Just really getting into this because of my grandson’s obsession with trains and my own fascination long supressed. We’re starting with a small, simple 4x6 layout that he can take home at some point when we “finish” with the scenery, etc. The starting point was an old(1970s) AHM trainset my sons never got interested in. We’ve added one turnout- Atlas 540 snap switch and I bought a new Bachmann SD40-2 locomotive. My problem is that the rear truck of the loco derails at the turnout - not every time- but just when I think everything is OK, boom - there it goes. If I flip the locomotive around and run it backward, the new “back” truck derails, always at the exact same place (the frog) and the same way. Very frustrating. Rolling stock never has a problem. I’ve read posts about solving derailment issues and I sort of understand the principles of checking the track guage, alignment, etc. Any other suggestions?
You might try a new switch.
Yes, check the track for gauge, but also use the flangeway side of the NMRA gauge to check those.
I can’t recall about that Atlas switch, but if it is a sharply diverging one (#4?) they sometimes give 3-axle trucked units fits. Still it probably should work. Als, if a plastic frog as some Atlas switches are, check to see if it is smooth along the top where the rail and frog meet.
Also, don’t forget to check the gauge of all wheels on the loco. Even though new, there could be ones out of gauge.
The only turnout issue I ever had was cause by a poor roadbed under the turnout. It wasn’t well supported at all points and would bend ever so slightly when a heavy steam loco went over it. I finally discovered what was going on by sticking a video camera on the trouble spot and then watching it frame by frame on the big screen.
I have taken the file to more than one turnout to tune them up. Usually to make the flangeway a little deeper as the wheel woulld ride up at the frog.
I have a bunch of Atlas Snap-Switches on my BRVRR layout and have had no problems for a long time.
Your derailment problem sounds like a wheel gage problem to me. Check the wheel gage on the loco trucks, I’ll bet they are not the same.
To reduce or eliminate the problem if it is wheel gage and not an obstruction in the flange way, make your gage just a hair tighter than what is recommended.
Good luck.
Another thing to check is the swing of the offending truck. Make sure both trucks have the same amount of side to side rotation. There may be a wire or some other obstruction inside the body that is preventing the truck from swinging all the way.
Joe
Well, it’s either the turnout or the locomotive. Do other locomotives have trouble at the same place? Is the turnout the only place on the layout that derails the SD40? The SD-40 is a six axle locomotive which is harder to get around tight corners and turnouts. Any chance of exchanging it for a four axle locomotive such as a GP-40? Or exchanging the turnout for a higher numbered one? Atlas makes some #6 and #8 turnouts which are easier for a big locomotive to handle.
All that said and done, I would expect a Bachmann locomotive to handle 18 inch radius curves and Atlas Snap Switches, UNLESS, the packaging or instruction sheet plainly requires broader curves.
I might take the shell off and run the just the chassis thru the turnout looking for things like excessive angle on the U-joints, or the trucks hitting some obstruction as they try to swing out to make the curve. Does the problem occur running just the locomotive by itself?
Body mount couplers work best when the two pieces of rolling stock are the same length. Is the locomotive significantly longer than the car behind it? Does the problem go away when you just run the locomotive by itself?
Let us know what you find.
Since the engine is derailing at the frog I would inspect the frog for any foreign matter or wear since the 540 snap switch has a plastic frog.
Every time I had trouble with an engine truck or a trailing truck, it was something happening between them, often near the frog. As Brent wisely suggests, the turnout may need some work midships. Because of their wheel mounting, steamers’ drivers horse the entire frame above them one way or another, and this puts stress on the trucks at either end. If a frog is high, or there is a pinched flange path through a guard rail, the frame gets tilted as the affected wheel(s) get forced upward. While they may stay railed and fall back into place, they cause havoc nearer to the ends of the long frame.
While I have mentioned steamers, this could also be true for diesels. Something happening way over at the other truck could be impacting all the way back where your rear truck derails.
Does the turnout lie completely flat, on a plane, when viewed at eye height and with it set flat on a countertop or a small pane of glass…or a mirror? When it is laid flat, does a good straightedge laid along its major axis show light below it, or are the rails clearly supporting the straightedge along their entire lengths? Gaps will show.
Lastly, it could be the truck itself. If the flanges are in gauge, maybe its swing is being restricted. Maybe there is some flashing on the mount or the bearing surface. Screw a bit too tight? Something g
Hello All,
Definitely run the loco through the turnout alone and see if it derails.
If it does not derail running alone I suspect it might be the lack of coupler swing; the side to side movement of the couplers.
