Which Couplings ???

neilp4f1
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Which Couplings ???

Postby neilp4f1 » Tue May 17, 2011 7:57 pm

I have been dabling with P4 for a while, but trying to get going again and really can't decide which couplings to use!
The sheet about AJ couplings mentions positive points, are there any negatives?
I have some 3mm Sprat &Winkle couplings which in some ways look a little more realistic, but I am guessing may be harder to locate?
Or do I use 3 link, already pondered over how to get under the end of a coach - probably better to use the coach coupling to hook onto the loco.

Has this debate been had before? All views for and against would be most welcome.
Cheers
Neil

martin goodall
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Re: Which Couplings ???

Postby martin goodall » Tue May 17, 2011 9:20 pm

Negative points re AJ couplings.

The following is an extract from an unpublished article reviewing various 4mm scale auto couplings:

"The Alex Jackson coupling has always appealed to finescale modellers. It is an elegant design, involving two identical opposed hooks, and is by far the most inconspicuous auto-coupling ever devised. When it works well it intrigues audiences at model railway exhibitions, as the wagons are coupled and uncoupled seemingly invisibly, ‘as if by magic’.

Nevertheless, the ‘AJ’ coupling has two significant drawbacks. The first and most important of these is that accurate alignment is absolutely critical to its operation. Users of this coupling have devised sophisticated setting jigs to make sure that the couplings are mounted in exactly the right plane both vertically and horizontally. Even a minor discrepancy in the setting can make all the difference between success and failure in their operation.

This sensitivity in the setting of the coupling extends to any subsequent knocks, for example when transporting stock in boxes, getting the models out or putting them away, or even on the layout itself. It takes very little to knock an Alex Jackson coupling out of alignment. Constant checking and adjustment is the only way of preventing malfunctioning of these couplings on the layout.

There are two other ways in which the need for accurate alignment can cause problems. ‘AJs’ can couple only on straight or nearly straight track. Coupling is not possible on a curve of less than 4-foot radius. The problem may be compounded by any tendency for wagons to ‘hunt’ or ‘yaw’ on the track. This depends on the running clearance of their wheelsets (the distance between the outside of the flange and the inside of the rail-head). If the combination of track gauge, flange profile and back-to-back setting allows more than a fairly tight running clearance, then wagons will not always run or stand parallel to the rails, and in some cases this can result in the coupling hook being presented at enough of an angle to prevent its coupling with its neighbour.

The second drawback relates to the flexing of the steel wire. This, too, is critical to the successful operation of these couplings. In 4mm scale, 11-thou straight steel wire (11-gauge guitar string) must be used; anything thicker will not have the required flexibility, and anything thinner will be too flimsy. Even so, the requirement for the wire to flex can cause problems. The hook wire must be sprung up against its stop/locating guide just enough to ensure that it is held in the correct alignment for the next shunt, but it must not be sprung against the stop so hard that it will not flex downwards easily when it meets an opposing hook, or when pulled down by a magnet. Here again is another tricky adjustment problem.

One of the snags encountered by quite a few modellers when using Alex Jackson couplings is that with very free-running wagons (with compensated suspension and pin-point bearings) the coupling hooks will not always depress and engage before the vehicle to which one is attempting to couple begins to be pushed away. The practical answer is to insert a small piece of foam plastic between the wagon axle and the floor of the wagon to act as a brake and thereby prevent the wagon from being pushed away as the couplings make contact with each other, but this is hardly ideal.

This may explain, at least in part, why some users of the Alex Jackson coupling have adopted a pivoted version of the hook in place of the flexed wire which was originally recommended, although it has been suggested that this can cause its own problems. Like other modellers, I also discovered that the action of a magnet on the dropper, which is pulled down vertically, seems to be less effective than one which is pivoted and which swings under the influence of the magnet (e.g. DG, Dingham, etc.). As I mentioned above, this will be compounded if the flexed wire usually used for the AJ coupling is sprung up against its stop, thus offering additional resistance to being pulled down by the magnet. The other reason for fitting a pivoted hook is that it is difficult to accommodate a flexed wire of the required length under a bogie vehicle.

