Brian Kirby uncoupling - problems

[checkrail]

Hi

 

I'm at the stage of choosing a 4mm scale coupling system, and after trying various aftermarket couplers I've settled on the Brian Kirby modification of the Bachmann mini-tension locks - or I thought I had!

 

It's ingenious, elegant and effective, but ............  A thorough search of coverage on this and other forums back to 2009 hasn't thrown much light on the problems I'm having and I'm wondering if it's just me or if others have overcome similar problems and are willing to share experience or suggest solutions.  The problems are: (1) involuntary recoupling immediately after disengaging and starting to pull away, and (2) unwanted uncoupling when stock is pulled over the magnets.  I've converted 16 Bachmann and other PO coal wagons and after a week or so of testing and swearing I think that the magnets are exerting such a pull on the axles that they're stopping the set-up from working as intended.  (On one bizarre occasion I dropped the last 2 wagons of 5 in a siding and reversed away.  When the gap between the 2 parts had got to about 2 inches the 2 wagons started following their companions, and the more speed I put on the faster they chased. They only came to a halt when they encountered some pointwork after about 2 feet.  Fortunately I've not been able to repeat this!)

 

With problem (2) it seems that every time I pull a string of wagons slowly over the magnets at least one (not always the same one) will disengage.  I think that what's happening here is that sometimes as a coupling pair approach an uncoupling point the magnet attracts the forward axle of the trailing wagon causing it momentarily to surge forward at a faster speed than that of the train as a whole, allowing the hooks to come out of tension and rise. This wagon and any behind it thus get left behind. As with 16 wagons there are numerous potential coupling pair relationships this can (and does) happen at random, seemingly with any vehicle.  

 

I first tried adding some friction to the axles with pieces of plastikard glued to the floor or coupling mount. This didn't really improve things much.  It did however cause my Hornby 28xx to refuse to pull this train, though my Bachmann pannier, prairie and Hall had no problem.  Today I started adding a piece of springy steel wire to each wagon chassis, bearing down lightly on the axles, on a case by case basis.  Result?  No more unwanted uncoupling but even my Bachmann locos now wouldn't pull the train!  So I've just slackened the pressure exerted by the steel wire a bit and the unwanted uncoupling has started all over again.

 

Questions:

1. Has anyone had similar problems and if so how did you overcome them?

2. Do people achieve successful slow-speed shunting with this method?  (I don't want to shunt the yard at 50 mph to keep the hooks in tension.)

3. (Long shot this!) Is it possible to obtain fine scale metal wagon wheels with non-ferrous axles?

 

Any help gratefully received.

 

(For the record I've followed the BK script to the letter.  All stock has Bachmann 36-030 couplings with straightened dropper and added staple, checked for coupling loop height and alignment, uncoupled by pairs of Screwfix door-catch magnets laid in the ballast under C & L sleepers.)

 

John C.

[Rowsley17D]

I think the solution is to use electromagnets instead of permanent ones.

[CloggyDog]

Kadee users sometimes have similar problems - steel axles/wheels (even the steel wagon weight) can be attracted to permanent uncoupling magnets, leading to unexpected uncouplings and/or failures to uncouple when required.

 

Our colonial cousins get around this by using non-steel axles (Kadee's own wheelsets have delrin axles, other makes use brass), but I'm not aware of any UK outline wheelsets which avoid steel on wheel and axle (plenty of non-steel wheels out there, e.g. Romfords, but all, afaik, mounted on steel axles.)

 

I'd second Jonathan's suggestion to replace the permanent magnets with switchable electromagnets.

