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Locos derail.

Posted: Wed Jan 06, 2021 3:09 pm
by Steamingon
I recently bought secondhand, the Hornby Digital Mixed Freight. I guess it is about 10 years old. The two locos are D4174 shunter & 68478 tank loco. I notice both tend to derail a lot. Sometimes they may go round many times, other time they they derail every circuit. Sometimes one direction is better than the other, also back/forward. The track looks fine where they derail. With the set was a Hornby analogue 272 Panier tank loco. It goes around the track & never derails, neither do the wagons. The little 272 can go many times faster & still never leaves the track. Any thoughts?

Re: Locos derail.

Posted: Wed Jan 06, 2021 3:36 pm
by Bigmet
These three locos are all on what is basically the same mechanism, BUT, Hornby have varied the arrangements over time. Look for differences between the 2721 and the other two which derail. Do they all have the bouncy sprung rear axle, do they all have traction tyres, are their grooved tyres from which the traction tyre is mssing, are the wheels all set to the same gauge, are all the side rods straight, do any wheelsets have wobbly wheels, can the couplers or other parts touch the track?

Also the second hand aspect has to be considered. Is there any evidence of modifications to the mechanisms, or parts removed and not replaced correctly? A projecting screw or clumsily glued on part can be enough, if it is in the wrong place...

It's often a slow and patient investigation that's required to sort out such problems.

Re: Locos derail.

Posted: Wed Jan 06, 2021 11:26 pm
by Steamingon
Thanks for the reply. Both locos don't seem to have traction tyres. All con rods etc are straight. No modification has been done, & there is nothing loose that I can see with a magnifying glass. I ran them both today for quite a long time with no derail, I haven't changed anything. I will look further tomorrow.

Re: Locos derail.

Posted: Thu Jan 07, 2021 1:31 am
by stuartp
If 272 is the CR 0-4-0 then it has a shorter wheelbase than the others and is inherently more stable and harder to derail. The absurd top speed is a feature of the design although it has apparently been tamed a bit on more recent versions.

Is your track fixed to a board or set out loose each time ? Although Hornby track is robust and fairly tolerant of slight misalignment, if it is kinked or not fitted together properly it can cause derailments at rail joints. Look along each piece for twists, these cause grief on real track as well! Points are another risk area, the ends of the point blades are quite delicate and easily bent, if one is catching a wheel flange on the way past it will lift the wheel up. If the derailments are occurring in the same place every time I would suspect the track.

If they are not then I would suspect the locos or stock. Both the 0-6-0s have the same chassis (more or less), check the wheel treads and flanges for damage (unlikely) or misalignment (more likely). Are the wheels on straight and do they run without wobbling ? On DC you can hold the loco upside down and hold a couple of bared wires onto one wheel each side to run the loco slowly while you watch for wobble or anything sticking, not sure if you can do this on DCC so easily. Check that the pickups (bronze strips behind the wheels) are not catching anything.

Check the back to backs on each wheelset, it should be about 14.5mm on each and it should be consistent. If it is less then the wheel flanges will catch on check rails, the plastic guard rails in your point work.

Finally check for drooping couplings. On most designs there is a bit at the back of the hook which hangs down, if this is too low and catches on pointwork it will bring the wagon off.

Re: Locos derail.

Posted: Thu Jan 07, 2021 10:45 am
by RAF96
Turn them upside down and run them with a 9v battery across the wheels (if decoder allows DC running) and look for buckled wheels. I have a couple of 0-4-0s that waddle along due to this.

Re: Locos derail.

Posted: Thu Jan 07, 2021 1:47 pm
by whufcfan
Hi, all the above advise is good, you mentioned they do not have traction tyres, not 100% certain but I think those two models should have traction tyres, check that the two centre wheels have grooves that would take a tyre, if they match the other 4 wheels then all is fine, if not and a groove is present then this could be the problem & tyres will need to be sourced.

Sorry, just noticed Bigmet has asked the same question!