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QUOTE The diesels and DMUs are ok but some Hornby steam derail quite regularly. None of my German locos derail at all!

How common is this. The only issue I ever had was with a Bachmann Class 4MT when the front bogie kept coming off on a certain point. The answer was to not run the loco across that part of the layout.

The thing is Hornby and Bachmann don't deliberately design trains to derail, and surely they carry out extensive testing prior to putting a model into production.

And Hornby have their roadshow and their trains run for many hours each day and do not derail.

So lets have a definitive discussion on this subject.

Why do trains derail and how can you prevent this from happening?

Convince MRF members that it is the loco that is at fault and not some other aspect.

And what makes German steam locomotives stay on the track better than British locomotives?

German steam locomotives have smaller wheels and run more slowly as HO scale speeds are slower than OO so is this a factor?

Do German locomotives have bigger flanges than their British counterparts?

Happy modelling
Gary
 

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Unfortunately, no discussion on these lines (!) can ever be 'definitive', because so much of what is said is based on age-old entrenched beliefs and personal opinions rather than clear, measurable facts.

A good example of this is the constant jibing about German/British quality, which I do not want to progress any further. I'll just say that I have a lot of experience with both (and many others besides), and until quite recently, almost anything not of German or Japanese origin was unmistakably inferior in almost every respect. I would add that I HAVE had the odd duff German item too, but those have been very few by comparison. Hopefully, quality improvements will continue, though it needs to be said that that is not much help to people who have already made their investments! Enough of that.

QUOTE . . . The answer was to not run the loco across that part of the layout.
It might have been AN answer but not THE answer. It's clear that there was a problem with that part of the layout, equally obviously track related, and THE proper answer would have been to investigate and fix the problem at source, rather than running away from it. How many bits of track does one designate a No-Go area, before deciding to identify and fix the REAL problem, the root cause?

But that anecdote is a useful pointer towards the most usual reason for derailments being track that is faulty in one or more of several ways. It could be poorly designed in the first place, badly manufactured in the second, damaged at some point in time thereafter, incompetently laid or, more than likely, some nasty and hard to identify combination of SEVERAL of those factors and perhaps ALL of them! While one factor alone MIGHT result in a derailment, it is more likely to be an accumulation of several small faults which, combined together, eventually produce a crash.

While track problems are the most probable causes for derailments, all of those track factors are very often also combined with a lot of additional factors in the vehicles running upon it. The same factors noted against the track can also be pointed at the vehicle running upon the track plus some extra ones too. Unfortunately, at this point, there are so many accumulated variables involved in the combination of these that it can be extremely difficult, close to impossible in some cases, to pin down the exact causeS for the derailment - another good reason why a discussion just cannot be 'definitive'. I haven't mentioned idiots driving their trains like maniac racing car drivers, but that is a common factor too!

I laughed out loud at the suggestion that any difference in 'scale speed' between OO and HO had anything useful to contribute! As if the average home train player, whom Gary seems to feel he represents, would have the slightest idea as to what scale speeds either actually are or what they should be, in either scale, let alone possess either the ability or the inclination to drive carefully in accordance with them! Oh, I needed a good laugh today!


It is my personal opinion that most (but NOT all) derailments are primarily track related, but these are exacerbated by locomotives and other rolling stock, each of which can have a myriad additional tiny faults, that contribute to one particular vehicle derailing more than others on the same track.
 

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>Why do trains derail and how can you prevent this from happening?

This is simply a question of "mechanics", that is to say the mechanics (Newtonian?) which is a branch of applied mathematics rather than relating to machinery. For most people it is not a simple question to answer and I won't attempt to do the maths for fear of embarassing myself and boring people to death. However, by examining the principles of Mechanics we should be able to deduce a set axioms that will allow us to analyse why our trains come off the rails.

So here's a few axioms to start us off:-

1) A body in motion will continue in a straight line unless it encounters a force which acts on it to change its direction. EG. A pool/snooker/billiard ball will travel straight on until it hits another ball or a cushion.

2) All forces acting on a body can be resolved into 3 dimensions - vertical, horizontal (left / right), horizontal (forward/back). Once resolved into these 3 dimensions, an increase in force in one dimension has no affect in the other two. For example if our pool ball rolls off the table, it will drop straight down without deviating left or right from its original course.