[Jeff Smith]

It sounds as though you are having very similar problems that I had with steel axles and wheels with Kadee knuckle couplers over Bachmann under-track magnets.  This was with Peco O-16.5 coach and wagon kits that come with very nice steel tyred plastic spoked wheels on steel axles.  Although weighted quite well they always uncoupled when being pulled over the magnets.  My solution was to get some Hornby wagon wheels (R8098) which are die-cast in a non-ferrous material but fitted to steel axles  , and re-fit to 2mm brass axles as supplied by Andy Reichert at the Proto:87 on-line store (he can ship to the UK).  These now pull and push perfectly without un-coupling.  I suspect spare Bachmann wheels (36-014) are similarly constructed but could not get hold of any to try them.  If you have recent stock you may find that they are already fitted with non-magnetic wheels so just need some brass axles - make sure you get the correct length though.  Also it does help to put a little drag on the wagons as if they are too free-running the wagon will be attracted to the magnet by the trip pin or whatever the equivalent is in your coupling type.....

[Stubby47]

I only use one adapted coupling - the wagons are 'handed' so the other end has the bar but no hook at all.
This means I only need one magnet.

Pros : Simple (r ) to fit the magnets and staples, mostly good in operation.
Cons : Occasional unwanted uncoupling - much improved with smoothly working locos ( clean track & wheels, etc)
Also any out of spec staples can get caught in the track & either break off or derail the wagon.

Have also tried Pete Harvey's etched version. This I find to be too unbalanced with the staple soldered on, so the hook is very light & prone to lifting.

So, ideas for you.
Shorten the horizontal part of the staple.
As you are using C&L this track is thinner than the Peco, so the magnets are stronger ( not sure if you could bury them deeper).

Hope some of that helps.

Stu

[philsandy]

I have had problems with unwanted uncoupling on certain wagons but deduced this was down to Bachmann's tension lock couplings rather than Brian Kirby's system.

After close inspection at very low speed I noted the following:

 

As the wagons were pulled over the magnets, wagon No.2's hook lifted, as it should, because it's hook is not under tension. Wagon No.1's hook can not lift when being  pulled as it  is  under tension, regardless of any magnets. And theres the rub.

The barb of the hook on wagon 1 was not fully engaged  completely around the bar of wagon 2,  but just enough to be able to pull No. 2 wagon, but as soon as it encountered the magnet, because it was not locked around the bar it also lifted. 

The couplings all have to be set at the same height, and I mean to within about 0.5mm, and it's surprising how many of Bachmann's couplings vary in height.

It takes a bit of adjustment, most couplings were all of the same height, there was just a few here and there that needed adjusting.

I felt it worth persevering with because when it is working correctly it's a brilliant system.

 

Regarding actually uncoupling when you want it to, I found that the length of the staple is a factor, as you can sometimes get one wagons hook dropping down a split second  before the other wagons hook has lifted.

[Brian Kirby]

Hi John C/Checkrail and Everyone,

    I'm sorry to hear that you having a few odd uncouplings, i think you'll find it's down to the fit of the Bachmann tension-lock hook around the bar. The tension-lock dates back to Tri-ang Railways days in the 1950s, the principle is that the squared-off inside of the hook with horizontal planes, should fit around the rim of the bar, sufficient to stop the strongest magnet, or even the permanently sprung Tri-ang Hornby or Peco uncoupling ramps, from forcing the hook upwards. We can never have all our couplings at exactly the same height, so perhaps your hooks were not exactly engaged, one adjustment fix is to file down the bottom of the inside of the hook, but still keeping it horizontal, this will allow more vertical movement, i'd start with the most affected stock. In theory one locked hook should still be sufficient, pairs of couplings are often seen like this, caused either by curves of different heights of coupling bars.

    As you've probably already read, the need for the little chore of straightening the dropper becomes apparent with later use, since as the system is used, the attracted staples can become slowly magnetized and the part that wraps around the dropper would be very close to it's opposite mate if kinked as supplied, and thus could also attract a very free-running wagon. Straightening the dropper makes the staples handed, rather than centralized, so are now far enough away. I agree with others, electro-magnets are a safe bet for running lines, giving more security, but more bother to fit. Regarding positioning of magnets in sidings, well of course you could add as many as you wish, but if fitting just the one pair, i always favour fitting just beyond the fouling point of each siding, then there's always room to push back and re-couple. If problems persist, do not hesitate to ask. Thank you for all the other kind comments.

                                                                  Cheers, Brian. 

