No. 171 The Long Haul

It would be January 2021 when Bachmann introduced their 94xx models.  I bought the basic version.  It had a lovely copper cap to its chimney and it ran perfectly without any trace of a wobble.  Three years later and I have just purchased a sound fitted version.

Bachmann 9479 – 32-27SF

I have titled this Post ‘The Long Haul’ in recognition of the time that I have spent in recent weeks changing CVs to enable the engine to run on analogue.  It would help if I knew what I was doing!  The 94xx has a coreless motor which is super efficient.  As a result the engine needs a whole different range of CV values to the ones I would usually apply.  I would say it is still a work in progress.  However I would say work is sufficiently advanced that I would give the engine a run around the layout.


Hornby Bow Ended Colletts
 

What carriages might be suitable?  I had rake of Hornby Bow Ended Colletts parked up in a siding.  These arrived on the layout in June 2021, so not long after the Bachmann 94xx.  Why were they parked up?  Ah well a quick trip around the layout reminded me that one of the coaches had a tendency to leave the track.  After exiting a section of curved track the leading bogie was reluctant to rotate and would jump the track.


The offending Bow Ended Brake Coach

 
These Hornby coaches are super detailed models.  Perhaps a little light weight.  I have close coupled my set using Roco 40270 couplers.  Now why don’t they stay on track?



Hornby Coupling Mechanism Exposed!
 

Removing the suspect coach from the track confirmed that the offending bogie did not always rotate smoothly.  With the coach upside down on the kitchen table the bogie could be popped out of its housing with the blade of small screw driver.  To fully investigate the close coupling mechanism it is then necessary to remove the keeper plate which is held in place with two screws.


Bogie and Keeper Plate



How straight is your Keeper Plate?
 

On first inspection my keeper plate was bent in the middle and rubbing against the underlying close coupling mechanism.  A quick massage to straighten the plastic and ‘all sorted’ – so I thought.  Well it was nearly very good, especially after I had smeared it all with Vaseline.  

Sadly a little later and the leading coach was still leaving the track. The coach and the Close Coupling Mechanism was given a further closer inspection.  Studying the mechanism at the opposite end of the coach suggested a possible cause.
 

Stepped Close Coupling Cam
 

Operation of the close coupling mechanism relies on a ‘Cam’.  I have retrofitted such a mechanism to a Mainline Buffet car and simply cut a Cam shaped opening in the coach floor.
 

Home Made ‘Cam’ for Mainline RB
 

Hornby however have made a stepped cam to accommodate the protruding ‘tooth’ which is used to hold the mechanism up against the coach floor.   


Hornby Mechanism with tooth.
 

Comparing the two mechanisms from opposite ends of the coach showed that the faulty mechanism had a much larger tooth which was presumably interfering with the smooth rotation of the bogie.  A few quick cuts with a craft knife to shorten the ‘tooth’ and the issue was sorted.


Now how does the 94xx perform with its rake of Bow Ended Colletts on analogue?  I would say rather well!





Comments

Andrew said…
Pleased your back posting articles, they are interesting, especially the faulting finding and cures. Congrats on getting the coupling to work properly. Hornby (still) have no clue when it comes to close coupling cams or NEM compatibility.
regards
Andrew
20 April 2024 at 03:53
longsheds said…
Cheers Andrew, Hornby in my opinion just are not consistent. Some great models and then some strange mismatch items like the smoke box darts on the latest 8F which have reverted to solid mouldings some twenty years after they introduced their finely detailed separate darts. What they are thinking about with the moulded lights on the latest Black Fives..... Thanks for popping in and commenting, Regards Ray
20 April 2024 at 05:18
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