Hunt magnetic couplings: Adventures with the screw-on type, for Bachmann Mk1 suburbans and ex-LMS BG

[Dr.Glum]

I have long been fed up with the toy-like gap between my passenger stock, so I bought two types of Hunt Elite magnetic couplings to try (at ModelRail Scotland in February): the standard flat close type and the T-piece screw on type to treat my Bachmann Mk1 suburbans.

I show some results below, so it’s important that I state the conditions that my stock has to run under. My minimum radius is strictly 30 inches and no reverse curves of note. All points that passenger stock are expected to go through are Peco code 100 long. Apart from circulating on the layout through the minimum curves, my testing includes pulling and pushing through cross-overs.

 

My first image shows several things. Firstly that packet is of ‘NEM sockets to fit Bachmann suburbans’, but my carriages (bought in year 2000) must be very different from what they’re designed for – I can see no way of using the Hunt sockets, because they would foul the axles. Secondly, some of the magnets were not square in the moulding (not a problem with later purchases). As the T unit will have no flexibility when attached, I had to correct the end profile with a file. I know that this (along with hammering or unnecessary pulling magnets apart) could potentially reduce the strength of the field, but testing in a train showed me that the magnet had to be presented to the next vehicle square on and centrally between the rails. If one magnet wasn’t, bogie derailments were possible, often coming off a curve onto the straight or through points.

Top left is an original coupling and the pair lower down have the original screw through the Hunt T bar into the lip of the bogie. Look at the massive distance that results: not acceptable. Instead I removed any moulded bumps on the bogie lip and glued the T bar level with the back edge of the bogie lip. This resulted in the image below.

 

Actually not a great spacing improvement, but a definite gain losing the horrible big coupling. The finished train looked very fine to my eye. (But see later experience.)

 

 

It was while running this that I found what I said above: the importance of these fixed couplings lining up properly. I had glued one T bar not quite straight: the vehicle or the adjacent one was prone to derailment.

Overall I could see the benefits and made a decision that I would fit Hunt couplings to a proportion of my carriage rolling stock, with especial priority to problem rakes.

 

When I had a loft layout I was able to run long trains (11 plus), but found there were problems with some vehicles on plain track, usually coming off curves. The drag of the train seemed sufficient to stop the coupling hook sliding back to its straight position on the bar it was hooked on. Hornby Pullmans (bought 2005 and 2007) gave a lot of problems, and blow me much more recently with Hornby Gresley full brakes (which I want to run behind the engine as is shown in so many train photos) had the same problem.

The Pullmans are why I bought some Buckeyes to try (see below). Since I’d started with Hunts, I had not been clear as to which way up they should be installed. The photos on the web site do not always clearly show. Now I had the Buckeyes I could see, and then I found that I had chosen the other way up on my suburbans! Bah! Oh well, learning curve and I do now have a new ‘standard’.

I had glued them onto the suburbans with Bostik All-purpose Clear Glue and I’ve found it is possible to get them off as it doesn’t chemically bond with the Bachmann plastic.

 

So much more recently I bought a pack of various other types from West Hill Wagon Works so I could do a lot of experimenting. Up till then I had only had the T-bar screw sort and what I at that time regarded as the standard close coupling (on the packet: Close coupling – Couplings for NEM sockets), the shank of which is straight. I now also had:

Standard stepped (Mk1/Mk2/Pullman Stepped Close Coupling NEM sockets)

Buckeye (** Buckeye ** Mk1/Mk2/Pullman Stepped Close Coupling NEM sockets)

Extra Close (Hunt Couplings ELITE – Extra Close Couplings for NEM sockets)

Ultra Close (Ultra Close Coupling - Couplings for NEM sockets)

 

I’ll deal with them all in later posts on a variety of vehicles, but the proper solution for my old Mk1 suburbans is going to be what I’ve now found with the ex-LMS BG bogies, which have a very similar design. I glued Ultra close Hunts under the bogie lip (where the screwed coupling had been), but in testing I found it was too far off the standard height when coupled to stock with different Hunt couplings.