3) If you pull on two ends of a piece of string it will form a straight line between the two points where the force is applied. Now think about train couplings.

So how can we apply this to derailments?

For a derailment to take place, the flange of one of more wheels must rise above the level of top of the rail /and/ there must also be a sideways force to push the wheel outside the confines of the track.

So having established that we need forces in two of our three dimensions for a derailment to take place, where might these forces originate?

From the first axiom, we can deduce that forces will arise if the wheels hit something in their path. This could be:
entering a curve
hitting a frog or check rail in a point or crossing
riding over a joint in the track

In each of these cases, there will be both a sideways and vertical component in the force. In the case of entering a curve, the vertical force arises from the profile (shape) of the wheels which have a slight camber to them. On entering the curve, the wheel wants to travel straight on, so the curved wheel profile will start to raise the wheel. The force acting against this upward vertical movement is the weight of the vehicle.

The case for force resolution into sideways and vertical dimensions for points is much clearer. The jolt of a check rail or frog will produce a sideways correction and almost certainly an upward movement as well.

Another force acting against perfect running was mentioned by Columbo in a recent thread on couplings. If the link between vehicles is not made through the centre line of those vehicles, a turning force will be applied the them. (cf axiom 3 above) The "neutral" position for that vehicle coupling (ie no more sideways component) occurs when the line of action of the force through the coupling is parallel to the track. Since the line of action of the coupling force is not through the vehicles' centre line, this neutral position cannot be achieved until one of both vehicles is off the rails - ie this is a derailment waiting to happen; there is plenty of sideways force ready and waiting for sufficient upward force to attain equilibrium.

So how can we prevent derailments?
From the above it is apparent that by reducing all opportunities for disturbing forces to be created, derailments can be also be reduced. To do that here are some guidelines. I am sure there are many more:-

1) Be fastidious when laying track. This is more important for flexible track than set track. Any uneveness in rail height creates a location for vertical movement.

2) Don't place points too close to the start or end of a curved section. In a small space it is tempting to squeeze a quart into a pint pot by ending a curve and placing a point but in my experience it often ends in tears.

3) If a particular vehicle has problems with a point or crossing, check the wheel set is within specification for the standard of rail you are using - This problem has been mentioned quite a few times in threads on this forum

4) Don't allow large gaps between rail ends. If the gap is large enough, the wheels will drop in and then bounce up again on the way out. Any sideways movement through the coupling and you have a disaster. (I have this particular problem on a code 100 section of my layout at present).

5) Ensure that all vehicles run freely and are reasonably matched for weight. Light vehicles at the front of a long train with heavy vehicles at the rear can easily result in a derailment round a bend.

6) Ensure that all couplings mate so that the force under tension is distributed so that it is acting along the centre line of the vehicle when it is on a straight section of track.

The NMRA has guidelines for things like wheel profiles, vehicle weights and so on and I am sure they are the result of a mathematical analysis.

For what it's worth, I can run a Hornby A4 drawing 6 Gresleys at full speed over code 75 pointwork, forwards or reverse.

At the end of the day it is all governed by the laws of physics. There's no magic or black art to it.

David
 

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QUOTE I laughed out loud at the suggestion that any difference in 'scale speed' between OO and HO had anything useful to contribute! As if the average home train player, whom Gary seems to feel he represents, would have the slightest idea as to what scale speeds either actually are or what they should be, in either scale, let alone possess either the ability or the inclination to drive carefully in accordance with them! Oh, I needed a good laugh today!
Unbelievable. It stopped me in my tracks too.

QUOTE And what makes German steam locomotives stay on the track better than British locomotives?
They apparently have wider wheel flanges. In the USA they prefer accurate scale ones, RP25, whereas the Germans go for operational efficiency. Bachmann UK wheels are pretty much RP25.

The specific problems I have encountered are the front bogies on some Hornby steam locos. They are light and loose and prone to rise over the track and derail.

Another issue is those UK outline couplers. This issue was dealt with by dwb and can be rectified if the couplers are changed.

