What are common causes of derailment?

yellow_cad

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All of my freight cars are Bachmann Big Haulers of various types made from kits. My locomotive pulls five passenger cars with no derailment problems, but my freight cars are a little more problematic. They have been converted to metal wheels so I am looking elsewhere for a solution to the derailment problem. Any thoughts would be greatly appreciated. Jim
 

Greg Elmassian

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Weight of freight cars (not too light)
length of freight cars (40', 50' ??)
wheel gauge / back to back
sharp curves - state minimum radius/diameter (and specify which)
coupler mounting on the freight cars?
brand of freight cars?
checked axles for free rolling?

Greg
 

phils2um

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Do the trucks on your freight wagons equalize? I don't know if the trucks come pre-assembled in Big Hauler kits. There should be a little bit of play in the truck side frames so all 4 wheels can stay on the rails over uneven track. It might be a contributing factor if they are screwed down tight and can't move. I just checked a new in the box, assembled Big Hauler flat I happened to have handy. The side frames on it do have a little play - not nearly that of LGB's 4 axle wagons - but some.

Just for your info, LGB's bogies have one side frame fixed. The other is very loosely mounted on a radiused support. They equalize without any problems which helps keep them on the tracks.
 

Greg Elmassian

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Stock big hauler freight cars are WAY too light.... they were the first to be thrown away.
Bachmann metal wheels not too whoopee on gauge out of the box
big hauler freight trucks not equalized as I remember.

Greg
 

yellow_cad

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I'm not sure I fully understand the equalizing. Please tell me more.
Is there a weight I should shoot for? I have 1/2 oz wheel weights, but wasn't sure how much and where I should use them.
 

phils2um

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The truck side frames should be able to twist around the bolster a little bit. Each wheelset is fixed. If the side frames are fixed too, one wheel will ride up on uneven track. On a real RR truck the springs keep this from happening equalizing the load on the wheels. Think three legged versus four legged stools on an uneven floor. Very few models have real springs in their bogies. Loosely mounting one or both sideframe(s) so they can twist a bit gives the same effect in our models.
 
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yellow_cad

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I have about 1/4 inch of wobble on the pivot screw. Should I just loosen the pivot screw I turn or so to get more of this wobble? Not sure what you are calling the bolster.
 

Greg Elmassian

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Equalization is between axles, not the truck to the chassis.

I'd start at the beginning.

Besides the things I have already suggested, how many freight cars are we talking.

When I first ran on my inner loop, I could not run more than about 7 cars, without one derailing.

Same loop with 45 cars: (moral, get your cars proper weight, couplers working, wheels gauged)
 

Gavin Sowry

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I can not over emphasise the importance of maintaining good standards of trackwork. I've been a Track man for 49 years 11 months, and 6 days, now. Part of my job is doing Derailment Analysis.
Sure, there are important things like track gauge, and the interaction with wheel gauge on your rolling stock, but by far, the biggest cause of derailments, both model and prototype, is twist in the track.
Let's consider, in no particular order, the parameters of track measurement.
Line. This is what it says, a straight should be straight etc. On curves the line should bend evenly. Peeky joints are the biggest line fault.
Top. This is the evenness of the tops of the rails. Dips at the joints can cause problems. With models, poor top can cause uncoupling etc.
Gauge. There is tolerance here, too wide, or tight and coupled with wheels not being right, you get squeeze offs, or drop ins.
Cant. Or superelevation, for our American friends, is a scientific value to stop trains tipping over sideways on curves. It is speed related. Avoid it with models, because you have to deal with
Run Off, which is the rate of change of cant in the transition/spiral. In reality, you need a pretty long spiral to do it right. Do it too short, then all 4 wheels will not be on the rails at the same time, which will have the same effect as
Twist. This is where there is a big change of cant in a very short distance, particularly fatal on curves.

So, now, before you go disassembling your loco and rolling stock (and I've seen this done numerous times), check your trackwork. By now, the world is conscious of bubbles, and the bubble is the trackman's friend. If you haven't got one of those Aristo Track Gauges (best investment I ever made in the model sphere), get a cheap spirit level (some builder's squares often have one in them) for checking and levelling up your track.
 
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JimmyB

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I did have a bit of an issue when i converted my stock to Bachmann metal wheels, it would seem some of the back to back gauge was out, the wheels were not tight up against the axle spacers.
 

Gavin Sowry

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I did have a bit of an issue when i converted my stock to Bachmann metal wheels, it would seem some of the back to back gauge was out, the wheels were not tight up against the axle spacers.
Had that problem, too. I wriggle the wheels out to correct back to back, then dollop a bit of superglue down the spacer crack.
Once, I had to cut one of the spacers to actually narrow the gauge back to correct measurement.
 

Rhinochugger

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Yep, as Greg says, let's start at the beginning.

So we are using curves that, even with 8 ft diameter are way tighter than anything in 1:1 land, and to compensate for that, our model trains have deeper wheel flanges and the flanges are expected to keep the trains on the track.

Given that the passenger carriages stay don't de-rail, I'd tend to discount track laying problems. The Bachmann Jackson Sharp carriages are longer, and have longer bogies than the freight cars, so in theory, would be more susceptible to uneven track.

I'd go for added weight in the first instance.

The next things is to check that the bogies swing freely, that the pivot screws are not too tight.

