Crank pin wear on Hornby Q1

QUOTE (pedromorgan @ 27 Oct 2008, 09:12) <{POST_SNAPBACK}>I have only seen that damage on old O gauge loco's.

you are correct its probably the weathering powders that have contributed to it but i suspect that little or no lubrication would have also been a factor.

its interesting that the screw has worn only on one side rather than waisting. this would suggest to mee that the wheel was not perfectly centred. as it seems that this side has been doing all the work i wonder what the con rod on the other side looks like?

i wonder what richard would have to say on this one?

Peter

*** That kind of specific wear pattern is nothing to do with lubrication or weathering powder at all. Hornby should fix this at no charge. It is simply a result of bad assembly.

Its a very symptom of what happens with the typical hornby chassis: 95% have a definate tight spot and lope along at slow speed or under load - this is the source of the hornby "waddle" that is almost always there on every hornby and nmany bachmann steam loco!

Why" - because most have a lump or slight burr or two on the axle bearing area which make one axle very slightly out of alignment and this causes a tight spot once per revolution of the wheels. This can be greatly reduced by running in but its really only "wearing it in" as the crankpin shows, and is best fixed at the source!

Removing the axles/driving wheels from the chassis and smoothing the ends of each axle slot very gently with a fine rat tailed swiss file or 600 grit or finer wet and dry around a toothpick will always remove the tight spot, greatly improve running and stop this sort of problem.

regards

Richard

QUOTE (Richard Johnson @ 27 Oct 2008, 03:57) <{POST_SNAPBACK}>*** That kind of specific wear pattern is nothing to do with lubrication or weathering powder at all...

I should have mentioned that there are three screws with almost identical wear; both back wheels and the centre left, which is the one that I photographed. Why not the centre right is a puzzle; perhaps something to do with the lubricator crank that makes for a different arrangement on the left side. Presumably a quartering error should be near impossible.

The engine has always run very well with no sign of binding or waddle, so if it wasn't for the oddity of the centre wheel that didn't wear, the wear pattern would be symmetrical and as expected. The one-sided wear of the screws is of course normal, because if the engine goes mostly in one direction it is always the same side of the crank under stress. There was a trace of oil on the con rods so I don't suspect lubrication failure.

The Q1 regularly pulls trains that lesser 0-6-0's won't, so this is perhaps just normal wear of a hard-working engine, possibly exacerbated by the weathering. In any case, I am going to keep an eye on it and get another spare set of rods.

David

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.

QUOTE (Saint Johnstoun @ 28 Oct 2008, 15:40) <{POST_SNAPBACK}>.. Strange to say I have had more glitches with Hornby than Bachmann.
That matches my experience on the new designs introduced by both makers from 1999 (ie Bachmann 'Blue Riband' and Hornby's post Merchant Navy introductions). Design weaknesses which contribute to assembly errors, and poor factory control of tolerances (remember the screaming 08's?) have affected about half my Hornby loco purchases. I buy far more Bachmann locos and have yet to have any mechanical problems with them. Like you I check over and then test run carefully all new purchases and it is the Hornbys that have to be sorted mechanically. (Both makes usually require adjustment to pick-up wipers; Hornby to soldering up pick up connections, Bachmann to reducing springing on carrying wheels, adding springing to Hornby carrying wheels.)