ejstubbs Posted September 10, 2021 Share Posted September 10, 2021 ...but only in reverse. It's smooth as a nut going forwards. If it were any of my other locos then I'd be investigating the pickup wipers since it sounds exactly like a badly adjusted pickup wiper catching on the spokes of a driving wheel. But as it's a Bachmann split-chassis example, it can't be that - but I can't work out what is causing it. I can't see anything obvious that could be interfering with the wheels, but I've not disassembled it fully yet (it would be the first time disassembling a split-chassis for me if it does have to come to that, so I'm a trifle trepidatious). I have tried running it with the body off and it still makes the noise, so that would seem to rule out anything relating to that, such as the sanding pipes (which I've verified are where they should be in any case). Has any other forumite had a similar issue with one of the Bachmann split-chassis locos - or indeed the Royal Scot in particular - which might give me some clue as to where to look for the problem? Any suggestions would be most welcome! Link to post Share on other sites More sharing options...
cypherman Posted September 10, 2021 Share Posted September 10, 2021 (edited) Hi, Sounds like it is the axel bearing surfaces are wearing away and getting sloppy. If it is there is very little you can do except replace the chassis. If it is not too bad you might get away with replacing the original axel contacts with wiper blade contacts on the wheels and making sure that the bearing surfaces are well greased to take up the slack. It is easy to check. Just see how much play you have by moving the wheels side to side. There should be no real movement. Here is a link to a post I did showing how I tried this out. I was using a Mainline 4MT as the test subject. Edited September 10, 2021 by cypherman 1 Link to post Share on other sites More sharing options...
ejstubbs Posted September 11, 2021 Author Share Posted September 11, 2021 Well, today I bit the bullet and disassembled it as much as I dared. I didn't fancy dismantling the valve gear: too many teensy weensy screws for my liking, and although I the spanner I have got the coupling rod screws off the front and rear drivers, it seemed to be too big to undo the screws on the centre drivers (the service sheet I have does seem to suggest that the screw for the centre drivers is different to the one for the front and rear ones) so I left it at that. With the drive gear for the centre drivers disengaged the motor ran smoothly and pretty quietly, which was nice. Having found nothing obvious that might be causing the noise, I gave everything a good clean and a judicious re-lube, and reassembled the chassis carefully. Checking it on the rolling road it seemed to run well in both directions without any nasty noises, and continued to do so with the body back on. I did notice when re-assembling it that the front screw of the two which holds the axle retainer plate on seemed a bit reluctant to engage properly with the insulating spacer between the chassis halves. This turned out to be because the axle retainer plate wasn't properly seated against the chassis at that point. It seems that you need to install the axle retainer plate at the front first, so that it fits over the cylinder assembly properly, and it then slots easily into place along its whole length and can be screwed securely in place. My theory is that the axle retainer plate hadn't been properly seated the last time the loco was apart (can't remember whether that was me, or the previous owner), so the front drivers were loose in the vertical direction. That would probably have the same effect as that described by cypherman above if the bearing surfaces were badly worn (which they definitely weren't). I'm therefore closing this case as resolved for now. Fingers crossed it stays that way! Link to post Share on other sites More sharing options...
RMweb Gold The Johnster Posted September 11, 2021 RMweb Gold Share Posted September 11, 2021 Lump of BluTac, plasticine, or chewing gum at a push, stick small bits like crankpins in to prevent them sacrificing themselves to the Carpet Monster, keeps them safe until you can put them back where they belong. Glad to hear your Scot is running properly again! Link to post Share on other sites More sharing options...
33C Posted September 11, 2021 Share Posted September 11, 2021 Carpet monsters can be overcome with a BIG magnet on a stick (bit of broom handle on an old speaker ring mag) and you don't have to leave your seat! 1 1 Link to post Share on other sites More sharing options...
JeremyC Posted September 11, 2021 Share Posted September 11, 2021 Regarding the crankpins on the centre wheels, assuming they're the same as on other Bachmann / Mainline split chassis, these don't unscrew. Instead the return crank is held on by a tiny circlip. Once that is removed the return crank and connecting slide off. Link to post Share on other sites More sharing options...
ejstubbs Posted September 11, 2021 Author Share Posted September 11, 2021 Ah, useful to know, thanks. I did think there was something that looked like a circlip on the service sheet but I couldn't see how it might attach or (more importantly when attempting disassembly) detach, even with +3.5 supplementary specs clipped on top of my normal varifocals ... Link to post Share on other sites More sharing options...
cypherman Posted September 11, 2021 Share Posted September 11, 2021 Hi all, Just be careful about the circlip as they are to get back on. Link to post Share on other sites More sharing options...
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