Hornby Pullmans derailing

[resin001]

I have 6 Hornby Pullman coaches - latest type with table lights - all fitted with Kadee No 18 couplings

 

Now that my layout is built , I can run above in a full rake , which is where my problem occurs.

 

If I run 5 coaches coupled together then the coaches will run around my minimum radius curves ( 21" ) and over complex pointwork without derailing ( All code 75 , C& L Finescale and Peco points ) , if however , I add the sixth coach I get derailments occuring through the curves and across the points.

 

I have checked coupling heights , no buffer locking , wheel back to backs , wheel rotation etc , everything seems OK.

 

When I get derailments it is always between the 2nd and 3rd coupled coaches at the front of the rake , changing the formation of the coaches in the rake does not help. I have read in an earlier post that this phenomenon is due to the self aligning drawbars used in these coaches

 

Has anyone else experienced above? - will changing to an alternative coupling system such as the Roco type drawbar help ?

[brossard]

Make sure the cam mechanism* on all coaches is swivelling freely. I have noticed that they sometimes jam. A mate has a similar problem and he has agreed to let me look at them to see if I can do something. No 18s might be a tad short, on Bachmann Mk 1s I find No 20s work well, but these coaches don't have sprung buffers. Coaches have to be able to slide laterally when traversing curves and pointwork, make sure there is nothing preventing this. I suspect the Pullmans are a bit light on their feet (150 gms is about right) - I KNOW the observation car is. Try some weight in the bogies.

 

*The mechanism that allows the distance between coaches to increase around curves.

 

Another thing occurs to me - it is common for the couplings to be too low - specifically the dangly bit can droop below rail head height. If it does, it can/will hit pointwork and derail. Never assume that Bachmann, Hornby or any of the OEMs are sensible enough to put the pocket at the right height for Kadees.

 

John

[RFS]

If your coaches are run in a fixed rake you could try different internal couplings than the Kadees as these are not best suited to the close coupling mechanism. I have a rake of 8 of these Pullmans plus a bogie luggage van on the end, and the internal couplings are the Roco ones (not the Hornby-Roco ones - the real Roco ones that are shorter). As these couplings are rigid, unlike the Kadees, I don't get any problems. I have Kadees on the end of the rake.

[MG 7305]

What a coincidence. This very weekend I too faced up to and solved this one. If the coupling mechanism is the same as that fitted to the Hawksworth coaches, then I too have found that the cam mechanism jams. I run mine on No 20 Kadees and it became obvious that the weight of coaches behind the offending coupling was causing the jams, allied to the Kadee characteristic of exact lateral location (compared to the hook and bar system which has some lateral leeway between couplers). Running the train slowly I could see the mechanism sticking before snapping over once the friction was overcome but not always. If the cam jammed the bogie cannot rotate, hence the derailing. I have removed the entire cam system and, using Loctite superglue plastics, glued the Kadee on top of some plasticard and then glued the plasticard to the bottom of the bogie and the height is spot on! Good old fashioned direct fixing and now everything is back to normal. I had previously tried trueing up the cam, dry graphite and then grease but no joy. The cam mechanism just does not do long rakes and curves with Kadees.

[resin001]

Thanks for all the replies - looks like 2 options - Roco couplings or fixed kadee couplings

[Adrian Wintle]

The issue is a long-standing one with close-coupling mechanisms. These mechs are intended to work with couplings that act as a solid bar when coupled (Hornby or Roco close couplers, Fleischmann Profi, Bachmann pipe...). If the coupling in use allows lateral freedom, an increased tail load overpowers the relatively weak spring (whose sole purpose is to re-centre an unloaded coupling so cannot be made stronger without adverse running qualities). This then allows the coupling mechanisms to extend and (by design) move off centre. This, in turn, forces the bogies to run skewed to the track, allowing the leading flange to climb an imperfection (track joint etc.). Since the load on the coupling spring is dependent on the tail load, you tend to see this happen with the leading bogie of the second coach in a train (the loco usually doesn't have a CC mechanism, which prevents this from happening on the lead coach). 5 coaches tends to be about the limit before this happens, but the actual design of the interface between the coupling arm and the bogie is also important (Bachmann Mk1s have a much bigger cutout in the bogie, which allows the motion of the coupling arm to be more independent of the motion of the bogie and vice versa). This phenomenon has been showing up since these mechanisms started showing up on coaches, but it was the Gresleys where it really became in issue (shorter wheelbase bogies compared to the Pullmans meant that the skew angle was larger, so the chance of derailments was higher).

 

The jam/snapover effect noted above is a symptom of this, rather than any sticking in the mechanism (although that can be a problem too, but is less likely to be the culprit on a long train)

 

The best solution is to use a coupling within the rake that is designed for this type of mechanism. Roco close couplers work quite well (the Hornby variant are a bit long).

