Coupling Problems....potential solution...

[pheaton]

So.....lets start with my investment stakes...

 

 

5 class 31s (2 DCC sound)

4 Class 50s (1 Dcc Sound)

3 Class 60s (1 dcc sound)

4 Class 56s (3 Dcc sound)

 

So i suffer from the issue of derailing wagons....id say this only affects 56s and 60s the 31s seem ok for now and 50s cant derail any of my Bachmann coaches...However stick 26 haa's behing either the 60s or 56 and you will run into trouble on a curve (even as slight as 3rd and 4th radius)

 

Not clever for a loco that routinely demands a 3 figure sum....

 

So now one of my 56s has come up for a heavy repair (more on this later) i have decided to look closer at the issue ideal whilst my 56 has been reduced to all individual parts.

 

I have found 2 issues.

 

1,) the centre spring isnt "man enough"

 

2,) the area for which the coupling moves isnt in most cases the facing edge isnt machined properly and has "burrs"

 

For those not familiar with the term "burr" a burr is material left behind when something is cut or machined if you cut a piece of metal with a hack saw and run your finger down it it will feel rough, these are burrs.

 

This problem is exasperated when the chassis is painted all this does it make the burrs worse.

 

This when youve got close to a kilo of weight dragging off it will cause the over complicated coupling to snag and when your loco exits a curve the coupling isnt able to centre and drags the nearest wagon off the track....of course the more fine scale your track the worse the problem.

 

Ive seen various methods tried including paper clips that force the coupling back into position. All require extensive and intrusive mods to the loco...

 

so...during the strip down i gently filed the edge the coupling runs along back to bare metal ive also removed the centre spring...the result a coupling that moves freely back and forth with up to 1.5 kilo's dragging off it... use as finer rounded file as possible, rounded is very important to maintain a good profile.

 

 

you will need to take the body off and the coupling compartment cover to do this AT YOUR OWN RISK

 

havent put the loco on the track yet but will post a video when i do this weekend.

[brossard]

I assume you are talking about the standard tension lock couplings.

 

I would advise that you check the weight of your wagons. A 4 wheel wagon should be ~50gms and add 10gms for each additional axle. This is very much a rule of thumb. All the wagons in the rake should weigh about the same. I don't know the radius of your curves but for a very long train the side forces could pull a wagon off.

 

I think you are right to fine tune your couplings - things can only get better.

 

My solution is, and has been for more than 20 years, to use Kadee couplings.

 

John

[pheaton]

Hi John,

 

the problem isnt with the tension lock its with the pocket and the way its mounted on the locomotives chassis, Bachmann Heljan and vitrains and most others mount the coupling on the bogie...Hornby for some in explicable reason mounted it in very over complicated way on the chassis, the result after exiting a curve the coupling jams in the extreme left or right postion dragging the wagon off on the exit of the curve, its the same with one wagon or 26.....Hornby tried to re-invent the wheel and failed...kadees mounted in the pocket have the same issue on the affected locomotives.

[brossard]

Ah, I see. Well, carry on with the fettling and let us know how you get on. Pictures are always welcome.

 

John

[34theletterbetweenB&D]

Your mod is not likely to work any better than original form I am afraid.

 

Hornby, for reasons best known to themselves, decided to put the same close coupling mechanism they have been fitting to bogie coaches since the lit Pullman cars on their newer diesel models. This mechanism needs a coupler system that provides recentering force after the loco leaves a curve. Of all coupler systems, the tension lock is one of the least suited to this role. The ideal system is one that forms a rigid bar, and Hornby now sell such a thing in the form of their R8220, a clone of a Roco pattern coupler. The Roco version is better, being shorter it brings the vehicles to a more realistic spacing on stragiht track, opening out the gap on curves as required. ( Irrelevant to this thread, when Hornby got around to renewing the HST power cars, a diesel loco with a gangway connection where the close coupling mechanism really comes into its own, they didn't install it, make of that what you will...)

 

I feel there are two simple choices. Use the R8220 or a similar 'rigid bar' coupler between the diesel and the first vehicle (which will need an NEM pocket on the vehicle). Or take enough of the mounting off to prevent fouling and either body mount or bogie mount a coupler of choice. On my class 30 chassis I have glued a metal strip to the bogie baseplate, and made the end into an NEM pocket. Works as well as any other bogie mounted coupler on other maker's product.

