Thursday, March 11, 2021

How I designed and made my own hook and loop couplings

You may have seen from my various posts and videos over the years that I am particularly keen on operating my railway as realistically as possible. For reasons of convenience and reliability, I have always used LGB hook and loop couplings from the early days when the only rolling stock I possessed were from the LGB Starter Set. The couplings may look ugly and unprototypical but they are cheap, easy to use and are almost 100% reliable. However, they are particularly obtrusive when taking photos and videos at track level.

For years, I experimented with various alternatives. Ideally, I wanted to use chopper couplings as these were (and still are) the most common on narrow gauge railways in the UK - but they can be tricky to hook up, are not always reliable and, more importantly for someone whose railway has been built on a budget, are quite expensive.
About four years ago, I started experimenting with variations on LGB hook and loop couplings. After all, they had served me well for around ten years and, if I could create something which was compatible, I could slowly change over to my new variant gradually. I have around 90 items of rolling stock and so it was going to take time to replace the couplings on all my stock.
After a couple of years of experimentation, trial, error and improvement, I believe I have arrived at a solution which is reliable, compatible, cheap and fairly easy to construct - the RJB Hook and Loop!


My first version was fairly basic. As you can see, it comprised a folded sheet of brass to which was soldered a hook and a loop both made from bent paper-clips.

I fitted three or four wagons with this style of coupling and tried them out on a couple of operating sessions to see how they performed. They proved to be compatible with standard LGB couplings ......

.... and with each other - but I quickly realised I needed to equip all my stock with centre buffers as the wire loops weren't thick enough to allow stock which were both equipped with wire couplings to be propelled back against each other.

A later variation used brass rod for the loop and phosphor bronze for the hook. This proved more effective as the phosphor bronze is more flexible than a steel paper-clip.

Construction was fairly straightforward, but creating a double-fold in the brass sheet wasn't easy with the basic workshop equipment I possess.

.....So a simplified design as created, with a single fold. At the same time, I widened the loop to give the hook a larger target area on which to latch when coupling-up. I had found that my original loop couldn't cope when wagons needed to couple together on a curve.

This version of the coupling was much easier to produce and proved to be quite reliable. However, it was all too easy for the hook to ride up over the loop unless the hooks and loops were perfectly aligned. The simplest solution was to bend the hook back on itself to provide a dangling tail. This simple expedient helped ensure the hook was more likely to pass beneath the loop.

Until now, I had been using Binnie Medium Carmarthen buffers for stock such as Hartland Loco Works (HLW) mini series wagons which didn't have any buffers. I had bought around twenty of these when I was experimenting with different styles of couplings. 

I simply snipped off the coupling hooks and then filed the remnants smooth.

To ensure the buffers were attached at a uniform height above the rail, I created a simple jig which slotted into a piece of test track.

The buffer was slotted into the jig and given a generous coating of thick superglue.

The wagon was then wheeled up to the jig, making sure the buffer was central ......

..... and then a large elastic band passed around the jig and the wagon to hold everything in place while the glue set.

NOTE: Since those early days, I now apply a superglue activator spray to the headstock of the wagon which sets the superglue almost immediately on contact with the buffer, so there is no need for the elastic band.


Replacement buffers for LGB stock

Experimentation revealed that the small round buffer heads with which most LGB goods rolling stock is equipped weren't wide enough to prevent buffer-lock when stock was propelled backwards.

Rather than removing these buffers and mounts completely and replacing them with Binnie Carmarthens, I explored a different solution. I discovered the head of the coupling could be readily removed from the mount. The head is a tight push-fit and can be prised off with a pair of pointed-nosed pliers. Once removed, I found that a ¾" No. 8 woodscrew was a perfect fit into the hole. 

To make the buffers, a 25mm x 12mm piece of 0.75mm thick brass sheet was given rounded corners with a file .....

 The head of a ¾" No. 8 brass screw was then tinned with solder as was the middle of the buffing plate.

 The two surfaces were then put together and heat was then applied ....

 ...... until the two components fused together.

 Once it had been blackened (see below), the buffer assembly was simply screwed into the mount

Couplings for LGB rolling stock

Although the couplings for LGB and HLW rolling stock are compatible, the couplings themselves differ in design as do their mounts, and so a slight variation is required for the two types of coupling.

After initial experimentation (see above), I decided that he most efficient way to construct the couplings was to mass produce them in batches. This is particularly so for the LGB style of coupling which requires an 8mm diameter hole to be drilled towards the front. It's much easier to drill these holes when the coupling plate is still part of a larger sheet.

The mounting plates were marked out on to a sheet of 0.75mm thick brass sheet with a pointed scriber.

