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Hornby Drummond 700


Robin Brasher
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Great model I have 3 Hornby and a white metal 700 which is 30368.

 

Can't help on the DCC probs sorry!

 

Kind regards,

 

Richard B

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  • 1 year later...

I posted about this on my own thread (after Googling) and had very little response, so I'll post it here.   Maybe I am the only person to have encountered this problem.

 

We bought a 700 for Ormesby Hall when they came out - a few were superheated before the end of the LSWR, so we can justify it.  it still awaits repainting into LSWR green.

 

After a couple of seasons of faultless running it became jerky and eventually wold only run in reverse.    On examination, the driven crankpins (the ones on the trailing wheels) had worn almost through.  The coupling rod had sawn through the pin just behind the hex head until there was almost nothing left. 

 

At the time we needed it fixed, so I replaced rods and the defective crankpins and put it back into service.   At the end of this season I was told it was showing the same symptoms and indeed had developed exactly the same fault.   This time I've replaced the crankpins with Romford (the threads seem to be the same), soldered a brass washer onto the front of each coupling rod and used a small top hat bearing on the crankpin.   Remarkably, considering how unscientifically I did it, it runs.  We'll see how long that repair lasts.

 

100_2589_small.jpg.b1a28eda9f485f9d517db17daf711207.jpg

 

Has anyone else had this same problem?   I know our locos work far more than most, but it seems odd that only ours has been affected by now.

Edited by jwealleans
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But I wonder what causes it; I have never heard of that with any other Hornby Locos?  For example I've got two J15s which are probably quite similar mechanically and have run quite a few miles but the crankpins seem quite OK.

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Maybe the coupling rod is ever so slightly too long, or the hole in the rod just slightly out of place in relation to the hex bolt, so its grinding on the pin ?

 

Spares are available, maybe experiment with a set by slightly (0.25mm ) enlarging the hole in the rod to give it a slight bit more flex as the wheel rotates ?

 

it could also be the wheel slightly out of true, or even the axle hole not quite 90 degrees to the wheels and moving about ?.. either way it sounds like if its not impacting performance its a minor amount of adjustment needed.
 

Does the wheel not have any protruding bush for the rod to sit on ? - usually the bolt is to stop the rods coming off, rather than for the rod to sit / rotate on… I have seen some where the bush/screw thread has moved slightly towards the inner side of the wheel.. simply pushing it back out works, then hang the rod back on it.

Edited by adb968008
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I did change the rods, although there was no visible difference in the new pair from the old.   I wondered about quartering, but the running was superb right from the off and given that this is the driven axle, I didn't want to compromise that.   There is no protruding bush on any of the wheelsets, that was one of the first things I looked for.  If that is the problem then it's happened on all three, which seems too much of a coincidence.

 

We ruled out enlarging the rod holes - there's not much material there to start with and the root of the problem was reduction of the crankpin size - which is another way of achieving the same thing, so we decided against.  

 

The loco will go back ready for reopening in February and we'll keep an eye on it.

 

 

 

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My feeling on this is that it was the early models that had very lose connecting rod hinges, such that there was a lot of slop, given this is the driving acxel I think this is the cause.

If you buy new rods X6941 the slop is not there, the rivet is there but it does not move.

 

New rods should then solve it hopefuly?

 

 

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