As the loco and the trailing car move through the diverging side of the turnout the couplers move from side-to-side roughly following the arc of the track.
To see this happen take two coupled cars and move them through the turnout by hand. From directly above watch how the coupler heads move from side to side. You might need to shine a light between the cars as you do this to see this action.
If there is not sufficient side-to-side movement uncouplings and derailments can occur as you described.
Also, if the coupler on the loco or trailing car is truck mounted this too can limit the coupler swing and cause derailments. This is why body mounted couplers are preferred. The trucks can follow the path of the tracks while the couplers move independently.
If lack of coupler swing is the problem there are a few solutions:
- Body mount the couplers; on the loco and the rolling stock. This conversion has been discussed at length in this (http://cs.trains.com/mrr/f/88/t/250477.aspx) and the Kadee forums.
- Replace the existing couplers with one with longer shanks. This will increase the swing of the couplers and allow greater side-to-side movement.
Hope this helps and let us know how it goes.
Whenever I have had this problem with the trailing truck derailing it was because the wheels were out of gauge. They were spread too wide. And/or the wheels did not freely move up and down so they could not absorb any differences in track height. There always needs to be a little slop in loco wheels, especially six axel diesels.
Another problem could be that the turnout doesn’t stay in place when the loco goes over it and the points do not stay up against the rail.
Check the wheels on the loco. Also know that six axel diesel locos don’t run well on tight curves or turnouts. Get a GP40 instead. They are far more reliable and better for kids.
[#welcome]
Well, with grand kids you need a fine running system. Check each and every rail joiner for alignment both right and left, and up and down. Sometimes it is actually off the track before it gets to the switch, it only becomes obvious at the switch when it gets worse.
Looking at the flangeways and frog of the switch is important.
How close is the turnout to a curve? Is it set on a “S” curve. You need at least a 9" section between a right curve and a left curve. (Actually that is supposed to be the length of you longest car–but we’ll just call it 9")
You probably do not have an NMRA gauge to check the wheels and rails, but then I have 14 scale miles of track and I do not own one either. (I do have the gauges for 1:1 scale equipment, but that does not help either of us). I am not sure that I would run out to get one for your situation, but just slide the equipment through the turnout looking at it very carefully from both sides.
Is all of your track code 100? Run your finger along the rail, and see if there is any tactile defect.
Best of luck with this.
ROAR
Gidday, [#welcome]to the forums.
hmmmm…
BTW here’s a link to the NMRA HO gauge the guys are referring too. Using the Mark 1 eyeball and running the finger over the offending area, in fact all the tips you have been given, are very good suggestions, but the gauge doesn’t lie.
[url]http://www.nmra.org/standard-s-7-clearances-and-nmra-gaugeI would presume that the track from the AHM trainset would be Code 100 whereas the Atlas 540 snap switch is advertised as Code 83. To my mind, there’s the problem! The rail height difference wouldn’t bother larger flanged wheels on an AHM loco but with the smaller flange wheels on the new Bachmann,
Cheers, the Bear.[:)]
Hello All,
Brilliant observation!!!
If that is the case then transition rail joiners from code 83 to 100 could be the answer.
Sometimes the simplest observations lead to the simplest solutions.
Is the turnout a facing or trailing point? Also, does the loco derail consistently traveling through both the through and diverging route?
Is there enough room on the truck to mount and hide some weights?
Dante
What color is the locomotive?
Thanks for all the replies and advice. I’ve come to realize how much I didn’t know when I started working on this. The old AHM track I had on hand was evidently code 100 (I didn’t know this) and a couple of pieces I added along with the turnout are code 83 - problem right there which I’m fixing with transition joiners.
Also not knowing what I was doing, I bought the SD40 six axle locomotive which I’ve become convinced is the major issue trying to run it on the 18" radius layout. The old four axle locomotive that came with the set doesn’t run well at all but does’nt derail. I think I’ll be replacing with something like a GP9 and all should be well. And I’m certainly going to keep reading and studying all the information available here.
Again, thanks for the replies.
Blue with yellow polka dots. [swg]
Better question: is it everyday, or only on the second Tuesday of the week, but only when the date is after the 32nd day of the month. (Except when it is blue with yellow polka dots day, then it must occur on the third Tuesday of the week, but only when it falls on a even date, odd dates for blue with yellow polka dots day must be the forth Wednesday of the week…) [(-D]
My best guess, either the change in track code, OR it is occurring before the turnout altogether, and the frog is the final point that the derailed wheel (Still Close enough that it follows the track, but off just enough to catch on the turnout.) can go before being thrown off to far.
What if it turns out to be undecorated? [8o|]
Rich