Yet another thread on the old question of couplings.
However, this thread is not looking for advice on which coupling to use - after much reading on the forum and elsewhere I have (in theory) settled on the Greenwich Coupling. My question is in regard to tips on assembling them for trouble free operation. My initial attempts are too "stiff"; i.e., shape and movement appears fine, but gravity is not strong enough to drop the loop. Initially I though first attempts were compromised by my fat fingers and in-appropriate tools but having invested in a couple of sets of bending pliers I still have the same issue.
My assumption is that I'm not quite bending the ears for the pin in quite the right way. Will be embarking on much prodding and tweaking, but if anyone has any advice on a) tips for making them work first time and b) tips on fettling the couplings, it would be much appreciated.
Regards
Hugh
Could the stiffness be due to the pin binding in the etched holes? I'm trying to remember if I ran a [edit] reamer broach through the holes.
Also, having fairly recently bought some brass (not just brass-coloured) pins for another job I must look at using them in place of the pins that came supplied as they are very hard. It is possible that the materials used by Greenwich have changed as it is many years since I bought a batch so newer coupling kits may be easier to make.
Some tips on Greenwich Couplings ----
1. Open up the holes on the tabs using a reamer,
&
2. Use 0.33mm brass wire to pivot the loops.
Garry
Not sure what happened that caused me to reply to myself but I think it may have been an attempt to edit my message, so I've deleted it.
What I meant to add is that by using a softer wire it is possible to squeeze a small neat 'fishtail' in the wire and trim it to length with cutters to stop the wire falling out of the reamed holes. I find it easier than trying to put an L bend in the wire close to the end. If the reamed hole is nice 'free running fit' it take very little deformation of the wire to stop it falling out.
As others have suggested I run either a tapered cutting broach or a small drill (about 0.5mm from memory as the supplied track pins are about the same size) through the set of 4 pivot holes once the loop and buffer(including the pivot 'ears') have been bent to shape.
Often all that you ned to do with this is remove the etching cusp (an artefact of the chemical etching process that you can see on the edge of and etched kit) and maybe some of the blackening (if you have black rather than bare metal couplings) in the holes, but also with any etched kit it's good practice to etch holes undersize as one can drill them out to the correct size. It is much harder to add metal to make an oversize hole smaller...
Once I've opened out the pivots I test them with the pin in place but before I've bent it & cut it. This essentially consist of moving the coupling from horizontal to vertical (buffer at the top) to make sure the loop flops back, then moving the coupling back again to ensure the loop drops back into place. This also allows me to see what is going on and where the bind is.
If the loop is a bit 'sticky' it's usually because the pivot ears on the coupling are too wide apart or are not bent down to the same angle. The careful application of pilers to gently squeeze them inwards - and parallel action pliers may be better for this - can help with the former, and some careful manipulation sorts out the latter, but the bent brass can get quite brittle so be careful not to snap the metal. Bending the ears on the loop outwards very slightly but is probably a little harder to do evenly on both sides.
The danger of this sort of adjustment is that the pivot holes may go out of alignment, so you may need to run the drill through again, but check with the pin first.
Hope that helps.
Regarding blackening, any recommendations for a suitable chemical blackening (as opposed to a Sharpie)?
On a small batch, in a bout of enthusiasm, I reinforced the zig-zag bend at the buffer face with solder. I did it partly due to an earlier over zealous bending of couplers that resulted in the bend breaking and I was not certain the next attempt was not going the same way.
Thank you all for your advice - a few things to try. I did try reaming with a drill, but only the size suggested in the instructions which from memory is less than 0.5mm - so either finer wire or a larger drill makes sense.
If you have a suitable sewing needle that could be 'sacrificed to the cause' if necessary you could try putting it in a pin vice or similar and using it as a smoothing broach as they are of vaguely similar profile *. Given the likely amount of material that needs to be removed (possibly just a tiny bit of the etching cusp) a little bit of twiddling of a needle in the holes may be all that is needed. It might be more of a burnishing over of the cusp than cutting it away.
* Possibly bit too severe a change in diameter to run through all holes stacked together.
Quote from: Hugh Ransom on September 13, 2022, 20:07
Thank you all for your advice - a few things to try. I did try reaming with a drill, but only the size suggested in the instructions which from memory is less than 0.5mm - so either finer wire or a larger drill makes sense.
The drill needs to match the size of the track pins. I've not measured any of the pins for a while, but I have a feeling they were either 0.5 or 0.55 mm in diameter and the drill needs to be a smidgen larger.
In that respect it may be easier to use a tapered cutting broach (a 5-sided tapered cutting tool) that will gradually open the holes out until the pin goes smoothly through the hole.
I think you will find that the latest Greenwich couplings do not come with the pins anymore that were very hard to bend, only wire.
They are also no longer black anodised and are unpainted brass.
I use 0.45mm brass handrail wire - no need to open out the holes. I gave up using the supplied track pins a long time ago (they had a unvarying knack of burying themselves in my fingers)
100% agree with not using the pins as supplied they hurt and take ages to fit. I have been using thin bits of of wire left over from from the legs of electronic components, which bend down easily.