I now treat the Stepped Close coupling which is perfect for Bachmann Mk1 ordinary carriages (but not to get minimum vehicle spacing possible with the Mk1 TPOs for example.) as my height standard. But it is a little more complicated than that as I wished to run parcels trains with a mixture of Bachman ex-LMS BGs, Bachmann Mk1 BGs, Hornby Gresley BGs, Hornby Hawksworth BGs, and a variety of 4 wheel vans. Shades of Red Bank Parcels.

I’ll cover other vehicles in later posts, but for now I’ll illustrate two options with the T bar replacements, using the BG bogies as the test bed.

 

[Above] The LH Mk1 has the standard stepped coupling, being dragged down by the T bar fitting on the right. The height mismatch is too great when part of a heavy test train.

 

The solution was to glue the Ultra Close to the upper side of the bogie lip. Unfortunately some bogies of this vintage have a raised profile on the upper side (upper example) so I have had to saw/scrape a flat recess so the T bar can sit near enough to the axle (lower example). Note the X scratched on the coupling. Other couplings in the range have a moulded figure (C, XC or X) on the shank which should be upwards on the vehicle. (To avoid accidents of gluing anything on the wrong way up, I always keep a fitted vehicle on the workbench.

 

The next shot shows the same Mk1 with the standard stepped coupling with the crimson and cream BG fitted with the coupling glued above the bogie tab. Compared with the previous image, the standard coupling is less out of place, although the two magnets do not line up perfectly.

 

I should stress I have found no tendency for the magnets to part in any of my testing.

I will keep the two BGs with the two different coupling positions, for now. Other vehicle types may end up coupled to them, as in the next two images. The van has Ultras as the stepped standards stick out way too much.

 

The last two images show two BGs on the straight, and then on a 30 inch curve. Not so much a chance of buffer locking, more the corridor connections. (But it works; the vehicles do not tilt.)

 

So I will run more test trains like the one below with both ex-LMS BGs in and see if I hit any problems. And sometime I’ll treat my suburbans with Ultras and show the results here.

[Mike Harvey]

Interesting research. One general observation is that couplers fixed rigidly to a bogie are much less magnet friendly than ones with pivoting couplers or kinematic couplers. On a curve the contact face between magnets becomes much smaller and couplers can part or easily misalign, especially when propelling. Not surprised that the NEM couplers were not ideal for bogies without NEM pockets. Almost all of my stock is equipped with NEM pockets in either pivoting mounts or in kinematic self-centring close couplers and I do not have derailments on curves or unplanned uncoupling incidents. I am careful how I use vehicles with couplers rigidly mounted to a bogie or underframe whether fitted with magnetic or mechanical couplers.  I am working in N but the laws of physics apply equally well to 00 gauge.

[Dr.Glum]

Thank you Mike Harvey for your input. Working on other vehicles since I wrote the first post, has altered my thinking about maybe not using the T bar version. Luckily with the rake of 7 carriages I have not had any problems of disconnection. In 00 the magnet size and the force is such that two free running vehicles  will pull themselves together from about an inch apart. The contact face you mention does not open out, or at least not with my minimum track radius. 

[Dr.Glum]

Light is dawning. I downloaded the PDF from the WHWW site (highly recommended for understanding the range, and recently updated including information not on the product pages of the website) and found the following (extract) which explains my puzzlement over what WHWW had sold me – different bogies on my carriages!

 

The PDF file is: Hunt Couplings Guide v3 - 4 Nov 2022.pdf

I shall return to the subject of fitting to my Bachmann suburbans later, but have been continuing the development of my parcels traffic. Testing of the two old Bachmann ex-LMS BGs (see previous post) shows a slight bias towards the lower position (T bar coupling glued under tab on bogie). Next image shows potential problem when coupled to my ‘standard’ of Stepped Close Coupling fitted to Mk1 stock.

 

In practice the screw head holding the bogie to the BG underside limits such movement, but there have been a couple of derailments for no apparent explanation, depending on the height of coupling on the adjacent vehicle.

 

The other line of development has been trial fitting to vans and brakevans so that I can add 4 wheel fitted vans into my parcel trains. Tests so far:

Vehicles fitted with NEM sockets such as Bachmann vans and BR 20ton brake, and Dapol Fruit D. The height ends up as ‘standard’; the vans take Ultras and the Fruit D Extra Close. These will go through Peco medium radius points. (I don’t have any medium cross-overs, only long.) They run in trains with the bogie stock OK. A couple of the Ultras pulled out when separating vehicles and had to be glued in place. (One way of using any with a broken leg.)

