The wonderfull world of HO couplers

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Re: The wonderfull world of HO couplers

Postby Tom@Crewe » Tue Nov 14, 2017 8:58 am

I see it now :oops:

I will have to get some small magnets to attach to the coupler

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Re: The wonderfull world of HO couplers

Postby Bufferstop » Tue Nov 14, 2017 10:40 am

So my question is why BK's way?

Because it works.
looking at the coupling with the hook sticking out to the left, just above the line of the pivot, the tail sticks out to the right. The magnet pulling down on the tail tries to lift the hook, it will if it's not trapped under the buffering bar.
The method has the advantage that the magnets can be installed anytime, two 3mm diameter x 4mm long neodymium magnets, glued into holes drilled between the sleepers, two or three sleepers apart. They are so inconspicuous I have to put some kind of marker to know where they are.
The materials for the coupler are cheap, Bambi staples or florists iron wire.
It works for most narrow tensionlocks, the only exception is the Hornby version where the hook is longer and made of steel. I get round that problem by exchanging the Hormby couplers on wagons etc with Bachman/Dapol/etc from the centre of fixed rakes, where not uncoupling is an advantage.
Fitting the wire is even easier with NEM couplers as you can unplug them and do it without handling the vehicle, and leaving the hook still on the coupler. Removing and replacing the hook is best avoided as they pivot end can open up when they are pulled off, making them insecure when replaced.
Geoff (Dad-1) has his own addition to the mod, a short piece of the wire superglued to the top of the tip of the hook. It makes hand uncoupling easy using a small magnet on a rod.
I regarded it as a reasonable alternative to converting to KDs, but this thread and Dad-1's experiment with KDs have convinced me that apart from appearance this method is as effective, and a lot cheaper.
Anything fitted with the old Hornby D coupling, particularly the moulded into the chassis version has either been modified to the narrow type couplers for appearance sake, or donated to the grand kids and replaced with a better model.
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Re: The wonderfull world of HO couplers

Postby Bigmet » Wed Nov 15, 2017 12:08 pm

Tom@Crewe wrote:...I will have to get some small magnets to attach to the coupler

Are you proposing to get the small magnets to enable uncoupling by repulsion?

This is not so easy, but then again solving the problems may be part of the fun? Just so you know what has to be tackled.

The track and coupler magnets both have to be mounted in consistent orientation for repulsion - obvious enough - which means some attention to detail.

The repulsion force has to be sufficient to lift the combined weight of hook and magnet. Basically this means there is more field required for the lift of the hook compared to the BK method because the magnet will be heavier than the staple, but this is not impossible to provide, and a single coupler on the track magnet can be got to lift reliably.

However, we need a pair of hooks to lift reliably for both coupling and uncoupling, and here's where the problems have to be solved.

The magnets on the coupler hooks are also going to repel each other when the coupler hooks are in matching positions. They must not repel so much that when coupled the couplers move apart enough that the hooks are always locked on the bumper bars and so cannot lift.

The magnets on the coupler hooks will attract when the hooks are in non matching positions. If one hook starts rising before the other the raised magnet will be attracted to the opposite pole of the magnet on the other hook. That hook will fail to rise properly and this can leave the pair of coupler hooks unsatisfactorily positioned: not securely coupled up with both hooks engaged on the bumper bars, and magnetic uncoupling disabled.

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