For all these reasons I decided that the Alex Jackson coupling was not for me, the real clincher being the fact that I have curves on my layout of less than 4-foot radius on which I want to couple stock."

I ended up designing my own auto-coupling (the 'Burford' coupling) and I vaguely recall that I posted details of the design and assembly of this coupling on this website some time ago, but I don't have a note to hand of the whereabouts of that posting. Maybe Keith Norgrove knows where it can be found.

craig_whilding
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Re: Which Couplings ???

Postby craig_whilding » Tue May 17, 2011 9:51 pm

martin goodall wrote:Negative points re AJ couplings.
Nevertheless, the ‘AJ’ coupling has two significant drawbacks. The first and most important of these is that accurate alignment is absolutely critical to its operation. Users of this coupling have devised sophisticated setting jigs to make sure that the couplings are mounted in exactly the right plane both vertically and horizontally. Even a minor discrepancy in the setting can make all the difference between success and failure in their operation.

I wouldn't call a pin a set distance above the track that 'sophisticated', you can buy an etched one from the stores now anyway that sets the buffer height too.They do have to be quite accurately set up but i've not had any issues with my pivoted ones since I built them and my current stock box is decidedly ropey! I also use 10 thou wire and build the couple upside down as per Nigel Cliffe when he fitted them to 2mm stock.

Coupling of longer wagons under 4ft radius can be a bit of an issue.

Coupling debates have been done to death before but mainly on rmweb, its generally up to your personal requirements. Start with some 3-links on your hooks and see how you get on with uncoupling them and then go on to trying autocouplers i'd say..

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grovenor-2685
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Re: Which Couplings ???

Postby grovenor-2685 » Tue May 17, 2011 10:12 pm

I ended up designing my own auto-coupling (the 'Burford' coupling) and I vaguely recall that I posted details of the design and assembly of this coupling on this website some time ago, but I don't have a note to hand of the whereabouts of that posting. Maybe Keith Norgrove knows where it can be found.

Not that I remembered but there is a search box at the top of the page, type in Burford and hit search, amongst the results lurk the couplings, a whole attached pdf file of instructions.
Regards
Keith

martin goodall
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Re: Which Couplings ???

Postby martin goodall » Wed May 18, 2011 9:53 am

grovenor-2685 wrote:
I ended up designing my own auto-coupling (the 'Burford' coupling) and I vaguely recall that I posted details of the design and assembly of this coupling on this website some time ago, but I don't have a note to hand of the whereabouts of that posting. Maybe Keith Norgrove knows where it can be found.

Not that I remembered but there is a search box at the top of the page, type in Burford and hit search, amongst the results lurk the couplings, a whole attached pdf file of instructions.
Regards
Keith


Searching 'Burford' is probably the quickest way of accessing it. The instruction sheet (a PDF attachment) is the 15th item in the list. There is just one amendment - I now make the hooks from 0.33mm brass wire (same as the over-riders for advance uncoupling), whereas the loops are 26swg steel as stated.

A more detailed article is awaiting publication in MRJ,

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Tim V
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Re: Which Couplings ???

Postby Tim V » Wed May 18, 2011 11:34 am

Unpublished? I've read that article somewhere before. No mention of the society's seminal book on AJs.
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neilp4f1
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Re: Which Couplings ???

Postby neilp4f1 » Wed May 18, 2011 7:03 pm

Thank you all for the advice and direction, the Burford pdf looks comprehensive and I have now found a number of relevant discusions on RMWeb.
The can of worms has now been opened - I think deciding will be the hardest part!
Many thanks
Neil

nigelcliffe
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Re: Which Couplings ???

Postby nigelcliffe » Wed May 18, 2011 7:23 pm

martin goodall wrote:The second drawback relates to the flexing of the steel wire. This, too, is critical to the successful operation of these couplings. In 4mm scale, 11-thou straight steel wire (11-gauge guitar string) must be used; anything thicker will not have the required flexibility, and anything thinner will be too flimsy. Even so, the requirement for the wire to flex can cause problems.