Also make sure that the axle boxes are lubricated - you can either use a light model oil or the dry graphite made by Eze-lube.

Lastly, as others have said, check the back-to-back measurement of the wheel flanges, but again, errors in gauge are more likely to cause de-railment through point work rather than on plain track. The back-to-back measurement - the distance between the backs of the wheel flanges, should be about 40.5 mm.

I appreciate what Gavin has said about track laying, and strictly speaking he is correct, but I am an expert on some of the worst laid track that you're likely to see, and my trains stay on OK, so I'd look at the rolling stock first.

If all else fails, get your head down at track level, run the train by slowly and watch what comes off and where it happens, then run that one wagon over the spot to try to eliminate the issues.
 
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maxi-model

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By now, the world is conscious of bubbles, and the bubble is the trackman's friend. If you haven't got one of those Aristo Track Gauges (best investment I ever made in the model sphere), get a cheap spirit level (some builder's squares often have one in them) for checking and levelling up your track.

Could not agree more Gavin. I've had one of those Aristo' levels/gauge a long time. Always the go to when an unexpected derailment happens.....that and checking for the odd obstruction a bird may have placed on the line. Superglue ? Egads ! My own preference is to reassemble using Loctite 603 to lock metal to metal or plastic (as in - insulator on axle). It's formulated to work in environments with a high risk of oil penetration.

Regarding derailments - Another area to check is how far the ends of cars throw out, overhang, from the centreline of the track on curves, relative to the next vehicle in line. The throw may be so great that the pivoting movement available from the coupling (and axles side to side) can no longer accommodate this degree of movement. The result is the car is literally dragged off the track by its neighbouring vehicle. The solutions to this issue are manifold - change of coupler mount type, moving axles/bogies closer to the car ends and if all else fails larger radii switches and curves. I even have to run a 2-6-2 tank loco tail first on my line's inner loop as the distance from the buffer beam to the lead axle at one end of the loco is far greater than the other. Larger radii and surgically shortening the valuable and prototypically to scale loco was not an option :D Max
 
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JimmyB

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If all else fails, get your head down at track level, run the train by slowly and watch what comes off and where it happens, then run that one wagon over the spot to try to eliminate the issues.
When diagnosing my derail issues, a wagon would derail when pulled by a loco, but not (always) by hand, so I coupled up another wagon to pull the culprit slowly over the offending area.
 

3 minutes of fame

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First thing to do is analyse if the derailments happen at the same point (No pun intended) or if it's a bit more random than that. If it always happens at the same locations - even if only with 1 or 2 cars, suspect the track. Random derailments are usually due to insufficient weight or poorly compensated or sprung bogies.

If the couplings are connected to the bogies, make sure that the curves are not exceeding the limits of the free play of the bogie. Reverse S curves and non-transition curves can make things worse. Any little lumps and bumps in the track coupled with a sharp curve or additional load on the axle can cause 1 car to derail while another will happily trundle over it.

Agree that back to back accuracy is crucial to smooth running. Whereas full size trains run mostly on the cone profile of the wheel, our little trains rely much more on the flanges and there is a propensity for them to climb the inside edges of the track if the gauge is a bit tight.

Compensated axles - allowing some sway and vertical movement while keeping some weight on the wheels helps a lot, but seems to be less common on G45 than on either 0 or G1, I guess the cost of the rolling stock dictates this to a certain extent. Metal wheelsets often have a smaller flange, which helps with the looks, but not the track holding.
 

Rhinochugger

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Compensated axles - allowing some sway and vertical movement while keeping some weight on the wheels helps a lot, but seems to be less common on G45 than on either 0 or G1, I guess the cost of the rolling stock dictates this to a certain extent. Metal wheelsets often have a smaller flange, which helps with the looks, but not the track holding.
Yes, I think that is because of the very large flanges that are used in G scale - so if you think about it, if a wheel without compensation lifts away from the rail slightly, the flange should keep it in place .......................... in theory :oops:
 

dunnyrail

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All of the solutions have been passed on here it is just which one you need.

My little two penny worth would be to carry on running and record what wagon and where for a week or two. Likely just one or two wagons will be involved at similar places. Then you will be able after some analysis of the data do an investigation as to causation exactly as Gavin would do at a real location.

If it is track issues a small spirit level may tell you about varying cahnges of Twist, Cant or RunOff that may be an issue.

If it is stock then a ylising what may be different between a wagon that is a problem and one that is not.

Finally do not discount turning a vehicle through 180 degrees, this may resolve a problem unless you have a reversing loop somewhere which could eventually bring it back.
 
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Greg Elmassian

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I have given my best inputs, and I have succeeded in raising the quality of my operation from derailing 7 car trains to the 45 car train you saw.

PLEASE answer the questions in post #2.....

We are all over the map with suggestions, but we know virtually nothing about your environment.

By the way, on weighting cars, try scale unladen weight.... find about how much your car weighs unladen in pounds (often printed on the car) i.e. the REAL car weight.

Then divide by the cube of your scale... it works well! Yes, it makes the cars heavier, and yes you cannot pull 100 cars with a puny loco, but this will put you in the ballpark, and interestingly, in this case, the physics of the situation scales to our models (you can use this for weighting locomotives also).

The cars that come with the Bachmann Bug Mauler starter sets are WAY too light.

Greg
 
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Gavin Sowry

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