i have a sd-40 atheran model loco and it runs good until it goes into the curves i have 18" radius tracks the back wheels keep jumpin off it has 12 wheels alltogether can any one give me some info on what could be causing it to derail
Lets see, i've had similair problems firstly, the SD40 (is it a -2 cos if it is thats worse) is a HUGE loco. the 18' curves are tiny. I have done it, but dont reccomend it then i'd try relaying your track, and try nudging the rail joints with pliers also, feel them with your hands too, if you feel bumps, try relaying the track hope this helps (if you need more help just ask, i'll try, but some guys here know heaps)
The problem might not be with your track. That being said, 18" radius curves are way to tight for six axle locos. 22-24" is much better. I had a problem with a 40-2 on a 30" radius. The rear truck would not rotate enough and derail. I found the problem was the L-bracket on top of the truck was slightly bent and would contact the shell thereby not allowing enought rotation. Once I straighten the bracket everything ran smoothly.
18 curves may not be ideal, but, beleive it or not, i've ran a SD40-2 ariund one at FULL SPEED and it stayed on
If the bracket is not hitting the shell: One other thing could be the rubber traction tires. Look at your rear truck to see if the traction tires are only on one side. Notice if when on the rails, this truck acts like the rubber tire might cause the truck to 'kick up' so the front axle flanges can ride over the rail tops and swivel to one side. It is usually because the rubber tire wants to keep going, while the rest of the engine wants to slow down because of the tight curve or #4 turnout. Add weight over the rear truck, check rail joints to 'feel' any sharp rail ends. File or sand them smooth. If that wont work, trade the diesel in on a good steam engine!
Watash, I was unaware that Athearn SD40-2's had traction tires. The three that I have don't have them - thank God.
I wasn't sure about the Traction Tires, but they have given me lots of trouble, so I added it into my post just in case.
Welcome Aboard the Trainboard express. . . 92Tempo, Welcome to Trainboard. . Does the Loco do the same in a curve in REVERSE? If so, if it is the same truck, the problem is likely the truck, if it is the other truck, I'd suspect the track. In any case the first thing I do when weirdness happens, is to gauge the wheels using my trusty NMRA standards gauge. I have tender on a Loco that hates kinks more than any other and the reason is actually pretty simple, one set of wheels on the tender is just a bit out of gauge, too wide. As said before, make sure both trucks rotate freely, properly and the full amount. They should be neither too loose nor too tight (binding) As for track, does it do it only on one section of 18" or does it do it on several. My point, if it is only on one section, you may have the dreaded KINK in your track, sometimes they are very hard to see or feel. Another tactic I use is to shine my very bright LED flashlight directly on the wheels while running the Loco over the problematic section. Your young eyes may be much better than my aged peepers, but excellent light can reveal flaws we just cannot otherwise see. Good luck and let us know what you find. Joe
Back in the day (late70"s-early80's) anything with 12 wheels was put on 22" raidus curves or bigger since my biggest curvers were 38". 18" were used for 8 wheels and switchers.
All my curves are 18" radius and all my locos negociate them with no problem, enen the big Athearn SD40-2's that I have, although at first one of the SD40's wouldn't do it. When I ran it without the shell on, it did fine. I put the shell back on and it derailed on the first curve it came to. The problem turned out to be that the pickup strip that sticks up from the truck was bent over to one side. After I bent it to the center like the other one I had no further problem with it and I still use the loco today.