[Jeff Smith]

Brian - surely even with perfectly aligned couplings and formed hooks you cannot rule out the effect of wheel/axle attraction to the magnet. As the OP observed, if the trailing wagon is pulled forward such that the buffing faces touch then the hooks will lift - they have to otherwise they would not couple in the first place......

[34theletterbetweenB&D]

...On one bizarre occasion I dropped the last 2 wagons of 5 in a siding and reversed away.  When the gap between the 2 parts had got to about 2 inches the 2 wagons started following their companions, and the more speed I put on the faster they chased. They only came to a halt when they encountered some pointwork after about 2 feet... 

 

That supplies a clue to another factor that may be contributing to the perceived problem, which caught me out when first trying Kadees. Gradients in nominally level track, sufficient for the more free rolling exampes among the stock to roll down.

 

I don't shunt wagons with the BK modified tension locks (wagons) or the Kadees (coaches) but use these couplers to drop off whole trains. The balance between free rolling stock and stability over the uncoupling locations (some permanent magnet, but mostly electromagnet, Kadee types) is one I have to live with, as free rolling is a pre-requisite of the long trains I want to operate. The train has to be drawn up very slowly and smoothly to the uncoupling point, otherwise there can be enough stored energy in flexing parts along the train's couplers to move it after the uncouple and cause an unwanted recouple. This movement definitely has nothing to do with magnetic attraction, as it happens just as well on vehicles with no steel or iron in them at the uncoupling locations.

 

What I want are automatic train brakes, but life's too short! A suggestion I have seen is to put some nylon bristle standing in the four foot to foul the axles, and thus hold the train. One of those things to experiment when I get a round tuit.

[checkrail]

Wow!  Less than 24 hours and enough useful suggestions to keep me busy for the next week.  Thanks to all.  Great forum.

 

Yes, electro-magnets, as suggested by Jonathan and CloggyDog, had crossed my mind, though I think they do rather detract from the wonderful simplicity of Brian's original concept.  Insofar as I understand them (i.e. not much!) electro-magnets are energised on a momentary basis only by a quick pulse, so while operating the magnet switch or push-button with one hand one has simultaneously (and smartly) to get the loco away with the other, before the hooks fall.  Have I got that right? Seems a bit of a faff. And I'd need two electro-magnets (presumably wired to one switch) per uncoupler, unless I adopted Stu's idea of hooks on one end only. But I'd be very interested to hear from anyone using electro-magnets with the BK system, e.g. type and source of magnets.

 

CloggyDog and Jeff both report similar issues with Kadees, so switching to these is obviously no panacea, besides the cost and the learning curve.  I don't like the look of them for steam-age UK goods stock anyway.

 

Stu might have a point re the C & L sleepers.  Rather than dig up the four-foot yet again, with all the attendant re-ballasting and colour re-matching I'll experiment by putting the staple that much further up the coupling dropper on a couple of vehicles.  I'll also try different lengths and alignments of staple.

 

Thanks Brian and philsandy for points about hook alignment.  I'll have a look at this.  I'm aware that given all the variables involved - slop, curves etc. - one can't expect both hooks of a coupling pair to be in tension all the time, though one should!  But as Jeff says, even when they are the magnetic attraction of the axle can do its dirty work (and it does).

 

Jeff's suggestion of trying Proto:87 brass axles is promising, and something I'd never have known about.  I've been online this morning and ordered some from California.  Looking forward to experimenting with those. And I've also ordered some phosphor-bronze strip from Eileen's for any further necessary application of friction to axles - after popping wheels in and out round the ends of springy steel wire the end of my thumb is like a second-hand dartboard and I have some bloodstained coal wagons.

 

Thanks again - will keep you posted re progress.

 

BTW - have now added the mod to a few coaches.  No problems here, due to their mass I expect.  But it's immensely satisfying to see an express stop at the junction station while a tank loco comes out, detaches a through coach, and connects it to the back of the branch passenger train before running round and departing, all without the 'hand of God'.  Plus the reverse manoeuvre en route back to Paddington!  All thanks to DCC and the Brian Kirby uncoupler.