The centre point of each hole was then indented with an automatic centre-punch. This is to help ensure that the drill bit doesn't wander when the holes are being drilled. A hammer and nail could have been used as a centre punch.
1mm diameter pilot holes were then drilled .....
..... before the holes were then opened out to their correct sizes. I drilled the 8mm holes in stages, increasing the size of the hole in 2mm steps. I find this helps to prevent the hole from distorting.
The strip of mounting plates was then removed from the main sheet using a pair of heavy duty tin snips.
The individual mounting plates were then snipped from the strip.
Each mounting plate was then placed in a vice and checked for perpendicularity with a tri square ......
...... before being bashed into submission with a hammer.
The plate was then ready for assembly.

 The loops and hooks

A simple jig was constructed to help ensure the loops were bent to a uniform shape and size. The dimensions of the loop were firstly marked out on a sheet of graph paper.
This was placed on to a ½" (12mm) thick piece of plywood and two brass nails hammered in at the widest corners of the loop. Two 2mm diameter holes were drilled into the plywood at the base of the loop.
The heads of the brass nails were snipped off and the graph paper removed.

The jig was now ready for use. A short length of 2mm diameter brass rod had one end bent at right angles, about 8mm from the end (better to make it slightly too long than too short).
The bent end of the rod was inserted into one of the holes and then ....
..... bent around the nails. The end of the loop was then snipped off, about 8mm from the second hole.

A second jig was constructed to assist with soldering. An 8mm high block of wood was attached to the plywood and brass nails tapped in as shown - to hold the loop and mounting plate in position - the position of the nails is determined by the relative positions of the plate and the loop.
The loop was placed in the jig and the end of the loop bent downwards with pliers ......

...... to link with the plate
 The loop was then soldered to the plate.

 The end of a length of 0.9mm phosphor bronze wire was then bent at right angles approximately 3mm from the end.

 The bent end was then inserted into the 1mm hole in the middle of the plate ........

 ...... and soldered into place.

 I have marked on the jig where the hook needs to be bent (see dimensions above) .......

 The wire was then bent with a pair of pointed-nosed pliers ......

.... and then bent back on itself. After a while, I figured out the point on the pliers where the correct height of the hook would be.

 The end of the hook was then snipped off at the correct length

Replacements for HLW hook & loop couplings

Quite a few of my wagons have made use of HLW mini-series wagon chassis, primarily because they were cheap and quite plentiful when I first embarked on garden railway modelling.
As indicated above, the size, shape and mountings for HLW couplings differs from LGB couplings and so a slight variation in the dimensions was needed. I also use this design as a basis for couplings for other rolling stock - eg made from kits or scratch-built.

The production and construction techniques mirror those for the LGB replacement couplings details above. A slightly different jig is used for bending the hooks ......

.... and another for soldering the hooks to the mounting plates.

The mounting plates are slightly easier to make, as they lack the 8mm hole, but their marking-out, drilling, cutting and folding follow the same method as outlined above.

 Attaching the couplings to the wagon chassis

The only significant difference between the HLW version and the LGB version is the way in which they are attached the the chassis.
The LGB couplings are mounted as an exact replacement. The screw holding the coupling to the chassis needs to be about half the length of the original, as the mounting plate is much thinner, but apart from that it is screwed directly into the chassis.

The original HLW couplings were mounted on a pillar. 

This pillar needs to be removed. It often breaks off anyway when the old coupling is removed.
A slot is then cut into the web behind the pillar to make room for the tail of the hook.
And then the coupling is screwed into the pillar. I tend to use stainless steel self tapping screws rather than the originals because I have a ready supply to hand.

 Blackening the couplings.

Whilst it would be possible simply to paint the couplings, they are subjected to a fair amount of abrasive wear and so I decided to chemically blacken them. I did try Carr's blacking fluid for brass but found this to lose its potency within a short space of time and so now use Birchwood Casey Brass Black fluid (from Eileen's Emporium) which doesn't seem to lose strength no matter how many times I use it. I decant fluid into one of those small marmalade jars which you get in posh cafes or hotels (or can be bought empty in bulk on eBay).

I immerse the coupling or the brass buffer in the fluid for around 10 - 15 minutes

.... after which time it has turned a pleasant shade of black. The couplings are then inverted as I can only fit half of it into the jar at a time.

NOTE: Don't forget to remove the item after about fifteen minutes. If you leave it in overnight, you might find the coupling loop has disintegrated - you don't need to ask how I know.....!


Further modifications

Some vehicles need bespoke modifications to the standard buffers or couplings.