 

The brake van is a problem with that low coupling. The vehicle has one Hunt fitted as it is to be a barrier wagon between non-Hunt locos and fitted heads (parcels and/or vans) and so will take the full drag of the train. So far it has proved problematic, so surgery will be needed (to come).

The image from the Hunt PDF (see above) using the 4WH0300102 NEM socket spurred me to deal with a Dapol 4w van. Despite being basic models they run well and I used them a lot on the old layout, even though I didn’t like the large couplings. I have now fitted Ultra Hunts to a banana van and it behaves perfectly. The photo below shows the underside.

The plastic box holding the original coupling is sawn off (carefully, so as not to cut into the spring hangars) and the remaining surface made absolutely smooth, paring with a very sharp knife. When the NEM pocket has been screwed on it must be able to move (swing sideways) without catching on any ‘lumps’.

Experience (limited I grant you) suggests that in a mixed environment of vans and bogie vehicles with sprung or fixed couplings, the 4 wheelers need the face of the magnet to end up slightly proud of the buffer faces, about ½mm. This implies a notional distance from the front (outside) of the buffer beam to the screw hole of about 18mm or 19mm. Why ‘or’ ? Because the body and frame of this moulding is not symmetrical! The body only fits on snugly one way round!

I considered self tapping screws to hold the NEM pocket on, but in the end found some 10BA bolts. At the moment there is no nut on the inside, but I’ll fit them when trials are finished.

I broke an Ultra coupling trying to get it in the first pocket. Looking at 16 pockets most of them had a ‘growth’ inside that required some careful work with a small square file. Bit tedious.

I did wonder about the pivot points (and hence points of drag) being relatively close together but it seems to run alright under load, or without fishtailing when there’s little drag.

Coincidently while going through old copies of ‘Model Rail’ prior to passing them on, I found some articles by Steve Banks on Parcels Traffic. Extremely interesting reading. It gave me an insight into the role of fitted 4 and 6 wheel vans (‘vanfits’) in mixed trains.

e.g. Issue no.110 November 2007 pp22-28 “Masterclass: Parcels Trains in the steam era”.

 

Edited September 11, 2023 by Dr.Glum
bolts not screws - doh!

[teeinox]

On 30/08/2023 at 15:25, Mike Harvey said:

Interesting research. One general observation is that couplers fixed rigidly to a bogie are much less magnet friendly than ones with pivoting couplers or kinematic couplers. On a curve the contact face between magnets becomes much smaller and couplers can part or easily misalign, especially when propelling. Not surprised that the NEM couplers were not ideal for bogies without NEM pockets. Almost all of my stock is equipped with NEM pockets in either pivoting mounts or in kinematic self-centring close couplers and I do not have derailments on curves or unplanned uncoupling incidents. I am careful how I use vehicles with couplers rigidly mounted to a bogie or underframe whether fitted with magnetic or mechanical couplers.  I am working in N but the laws of physics apply equally well to 00 gauge.

Completely agree with this view.  The magnetic force in the Elite couplings is considerable such that in practice, coupled together, they form a rigid bar coupling, much like the Hornby/Roco mechanical equivalents do.  So, where attaching direct to bogies, I have used this type from the Hunt coupling range; the picture comes from the West Hill Wagon Works web-site.

The hole is used to screw the coupling in place on the bogie frame, with a bit of play to allow it to pivot.  If it is screwed on the underside of the frame, there may be a bit of droop, but that disappears when the couplings connect.  With this arrangement, my 8-coach sets run perfectly, whether hauled or propelled, with no derailments or uncoupling.

 

teeinox

[Dr.Glum]

Thankyou teeinox, I had wondered about that type in my musing for the bogies of the suburbans. I shall buy a pack at Stafford Show on 23rd September.

The 16mm spacing to the hole may prove problematic on the old Dapol vans as the edge of the hole in the van floor left by sawing off the unwanted block is a bit near that position. However, any I don't use for the carriages will fit nicely on old Bachmann vans made in Hong Kong.

[Dr.Glum]

Hello again, teeinox.  Looking at the image of the 647 coupling that you illustrate above, the hole looks to be a similar size to the width of the magnet, so nearly 3mm.

