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Accelerating to avoid derailment on 28" curve?

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Accelerating to avoid derailment on 28" curve?
Posted by kasskaboose on Monday, November 16, 2015 7:01 AM

On my 13x7' layout, my SD45 sometimes derails on a 28" ME code 83 track curve when I run it too slowly.  I fix the issue, slide the loco back, increase the speed, and no derailment.  Is that normal?  Perhaps my older brother was right when he told me to "accelerate through a curve" while learning to drive. 

The track and trucks are all aligned.  The track is secured w/ ME track spikes.

~Lee

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Posted by rrinker on Monday, November 16, 2015 7:06 AM

 An SD45 shouldn't derail on 28" radius curves at any speed. Run it slow and carefully watch the truck that comes off to see exactly where it goes off. You may have a spike driven in too tightly, causing the track to bow inward and tighten the guage, or you may have a surface dip in the roadbed, or a high spot. Or if it is at a rail joint, there may be a slight kink.

                  --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by richhotrain on Monday, November 16, 2015 7:14 AM

kasskaboose

On my 13x7' layout, my SD45 sometimes derails on a 28" ME code 83 track curve when I run it too slowly.  I fix the issue, slide the loco back, increase the speed, and no derailment.  Is that normal? 

You haven't fixed the issue.  What is probably happening is that one or more of the wheels is lifting up off the rail and then coming back down on the rail again. The faster the speed, the less time it takes to come down again.  I have observed that phenomenon on my own layout.

To fix the issue, follow Randy's advice.  The possibilities include uneven rails, kinks, humps, valleys, obstructions.

Rich

Alton Junction

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Posted by ricktrains4824 on Monday, November 16, 2015 9:01 AM

Is it in a spot where you can follow the lead of the folks who lay the 1:1 scale tracks, and "sight down" the line? 

Thats how I found a problem spot on my old layout, is I got down to eye level and looked down the rails. Found a tiny dip in a joint, running one direction, at a somewhat quicker speed, nothing happened. Running for the other direction at any speed, nothing happened. But, slow speed, (or at breakneck speed... Very unprototypica....) in one direction it would derail every locomotive I owned. (Of course, my smallest is a 4 axle road switcher, no actual small switcher as of yet.) On one joint, just one rail, it dipped down just enough that, as was mentioned above, the leadwheelset would come off of the rail, then when it settled back down, it was beside the rail, not on it.

So, if you can get to close to eye level just above the rails and look down them, I highly recommend it.

Ricky W.

HO scale Proto-freelancer.

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1: It's my railroad, my rules.

2: It's for having fun and enjoyment.

3: Any objections, consult above rules.

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Posted by selector on Monday, November 16, 2015 1:34 PM

Curves that have derailments usually have a dip somewhere on the outer rail.  Either that or the truck on the locomotive is being prevented from either adhering to the rail or from pivoting sufficiently that the flanges don't ride up on the flange face to accommodate pressure to displace them outward.  Maybe there is flashing or something where there shouldn't be.  Maybe an axle is not properly seated in the truck.  Maybe a bent stirrup or something else is preventing sufficient pivot of the truck.

As the others have said, look at eye level with good lighting and use very slow speeds.  Or, use enough speed that you can reliably replicate the problem.  Watch for the first deviation of the axles that wants to lift out of the gauge.  Is it really that truck that is having the problem, or is it what is happening to the entire frame above it?  Often longer locomotive frames are being tipped by what is happening at the rear-most truck, say a high joint or a low inner rail.

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Posted by Lone Wolf and Santa Fe on Monday, November 16, 2015 1:48 PM

Six axel locos often derail because the wheels don't freely move up and down, and/or they are out of guage (spread too wide). The wheels should be able to absorb minor track problems.

Modeling a fictional version of California set in the 1990s Lone Wolf and Santa Fe Railroad
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Posted by tomikawaTT on Monday, November 16, 2015 2:04 PM

This is either a track problem or a rolling stock out of tolerance problem.  For either, there are three very useful tools:

  1. NMRA Gauge.
  2. Small frameless mirror.
  3. Human eyeball, Mk1 mod0.

The gauge should be applied to the wheels - EVERY wheelset.  Finding one or more that aren't in gauge is unlikely - but not impossible.

Then apply to the rails (with power off, please)  Feel for tight and loose spots.  If the little shoulder drops between the rails you have a spot with wide gauge.

The mirror is useful for getting the line of sight right down on the rails without having to plant the head in the scenery.  It can also be placed beyond the locomotive when you're checking the wheels for horizontal and vertical alignment - a very useful second point of view.

It doesn't take much to cause a derailment.  One high spike under the flange of the second axle's wheel can lift the front wheel flange right over the railhead.  The same is true for a tiny speck of solder left over from soldering a lead to the rail.

As far as accelerating out of a curve, NASCAR thinks well of the practice.  Our Class 1 (12":1' scale) brethren prefer to traverse the curve completely before accelerating.  A few years back there was a messy accident in Switzerland when accelerating with cars still on a sharp curve whipcracked a load of tourists off the rails.

Chuck (Modeling Central Japan in September, 1964 - with track as bulletproof as I can make it)

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Posted by RR_Mel on Monday, November 16, 2015 2:14 PM

 

If your SD is an Athearn check the wheel clearance to the frame.  I have two Athearns that the power contact pivot on one of the trucks was compressed and I had to slip a small screwdriver under the contact to bend it slightly to give the wheels more clearance. Stopped the derails.
 
 
Edit:  Put your SD on a super smooth surface (glass in my case) and swivel the trucks back and fourth, if you feel even a slight drag on either truck it will derail.
 
Mel
 
Modeling the early to mid 1950s SP in HO scale since 1951
 
My Model Railroad   
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.
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Posted by kasskaboose on Tuesday, November 17, 2015 7:09 AM

Thanks all for the responses.  I sent you PMs to get more clarifications.  After putting down masonite instead of shirt stock, and gluing down the cork w/ liquid nails, I think that resolved things.

How to address the trucks being mis-aligned or the trucks dipping?  Could the latter happen from not enough weight underneath the cork?

~Lee

 

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Posted by richhotrain on Tuesday, November 17, 2015 7:13 AM

Good news, if you resolved that issue.

Probably not a misalignment issue with the trucks.  They are designed to ride on the rails.  When they don't, it is almost inevitably a track problem.  The track always needs to be secured in some fashion on a stable surface.

Rich

Alton Junction

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Posted by Wazzzy on Tuesday, November 17, 2015 8:49 AM

I am also using micro engineering (code 83) flex track for my ON30 layout. I learned quickly that some of the ends of the flex track appear to have been slightly crushed as the rail is cut to length during the manufacturing process. It wasn't obvious when I layed the track, but when cleaning the track, I could "feel" a shallow dip exactly at the flex track joints.

Luckily I didn't have too much done and the repairs were minimal. I now trim 1/2 inch off the flex track ends and this problem went away.

Hope you find the cause of your frustration...

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