Derailing USA Trains SD40-2

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electricity_bill

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Hello
I have recently acquired a USA Trains SD40-2 which does not want to stay on the rails. If I run the loco pulling a train, the leading moveable driven axle on the front six wheel bogie is riding up and over the rail and de-railing the loco usually at the next set of points. I have checked and corrected it for wheel gauge and movement and checked the track for level and gauge, all to no effect. It tends to happen when the loco comes out of a corner and it is not a minimum radius issue. If I run the loco light engine, the problem does not occur. Any ideas?

Bill
 
Mmmmm - ist it something at the other end? Have you checked both bogies for gauge, pivot, and axle side-play?

Or is the bogie moving in a way that it shouldn't when under load?

Is the bogie not returning to centre(ish) when coming out of a curve?

All probably helpfully unhelpful, but sometimes it's useful to punt ideas around :emo::emo::emo::emo:
 
Is the front bogie free to move in all planes, compared to the rear?
Is the rear coupler height about right? - Not too high in comparison to the stock behind?
Can you run it on rollers? - Are the motors running about the same speed?

Just a few more things to check..
 
There has been a few instances of the three axle USAT bogies becoming problematic.
Here is one thread on the Large Scale Central forum about it.
http://largescalecentral.com/forums/topic/7696/usa-trains-sd70-mac-truck-problems


The USAT 3-axle bogies can be very sensitive to track aberrations.
If it is happening in one place in the curve, check very closely the rails themselves.
I once had a problem in one place on the layout that affected an SD 70 (uses the same USAT 3 axle bogie block), I checked the gauge, the level, ballast in the sleeper chairs etc and all seemed fine..... but on closer inspection there was a small ridge on one rail (probably due to a bit of mistreatment some time before) which did not affect any other rolling stock, just the SD70.

Also it is worth checking (as has been already mentioned) that the swing of the front axle is totally free of restrictions.....
 
Gents
Thanks for your collective help and advice. I finally got round to running the loco today and tried another solution. I ran the loco backwards and it ran perfectly!!! Perhaps that suggests that there is a problem with the "lead" bogie and I will get round to swapping them over when we get back from holiday.
Thanks again
Bill
 
The plate that guides the swiveling of the end axles is often rough and when there is upwards pressure, the sliding part often binds... with the loco on it's back, there is no pressure, and it will appear to be free. lube liberally with grease and check for rough spots, smooth the metal and deburr the curved slot if necessary.

Also, some of these plates had a rough surface, like sandblasted as opposed to smooth plating.

Properly lubricated, I find that these truck track exceptionally well, but unlubricated I had derailments.

Greg
 
Actually, just for fun, I'm betting it's not twist (crosslevel) in the track. The "floppy" leading axle has a lot of travel and can handle irregularities well.

But if there is friction in the plate and slider, that is exactly when it will derail, entering or leaving a corner.

Let's just see what fixes it... all it takes is physically checking the friction (under pressure) and lubricating. I have never seen one lubricated from the factory.

Greg

p.s. to the OP, it is indeed the lead truck that derails, right?
 
Last edited:
Greg Elmassian said:
Actually, just for fun, I'm betting it's not twist (crosslevel) in the track. The "floppy" leading axle has a lot of travel and can handle irregularities well.

But if there is friction in the plate and slider, that is exactly when it will derail, entering or leaving a corner.

Let's just see what fixes it... all it takes is physically checking the friction (under pressure) and lubricating. I have never seen one lubricated from the factory.

Greg

p.s. to the OP, it is indeed the lead truck that derails, right?
Click to expand...
Yes it is the lead truck i.e. the front one going forward.
 
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