What sort of screw or bolt do you use? The BA or metric bolts that I have with a similar width also have a relatively big head, and I have limited clearance either to the axle or to the carriage underside.

Cheers

[teeinox]

23 hours ago, Dr.Glum said:

Hello again, teeinox.  Looking at the image of the 647 coupling that you illustrate above, the hole looks to be a similar size to the width of the magnet, so nearly 3mm.

What sort of screw or bolt do you use? The BA or metric bolts that I have with a similar width also have a relatively big head, and I have limited clearance either to the axle or to the carriage underside.

Cheers

The screw I used was 2mm.  There is slop.  You could be right that the hole is about 3mm: it was designed to go over a plastic spigot, not take a screw.

[Dr.Glum]

Before doing anything more with the old Bachmann suburbans, here’s the results of two purchases at the Stafford Exhibition (a very good show).

Firstly I’m trialling ‘Close couplings for Clip Socket’ (serial 647) following a suggestion by teeinox. I needed a Hunt coupling on my R2231 Duchess of Rutland (bought in 2002) and this was right for it. The first image shows the underneath.

Out of sight under the bar of the coupling should be a screw holding the end of the tender’s base plate, but it is impossible to re-fit, being covered by the bar of the coupling. Seems held rigidly enough regardless.

The second point is I had to take a scalpel to the moulding that the missing screw would go into, as there was a ‘roughness’ that hindered the sideways free swing of the coupling. In the image below, the gap is at least 1mm wider than it needs to be, so I should have bought serial 651 which is 15mm rather than 16mm of the 647 (magnet face to hole c/l).

The other new fitting is ‘Close Coupling Stepped for NEM socket’ (on the packet, but confusingly described on the receipt as ‘Close Step NEM 00’ code HCNSSCLC).

Anyway, you’ll need code 649 for Bachman Mk1 with minimum 30” radius curves.

Above, with no tension on the coupling. Below, under load, with the standard weak Bachmann springs extended. Still, that is only visible on a sight line at right angles, and overall a vast improvement.

 

[teeinox]

Yes, there appear to be a variety of lengths available in the type of coupling that can be fitted with a screw, all called "Clip" by West Hill Wagon Works because they are designed to be clipped over a spigot.  As well as wagons, some are for Airfix Mk2s, others for various elderly Hornby productions.  I've found lengths from 14.7mm to 16mm available.  When I bought the 16mm ones, it was the nature of an experiment and I simply didn't know what size I would need: a leap in the dark!  In fact a shorter one would have been better.

[Dr.Glum]

Now back to the old Bachman Mk1 suburbans.

I’m trying two solutions. Now they are done I will put them into traffic and check if there are any issues under tension in a train or propelling, how they behave through curves and pointwork, and coupling with a variety of other types. Will report back in due course.

In both cases I remove the nearest wheel set so I can saw off the ‘tab’ to which the original screwed coupling was fitted. Part of the upstanding end of the bogie is removed (saw cuts, paring off with sharp knife, then final filing to polish). The plastic is very tough.

I have used 8BA bolts (normal or screw-headed) and make a tight fit hole so that the bolt of screw can self-tap. I had spare UltraClose Hunt couplings which call for the hole to be 11.5mm from the bogie edge, which puts it half under the axle. That’s where I use a screw head without a washer. With the 647 Clip fit coupling, the hole is 3.5mm from the edge and a bolt (with the bigger head) can be used. In both cases, for safety I do fit a nut, part off the spare length of the bolt with a slitting disk (to clear the carriage body) and secure with a blob of Bostik.

If I had spare standard close Hunts I’d use them as it puts the hole back clear of the axle.

The 647 coupling needs a ~2mm height spacer, for which 80thou plasticard is fine.

The photos below show the two ends of Crimson Compo M41006. Dunno where the buffer went!

1 bolted NEM102 + Ultra (11.5mm)

1 647 bolted 8BA (3.5mm from edge), , white plasticard spacer visible

That 647 above is a bit far back maybe, but so far it has worked OK. (I was a bit slack measuring up for the pilot hole, maybe 4.5mm.) [Later edit: not OK, see later post.]

