Magnetic uncoupling - tension lock couplings

[Steve M]

A couple of threads have recently touched on couplings and in particular uncoupling, either manual or automatic.
A couple of months ago I experimented with Dingham autocouplers - beautifully made, but requiring a small amount of modification to the stock, so I decided that wasn’t for me.

While researching, I stumbled upon a modification to standard tension lock couplings, originally published by Brian Kirby. This, in its basic form, required a staple to be glued to the tail of the coupling which would be pulled down by a permanent magnet under the track.

20180813_111702 by Steve Mumford, on Flickr

Note that this method needs to use Bachmann hooks as they are non-ferrous. It works well enough but does suffer from recoupling if you are not careful. Also unwanted uncoupling can be the result when using permanent magnets.

[Paul-H]

Hi

You could replace the permanent magnets with electro magnets so you only get intentional uncoupling.

Paul

[Steve M]

Hi

You could replace the permanent magnets with electro magnets so you only get intentional uncoupling.

Paul

Patience Paul.

[Steve M]

While experimenting with the Dinghams I had made some electromagnets from a few spare Seep point motors. Carefully cut them in half and wire them to a suitable power supply via a push to make switch and drilled a hole through the baseboard and hotglued the motor to a small block.

20180723_145911 by Steve Mumford, on Flickr


I found that the original core of the pointmotor was too small for ‘spotting’ the coupling so I replaced it with an iron nail with a larger head. I also included a small led next to the track to act as an indicator.

20180817_134328 by Steve Mumford, on Flickr

More installments soon.

[Steve M]

I had also come across a modification to help with the problem of recoupling when the unhooked stock is being pushed.
All you need is a staple, a short length of 0.5mm brass wire and as previously stated the hook from a Bachmann coupling.
These are the component parts laid out prior to assembly.

20180814_194355 by Steve Mumford, on Flickr

And the measurements - these are different from the ones the original publisher stated online.

20180814_195528 by Steve Mumford, on Flickr

Fully assembled.

20180814_110827 by Steve Mumford, on Flickr

[Chris]

interesting to see all the different ways to achieve the same thing. I have some more little magnets on order and will have to see what fun effects I can come up with.

[Steve M]

In operation:
Note only one hook is used, so the stock is ‘handed’.

Under tension, approaching the electromagnet.

20180814_110940 by Steve Mumford, on Flickr

Stop with the tail of the coupling over the magnet, activate the electromagnet and the coupling should pop up about halfway until stopped by the bent brass wire.

20180814_111031 by Steve Mumford, on Flickr

Still with the magnet ‘on’ pull the loco forward and the coupling pops up all the way.

20180814_111059 by Steve Mumford, on Flickr

Either continue driving the loco away or reverse back up to the wagon and release the switch and the hook will fall but will not recoupling as the wire stops it from going too far.

20180814_111116 by Steve Mumford, on Flickr

[Steve M]

One issue that did show up in operation was that the hook would not always cleanly lift as the tolerances are quite tight, so a final modification was to replace the plastic cross bar with a length of 0.5mm brass wire. The height of this can be adjusted by using either standard or cranked Bachmann couplings.

20180816_103101 by Steve Mumford, on Flickr

[Steve M]

Finally, a short video to show it all working.

0EBDECFA-E0E5-41F3-94BF-BDBBB836043A by Steve Mumford, on Flickr