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Old 31st January 2011, 20:20   #1
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Default Unusual problem

I have a 75001 loco and two of the small pins which secure the traction rods to the wheels came off. In the process of reassembling the traction system it was necessary to separate a pair of the wheels. Now the loco is reassembled, when it is placed on the line the centre pair of wheels will not go round but oscillate instead. It appears obvious that I haven't assembled the wheels together correctly. Can anyone tell me how or supply photographs of both sides of one of these locomotives so that I can ensure each pin position is in the right place relevant to the adjacent ones (I hope this make sense!) and get my loco running again?.
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Old 31st January 2011, 20:46   #2
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Default Re: Unusual problem

I don't know the concerned model, but your problem is not so unusual as, I think, soon or later occurred to everyone who has dismantled (more or less voluntarily) loco's rods.
First thing to do is to take out the "power rods" (those connecting cylinder to wheel) from the cranks on powering wheels.
Then take out the connecting rods from each wheel, realign cranks on one side and fix the connecting rod (on the other side realignment should be consequent).
Then re-fix power rods
Everything should work right now!
Hope have been useful
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Old 1st February 2011, 10:58   #3
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Default Re: Unusual problem

Thanks very much for a quick reply. Unfortunately it's more complicated than that! If you Google Hornby train 75001 you will see that there are 3 sets of wheels plus a number of pistons etc. I suspect that the configuration on one sie of the wheels should be different to the other side but as yet I cannot deduce what this is.
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Old 1st February 2011, 13:04   #4
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Default Re: Unusual problem

Originally Posted by RSPLTD View Post
... In the process of reassembling the traction system it was necessary to separate a pair of the wheels ...
By this I presume you mean that you took one of the wheels off the axle (or split the axle in half). When reassembled the wheels should be a quarter of a revolution out of line with each other, examine the other sets of wheels to see what I mean. If they are not exactly a quarter out of line they will bind when the motion is reconnected on the second side.

On the prototype this is so that the cylinders on each side of the loco follow each other in their push/pull sequence, they are a quarter of a turn out from each other so that they are never in opposition and the engine can be stopped (and restarted) with the pistons at any stage in the sequence.
Bob Hughes
Playing Trains
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Old 1st February 2011, 23:59   #5
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Default Re: Unusual problem

Thank you - I will have a try at that configuration tomorrow
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Old 3rd February 2011, 10:55   #6
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Default Re: Unusual problem

No luck I'm afraid so there must be something else going on. Will have to seek out a loco doctor methinks! Thanks for the advice
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Old 3rd February 2011, 16:16   #7
RW James
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Default Re: Unusual problem

From your description, I'm pretty sure the problem really is out of quarter. It's not so easy getting them back into quarter. I speak from experience here - I had to buy a quartering jig to get the job done.

But you may still need to get professional help - depending on your level of experience.
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Old 7th February 2011, 19:14   #8
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Default Re: Unusual problem

Your problem is 99% sure to be a combination of quartering and rod binding, perhaps due to the valve gear being 'reversed' during assembly.

In order for steam locomotives to be able to reverse or advance from any stance merely by using the Johnson Bar or reverser the valves have to be within a quarter cycle of each other. So, because the valve gear and rods are mirror images of each other, all the cranks and the eccentric crank have to be matched on each side, and exactly one quarter cycle apart. Usually the engineer's side cranks lead those on the left side of the engine by 90 degrees. Many assume that they are opposed at 180 degrees, but that is not the case.

It probably means one crank is slightly out of position, and not at the 90 degrees that its same-side mates are from those on the other side of the engine. A quartering tool is the sure-fire way to correct this, but a patient and determined fella can gently twist and try the one bad driver set until the rods no longer bind. Just ge sure to use some cyano-acrylate glue to bind the rotated driver wheel to its axle or it will quite likely rotate again in time.

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Old 8th February 2011, 03:53   #9
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Default Re: Unusual problem

If your drivers have spokes with empty space between them (not all of them do!) you can possibly sight from one side to the other and see how the spokes line up. Have a good look at the ones you didn't take apart and see where the spokes are and then try to shift the suspect ones around. OK: there is sometimes a problem rotating wheels around the axle, so be gentle.
Also, you may not have got them square to the axle when they went back. This is always tricky and I have a back-to-back gauge that should do it for me.
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