If one uses the "bent backwards" design for the AJ hook (looking along the coupling from wagon, the first bend goes down and back, rather than up and away) one can use a much finer gauge of wire. I think this was devised by Vincent de Bode and used on his GER layout.
The "bent backwards" hook will interwork fully with the conventionally bent AJ hook, and due to where the load is taken on the wire (on the first bend, rather than flexing the 180 degree bend), it is probably stronger than a conventional AJ construction.
The finer wire makes it even harder to see, and overcomes some of the problems in the standard 11thou of being a bit too stiff to couple light stock and a bit too stiff to uncouple cleanly on shorter wheelbase stock. 8 thou is quite credible, and Vincent claims it is less prone to being bent out of alignment. My limited tests support this, but I need to make more stock to be able to confirm it fully.



- Nigel

martin goodall
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Re: Which Couplings ???

Postby martin goodall » Wed May 18, 2011 8:54 pm

Tim V wrote:Unpublished? I've read that article somewhere before. No mention of the society's seminal book on AJs.


The unpublished material (in quotation marks) is part of an article I wrote, which has never seen the light of day.

The article on the 'Burford' coupling awaiting publication in MRJ omits this material.

David Knight
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Re: Which Couplings ???

Postby David Knight » Thu May 19, 2011 9:59 pm

I guess the first thing that has to be determined is what sort of operation will you be doing? Will you be doing a lot of shunting or will the trains just go 'round? How far from the edge of the layout is the track the furthest siding you will want to shunt? How many tracks will you have to reach over in order to achieve this move. If all is close to hand 3 links are fine, if you want to be able to set wagons out at a distance then you might want to check out Dingham couplers which I reviewed in Scalefour News 147 or have a look at; http://www.dingham.co.uk/. Usual disclaimer applies here. They have their limitations, if you frequently turn stock then it should be pointed out that the couplings are unidirectional and some assembly is required and they also prefer broad curves for coupling wagons of greater length.

HTH

David

nigelcliffe
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Re: Which Couplings ???

Postby nigelcliffe » Fri May 20, 2011 6:10 am

Another comment or two on the Burford (which is a very neat design):

Its clearly designed for a layout where there are uncoupling magnets in pre-planned positions. There is no problem with this, and it can give very good operation. But, if wanting to use the optional delayed uncoupling bar, the coupling requires a "Kadee Shuffle" into movements where a train has to backup to slacken the coupler, pull away, then backup again to propel the train. Some people find the Kadee Shuffle to be very annoying. (btw. the Kadee Shuffle can be programmed into some DCC chips so the action happens from a single function key with a pre-set controlled speed and distance of movement; CT, Zimo, some ESU and some Lenz chips can do this, and possibly a few other European makers)

With my pet interest of locos fitted with DCC controlled uncoupling devices (ie. not relying on electromagnets in the track), the Burford design is very well suited to this. I'd look at fitting a small fixed magnet to either the tail of the loop section or to the shaft where it rotates in the pivots, and then add an electromagnet coil behind the buffer beam.

martin goodall
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Re: Which Couplings ???

Postby martin goodall » Fri May 20, 2011 10:57 am

nigelcliffe wrote: But, if wanting to use the optional delayed uncoupling bar, the coupling requires a "Kadee Shuffle" into movements where a train has to backup to slacken the coupler, pull away, then backup again to propel the train. Some people find the Kadee Shuffle to be very annoying.


I have to confess that if one chooses to use the advance uncoupling feature designed into the 'Burford' coupling, then one is faced with the dreaded shuffle. This also applies to advance uncoupling with Sprat & Winkle couplings. I was not aware that the same problem also occurs with Kadees.

I am not at all happy with having to perform this shuffle, and so I have avoided using the advance uncoupling facility so far as possible by installing more magnets on the layout than might strictly be 'necessary'. I also found that if 0.33mm brass wire is used for the hooks, rather than 30swg steel wire as originally specified, there is no tendency of the loop to 'stick' to the hook as its draws away, and so one only needs to draw back about 2mm to disengage the loop from the hook, before propelling forward again with the loop resting on top of the over-rider. Done in this way, the manoeuvre is reasonably inconspicuous.