The other problem I have is with large articulated trains with RP25 wheels. They have small wheel flanges and do not grip the track as well. The problem I have here is narrow bends. This is something I can accept as I cannot really make my curves any bigger so I run these locos at lower speeds.

I would note that no Trix, Roco, Bachmann, Lilliput, BLI loco has derailed. I can go off and leave them to run round for hours. The problems I have are with some Hornby steam locos and coaches. Given that this does not happen with any other company it would seem reasonable to conclude that the problem lies with Hornby design.
 

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QUOTE it would seem reasonable to conclude that the problem lies with Hornby design

I would hate to make the assumption that there is some design flaw. I would much prefer it to be a manufacturing problem that can be fixed with the checking of gauge, adding weight, coupler height or binding or bad track that effects the Hornby locomotives more than others. It is true howevre that Germans locomotives have out of scale wheels compared to American locomotives and from what I have seen they also do operate them at a faster speeds and more often unattended. The US is the capital of Cab Control and slowwwwwwwwwwwwwwwwww moving trains.
 

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QUOTE I would much prefer it to be a manufacturing problem that can be fixed with the checking of gauge, adding weight, coupler height or binding or bad track that effects the Hornby locomotives more than others

I did actually read on another thread that someone had solved this problem by adding weight to the front bogie.

QUOTE It is true howevre that Germans locomotives have out of scale wheels compared to American locomotives and from what I have seen they also do operate them at a faster speeds and more often unattended. The US is the capital of Cab Control and slowwwwwwwwwwwwwwwwww moving trains.

I think this could be the basis for the differing opinions. We all expect different things from our layouts and trains and have different requirements. Obviously not all trains will be suitable for the same functions and this could be why some people discover faults that others don't. My preference is for fast express trains that run for hours unattended. Which is why I discover the derailing properties of Hornby. Whereas some one running these slowly for shunting will not find these problems at all.
 

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This is what I have been trying to get across since I joined this board. I have been lucky in the fact that I travel quite often and can see what the different groups (Continental, UK and American) are up to. The American hobbyist can be quite a fanatic when it comes to flange depth and track code. They'll just work to get it right. I and I think Neil are more interested in watching the trains run where in the UK they are somewhere in between. They I think are more about staging and running their trains through a scene. I only say this because the majority of layouts I saw in the UK were very small and had scenery only in certain places with fiddle yards and what have you in areas where you were not to focus on.

We have an organization in the United States that's quite large called the ETE or European Train Enthusiasts. Whenever I have seen their layouts in operation they seem to run their trains at 100 mph and yes passenger trains are very popular with them.

These differences also lead to what features are important in DCC. Multi-train consists are very important in the US. In Europe they are into automation so computer interfaces, and things like RailCon are very important.

Hopefully we can all learn from each other and more importantly find enjoyment in seeing what each of us is doing.
 

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>I only say this because the majority of layouts I saw in the UK were very small and had scenery only in certain places with fiddle yards

And what a yawn it can be to watch them - or maybe that's just me.... I'll try to do better at Railex at the end of the month.. promise


David
 

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Discussion Starter · #11 ·
QUOTE To be honest my first train show in the UK was kind of a let down. I was very suprised by what I saw.

Which show was it?

The big national shows are the ones that have the major layouts. These simply will not fit into many of the smaller events held and advertised locally only.

Railex is pretty good but remember that the focus of this show is finescale and kit built/hand built models and the mix of traders there reflects this. There is not normally much RTR for sale. A very high proportion of kit bashers attend as a result. The Railex organisers consider their show to be the leading show of its type in the country.

And taking this back on topic there were finescale locomotives that derailed when I attended Railex last year so the issue is not just confined to RTR models.

