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Author Topic: Twisted Trucks causing derailments.  (Read 3360 times)
Redtail67

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« on: April 14, 2008, 04:24:47 PM »

Newcomers might find this of interest as I am sure the "oldtimers" here have already figured this out.

I have spent the better part of a week going over my grandsons layout trying to identify and cure all causes of derailments. My efforts have vastly improved the operation.

I had bad alinement and out of crosslevel spots in my track, some noticeable and some that were hard to spot except when running at high speed. The slightest problems were amplified at the higher speeds..just like in the real world. The slightest bump or ruff spot at HO Scale is bad news.

Some were problems associated with hook and horn couplers..they did not swing as needed or then had too much up and down movement in them. in the curves even after I worked on them. So I started changing all the freight cars out to KADEE 148 and that helped .

I had cars that were derailing every time around. They might go around twice then hit the ground. These were problems were cured by using weights to bring the cars up to or slightly over the NMRA standards.

One thing I found out is to remember to keep the weight as low as possible in the car or you have bad derailments account of a high center of gravity.

Also, by putting slightly more weight centered over the trucks then spreading the rest out evenly in the car. In my opinion this held the wheels down on the rail better over frogs and switches. I changed most of the cars out to Model Power RP-25 Trucks with Steel Wheels. That really helped the operation. The rest will be changed out soon.

At each stage of this I had a noticable improvement in reliability of operation.

Then I was left with two cars one was a 50' flat and the other a 40' wooden box car. These two cars had been weighted and couplers had been changed to KADEE 148. They had steel wheels in plastic trucks.

I would run them at slow speeds and no problems and then a little faster until I noticed a slight shimmy in the cars even though it was very, very slight. Then as I increased speed they would start derailing. However, as the shimmy did not look bad so i did not really think much of it.

Then I thought of the real world where trucks that "HUNT" or wobble are bad news and will cause derailments. So I am thinking that this slight shimmy at this scale would translate to a real bad shaking in the real world.

I took off the trucks and laid them on a flat surface and lo and behold they had a slight twist and would not sit flat on the table. I looked at them real close ( my eyes ain't what they used to be) and I could see it. I then twisted them back straight and that was it.

Then cars started tracking straight and true no shaking at any speed and no derailments. I was really proud of my investitgative skills.

Then I got up this morning bragging to my grandson "Papa is the smartest railroad man on the planet". I then tell him how I have fixed those cars and now we could play trains with no derailments.

I put the engines on all the cars and a caboose and told him start it out slow and increase your speed and you will see how good Papa fixed your
train.

Well away he went about 3/4 around and all cars and the engine went in the ditch. He said "PAPA! Somebody must have broke them while we were sleeping!"

Man I was speechless after bragging to him like I did. When looked at the cars the twist had come back in them. I guess they had a "set" in them and went back to it even though I had straightend them last night and they ran fine.

So I found some that were straight and put them in and threw the old ones away. I have been running them for 3 hours now with no problems.

So I am sure all you "oldtimers" here have been through this and know about it. However, someone like me who is new might find this of interest and check their cars out for even very slightly twisted trucks and if they are get rid of them. They might have a memory set that they return to even if you straighten them out.

Redatil67

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Virginian

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« Reply #1 on: April 14, 2008, 04:44:47 PM »

Good job.  Weight evenly distributed has the same effect as weight "centered" over the trucks.  No matter how good it feels, physics, statics, and dynamics are constant.
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"What could have happened... did."
Jim Banner

Enjoying electric model railroading since 1950.


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« Reply #2 on: April 14, 2008, 04:45:13 PM »

One old-time trick is to put the truck on a mirror instead of directly on the table top.  It makes it easier to see which wheels do not touch when you rock the truck.  The very best mirror is a front silvered one such as from a truck mirror.  I got one of these for free from a truck dealership - it had been replaced because one of the little motors that tilt the mirror had quit.  As a bonus, the other tilt motor worked perfectly, and even came with a worm and pinion.  Sometimes you have got to love our throw away society.

Second tip - if you want to keep the plastic from returning to its original shape, heat it slightly.  If you over heat a few and ruin them, you are no worse off than throwing them out anyway.

Thank your grandson from all of us who have ever had an embarrassing derailment when we are showing off our layouts.  Next time we have cars derail, I suspect many of us will be saying that "Somebody must have broke them while we were sleeping!"  At least it will be a change from "The cat did it."

Good job.  Weight evenly distributed has the same effect as weight "centered" over the trucks.  No matter how good it feels, physics, statics, and dynamics are constant.

