Hi all, I have an Atlas U23B which is about 7 years old. Never a problem with it until a few nights ago when the engine will only go in the forward direction [cab forward]. In reverse, it screams loudly, wheels slip and only will go if the throttle is all the way. It's DC, the wheels and track are clean. When going forward the engine is still silky smooth. Any suggestions? Also my eyes aren't what they used to be but looking at it upside down it looks O.K. Thanks for your help. Paul
Sounds like something may be binding on the gear train or a cracked gear or universal somewhere. First check the trucks externally to see if anything is stuck or wound around something. If things look good, you'll probably have to open up the shell and check what happens when running in reverse.
My first thought would be a piece of ballast (or similar) in the gears on one truck. In one direction the gears kick the piece out of the way, but in the opposite direction the piece is pulled into the gears locking them up. This would cause the drive to that truck to squeal and the other truck to spin as it tries to drag the locked up truck along. Turning the throttle all the way up is needed to make the drive to the stuck truck slip (VERY BAD by the way). Pull the bottoms off the trucks and look at the gears.
Yes. Wheels from both trucks are spinning in reverse. I took the shell off and didn’t see anything binding from any foreign material. Tomorrow I’ll check the gears. Hopefully I won’t make matters worse. Thanks for everyone’s help so far.
If all(?) the wheels are spinning on the railhead, I would think that the problem lies outside the drivetrain. Perhaps a pilot or the fuel tank is drooping at one end and snagging on the rail? This easy fairly easy to miss. I had an Atlas GP9 behaving similarly and giving me fits, until I finally noticed the fuel tank was misaligned and contacting the track. All wheels vs. some wheels spiining would be an important distinction. If only some of the wheels are spinning, then it indeed lies in the drivetrain.
It will go very very slow in reverse then the screeching starts. Very loud, then stops No obstructions from anything hanging down or on the track
My experience is screeching with some slowing while it is happening is a fairly common issue that is related to a lack of lube at the worm bearings and/or at the motor bearings. My experience is that is usually occurs in both directions when this is the issue and I've never seen it make a loco completely stop, so I keep thinking it's something else....especially if the wheels are spinning on the railhead while it's stopped. Just to confirm one last time, all 8 wheels are spinning on the railhead while the loco is not moving but all the while making a screeching noise? Perhaps one of the ball joints that connects the worm shaft to the flywheel is loose but only causes a problem in one direction only? ...regarding adding lube at the motor bearings. My experience is too much oil can seep thru the bearings and into the motor itself, potentially damaging the motor.
Ok just went to the layout flashlight and glasses in hand. In the forward direction All wheels are turning no problem. In reverse it appears one truck is fine and the other isn’t turning too well. It is now being pushed along. Metal on metal sound. Thanks
Ok, starting to think it could possibly be that a ball joint might be loose...although I've never experienced this per se. I've had an Atlas N SD9 (Chinese version) that has a tiny, plastic, doughnut-shaped connector that cracked and caused something sort of similar, but I think the ball joints are quite a bit hardier. Still, I suppose it could become loosened on the worm shaft and slip, causing the screeching and loss of power to one truck. If you haven't seen it, here's the exploded diagram of the Atlas N U23B... http://download.atlasrr.com/pdf/PartsPDFs/NParts/NU23BLoco.pdf All this said, you're probably going to need to disassemble to loco and check to see if the trucks roll freely out of the loco first. If you haven't disassembled a loco before (sorry, don't know), take care to notice how things are orientated and be careful when you loosen the frame that the trucks don't come flying off and crash to the floor. If you don't want to tackle this, you may want to contact Atlas to see if they can help.
I looked very carefully over and over again and don’t see anything that jumps out at me as being the cause of the noise. I don’t have any real experience with taking engines apart and while YouTube videos are helpful, I feel it’s best to send it back to Atlas. It’s boxed up right now going to the post office later. I do have 2 other Atlas engines to fill in for the time being. Thanks again for your help, I’ll let you know what Atlas comes back with. Paul
I got off the phone with Atlas today. The rear drive components have to be replaced along with the wipers. While its there, the front drive components will also be changed. There is a lot of wear and tear on this loco as it gets a lot of use. Thanks for your help tehachapifan.
