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Very jerky and erratic running 9F

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  • Very jerky and erratic running 9F

    I've just purchased a "mint" unused 9f from Ebay which genuinely had only been previously test run. It is a 2S-013-001 9F, 92088. As soon as I started to run it in, it became evident that all was not well. After some 2 hours running, things have gone from bad to worse. In reverse, it will only run at all on a very high throttle. The whole loco. lifts off the track on one side when started in reverse and sticks unless touched. Running forwards is marginally better - it will run without too much faltering but not well at low speed. The tender also jumps the track at certain points. As a second-hand purchase it is out of warranty anyway so I have oiled the worm properly, checked for pick-up loco./tender and run the motor with the cardan shaft disconnected. Disconnected in this way, the motor runs satisfactorily in both directions. The valve gear does not appear to be binding (and why would it do so in one direction only). I have just tested the loco. again with the tender body removed and noted that the loco.will move in the forward direction (albeit not very well) but in reverse, there appears to be no drive taking place. The cardan shaft spins but the loco. wheels do not turn. I would appreciate any suggestions as to where the problem lies.

  • #2
    I have had cardan shafts split before now - both on Britannias - and the result was the shaft spins and the drive wheels don't move. It is the equivalent of split gears on Farish locos, but here the yoke splits because of the force fit. You should be able to get replacements from DCC Supplies if they have the correct yokes (I would imagine the Brits and the 9Fs would be interchangeable, but you cannot be certain in this world!
    HTH
    Bob

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    • #3
      I've also had this on a brand new Britannia bought from my favourite retailer who returned it to DCC supplies. However, for some reason, they said it could not be repaired (maybe that means it was not economical)

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      • #4
        Thanks for those comments. I've now dismantled the loco. and replaced the 16 tooth gear with a Farish one, as recommended on another forum. Only partial success: loco will now run backwards but going forwards, the whole loco. tilts to one side and lifts off the track. I wonder is this may be something to do either with wear on the worm, which seems to be jamming when forward running is attempted. This seems unlikely, as surely the gears would wear rather than the worm? Alternatively it may be to do with the fact that the Farish gears don't have such a thick "collar" on each side as the original Dapol one. I had to double them up and glue two together. Possibly there may now be insufficient sideplay for the gear to move when the running direction is changed?

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        • #5
          Good news! Having put both locos to one side for a day or so, I had an idea! I have now successfully replaced the 16 tooth gears in both locos. with Farish 16 tooth gears. The trick was to pack out the Farish gears slightly on each side to make them the same overall width as the original Dapol gears. I did so thanks to an old piece of Plastruct tube that I found from about 40 years ago! The internal diameter was exactly the same as the stub axle that the 16 tooth gears are mounted on and the external diameter just small enough to clear the gear teeth. I cut slivers off this tube and selected the appropriate thickness to glue on each side of the Farish gears. to my utter amazement, once I installed these replacements in both locos, they both ran perfectly. I'm now the very happy owner of 2 smooth and quietly-running 9Fs!

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          • #6
            Hi Doug22150, congratulations--maybe you've found a fix that we could all do with making a note of. In your post #4 you mention you found about this on another forum group, was this the NGF, or another group, but most importantly can you provide a link please, as it will make informative reading and probably give them a lead to solving their problems!!

            Chris
            Last edited by Chris Newman; 7 October 2017, 13:31. Reason: correcting spelling mistakes

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            • #7
              Hi Chris

              Here is one link to the NGF but I was originally put on the trail by a thread on another forum - I'll try to backtrack and post it separately.

              http://www.ngaugeforum.co.uk/SMFN/in...5747#msg465747

              Doug

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              • #8
                Chris

                Here is the original link that set me on the trail:- https://www.newrailwaymodellers.co.u...=35404#p442697

                Doug

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                • #9
                  Doug, Excellent --Thank you I've saved each of them to my favourites "UK N gauge" so I don't lose them, suggest you do the same or similar, and any other hints or tips you come across---you never know when they will be useful

                  Chris

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                  • #10
                    Thanks Chris. One thing that I have learnt from this is that the "tilting to one" without moving (see my other post under "9f review", with photos,) phenomenum is symptomatic of failure of the 16 tooth gear. Both of my 9Fs were doing this but replacing the gear has completely cured them.

                    Doug

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                    • #11
                      An update - after no more than an hour's running each of the two 9Fs began to show symptoms of the 16 tooth gear failing again. I have now replaced both with the earlier (Poole - era) Farish 16 tooth gears. With 2 washers each side, these are a snug fit between the frames with no side-play at all. This still didn't cure the problem and after many hours, I realised that the worms were not held tightly enough in place. They were lifting, allowing the tips of the 16 tooth gears to wear away until they no longer engaged with the worm at all. I then modified the worm clip by gluing 1mm wide brass shim at each end of the clip (actually 2 pieces at the rear end and one at the front). This prevents the excessive vertical movement of the worms and (so far) has resulted in much smoother-running locos.

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                      • #12
                        I've now been running the 2 repaired 9Fs for over an hour with no sign of the problems recurring - one has been pulling 30 wagons with no problems at all. They both look truly magnificent at the head of a long train and are now 2 of the best running locos in my collection!

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