 

Adrian

[brossard]

I am glad to see something of a consensus on the cam mechanism. For my fixed rake of Mk 1s, I used a homemade system based on something I saw in a Tony Wright DVD:

 

 

Bachmann Mk 1

 

 

Hornby ex LMS

 

 

Coupled up

 

Once the system is set up for the curves and points it will need to negotiate, it is very good. I keep Kadees on the brake ends for coupling to the loco.

 

John

[Adrian Wintle]

I should mention that I have absolutely no problems running 10-12 coach trains reliably with the close coupling mechanisms (or with a mix with and without mechanisms), including Bachman Mk1s and Mk2s, and Hornby Gresleys, Staniers, Maunsells, and my one Hawksworth (in my BR parcels train), as well as my own conversions using Keen, Fleischmann, and Roco mechanisms. It is all a matter of having the correct type of coupling.

 

Adrian

[pondy]

I too had this problem with my rake of 8 Pullmans and close couplings. I found that the quickest solution was to disconnect the internal lighting by firstly removing the wheels and allowing the metal strip on top of the axial to just dangle underneath. You do loose the lighting effect but lets face it, on the real thing in daylight the lights can't be seen anyway. Maybe one day I may reconnect the lighting using some sort of rechargeable battery in a luggage van and wires running the length of the train. For now the rake runs far more freely and therefore with less pull on the front of the train meaning very few derailments.

[resin001]

Latest update

 

Roco couplings ( 40270 ) fitted between coaches - results in no derailments on my min radius curves ( 21" ) although they still derail across peco long turnout junction (code 75). This is now due to buffer locking as the coaches are actually closer together compared to when fitted with Kadee 18's . So having searched through my spare part box , I actually found enough of the Hornby roco type couplings - these are slightly longer and as such solve the problem - no derailing at all - 6 coach rake perfect

[RFS]

The best way to prevent buffer locking is to retract the buffers. It's easy to do by simply taking a piece of plastic stripped from a length of wire and sliding it on to the shank behind the buffer beam. This keeps the buffer retracted but is easily reversed if needed. You really will need to do this if you are going to propel the Pullmans over points, eg for stabling in sidings.

[Matabiau]

Having followed this thread I noticed I am having the same problem with my rake of Hornby KFAs. Changing the tension locks for the Roco type couplings has solved most of the derailing problems. The connection to the loco is still a source of problems as it frequently comes uncoupled. I haven't been able to fit the Roco couplings to that as the loco does not have the close coupling mechanism. Any suggestions? I have ordered some continental style coupling to see if they are any more reliable.

[RFS]

Does the loco have an NEM pocket which is slighly flexible (butterfly fixing I believe it's called)? In which case the Roco couplings might still be OK. I use Kadees and have a problem with a Hornby West Country, where the tender pocket is too low, and its train is Bachmann Mk1s where the coupling pocket is too high so they frequently uncouple. As I keep trains in relatively fixed rakes I've used one of twin-pipe couplings from the Mk1s to couple the tender to the first coach. It's more rigid than the Rocos but works just fine.

[Matabiau]

I tend to use a Bachmann 70 so the NEM pocket does have some flexibility. I would prefer to avoid fitting the roco couplings to that as it would mean I couldn't use it on anything else without repeatedly changing the couplings. It is certainly worth a try though to see if it relieves the problem.

[Adrian Wintle]

Roco also make a 'height-adjutable' version of their close-coupler (40287) that can be used in situations where one of the coupling pockets is not quite at the correct height (it will handle the difference between a Bachmann Mk1 and the NEM standard). It comes out longer than the standard Roco coupler, but a shade shorter than the Hornby version.

 

Also, the Roco couplings will work if only one end has a close-coupling mechanism.

 

Adrian

[jwd]

re. Hornby Pullmans, what era are the RTR pullmans?

 

any of them suitable for 20s/30s?

[Adrian Wintle]

Does the loco have an NEM pocket which is slighly flexible (butterfly fixing I believe it's called)? In which case the Roco couplings might still be OK. I use Kadees and have a problem with a Hornby West Country, where the tender pocket is too low, and its train is Bachmann Mk1s where the coupling pocket is too high so they frequently uncouple. As I keep trains in relatively fixed rakes I've used one of twin-pipe couplings from the Mk1s to couple the tender to the first coach. It's more rigid than the Rocos but works just fine.

 

The other thing you can do is get some of the Keen replacement drawbars for the Mk1s. If you replace the drawbar on the end of the rake with one of these, it will put the coupling in the correct location to couple sensibly with the loco.

 

Adrian

[RFS]

The other thing you can do is get some of the Keen replacement drawbars for the Mk1s. If you replace the drawbar on the end of the rake with one of these, it will put the coupling in the correct location to couple sensibly with the loco.

 

Adrian

 

Yes - I have tried one of these but the problem with the WC is that its coupling pocket is too low. It probably just needs me to make a stepped Kadee coupling for it. I have a number of Bachmann MK1 coaches now and some of them are actually at the right height, but not all.