Or you can put all the weight at the middle of the car floor (i.e. at about the center of gravity.)  But remember, these three weight distributions (over the wheels, centered, or evenly spread out) are identical ONLY in a rigid system at rest.  They are not identical dynamically as the moment of inertia is different in all three cases.  But often the bottom line is that you stuff in weight wherever you can find the room.
« Last Edit: April 14, 2008, 04:53:32 PM by Jim Banner » Logged

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Redtail67

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« Reply #3 on: April 14, 2008, 05:43:10 PM »

To all:

Do you belive that harm is done by exceeding the NMRA guidelines? I have added an ounce or two above the recommended weight and it seemed to help the cars more.

I know not to just pile it on, but does it hurt to be over somewhat with some cars?

Just wondering..

Redtail67
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Redtail67

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« Reply #4 on: April 14, 2008, 05:51:45 PM »

Jim,

Thanks for the tip about the mirror thats a great idea and I will give the heat trick a try just to see what happens.

Redail67
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WoundedBear
A Derailed Drag Racer


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« Reply #5 on: April 14, 2008, 07:23:23 PM »

Bravo Redtail. Too many people would have been complaining about shoddy manufacturing and asking where to call to start hollering.

It's refreshing to see someone take the old hands-on approach and actually work out a solution for himself.

I see railroading akin to hot rodding.......I can buy the best pile of parts there is, but it is still going to take some initiative and creativity on my part to make them work as a unit. Tweak and test and test and tweak.

We've also chuckled for years about the automotive catch-phrase...."Bolt On". Yup, once you modify everything around this piece....it definitely bolts on....lmao.

Sid
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Yampa Bob

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« Reply #6 on: April 14, 2008, 08:23:53 PM »

Red is being too modest.  I happen to know that the boxes of cars his daughter sent him were in real need of repair and maintenance (R & M).  Horn couplers, plastic wheels, missing trucks, you name it. 

He received a bunch of beautiful locomotives that were sorta inoperable. By necessity, he learned in a month what it took me a year to learn.  It was only after a friend gave me a box of culls that I began to learn.

Congratulations Red, you have the right to be proud, even if the "Train Fairy" breaks stuff during the night.  Cheesy 

Bob
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Rule Number One: It's Our Railroad.  Rule Number Two: Refer to Rule Number One.
SteamGene

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« Reply #7 on: April 14, 2008, 09:45:15 PM »

Good job.  I like my weights over the wheels if possible, but spread evenly if that is what must be (gons, hoppers, and flats).  I've found that I can run hoppers with the "as built" weights in them with no trouble.  In fact, I'm removing previously installed lead bird shot from hoppers to use elsewhere.
Gene
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Chief Brass Hat
Virginia Tidewater and Piedmont Railroad
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cmgn9712

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« Reply #8 on: April 17, 2008, 05:47:00 AM »

I ran a molding operation for a model RR company for years. Generally the warped trucks are from sticking in the mold and twisting when ejected. The twist is molded into the memory of the plastic and will return to the twist regardless of heat or pressure. Just throw them away and replace.
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Yampa Bob

Y.V.R.R.


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« Reply #9 on: April 17, 2008, 01:08:43 PM »

It has been my experience that it is difficult to change the molecular memory of most plastics.  You might attain a temporary "fix" but it seems to eventually return to its molded shape.

There is a plastic called Optyl that can be heated to a rubbery state in salt and talcum powder without melting, reshaped and submersed in ice water.  It was developed for the manufacture of eyeglass frames.  Other materials such as Nylite and Zylite also had excellent reforming qualities.

Delrin and Celcon seem to be the standard for bearing surfaces, but the plastics and metal technologies are constantly changing.  If only we could develop "transparent aluminum" like Scotty did.  Cheesy

Bob     
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I know what I wrote, I don't need a quote
Rule Number One: It's Our Railroad.  Rule Number Two: Refer to Rule Number One.
Redtail67

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« Reply #10 on: April 18, 2008, 01:10:08 AM »

Funny you guys mentioned the memory would return..I just looked at mine, after reading your post, that I had straightened out or so i thought.

Yes sir as crooked as the first time I saw them..lol

They are now in the trash.

Redtail67
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r.cprmier

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« Reply #11 on: April 18, 2008, 05:33:50 PM »

Do you belive that harm is done by exceeding the NMRA guidelines?

Only if you don't subscribe to thinking out ot the box.

Suggested reading:

Any story on the life and times of Les Paul-AKA- The Wizard of Waukesha.

The old reprobate
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Rich

NEW YORK NEW HAVEN & HARTFORD RR. CO.
-GONE, BUT NOT FORGOTTEN!
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