[Stevelewis]

I assume you are talking about the standard tension lock couplings.

 

I would advise that you check the weight of your wagons. A 4 wheel wagon should be ~50gms and add 10gms for each additional axle. This is very much a rule of thumb. All the wagons in the rake should weigh about the same. I don't know the radius of your curves but for a very long train the side forces could pull a wagon off.

 

I think you are right to fine tune your couplings - things can only get better.

 

My solution is, and has been for more than 20 years, to use Kadee couplings.

 

John

 

I can second these comments:

 

Check your weights and use Kadee couplings, not only do they work well, they eliminate the "loose coupled train" effect which hook & loops give

 

AND the big plus of remote hands off uncoupling with just a simple between the rails magnet.

 

( for those unfamiliar with Kadee couplings, a single magnet placed at the entrance to a 'fan' of sidings will allow vehicles to be uncoupled and then propelled to any desired position without recoupling)

[Adrian Wintle]

The issue is as 34'C' states. It has to do with the mechanics of the close coupling mechanism.

 

Also, the reason the spring isn't 'man enough' is that it's sole purpose is to recentre the mechanism under no load. Either use a close coupler (Hornby R8220/Roco/Fleischmann Profi) between the loco and the first wagon, or disable the close coupling mechanism by fixing it in the centre position and use a Kadee or tension lock,

 

Adrian

[Barry Ten]

Hornby tried to re-invent the wheel and failed...kadees mounted in the pocket have the same issue on the affected locomotives.

 

The cam-operated coupling system isn't unique to Hornby diesels, though - one of my Roco models has it and it works flawlessly. I think it's

more likely that the Hornby implementation hasn't been done very well, not that the idea is flawed.

[stewartingram]

Many years ago, we had 'Triang' couplings. They progressed from the original 'half-complete' design, through to the standard metal pressing that served Triang & Hornby for many years. (Someone will fill in the recognized names for these no doubt). Then along came the opposition, firstly with Mainline, with its plastic moulded coupling which looked like a smaller version of the Triang/Hornby one (but wasn't, I'll come to that in a moment). Soon after, Airfix appeared on the market with their 'small' coupling, which to all intents is the standard coupling we have today, though it now comes with the easy-fix fitting (is it known as the NEM pocket?).

So, way back when, I investigated the types available and decided at the time to go Mainline, but that is irrelevant, it was MY choice. What I did discover though might be useful.

 

The Tg-Hy coupling was reliable. Being metal, if you dropped the wagon and bent it, you could bend it back, or replace it with an easily obtained spare. (Remember those days, oh how I wish with spares today....). The hook was rivetted on, with no sideways movement so was precise in location. But it was huge & ugly, however to me the big bonus was....

 

The arc of the loop followed the correct radius!

 

Then we had Mainline couplings: Altogether a much neater design, plastic moulded, and with a coil spring pushing against the back (wagon end) of the hook. This gave a precise movement and location of the hook. They were smaller, and therefore neater, basically reliable in operation, but they had a significant downfall:

 

The arc of the loop did NOT follow the correct radius!

 

Then there was Airfix, now our standard today: A lot smaller, no spring action at all on the hook, and a sloppy pivot point for the hook. Also (guess what?)

 

The arc of the loop did NOT follow the correct radius! Though I think better than Mainline at this, the small arc and sloppy coupling could lead to problems. Note I am talking train set curves, ie extremes.

 

Now what is this correct radius?

If two vehicles are coupled together, and traverse a curve, my definition of correct radius is that the loops touch around the whole of their arc. Thus when pushing, the loops act as a form of solid buffer. When pulling the hook glides smoothly around the arc. If this radius is not correct, it can lead to derailments, I found more when pulling than pushing. I suspect because the 2 loops were now separated further due to wrong radius arc, the pulling action of the hook tried to close the gap, and thus pulled the wagon (wheels) out of alignment, leading to derails.

Today with the NEM fitting, the 'Airfix' type also pivots to a certain degree, but it is a poor mechanical design in my opinion, and still retains sloppy hook pivots.

 

I found this by trial & error, in a fairly methodical way. It certainly was more noticeable with mixed makes of couplings, which made me investigate further. Nowadays I've gone away from tension-locks, so it is irrelevant to me, but thought I'd mention my findings.

 

Stewart