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Stour Valley Dream - first uncoupling magnet

Fen End Pit

Entry posted by Fen End Pit

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I designed and printed a servo operated uncoupling magnet for the Alex Jackson couplings I'm using on my P4 layout. Many people just use an electromagnet to do this but I don't really like the current these draw and get worried about them burning themselves out if left on for too long while you shunt wagons over them. One solution is to use a permanent magnet and move it up and down so it that it attracts the coupling (or doesn't).

As usual there were a few iterations in the design to get the sizes right but I managed to get a design that worked in the end. I used a short length of styrene  tube in the design as this is smoother than trying to print a tube and results in less friction.

As I already have all the infrastructure to control servos under the layout fitting the device was very simple.

The operation can be seen in this Youtube clip

 

https://www.youtube.com/watch?v=11sM5U8yVQs

 

Now I can waste hours shunting in and out of the coal siding.

 

David

 

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Stubby47
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Very clever.

I've thought about moving permanent magnets for my next layout, but sliding them horizontally to be under the track.

 

For the control boards, how far from the servo can they be?

 

I'd like to fit all the boards in a protective plastic box, somewhere that's easily accessible to allow adjustment to the settings.

 

 

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Fen End Pit
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1 hour ago, Stubby47 said:

For the control boards, how far from the servo can they be?

 

I'd like to fit all the boards in a protective plastic box, somewhere that's easily accessible to allow adjustment to the settings.

 

 

 

I'm using MERG circuit boards. A CBUS CANACC8 board switches the inputs of a SERVO4. I've not had any trouble with wires  connections from the SERVO4 to the servo of about 2'

 

David

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Stubby47
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Thanks.

I'm also planning on MERG boards, but using a PMP servo control (set-up) module for each servo ( 3 uncouplers and 2 points, plus any automation).

2 ft seems plenty.

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Dave John
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Good idea. I had the same issue with electromagnets and much prefer the moving magnet method. 

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Killybegs

I used to use sprung push buttons to operate the electromagnets and never had any problems. The electromagnets had a dedicated power source. 

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Fen End Pit
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On 17/07/2019 at 11:42, Killybegs said:

I used to use sprung push buttons to operate the electromagnets and never had any problems. The electromagnets had a dedicated power source. 

I must have been unlucky/stupid as I had lots of cheap push buttons fail over time on a previous layout. I also didn't want to have to provide another separate supply to each baseboard just for the magnets.

 

David

Edited by Fen End Pit
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Gordon A

One of the advantages of AJ's is that you have two chances of uncoupling one of each pair of couplings.

 

Like Killybegs  I have used push to make buttons ( https://www.ebay.co.uk/itm/2x-Red-Green-Mini-Switches-Square-Push-Button-Momentary-250V-2-Pin-1-5A/223069608018?epid=19020353552&hash=item33effc1852:g:9dMAAOSwlBZbUn1Y ) to operate the uncoupling magnets with out any problems.

Don't use cheap push to make buttons.

 

I have experimentally used a DCC decoder for point solenoids to operate Gaugemaster uncoupling magnets which drew approx 1 amp. 

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Fen End Pit
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I made a few more changes to the model. I added a tube to give a bit more guidance for the 'plunger'

The result works fine and prevents the risk of the plunger slipping out of the plaststruct tube.

 

David

IMG_7294a.jpg

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