Dapol Maunsell Wheel Sets

[doug22150]

Has anyone else had problems with the wheelsets in Dapol Maunsell coaches?  I've now had 2 of these, on separate coaches, fall out and prove impossible to replace in the bogie because they appear to be too short.  In both cases, I was alerted during a running session to a coach becoming derailed.  When I lifted the coaches, one wheelset fell out of a bogie.  In the second instance, I noticed that the axle of the displaced wheelset was very bent.

Is it possible, because of the provision for coach lighting, that a displaced wheelset could cause a short-circuit and the heat generated bend one of the very thin axles?  It sounds unlikely, but I really can't think of any other explanation.  For the axle to be as bent as it is would have taken a great deal of force and there is no other sign of damage on the coach body. 

[doug22150]

I've now had 2 more coaches in which axles have become bent and the coach rendered unusable after a running session which had to be ended because of recurring short circuits. If it wasn't displaced axles causing the short circuits, are Dapol coach axles prone to damage when shorts occur and aren't immediately resolved?

[austinbob]

This is all very odd. Never had such a problem.

[doug22150]

Amazingly, I've just had confirmation from Dapol that my suspicions about Dapol N Gauge axles and prolonged shorting were correct!

In an Email today, Dapol stated "Having had a reply back from our Technical expert he has advised that what has undoubtedly happened is that the faulty point motor wiring has caused the short circuit due to the faulty track wiring described has heated and melted the axles".

Such a shame that these great looking coaches are vulnerable in this way.  When the damage occurred, the damaged coaches were a part of a much longer train of Farish coaches and there was another entirely Farish 9 coach train running.  None of the Farish coaches were affected by melting axles!

[Bob G]

Hello all

This is good news - but not to those who have suffered the problem.
I have had an enquiry via the NGS helpline about a similar occurrence and the chap was not pleased.
However, at the time, I did not know of any such issue being common. This helps me set that straight.

The only think I found with the Maunsells was that clearance for the close coupling mechanism has to be made in the factory by filing away part of the seating area at the lighting connector end. One of mine was not filed away and the bogie was stiff. I could fix it quite quickly once I had identified the problem, by comparing a good coach with a stiff one, but this could also be the reason for short circuits happening, so do check all your bogies are loose.

Bob

[Bob G]

I have had a further time to think this through, and here is a summary of the explanation I gave to the NGS member on the helpline, who has had a similar query since March this year.

My starting point is to say that all models should perform perfectly on track without points and crossings. Difficulty occurs when points and crossings are introduced, and different standards are used, and this is most commonly seen on short wheelbase wagons. This is also not a dead frog issue. You could get the same thing happening with live frogs. It is, however, a DCC issue, combined with the elderly design of current pointwork.

At the frog of the point, the base of the frog was originally designed to support the rim of the old-style wheel. These wheels were known as pizza cutters because of their silver appearance and their deep rims. The Peco point designs are from the 1970s, and 1980s, and allow for both types of wheel to run through them.

Now almost all wheels have narrower, more realistic rims, but this comes with a penalty. The wagon wheel rims do not run on the base of the frog any more, and rely on the three other wheels maintaining contact with the rail surface for the short period of time when the wagon wheel is over the frog gap. If there is sideways or vertical stress on the wagon, e.g. whenever a wagon is not running in a straight line, it can fall into the "pit" where the rail support is missing where the point diverges. This is most common on 4-wheel wagons, and I was not aware of any problems on bogie stock until now.

There appears to be a possibility that when there is a short, on DCC, with Dapol Maunsell and Collett stock (but probably equally with any Dapol coach which is light bar enabled), that the axle heats up very quickly and distorts, causing the bogie to distort, and/or the axle to distort and the wheel to drop out of the bogie. This is only apparent on DCC because of the high continuous voltage system.

Now I do not agree with Dapol's interpretation above that it is the point wiring that is to blame. It is more reasonable to blame the point design that has this feature which allows older wheels to run through the point frog, but can also allow the wheel of more modern stock to drop into the frog.  I can see that it is possible that if the electrical pick up on the bogies for lighting purposes falls into the frog of the point, and creates a short, this could cause damage to the coach if not resolved quickly.

Do you feel this is a reasonable conclusion to come to?

Bob

[doug22150]

Bob

That sounds totally plausible and certainly matches a part of my experience.  With hindsight, the first hint of a problem was when a Dapol coach derailed after crossing a set of trailing points and I found a very loose wheelset. However, I did subsequently have even worse damage when testing point operation after installing Cobalt analogue point motors in my fiddle yard.  With some of the points, the frogs weren't switching correctly and shorts were being caused. When this happened with Dapol Maunsells in a train there was a loud, continuous buzzing from the accessory decoders that power my SEEP motors on the visible side of the layout.  As I continued testing to try to home in on the defective points, I noticed successive problems with the Dapol coaches in my trains.  By the time a 4th Dapol coach had developed loose (or severely bent, in 2 cases) axles I finally thought of removing the Dapol coaches from the trains!  I continued testing and there were indeed still short circuits because of fault frog switching.  However, without the Dapol coaches in a train, there was no buzzing sound. None of my Farish coaches that remained on the track throughout have suffered any damage

So, in my case, Dapol could have been correct in saying that the axle failures were because of short circuits.

Incidentally, I still haven't been able to resolve the frog switching problems and have now disconnected the frog wires on 4 sets of points.  I will rely on the inbuilt switching inherent in Peco Code 55 points - life's too short!