BartonStDavidSDJR Posted December 28, 2020 Share Posted December 28, 2020 Hi all, I recently acquired one of Bachmann’s SDJR 7F locos in the S&D blue livery. Since receiving it I have noticed one major flaw with the running quality, the mechanism will work fine and then will suddenly lock in place. I’ve tried to delve into the model as much as I can to try and find the issue, but with no such luck. The only difference I have found compared to normal locos is that I can push the driving wheels round - surely this isn’t meant to happen? I have also checked through the valve gear and con rods to see if anything is catching and it appears that all is well. Any ideas as to what the issue could be? Thanks in advance. Link to post Share on other sites More sharing options...
RMweb Gold ikcdab Posted December 28, 2020 RMweb Gold Share Posted December 28, 2020 If it's worm drive, like virtually every other mainstream steam loco, then pushing the wheels round is impossible. So something must be loose somewhere. If a gear wheel has come loose then the quartering might go adrift which would cause a lockup. So I guess as a first thing, check everything is fixed as it should be.... Link to post Share on other sites More sharing options...
BartonStDavidSDJR Posted December 29, 2020 Author Share Posted December 29, 2020 21 hours ago, ikcdab said: If it's worm drive, like virtually every other mainstream steam loco, then pushing the wheels round is impossible. So something must be loose somewhere. If a gear wheel has come loose then the quartering might go adrift which would cause a lockup. So I guess as a first thing, check everything is fixed as it should be.... One thing I forgot to mention above is that the gear on the driving axle can be moved round with the wheels. I know this isn’t meant to happen, so would that most likely be the cause of the issue? Link to post Share on other sites More sharing options...
RMweb Gold ikcdab Posted December 29, 2020 RMweb Gold Share Posted December 29, 2020 That would certainly explain why you can push the wheels round. So it needs retightening. I'm not sure how it causes a lockup, I'm not sure unless the loose gearwheel is jamming inside somewhere. Ian Link to post Share on other sites More sharing options...
BartonStDavidSDJR Posted December 29, 2020 Author Share Posted December 29, 2020 Thanks very much for your help, I have had a delve as much as I dare, but don’t really want to go any further, for fear of breaking a valuable model! I’ve sent it off to my local model shop to see if they can work out the issue-hopefully it’ll be running normally again soon. Link to post Share on other sites More sharing options...
cypherman Posted December 29, 2020 Share Posted December 29, 2020 You do not say if this happens when the engine is moving in a particular direction. Sounds like the worm gear is moving up and down the shaft. When it works it way fully up or down it binds the gearing. There fore locking up the wheels Link to post Share on other sites More sharing options...
JZ Posted December 30, 2020 Share Posted December 30, 2020 I have had 5 of these and on three the gearwheel has split. The first time I got a replacement from Bachmann. When the second went, I got Ultrascale to cut me a couple of brass ones. I also managed to get some replacements from Bachmann again, despite then denying that it had been a problem and they sent me a couple of extras. Hmm. 1 Link to post Share on other sites More sharing options...
BartonStDavidSDJR Posted January 3, 2021 Author Share Posted January 3, 2021 Thanks for your responses. I’ve had a response from my model shop and one of the gears has split. The only problem is that they’ve discovered all screws to get to the gear have been superglued in place and can’t be undone. Seems like whoever did this did it for a reason. So I’m left with two options now I believe: 1) Write the model off and get something different 2) Find a replacement chassis from another 7F and swap it with the non-working one I think the only component which I would have to swap across with the replacement chassis is the cylinder block, which shouldn’t be too hard. Any thoughts as to what I should do? On 30/12/2020 at 19:19, JZ said: I have had 5 of these and on three the gearwheel has split. The first time I got a replacement from Bachmann. When the second went, I got Ultrascale to cut me a couple of brass ones. I also managed to get some replacements from Bachmann again, despite then denying that it had been a problem and they sent me a couple of extras. Hmm. Link to post Share on other sites More sharing options...
Chrisr40 Posted January 3, 2021 Share Posted January 3, 2021 Isn't there a solvent that will loosen the super glue ? Might be a cheap first try. Link to post Share on other sites More sharing options...
smokebox Posted January 3, 2021 Share Posted January 3, 2021 Acetone should soften super glue if you can get it to penetrate the screw threads. Problem is that acetone attacks some plastics! Another thing that may help is to heat up the tip of an old screwdriver and use that to try to undo the screws. 2 Link to post Share on other sites More sharing options...
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