The other point is that (if using any of the three types of autocoupling mentioned above, including my 'Burford' coupling) one should avoid leaving a wagon fitted with an over-rider uncoupled over a permanent magnet, because coupling up to it again later would involve propelling it forward beyond the influence of the magnet (with the loop resting on top of the over-rider), drawing back to disengage the loop from the over-rider, propelling forward again so that the loop drops over the hook, then finally drawing away with the coupled wagon. This elaborate ballet is entirely unprototypical and very annoying. It can be entirely avoided by using electro-magnets in preference to permanent magnets. I have already eliminated most of the permanent magnets on my layout, and those that remain (e.g. in the carriage siding) are used to uncouple stock (i.e. passenger coaches) to which over-riders have not been fitted.

Subject to these observations, I am very happy with the 'Burford' coupling. The pivoted loop seems to operate far more smoothly and reliably than a pivoted or sprung hook. The DG coupling uses a similar method of operation, and the design of its delay latch overcomes the problem of the shuffle, but I found there were problems with that coupling which required various modifications and adapations which were frankly too time-consuming, and resulted in its becoming far too conspicuous. My wife said it looked like a Christmas Tree sticking out from under the wagon, and I have to admit she was right. Hence my decison to design what became the 'Burford' coupling.

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Penrhos1920
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Re: Which Couplings ???

Postby Penrhos1920 » Fri May 20, 2011 12:39 pm

nigelcliffe wrote:But, if wanting to use the optional delayed uncoupling bar, the coupling requires a "Kadee Shuffle" into movements where a train has to backup to slacken the coupler, pull away, then backup again to propel the train. Some people find the Kadee Shuffle to be very annoying. (btw. the Kadee Shuffle can be programmed into some DCC chips so the action happens from a single function key with a pre-set controlled speed and distance of movement; CT, Zimo, some ESU and some Lenz chips can do this, and possibly a few other European makers)


All couplings, model or prototype need to be slackened so that they can be uncoupled. The problem is that often on models that "Shuffle" has to be done in the wrong place and not where it would be done on the prototype.

nigelcliffe wrote:With my pet interest of locos fitted with DCC controlled uncoupling devices (ie. not relying on electromagnets in the track)


And some "mid-rake" rolling stock? Once you've got a DCC controlled uncoupling device then you can slacken up in the correct place and it looks ok.
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jim s-w
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Re: Which Couplings ???

Postby jim s-w » Sat May 21, 2011 7:34 am

Hi Neil

You could try mixing types, I am going to use smiths couplings on locos and dighams on rakes I need to uncouple. There's e bit about it in Nigels dcc Alex Jackson thread

viewtopic.php?f=26&t=225

Hth

Jim

JerryO

Re: Which Couplings ???

Postby JerryO » Sun May 22, 2011 9:06 pm

We at South Hants MRC have been using Dinghams on Lee-on-the-Solent for many years and more recently on Ogden Fold. They will also be the coupling of choice for Eastwood.

On fixed rakes of coaches we put the Hook/Latch coupling on each end. The Loco is then fitted with the Hook/Loop on the Rear/Tender end with a standard three link on the front end assuming the Loco is turned for return trip either within fiddleyard or on turntable. The rakes of coaches (and fixed groups of wagons) are interconnected with standard three links.

For Pick-up goods etc the wagons are fitted with a larger proportion of Dinghams with the dedicated Loco having Hook/Latch at Front and Hook/Loop at rear.

One addition I have implemented is the fitting of a Three Link to the Hook/Latch type coupling which provides some increased flexibility and realism as seen below (This can only be done with the Type 1 latch).
Attachments
Dscf1516a.jpg
Dingham Coupling with 3-Link

martin goodall
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Re: Which Couplings ???

Postby martin goodall » Mon May 23, 2011 8:31 pm

I tried out the Dingham coupling by playing with a couple of Dingham-fitted wagons lent to me by Andrew Ullyott, but there seemed to be problems with the latch 'sticking'. I was unable to find out what was causing this.

David Knight
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Re: Which Couplings ???

Postby David Knight » Tue May 24, 2011 1:34 am

Dingham latches stick for a few reasons. One is if the tab that is supposed to keep the latch from rising beyond the vertical is not in place or bent out of line. A possible second cause is excess solder on the cross pin causing the latch to bind or a third possibility is too much play in the latch so it falls off to one side or the other. All of these are fixable with a little fettling.

HTH

David


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