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Bachmann 7F running issues


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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.

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  • RMweb Gold

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....

 

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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?

 

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  • RMweb Gold

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

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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.

  • Informative/Useful 1
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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.

 

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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.

  • Agree 2
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