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Author Topic: SD40-2 Derailment issues for the Bachmann HELLO!  (Read 2298 times)
« on: November 13, 2013, 08:00:40 PM »

TO Bachmanns Best
I have a sd40-2 with DCC on board.Very good running engine, until UNDER FULL LOAD WHEN TESTING THE TRUCKS BASICALLY POP A WHEELIE so much that the end axle lifts off the rail causing derailment EITHER DIRECTION  if your going into a curve of course because the first axle is half way off the rail  ,,,the trucks are tight to the frame after we shimmed it up thinking that would take care of it.. Seems like the design ,,but not sure at this point, all the axles are even AND IN GAUGE, pushing down on the loco when this happens has no effect,pushing down on the end of the truck to force the wheels back on the rail takes some force to overcome the torque of the drive .The pivot point on the truck seems to be the problem LIKE A race care needing wheelie bars,, maybe,,,,,Big Maybe?Huh??there is no wobble in the drive ,wheels ect... AT this point I HAVE ran out of ideas,Hope there is someone out there that may have a suggestion .Usually have fun solving these mysteries but it is not fun any more!I FIND IT HARD TO ADMIT THAT I AM STUMPED this has not happen in a very long time,BEEN fixing (model railroading) for about 15yrs but I GUESS THERE IS A REASON FOR EVERYTHING,,,!Hope is a good thing I HOPE!Still hoping ,but after a few weeks my son asked me Where is the Bachmann???
« Last Edit: November 20, 2013, 01:57:01 PM by ALCO1000 » Logged

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« Reply #1 on: November 20, 2013, 02:46:47 PM »

Ref your "climbing" truck issue. You are on the right "track" as far as the pivot point is concerned. A few years back I had exactly the same issue with an N scale Rivarossi SW1500 engine. This loco used two stamped semi_circular pieces of metal to form a left and right side pivot. There was just enough slop in the assembly to allow the drive worm, under certain conditions, to climb up onto the top of the driven gear, and with the high torque motors Rivarossi was using, it would force the truck to rotate, as a plane rotates to lift off. I never did cure the issue, not enough time, patience nor parts availability. Maybe you can observe the interface of the worm and gear as the situation occurs. Hope this might help and good luck. You are also correct about the amount of force required to push the truck back down onto the track - and this was in N gauge !
Jerrys HO
« Reply #2 on: November 20, 2013, 05:21:54 PM »


You mention the trucks are tight to the frame. Have you tried loosening the trucks a little to allow them to pivot more freely? You may have to move the pc board to get to the screws. Hope this helps.

« Reply #3 on: November 21, 2013, 11:21:05 AM »

Thanks Guys! , Back into it I go ,had an Idea when you mentioned the truck mount and the worm carrier and slop in that area ,Amazing how you can have 2 of the same loco and one is fine and the other does this ,hate to swap out things from the good one just for the sake of testing ,I am a firm believer of the saying if its not broke don't fix it even in this sitchuation. ONCE I find the solution I will post it with some pics,Hopefully it will get back to whomever designed this set up for an improvement ,New and improved designe new set of  problems muffies law ! Grin

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« Reply #4 on: November 21, 2013, 11:28:27 AM »

I had a gp7 which derailed on curves right out of the box. the problem wasn't "too much slop" but that the truck screws were too tight and there wasn't enough play to negotiate the curves. backing the truck screws off by about 1/2 turn solved the problem. this is a 5 minute fix.

Jeffery S Ward Sr
Pittsburgh, PA
« Reply #5 on: November 21, 2013, 06:35:48 PM »

Well Thank you for all the tips ,but with all this inspired me to give it a hole harted effort!,The sd40-2 is and unusual Bachmann diesel ho loco in how the trucks attach to the frame with the worm cover clip assembly ,ALL IN ONE PIECE that snaps into the slots in the frame that centers you up with the centering pin unlike all the older spectrum and plus and standard flywheel drive diesel models //There is some play in that area , but the issue is basically where it attaches between the inboard and center axle,although close to the truck centerline  Almost!,
This engine was purchased in 2007 brand new and was run in a so called fleet of about 10 different engines in that time and has been lubricated cleaned ect ect..,Here are the findings after many tests, ///The offset truck pin puts more load on the center and inboard axle bearing/halfshaft wheel assembly that actually wore a even groove in it, changing the diameter of the circle/HALFSHAFT BEARING/WHEEL ASSEMBLY THAT CAUSED THE INBOARD AXLES TO WEAR OUT FASTER THAN THE OUTBOARD AXLES CAUSING THE TRUCK TO SIT CROOKID LEANING T WORDS THE CENTER OF THE ENGINE , CAUSING THE OUTER AXLE ON BOTH TRUCKS EITHER DIRECTION TO TORQUE UP EVEN MORE UNDER FULL LOAD LIKE POPING A WHEELIE,ENEN IF YOUR PULLING IN A CONSIST  THEN YOU HIT A CURVE IN THE RAIL AND YOUR LEAD WHEEL SET THAT SHOULD BE STEERING YOU INTO THE CURVE FLANGE catches a switch and theres a train wreck in the making,,,have another with just as much run time and signs are there to ,but for some reason it seems like the plating on the axle wheel assembly does not show any deterioration groove,,Strange that the metal wore out before the plastic resin that it rides in wore, So there it is ,I THINK IT DESERVES A NEW SET OF  TRUCKS  OR AT LEAST 8 WHEEL ASSEMBLIES MAYBE HUMMMM???
Thanks Again ! But WHERE IS MR. B??

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« Reply #6 on: June 29, 2018, 02:08:12 AM »

Had the same problem. Noticed loose wires when i removed the body.
The train only derailed in one direction. All the time, the front motor was dragging the rear with it.
The electrical wires were too short, and stressed when turned the bogies. 

I also rounded the edges of the plastic bogies, which made contact with the chassis in these sharp curves. Solving the narrowness problem.

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« Reply #7 on: June 29, 2018, 08:54:24 AM »

ALCO1000 - If you are having an issue with a Bachmann product you should contact the Bachmann service department and they will be happy to help. Bachmann moderators keep an eye on the forum to make sure everyone is being civil and respecting each other and they cannot be expected to have the answer to every question - that's the service depatments job.

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« Reply #8 on: June 29, 2018, 09:38:46 PM »

Whenever I have asked the Bach Man anything Iíve either gotten an answer or been directed to whoever had it... even had an off line reply once.  While I may not agree with some of their marketing ideas, Iíve found those guys to be top grade in customer relations.

Modeling the New Iberia and Northern 1945
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