Happy modelling
Gary
 

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When it all comes down to it you can't beat good track and benchwork. Model locos can derail when there is an obvious fault like an oversprung pony truck or wheels out of guage. But in the end it all comes down to trackwork and benchwork. If you lay track that looks like the Himalayas then you can't honestly expect a loco doing 100kph to stay on. If lay a curve that's not a constant radius then locos are going to come off. Benchwork is another factor. If you benchwork is to lightly constructed then it'll sag or deform and your already bad tracklaying gets compounded into something really awful. Take your time and spend a few extra dollars to build good bench work and then lay good trackwork. The dividends are no derailments. My base benchwork is all 4"x3' L girders on 3'x2' legs and was initally topped by 3/4" chipboard. It was a bit of overkill and i have since revised the specs for the new layout. The L girders remain the same but I'm changing to 10mm ply cut to profile. Track, which is Peco code 75, is layed on 8mm concrete expansion jointing and has not given an moment of trouble in 5yrs. The expansion jointing is very stable and is not effected to much by heat or cold and also acts as a sound deadener. It's easy to use and is just stuck down with a stuff called Bondcrete which is a concrete sealer similar to dilute PVA glue but with additives to make it go off faster. Track is treated the same way with the Bondcrete applied to the expansion jointing and the track pressed down onto it. I usaually hold the track in place with a couple of pushpins and and a couple of bricks. The glue sets in about 20 minutes and you can ballast with the same stuff just diluted a bit as you would with normal PVA glue. If your track and benchwork is good and locos still derail then start checking the loco for wheels that are out of guage, wheel out of round, wheel centers that have shifted and this is quite common on wheels with platic centers, rims that are twisted on the wheel center and bogies that are over sprung mostly Bachmann. There are other things that can effect running but these cover most. I've come to the conclusion over the years that the words Ready to Run and Plug and Play were invented by someone with nothing better to do.

Ozzie21
 

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>Ready to Run and Plug and Play were invented by someone with nothing better to do.
The marketing adjective you are searching for is "aspirational".

The technical equivalent of "Plug and Play" is "Plug and Pray".

David
 

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Excellent post by Ozzie21!
QUOTE Model locos can derail when there is an obvious fault like an oversprung pony truck or wheels out of guage. But in the end it all comes down to trackwork and benchwork.

You have to start with the basic foundation and make it good. Once that is established and eliminated as a cause, then trouble shooting the rest becomes much easier and more effective. Be methodical.
 

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All good postings, but the fact remains there is no accepted standard for 00. We have Peco doing their own thing, and Hornby and Bachmann sa slightly different version. Until there is an accepted standard for 00 track, back to backs, wheel flanges, which all the major player accept there will be problems.
All my stock is checked with a clock vernier prior to running for the first time, if it's wrong I adjust it, result few derailments.
 

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>if it's wrong I adjust it
What percentage of stock needs adjusting and which source heads the list?

David
 

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QUOTE (dwb @ 21 May 2006, 04:30) <{POST_SNAPBACK}>>if it's wrong I adjust it
What percentage of stock needs adjusting and which source heads the list?

David

Well to put it mildly all of it! Every loco, every coach, every wagon is usually has it wheels out of guage. Not much and it would probably fall into that 14.5 to 14.72mm back to back that manufacturers use and this is on both sides of the atlantic. Every piece of ready to run rolling stock I've ever bought has had to have it's wheels reguaged to 15mm back to back. There's no one offender in my book as they all do it, Walthers, Athearn, P2K, Hornby, Bachmann, Kato, Atlas the list goes on. I've bought $4,000 brass engines that derailed beacause the wheels aren't guaged properly. It all depends on which of the multitude of so called "Standards" the manufacturer applies, his own, the NMRA, the BRMSB, NEM?? Once upon a time there was going to be a "Standard" for the UK but no one could decide on the width the rails were to set apart to based on the scale. HO 3.5MM is 16.5mm, OO 4mm is 18.83mm but commercial concerns were the decideing factor so we got stuck with 16.5mm and that was it. Track was made to be roughly eqivalent to NMRA recommened practices but to run European rolling stock with it's then huge flanges meant code 125 rail so everything was opened up slightly to accomodate. Now we have fine scale rolling stock that runs on set track geometry and it's going to give problems. It'll run fine for the most part on code 100 rail but as the rail gets finer, code 83, code 75, code 70, code 55, so the derailments increase because of the sloppy set track standard used to set the model up to in the first place. With diesel models it's proably not a problem due to the weight in modern diesels but steam models are a lot lighter and are more prone to derailing so you have to be vigilant and check the wheels every model you buy.

Ozzie21
 

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What's a derailment? Is that the occurance when a rail vehicle leaves the track? I wouldn't know. I don't get derailments but then again I took time to lay my track properly
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