[Stubby47]

The process of stopping a goods train in Shepherds, pulling forwards with just some of the wagons, then leaving just one in the siding, all seemingly by magic, has captured the attention of quite a few viewers - most not having seen the staples. I like the hands-off approach, but you do need to know where the magnets are...

[Pete Harvey]

Pound Shop Kids fridge magnets are better as they are not as strong and smaller in size, you get a lot of them for .99p

 

Pete

[CloggyDog]

Yes, electro-magnets, as suggested by Jonathan and CloggyDog, had crossed my mind, though I think they do rather detract from the wonderful simplicity of Brian's original concept.  Insofar as I understand them (i.e. not much!) electro-magnets are energised on a momentary basis only by a quick pulse, so while operating the magnet switch or push-button with one hand one has simultaneously (and smartly) to get the loco away with the other, before the hooks fall.  Have I got that right? Seems a bit of a faff. And I'd need two electro-magnets (presumably wired to one switch) per uncoupler, unless I adopted Stu's idea of hooks on one end only. But I'd be very interested to hear from anyone using electro-magnets with the BK system, e.g. type and source of magnets.

 

 

Depends on the type of switch you use. A passing contact switch would give you that momentary activation, but a better bet would be a simple SPST on/off switch (toggle, push to make, etc) so you can keep the electromagnet live for as long as you need. And yes, you could easily pair two electromagnets off the same switch.

[dasatcopthorne]

Hi

 

I'm at the stage of choosing a 4mm scale coupling system, and after trying various aftermarket couplers I've settled on the Brian Kirby modification of the Bachmann mini-tension locks - or I thought I had!

 

It's ingenious, elegant and effective, but ............  A thorough search of coverage on this and other forums back to 2009 hasn't thrown much light on the problems I'm having and I'm wondering if it's just me or if others have overcome similar problems and are willing to share experience or suggest solutions.  The problems are: (1) involuntary recoupling immediately after disengaging and starting to pull away, and (2) unwanted uncoupling when stock is pulled over the magnets.  I've converted 16 Bachmann and other PO coal wagons and after a week or so of testing and swearing I think that the magnets are exerting such a pull on the axles that they're stopping the set-up from working as intended.  (On one bizarre occasion I dropped the last 2 wagons of 5 in a siding and reversed away.  When the gap between the 2 parts had got to about 2 inches the 2 wagons started following their companions, and the more speed I put on the faster they chased. They only came to a halt when they encountered some pointwork after about 2 feet.  Fortunately I've not been able to repeat this!)

 

With problem (2) it seems that every time I pull a string of wagons slowly over the magnets at least one (not always the same one) will disengage.  I think that what's happening here is that sometimes as a coupling pair approach an uncoupling point the magnet attracts the forward axle of the trailing wagon causing it momentarily to surge forward at a faster speed than that of the train as a whole, allowing the hooks to come out of tension and rise. This wagon and any behind it thus get left behind. As with 16 wagons there are numerous potential coupling pair relationships this can (and does) happen at random, seemingly with any vehicle.  

 

I first tried adding some friction to the axles with pieces of plastikard glued to the floor or coupling mount. This didn't really improve things much.  It did however cause my Hornby 28xx to refuse to pull this train, though my Bachmann pannier, prairie and Hall had no problem.  Today I started adding a piece of springy steel wire to each wagon chassis, bearing down lightly on the axles, on a case by case basis.  Result?  No more unwanted uncoupling but even my Bachmann locos now wouldn't pull the train!  So I've just slackened the pressure exerted by the steel wire a bit and the unwanted uncoupling has started all over again.

 

Questions:

1. Has anyone had similar problems and if so how did you overcome them?

2. Do people achieve successful slow-speed shunting with this method?  (I don't want to shunt the yard at 50 mph to keep the hooks in tension.)

3. (Long shot this!) Is it possible to obtain fine scale metal wagon wheels with non-ferrous axles?

 

Any help gratefully received.