Widened buffers

Whilst the Binnie or brass buffers are appropriate for most wagons, some locos need wider buffers because their buffer beams are distanced further from the driving wheels and hence there is more outswing as the loco takes curves. This is particularly important for locos which have to shunt wagons in sidings with tight curves.

Around a third of my locos have widened buffers ......

.... which enable them to stock, even through fairly tight reverse curves.

Mounting couplings and buffers on bogies

All my coaching stock and some of my locos have their buffers and couplings directly attached to the bogies rather than to the headstocks or buffer beams. Some of my curves are so tight this is the only way the couplings can cope.

They require extended mounting plates which are attached in some way (usually by self tapping screws) to the bogies. The length of these plates is dependent on the distance between the bogie and the headstock, but they all follow the same pattern.
Whatever the starting width and the length of the plate, it ends in a 15mm long x 20mm wide plate, with two 3mm holes, 5mm from the end and with 17.5mm centres.
These holes are countersunk.

 20mm x 20mm plates are created with similarly spaced holes at one end.

Once the end plate has been bent at 90 degrees, the square plate is bolted to it with countersunk headed 3mm screws, together with a Binnie buffer.

The bolts are filed or snipped off once the nuts have been tightened.

The hook and loop are then soldered to the mounting plate in the usual way. Once the assembly has been blackened and attached to the bogie, it is tested.

As can be seen, it can cope with even the tightest (R2) reverse curves on my railway.


As with normal LGB hook and loop couplings, my RJB couplings auto-couple in the same way ..

Uncoupling is achieved as with LGB style couplings by depressing the loops from above. I use plastic plant labels which are easily carried around in the back pocket of my jeans during an operating session.

As indicated at the start of this article, my couplings are compatible with standard LGB hook and loops, though it is necessary for the LGB equipped stock to have a centre buffer.

Further developments

I am experimenting with delayed uncoupling. Some of the sidings on my railway are tricky to access and so it would be handy if I could uncouple some wagons at the head of the siding and propel them to their desired location without having to awkwardly lean, crouch or even crawl over the top of the siding to do the uncoupling.

My speculative first design involved the use of an additional spur on the hook which would prevent the loop from re-engaging with the hook once it had been uncoupled.

Coupling-up happens in the normal way - one wagon is propelled towards the other ......

.... and the hooks engage with the loops

To uncouple, the tension on the hooks is released by propelling one or both wagons together ......

.... and a plant label or something similar is used to push down both hooks.

The wagons now continue to push against each other until they reach the desired place on the siding.

When they are now drawn apart, the taller upper arms on the hook arms pass under the loops to prevent the hooks from re-engaging with the loops.

The wagons can thus be drawn apart.

In theory this arrangement should work reliably, but in reality there are several confounding variables which interfere. It requires that the hook arms don't become bent out of alignment - something which is difficult to guarantee in a garden railway environment. Also, the additionally complication on the hook arm sometimes leads to couplings not properly engaging. And finally, the lengths of the arms on the hook are quite critical - something which my hit and miss construction techniques can't guarantee. 

So, for now, I have abandoned the idea - but it is something I might return to in the future. Particularly as old age creeps up and me and I am no longer as agile as I used to be.


Being able to run trains at realistic speeds and shunt wagons to and from goods trains is the main reason all my locos are battery powered and radio controlled (see Track v Battery Power - My perspective). 

When I have full operating sessions, I run passenger services to a sequential timetable and try to ensure that freight services are carried out in a way which attempts to mirror light railway practice as it might have been in the 1930s (see A Typical Operating Session). I have created a couple of simple freight management computer programs which generates semi randomised trains and keeps track of which wagons are where on the system (see Freight Management on the Railway). And so, having simple, cheap and reliable couplings are extremely important to me and the way I run my railway.

After two years of gradually converting all my stock to my new couplings, I am pleased with the outcome. The new couplings are far less obtrusive than the old LGB plastic versions. Although they look flimsy, they are surprisingly strong. I have tested them on trains of 25 wagons without problem.

Their weakness is their fragility. The hooks can easily become bent out of shape and so coupling-up is sometimes a bit hit and miss. However, the hooks can just as easily be bent back into shape and things returned to normal. Occasionally, I encounter a dry joint with my soldering - usually where the hook is attached to the mounting plate. Again, this is quickly remedied.
Occasionally, when long trains of stock are being propelled back into the storage sidings, the pressure on some of the buffers forces a wagon off the track - but this used to happen with the LGB couplings and so it's not much of a hardship.

So, am I regretting changing over my couplings? Certainly not! Close-up photography and videography is no longer an embarrassment. Just take a look at these two videos - before and after - to judge for yourself.