Somebody suggested inserting the track pin with a tiny amount of super glue behind the head to hold it in place, then trimming it the other side to make a nicely concealed pivot. I could not make that happen, I either glued the whole thing shut or the pin fell out.
I use a sharpie to colour in the bare metal, and then give it a quick blow over with the airbrush using Vallejo "German black brown" matt which takes the shine off. I use croc clips on sticks to hold them pointing upwards, spray with the loop up and then work it too and fro about 20 seconds later to make sure it doesn't stick.
The paint stops the copper wire from moving and I don't use superglue on the coil of wire, although I probably should.
I tend to make the whole packet at once, first the loops then the hook part and then jiggle them around into pairs that don't stick.
I tend to only use the hook part on locos or one end of wagons as it can make uncoupling easier. If it becomes an issue you can always go back afterwards.
I use the NEM pocket ones, but I must break the fold round bit at least one in 5 times, so I keep those for gluing directly to small wagons of locos that don't use pockets.
The Pocket ones normally fit very nicely into Peco wagons, but if loose I have gently sanded the bottom surface of the wad and spread some superglue over to make it thicker and a bit rough. Once its dried that tends to hold it snuggly.
Just to confirm the latest version of the Greenwich couplings will have 0.4 mm brass wire for pivots now. Not pins.
Also thicker, soft iron wire (0.3 mm) is included, halving the number of turns needed for magnetic operation.
As I mentioned they are also in unpainted brass.
The instructions have been updated to take in these changes.
Thanks for the update Brian - it has been a while (several years) since I bought any, and even then I don't think they were new (coming from the 009 Sales stand).
Quote from: B.Meldon on September 14, 2022, 18:28
As I mentioned they are also in unpainted brass.
The other changes would seem to be an improvement and has encouraged me to buy more, but coming only in bare metal will add at least one more step, which is going to be a nuisance.
Quote from: Stephen Rainsbury on September 17, 2022, 17:37
Quote from: B.Meldon on September 14, 2022, 18:28
As I mentioned they are also in unpainted brass.
The other changes would seem to be an improvement and has encouraged me to buy more, but coming only in bare metal will add at least one more step, which is going to be a nuisance.
From what i understand the blackening process is sadly no longer offered by etchers.
To get this done elsewhere, or change to another etcher would have been cost prohibitive.
In addition the black did, at times, tend to come off when bending the coupling into shape requiring painting, or at least touching up anyway.
Using a permanent black marker pen is a quick and easy alternative.
Quote from: B.Meldon on September 20, 2022, 08:52
Quote from: Stephen Rainsbury on September 17, 2022, 17:37
Quote from: B.Meldon on September 14, 2022, 18:28
As I mentioned they are also in unpainted brass.
The other changes would seem to be an improvement and has encouraged me to buy more, but coming only in bare metal will add at least one more step, which is going to be a nuisance.
From what i understand the blackening process is sadly no longer offered by etchers.
To get this done elsewhere, or change to another etcher would have been cost prohibitive.
In addition the black did, at times, tend to come off when bending the coupling into shape requiring painting, or at least touching up anyway.
Using a permanent black marker pen is a quick and easy alternative.
Equally dipping the built coupling into some brass blackening solution for a few seconds then rinsing off with water would be fairly quick...
Quote from: JulienW on September 20, 2022, 09:59
Equally dipping the built coupling into some brass blackening solution for a few seconds then rinsing off with water would be fairly quick...
Do you have a recommendation for a brass blackening fluid please? There appear to be different brands or formulations and have different behaviours.
Quote from: GraemeD on September 20, 2022, 11:23
Quote from: JulienW on September 20, 2022, 09:59
Equally dipping the built coupling into some brass blackening solution for a few seconds then rinsing off with water would be fairly quick...
Do you have a recommendation for a brass blackening fluid please? There appear to be different brands or formulations and have different behaviours.
I've recently had success with Carr's Metal Black for Brass, used on some DG couplings. First I washed them in Isopropyl Alcohol (IPA) with a piece of paper towel, then decanted a bit of the metal black into a small glass container with enough to cover a coupling. I dropped one in, taking care not to touch it with my fingers and swished each coupling around for 30-60 seconds and it came out pretty good. When out it went straight into some fresh IPA for a wash and then left to dry. Depending on how much use it'll get I may give it a spray of varnish so the blackened surface doesn't wear off.
Hope this helps :)
One of the best ones I had was one I made myself.
This used copper carbonate mixed in a 1:1 weigh to volume ratio with 0.880 SG Ammonia solution. It's rather pungent (eye watering!) so when I made it I did so in a fume cupboard. It was less stinky in use though, but you wouldn't want to leave the pot open for too long!
I still have a jar of copper carbonate, but haven't tried to get any of the ammonia (I suspect this might not be too easy) and I don't have access to a fume cupboard, so it's unlikely I'll be making any more.
Failing that the Carrs Metalblack for Brass has worked well for me, as has Hobby Holidays' Chemical Blackening. They probably need a little practice to get the right amount of time dipped in the solution - too much and the coating will flake off - before you wash off the solution with water.
You may need to degrease the couplings (dip in alcohol, acetone or butanone or similar for example - allow it to evaporate and try not to touch the couplings once dry) before you dip them in the metal black to get the best from these solutions.
Hope that helps...