 

(For the record I've followed the BK script to the letter.  All stock has Bachmann 36-030 couplings with straightened dropper and added staple, checked for coupling loop height and alignment, uncoupled by pairs of Screwfix door-catch magnets laid in the ballast under C & L sleepers.)

 

John C.

 

Hi John.

 

Been there, done it, got the T shirt  etc., etc.

 

Our Club has a DCC layout with a small freight yard where quite a bit of shunting is done.

 

When we built the yard, it was designed for BK style uncoupling and some magnets we had were set below the track (in the underlay). All the tests worked well before hand but things were somewhat different when operating the layout proper.

 

It was soon discovered, as you have, that the magnets (strong ones) attracted the steel axles and produced unwanted uncoupling. Also a high coupling would prevent the hook engaging properly with the adjacent loop.

 

Something had to be done as this is an exhibition layout and hand uncoupling is just not on the agenda.

 

A lot of experimenting was done with differing sizes of Neodymium magnets as we needed to be able to retro-fit them beneath the baseboards (6mm ply + track and underlay) so that track didn't have to be dug up.

 

I found a size of magnet that operated the couplings but did not pull on the axles and could also be fitted underneath the boards. The original magnets were extracted from the track by removing sleepers and then replacing and re ballasting.

 

One other point is that all couplings need to be exactly the same height. I think the standard is top of loop 8.5mm above rail level. I took an old Hornby 1 plank wagon and fitted this with a coupling at the exact height but with no hook. I now use this to set the couplings on all other items of stock.

 

It has transformed the operation of the layout when sorting wagons etc.

 

Well worth the trouble. Never considered electro magnets as too expensive when you need around 15ish.

 

Best of luck.

 

Dave

[Stubby47]

What size of neo magnets did you find most suitable ?

[dasatcopthorne]

What size of neo magnets did you find most suitable ?

 

Stubby47.

 

Here's what we now use posted from an older thread. Costs more reasonable than most suppliers. Also seem to work with 9mm baseboards.

 

Hope it helps.

 

Dave

 

 

 

<<<<<<<<<<<<<<<<<<<<<<<<<<<

The magnets used are from Spider Magnets Ltd. in Barnsley.  They were the cheapest by far and post free as I got them through their ebay shop.

 

This link should find the ones you want.   http://www.ebay.com/...iy-scalextric-/

 

They are 25 x 10 x 3mm N52 @ £4.37 per 5.

 

You need two per uncoupling point, laid end to end. As per photo above. Bear in mind that I have 6mm baseboard then 3mm underlay then track. If they are too strong, space them away from the underside with whatever you like. I mounted them first with doublesided tape then Araldite.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

[Stubby47]

Dave,

Brilliant, many thanks.

Stu

[dasatcopthorne]

Stubby47.

 

Search in the 'Layouts' sub-directory for Falcon Road.

 

There is a photo on page 7, post no 160.

 

Cheers

 

Dave

[checkrail]

Thanks for sharing your club's experiences Dave.  Very useful, and reassuring to know I'm not alone (not that I'm wishing defective uncoupling on anyone, I hasten to add!).  I'd probably need to experiment a bit to follow your approach as my track is laid on 3mm cork on top of 2mm EVA foam on top of 12mm MDF, so 17mm to get through.  I suppose an easy way to position the underboard magnets would be to drill 2 fine pilot holes through the baseboard immediately after removing the original magnets and before making good the sleepers and ballast.  The 'benchmark' wagon with loop only is a good idea - I've been using a home made height gauge from plastikard & balsa.  Incidentally I made it 8mm to top of bar.

 

So another avenue opens, but for now I'll now wait until my brass axles arrive from the US - they might be the answer.  Or then again ........ !

 

John.

[Brian Kirby]

Brian - surely even with perfectly aligned couplings and formed hooks you cannot rule out the effect of wheel/axle attraction to the magnet. As the OP observed, if the trailing wagon is pulled forward such that the buffing faces touch then the hooks will lift - they have to otherwise they would not couple in the first place......

