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Old 11-08-2019, 11:26 AM   #1
Dennis461
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Rare earth magnet uncoupling 'ramp'

I tend to call these locations uncoupling ramps because the old horn-hook uncouplers looked like ramps.

Anyhow, I started experimenting with the strong rare earth magnets readily available nowadays. I read several threads on how to implement this and my variation included 8 metric dimension magnets. Eight of the 10mmx5mmx3mm magnets spaced to fit tightly between the rails. Polarity is important.

Installed in existing trackwork by cutting three ties out and "dremeling" down to make a square pit in the homasote.

Works as good as the Kadee under track magnet.
My next implementation will be a retractable (downward) version under the ties.
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File Type: jpg 20191108_102901.jpg (4.03 MB, 7 views)
File Type: jpg 20191108_110653.jpg (5.20 MB, 6 views)
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Old 11-08-2019, 01:06 PM   #2
Fire21
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The part I don't understand is do they uncouple any time a car passes over it, or do you have a control to activate it on demand?
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Old 11-08-2019, 02:41 PM   #3
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@Fire21 -- I don't have any hands-on experience with this yet, but from what reading I've done on the subject it is similar to the horn-hook uncouplers in that you need a momentary hesitation in the train to provide some slack in the couplers before they detach from each other. In this case the magnet provides the force to pull the couplers in opposite directions and once there is slack they'll come apart. I believe this arrangement is normally avoided on a mainline because you can also get slack between the cars from slowing down or if your loco hesitates while going through a turnout.

The way I've seen this done in the past is by using a stack of 3x3x3mm magnets, which are approximately the same width as the tie. Cut out three ties and replace them with magnets, then paint over them and they blend in with the other ties. The main difference between this method and what is presented above is the orientation of the magnet. I guess it works in either direction?
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Old 11-08-2019, 03:17 PM   #4
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The principle is simple, Kadee magnets have a North and South pole at the top, the face we see looking down at the uncoupler.

Now a steel rod or pin in the vicinity of the magnetic field will align N-S. Since the coupler pin has only one way to move (it's attached to the coupler pivot, it rotates to fit the field.

Both pins rotate clockwise, and since the couplers are mirror images, they move apart.

So any combination of magnets that produce the field will work adequately. I uses the word adequately because as Shdwdrgn pointed out, the operation is not without some minor issues. Which is why I am building a retractable version. I could buy/build the electromagnet version but it takes more work and a larger hole in the roadbed.
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Old 11-08-2019, 04:55 PM   #5
wvgca
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all that's needed is a couple between the ties, smaller round ones placed vertically ...
and yes, if there is slack, they will uncouple, but that is not normally the case ..
once placed they are virtually undetectable, and a hairpin needle with a yellow glass cylinder is placed next to that spot ..

these have been in place for over six years now ..
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Old 11-09-2019, 04:28 AM   #6
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i just visited a layout and thought they were mounted under the ties, out of site
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Old 11-09-2019, 07:13 PM   #7
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Quote:
Originally Posted by gregc View Post
i just visited a layout and thought they were mounted under the ties, out of site
It depends on the uncoupler. Some are designed to fit under the ties, some are designed to fit over the ties between the rails. Kadee makes both types. https://www.kadee.com/ho-scale-uncou...c-274_280_300/
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Old 11-09-2019, 07:27 PM   #8
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the layout i visited used rare earth magnets under the ties
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Old 11-11-2019, 10:43 AM   #9
DonR
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A square of sheet metal UNDER the magnets will
increase their 'power'.

Under track magnets should ONLY be used on
spur or yard tracks. If in a 'main line' you will
get undesired uncouplng when train is pulled
over an under track magnet.

The proper procedure for auto uncoupling is to
back the car over the magnet. You should then
see the wires swing thus uncoupling. You can also
push the car on back if you do that when the couplers
are 'misaligned'.

If you want to uncouple on
a 'main line' use the Kadee electromagnet uncoupler.
It uncouples only when you push a button.

You should also make yourself a 'HOG' (Hand Of God)
probe to uncouple cars where there is no magnet.
Use a small wood or plastic stick filed to a thin flat
point. This is inserted in the coupler knuckles with
a flick, thus opening.

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Old 11-11-2019, 11:12 AM   #10
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if magnets are mounted under the ties, in an opening in the benchwork, couldn't they be mechanically lowered and raised as needed?
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