Three link couplings

[Bandit Mick]

Hope this is the right place to post my question. Please excuse my prototypical ignorance - I’m fitting some wagons with three links but did locos also run with couplings or just the hook? Again, sorry for what may be a question I should know the answer to and apologies for any incorrect use of railway terms. Thank you.

[Walkingthedog]

Yes they did. 3 link or screw coupling.

[Bandit Mick]

Thank you WTD.

[The Sligo Rover]

Ah - but do you couple the wagon to the loco, or the loco to the wagon?
I cannot remember what the correct practice is.

[Mountain Goat]

I do not think it matters, though when I operated loco and coaches the Mk2 coaches had their buckeyes lowered so one had to use the loco coupler (Screw link) as the coach coupler was not there.
There is also the instantainer coupling which is a type of 3 link coupling where the central link of the three link is shaped and is designed to drop and reduce the length of the coupling when in use so there is less distance between the buffers. It is a simple but clever design. Technically it is a shaped 3 link coupling. Screw links are used more for pulling passenger vehicles as they reduce the buffering effect (The jolting back and fore which causes buffer clashing noises one used to hear with trains of unfitted freight wagons) but as they take longer to use, freight wagons (Apart from high speed freight vans) tended to use the 3 link as they were much quicker to uncouple and couple in marshalling yards, and could even be coupled and uncoupled on the move to speed things up (If the managers were not around to see it). Fly shunting was quite common in the past.

Visually speaking, stick to the screw link or the standard three link types as the three link will also cover the rough look of the instantainer couplings as well.

What scale do you model in? The only downside to using 3 link types is that one can get buffer locking on sharp curves, especially where the curve turns in one direction and switches back to turn in the other direction.
0 gauge modellers often used to fit larger bufferheads to their buffers to compensate for this so they would avoid bufferlocking.
Bufferlocking is where the buffer of one vehicle will slip behind the buffer of the other vehicle on the curve, and cause a de-railment when the two coupled vehicles then reach a section of straight track, which is why 0 gauge modellers who used sharp curves would compensate by giving their models larger buffers so they were less likely to hook behind each other.

The bufferlocking problem is common if one tries to model using standard track geometry which is much sharper then the prototype uses.

For my 7MM narrow gauge models, a centrally mounted single buffer is less likely to bufferlock though my buffers which form part of the coupling are still larger then normal to ensure I don't have any issues on curves which are much sharper than the real railways use, even in narrow gauge (Though one may always find a real example of a very sharp curve on the prototype if one looks hard enough! )

[Walkingthedog]

I use drawing pin heads for bigger buffers in O gauge.

[Bandit Mick]

I’m modelling in OO. I think the 3 links will be for photographic purposes only - but they do look very nice. Coupling and uncoupling will be challenging as I have fingers like bunches of bananas!

[Mountain Goat]

I use drawing pin heads for bigger buffers in O gauge.

That is what I use in 0-16.5 as well for a centrally mounted buffer. Cheap and cheerful!

[Mountain Goat]

I’m modelling in OO. I think the 3 links will be for photographic purposes only - but they do look very nice. Coupling and uncoupling will be challenging as I have fingers like bunches of bananas!

I was actually dreaming up ways of making something like that work as a coupling without them being too difficult in use to couple and uncouple along with a way to avoid bufferlocking on sharp curves.

[Chops]

A troublesome feature is that some times the bars of bar and hook couplers press in on one another, particularly when running different types of hook and bar couplers between manufacturers, and the binding effect works as well as overlapping buffers, On occasion, with more obscure pieces, such as some older Airfix coaches, it was necessary to remove the offending couplers entirely and install a small length of chain to provide adequate clearances on curves.