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I have just noticed a problem with one of my locomotives, Hornby R3409 'King William IV'.

I think that I have only noticed it now, because I have another King, so this one does not get run very often.

 

When run, it sounds as though the wheels are not correctly positioned on the rails, for there is a rumbling sound as the locomotive runs.  

Yet when looking closely, I found that all the wheels were correctly positioned.

However, The rearmost set of driving wheels appeared to be oscillating as they went round, as if the wheel is not fitting 'squarely' on its axle.

When looking at the underside of the locomotive, I noticed that there is more play on the movement of the rear driving axle, than there is on the other two; to the point where I can pivot the wheelset slightly in the horizontal plane. It also have more up-down movement.

 

The locomotive has never been dropped or in any way handled carelessly.  There is no indication of any damage. Yet the difference in the amount of 'play' between the wheelsets is noticeable. 

 

I am running on Peco finescale flexible track which has been ballasted; all of my other locomotives run well on the track.

 

I have just sent off my query to Hornby and will be interested to hear what they say.  But I would also like to see if anyone else has this, or a similar, locomotive and have they experienced this problem too?

 

Thanks.

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Might be an assembly problem. I had a steam model to look at some years ago which a friend described as 'running oddly', and that proved to be caused by one of the brass bearing collars not located in the designed recess in the chassis block. As a result the sideplay was restricted, but the axle could slop about vertically and horizontally one side.

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Hi,

Take a look at the chassis block. Make sure it has not started to suffer from the dreaded Mazak rot. Slight distortion of the chassis block could possibly show up with the symptoms you have described.

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The real King William IV probably had running problems as well; he was getting on a bit when he came to the throne...

 

With the loco upside down, take the 'keeper plate', the plastic moulding that the pickups are attached to and that holds the wheels in place when you pick the loco up, off, CAREFULLY because the pickup feed wires are soldered to it.  It is held by small cross head screws; use the correct size screwdriver to avoid damaging the screw heads, and be careful not to lose the screws.  I push mine into a lump of blu tac to keep them from making a break for the border or sacrificing themselves to the carpet monster.

 

With the keeper plate off, you can examine the bottom of the chassis.  Lift each wheelset out in turn, making certain that the piston rods stay safely inside the cylinders (not a disaster if they come out, but faffy to replace) and have a look at the state of the axles and the channels they run in.  Check that they are free of anything that shouldn't be there, and clean them if you think they need it.  Relube very sparingly, using the bare minimum amount you can get away with, and put the axle back making sure that the brass bearings slot correctly into the rebates in the chassis block (they are prone to wandering along the axle, which will affect the running and possibly cause the rumbling you describe).  

 

With the bearings all sitting correctly in their slots, you can put the keeper plate back on.  This is a fiddly thing to do, as you have line the plate up correctly with the tapped screw holes in the chassis block and, at the same time, persuade the pickups to sit correctly, bearing on the back of the wheels.  When you have got it in place, replace the screws which you haven't lost because you put them in a lump of blu tac, didn't you?  Do them up tight, but not too tight as the keeper plate may bear on the axles or too loose as the axles will have too much play.  Test run the loco, which should be a lot smoother now.  

 

If this doesn't cure your rumbling KW4, you have at least eliminated some of the possible causes.  Please, bear with me if I'm teaching granny to suck eggs!  Hope it isn't Mazak rot, as this is pretty much a deal breaker and the loco is going to only be any further use cannibalised for spares.  Mazak rot is not connected to usage, it is simply a matter of time...

Edited by The Johnster

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