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I've only got one Q1 and it spends most of its time on the display shelf as my layout is basically Scottish Region, but I have experienced similar problems with Hornby Princess Coronations.
I would agree that it is mostly down to bad assembly in a few cases which brings on excessive wear to the crankpin. Another contributory factor may be the use on a layout with a lot of sharp curvature as if the coupling rods are not set up properly they do not get sufficient side play to cope with the bending stresses evident when the loco is on a curve and this too can cause wear.
If a crankpin comes loose on a loco with outside cylinders it usually fouls the connecting rod and the problem is immediately spotted - with the Q1 there is only the coupling rods. A crankpin not fully home can quickly wear the connecting rod as the pin has a shoulder onto which the rod should fit, if the pin is loose then wear can take place on either the pin itself or on the coupling rod very quickly. I suspect that where it happens there is burr left in the hole in the coupling rod, which then binds, loosens the crankpin and if this does not come loose completely then the fun starts.
I always check any new or acquired s/h locos by running slowly on the rolling road and inspecting the valve gear in operation using a magnifier. Any shortcomings can then be overcome and the loco carefully lubricated.
Strange to say I have had more glitches with Hornby than Bachmann.
I would agree that it is mostly down to bad assembly in a few cases which brings on excessive wear to the crankpin. Another contributory factor may be the use on a layout with a lot of sharp curvature as if the coupling rods are not set up properly they do not get sufficient side play to cope with the bending stresses evident when the loco is on a curve and this too can cause wear.
If a crankpin comes loose on a loco with outside cylinders it usually fouls the connecting rod and the problem is immediately spotted - with the Q1 there is only the coupling rods. A crankpin not fully home can quickly wear the connecting rod as the pin has a shoulder onto which the rod should fit, if the pin is loose then wear can take place on either the pin itself or on the coupling rod very quickly. I suspect that where it happens there is burr left in the hole in the coupling rod, which then binds, loosens the crankpin and if this does not come loose completely then the fun starts.
I always check any new or acquired s/h locos by running slowly on the rolling road and inspecting the valve gear in operation using a magnifier. Any shortcomings can then be overcome and the loco carefully lubricated.
Strange to say I have had more glitches with Hornby than Bachmann.
