Wednesday, June 24, 2009

Coupling

Well, I said last night that I would have a look at this, so may as well have a crack.

Couplers in Nz120 have historically been of 2 types; the Rapido style massively out of scale type, and the microtrains very nice but not quite prototypical type. The Rapido coupler has several pluses. It is ubiquitous (standard) and reliable. Its downsides are its the size of a bus. It is difficult to get it to remote uncouple. Its just plain ugly.
The Microtrains coupler is a very nice bit of kit. its made in a stack of different versions to suit the application, and it has a remote/delayed mode of action that is relatively easy to set up. Its only real minus is that its not prototypically correct (apart from passenger and unit trains).

So, what chance a scale working coupler in Nz120. after all its possible in S scale...

Unfortunately its not that simple. Lets have a look at the real thing.


In scale this would be about 2mm wide with a <1mm notch in the middle. To couple your wagons the hook has to hit this 1mm gap EVERY time. This is completely unlike the other 2 couplers who's important dimension is the vertical, which is far easier to sort out. The other main problem is Physic's. Those who haven't just fallen asleep can now follow the rest of the reasoning. for the hook to work, it needs to raise up into the buffer, then drop down again. in the real thing this is powered by gravity (and the hooks are a heavy sucker to boot). However by the time we get down to Nz120 we are talking about a tiny piece of brass with very little mass that has to do exactly the same job. not only do we not have gravity on our side, but we are also at the mercy of friction. This force does not scale, so the tiny light piece of brass has to move very freely as well. Now I'm not saying that this is impossible, but its not going to be a walk in the park either.

Pat Eade got around these problems by creating a permanently coupled bar between wagons. I can't see why a fixed non working coupler would not work equally as well. If you still want to shunt your wagons, you will need a working coupler, like a microtrains type.

Next time round I'll have a look at options available to the Brits, who have been quite inventive in this field

2 comments:

manaia said...

hi i've yoused the solid bar cuplers, not good for pooshing, also I've found some brass and white metal cuplers hooking them was a problem.

woodsworks said...

Need to think beyond the square - how about making the coupler out of steel, with a super-powerful neodymium magnet tucked behind the headstock? It might have enough 'stick' to pull wagons with. Locos, esp. DCC equipped, could have electromagnet-operated coupling/uncoupling. Alternatively the hook and drag pins could be magnetised, so that they might automatically align, and once they are in contact they are less likely to come undone