I’ve also done Maroon Brk 2nd M43257 (not shown) with one fixed NEM102 + Ultra (which is less work) and the other end 1 bolted NEM102 + Ultra 8BA (11.5mm).

Edited October 5, 2023 by Dr.Glum
Corrections to captions

[bourneagain]

I had the same problem with all my older Bachmann Suburban’s. My solution was much the same as described above, but with a couple of slight differences. I removed the old coupling moulding, flush with the bogie face with a fine tooth razor saw. As mentioned this plastic material is quite tough to cut through, so I used a slitting disc in a mini drill on a very slow speed to make a number of cuts through the front bogie bar wide enough to fit the adaptor plate, but leaving a very small amount of plastic material each side still connected to the base. This cut material was then removed by using a 20mm x 3mm grinding wheel, again on a very slow speed, making sure that all the material has been removed, making a flush surface with the bogie base. If necessary the adaptor plate can be trimmed down slightly each side of the NEM pocket to fit the slot.

Using the grinding wheel, I removed the 2 plastic pips on the reverse side, this  is to allow a newer type of bogie (if you have one), with the wheels removed, to fit flush on top, to act as a jig for the correct location of the adaptor plate securing screw hole. I pushed a 2BA bolt through the 2 centre fixing holes to keep them aligned and clamped both together in a vice. Using a 1.7mm drill in a pin vice, I then drilled a hole into the old bogie, using the newer bogie hole as the guide. If you haven`t got a newer type bogie to use as a jig, the adaptor plate fixing hole is 15mm from the front bogie face.

The adaptor plate can now be fixed into place by using the original coupling fixing screw, which will self cut a thread into the plastic and hold it in place.

[Dr.Glum]

It didn’t take much testing of the four couplings (that I list above) to find that the 647 has been located far too far in towards the bogie pivot, i.e. it doesn’t stick out far enough. See last photo above.

The others also had problems. In daylight I found that two of them were happily travelling with a 1mm gap between magnet faces with a further five carriages in tow. Gosh! The buffer faces were together on the straight, which is fine for carriages with springs on the coupling carrier, but these are rigid. On a 30 inch radius curve there were prototypical graunching noises (from the buffers) such as you might hear on preserved lines when carriages or loco tenders negotiate small radius points.

All very amusing, but not conducive to reliable running. I did comparative running with the original rake which had the T-bar couplings glued on (see head of this thread). This gave me the dimension on the straight for the gap between the buffers: nominal 3mm.

Previous attempts had shown me I was not able to install the couplings in a consistent manner. I took the time to build a jig, as I have 12 carriages to deal with.

The white card is just under 1.5mm thick and the buffers rest against it.

The carriage above is one that has its coupling set back too far – see the gap between the magnet face and the brown card cradle. My plan is mark any holes for drilling with the coupling lying on the bogie while in the cradle. I will report back.

[RFS]

For fitting magnetic couplings which are fixed to the bogie (ie there's no close-coupling mechanism) have you considered using the Hunt pivoting couplings?

[andythenorth]

4 minutes ago, RFS said:

For fitting magnetic couplings which are fixed to the bogie (ie there's no close-coupling mechanism) have you considered using the Hunt pivoting couplings?

+1

 

These are (slightly) the majority of what I fit now.  The flexibility is useful where NEM mounts aren't kinematic, or the kinematic mount is sticking or the spring is broken (I buy a lot of secondhand stock, so this is common).  

 

The only downside is that when both vehicles have pivoting couplings, the propelling performance can be degraded.  For fixed rakes it can be minimised by fitting one end of the vehicle with fixed coupling and the other end pivoting.  

[bourneagain]

23 hours ago, Dr.Glum said:

It didn’t take much testing of the four couplings (that I list above) to find that the 647 has been located far too far in towards the bogie pivot, i.e. it doesn’t stick out far enough. See last photo above.

The others also had problems. In daylight I found that two of them were happily travelling with a 1mm gap between magnet faces with a further five carriages in tow. Gosh! The buffer faces were together on the straight, which is fine for carriages with springs on the coupling carrier, but these are rigid. On a 30 inch radius curve there were prototypical graunching noises (from the buffers) such as you might hear on preserved lines when carriages or loco tenders negotiate small radius points.