Hi Jeff,

     Yes, i've had the odd wagon do it, albeit a very light and free-running example, i blame the yard shunter for not pinning the brakes down. I don't find it a problem with coupled wagons, but of course it would be made worse by using stronger magnets, are non-ferrous axles really necessary? You just need a magnet strong enough to pull down the staple and lift the weight of the de-tensioned hook, other factors are the length (leverage), mounted height (attraction) and thickness (attracted power) of the staple, with all these factors there's plenty of scope for fine tuning. On the subject of free-running wagons, several of mine make squeaky noises from either lack of lubrication or rubbing brakes, but i like this, it's reminiscent of the real brakes clinging and squealing, especially good when you hear the offending wagon approaching. If you're prepared to put in the extra work, there's another advantage with electro-magnets, namely when you reverse a long string of wagons over the uncoupling spot, all the hooks will remain down until the button is pressed, whereas with permanent magnets all the de-tensioned/slack hooks pop up and down in succession, although it does not affect performance. I hope it has made boring old shunting a bit more fun again!

                                                 Cheers, Brian.

[checkrail]

Yes, like Brian I too like the squeaky noises made by wagons to whose axles I've applied a bit of friction - lifelike squeals of tortured metal!  I've also noticed the castanet-like clicking of the rising and falling hooks as one backs a long train over a pair of magnets.  Like Brian I can live with that.  Meanwhile I'll keep tinkering.

 

John.

[sdw7300]

Hi

 

I'm in the process on adding the BK method to my layout so have not yet had chance to try much shunting yet, however from experimenting on my test plank it sounds to me like your magnets are too strong. I used 3mm diameter 10mm long N52 magnets (dirt cheap off eBay). The main benefit of these is you can add them to previously laid track by just drilling between the sleepers, pushing the magnets to baseboard level then touching up the ballast over the top. I found this size magnet provided enough "pull" without attracting the wagon axles.

 

For a couple of pic's see here http://www.rmweb.co.uk/community/index.php?/topic/76254-laoson-valley-1990s-to-modern-day-tmd-oil-terminal-p-way-yard/?p=1911395.

 

Cheers

[philsandy]

Hi

 

I'm in the process on adding the BK method to my layout so have not yet had chance to try much shunting yet, however from experimenting on my test plank it sounds to me like your magnets are too strong. I used 3mm diameter 10mm long N52 magnets (dirt cheap off eBay). The main benefit of these is you can add them to previously laid track by just drilling between the sleepers, pushing the magnets to baseboard level then touching up the ballast over the top. I found this size magnet provided enough "pull" without attracting the wagon axles.

 

For a couple of pic's see here http://www.rmweb.co.uk/community/index.php?/topic/76254-laoson-valley-1990s-to-modern-day-tmd-oil-terminal-p-way-yard/?p=1911395.

 

Cheers

Sam,

 

Do you know what the actual strength of these magnets is, ie. "the pull"?

I have used disc magnets, 15mm dia. 0.5 mm thick, buried just beneath the ballast and these have a pull of 0.28 kg. which is fairly low.

They do not seem to be having any effect on the wheels/axles, but am wondering if using a less powerful magnet would be beneficial.

[benachie]

Sam,

 

Do you know what the actual strength of these magnets is, ie. "the pull"?

I have used disc magnets, 15mm dia. 0.5 mm thick, buried just beneath the ballast and these have a pull of 0.28 kg. which is fairly low.

They do not seem to be having any effect on the wheels/axles, but am wondering if using a less powerful magnet would be beneficial.

Here is one seller with details

http://www.guysmagnets.com/view-product/3-mm-x-10-mm-neodymium-rod

Rod magnets have the advantage that you need only drill a (3mm) hole in the baseboard and push them through as far as will give the pull you want.

Alan

[sdw7300]

Here is one seller with details

http://www.guysmagnets.com/view-product/3-mm-x-10-mm-neodymium-rod

Rod magnets have the advantage that you need only drill a (3mm) hole in the baseboard and push them through as far as will give the pull you want.

Alan

Yep, they're the ones I used, from Guys Magnets.

 

As Alan said you can "adjust" the pull by pushing the magnet deeper in the hole you drill ;-)