alternative is to make a fusible link in case the push button jams. Wrap a bit of paper round the coil attach one end of the coil to a pice of solder and one of the leads to the other end of the solder  so the solder lays across the coil and wrap more paper over it. making sure there is enough space for the solder to melt into. 

If you have never solder wire to solder pass the end of the wire through a flame and push gently into the end of the solder remove the flame. It may take a bit of practice. We had a girl on the production line who was ace at doing it but she got pregnant and took maternity leave. The other girls on the line complained it was too difficult so I went onto the line and did some myself. Not wishing to be outdone by a mere man one of the girls had a go and was soon doing it faster than me. One smug girl, one happy production manager and me happy to report problem resolved to the development manager my boss.

 

Don 








Google Ads are only seen by non-members of RMweb - Create an RMweb account and you'll only receive modelling ads.