All very amusing, but not conducive to reliable running. I did comparative running with the original rake which had the T-bar couplings glued on (see head of this thread). This gave me the dimension on the straight for the gap between the buffers: nominal 3mm.

Previous attempts had shown me I was not able to install the couplings in a consistent manner. I took the time to build a jig, as I have 12 carriages to deal with.

The white card is just under 1.5mm thick and the buffers rest against it.

The carriage above is one that has its coupling set back too far – see the gap between the magnet face and the brown card cradle. My plan is mark any holes for drilling with the coupling lying on the bogie while in the cradle. I will report back.

I don`t want to dispute the sterling work that you are undertaking in finding the ideal solution to the coupling issues on your Suburban coaches, but I would like to share with you some of the tests I carried out some time ago to solve the same problem. I believe that your current measurement of the magnet ends of 1.5mm over the buffer faces is a little bit optimistic with a 30 in curved track.

I set out to establish which was is the best version of magnetic coupling to use on my layout with these Bachmann Suburban coaches, these I have already fitted with the adaptor plates, as described earlier, travelling around the minimum 30in curve on my layout.

The 2 couplings that I used were

The 641 Close 9.5mm length

And 642 Intermediate 11.4mm length

I did try some others that I had but were discarded as either being too short or long for use on these coaches.

With the 641 coupling fitted, the measurement over the buffer face was approx 1mm, with the 642 coupling the measurement was approx 3mm.

First test I tried, 2 carriages that had the shorter 641 couplings fitted, when pulled around the curve, I found that the 2 inside buffers came together, but as the 2 couplings are quite short in length, the magnets were pulled apart, resulting in the 2 carriages separating.

Next I tried 1 carriage with the shorter 641 coupling fitted and the other had the longer 642 fitted. The result was again the 2 inside buffers came together, but this time the 2 magnets were only pulled slightly apart, but they were still very close enough not to cause the 2 carriages to actually separate and continued together around the curve.

Lastly I had both carriages fitted with the longer 642 couplings, although the buffers came together the 2 magnets kept in contact with each other, which Is the ideal situation.

I have ended up installing the 612 Buckeye Stepped couplings (11.7mm length) on my Suburban coaches, although not strictly prototypical, they do hide the bright magnetic sides of the magnets. As they always travel in sets, the height is not an issue.

Although it doesn`t really matter where the MEN pocket is installed under the coach, it’s the distance over the buffer faces of the magnetic end that is critical in the smooth running of the coaches.

[roythebus1]

Some interesting things there. I've just started experimenting with Hunt couplings, I got a mixed bag of them online recently. I too hate the huge gaps between coaches. I'd already experimented with the Kean Coupling system which is basically a copy of the "standard" European coach close-coupling with NEM pocket. Kean provided flat bar couplings with holes and spigot which seem to work  but they gave problems. 

 

To fit the Kean units, some can be glued straight under the coach floor, others need a hole cut in the floor which makes additional work. On my parcels stock and goods wagons I use Kadees, a mixture of the NEM couplers and box-mounted for older stock and NEM/Roco KKs on coaches. The Kadees work well with the Kean coupler units, but are a trifle expensive since the B word has made importing them more expensive.

 

So the last couple of days I've been experimenting with some old Lima and Mainline Siphons, BGs and the like, also some Big four coaches from the same era. The advantage of the Kean mountings is that the coupler face moves out as the coach goes round a curve, so eliminates the problem of buffer locking. I use a minimum of about 30" radius on hand-built Templot-based track, so won't really have the train set track problem with sharp reverse curves. I found all the Hunt couplings in the trial pack were too long, a look through their catalogue shows they do some a 6.6mm, I'll order some of those and see how I get on. 

 

I've found that putting the Hunt magnets on the Kean units I get a corridor connection gap down to 0.5mm using an LMS open first and an Airfix Hawksworth Super Saloon. No buffer locking on curves either. Nice close buffers on the Siphons and BG with 1mm between buffers and no buffer locking. With the Kean units working out at about £3 coach, it's a bit expensive but worth it for the visual effect of seeing a train going along with no gaps between the coaches.

 

One of the lads at the Folkestone MRC has used Hunt couplings and found a problem is that if they are mounted too rigidly there is no twist or sideways "give" and that can cause derailments on uneven track.