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I have a BB Athearn SD40-2 that runs great (on DC) when going forward. But when in reverse, the rear trucks cause a loud whirring noise. I haven't dismantled it yet but wonder what could cause noise in only one direction.
I have a GP that grinds in one direction. Tower gears? Drive shaft? I've not been able to isolate the cause since I really didn't want to tear it apart. Guess I'll have to bite the bullet and do that.
As Larry sez, I had a loco that when reversed made the motor slide back on its shaft and do the coffee grinder thing.
Wait, I still have it and it still does. It's an RTR Athearn F7.
I'll watch for a how-to!
Just turn the engine over and poke at the holes in the bottom of the fuel tank with a toothpick. You'll probably find one or more of the rubber plugs are loose. Open up the engine and just press fit the motor back in place, so all the rubber nubs are snug in the holes. Some guys just cut off the rubber nubs and seat the motor using a few dabs of silicone, which won't work loose. That will hold the motor in place and stop the grinding noise in reverse.
Thanks for the tips. I'm in Texas visiting my sister and her family and am heading home on Monday. I have a few spare motor mounts so will check that first.
This seem to be happening often with athearn units, i had one who was doing that noise, i disasembled it completly and reassembled and the noise stopped, so i guess it was those washers
there's another problem you can look for sometimes. On the gear shaft on top of the trucks that goes to the driveshaft, there's a little square bushing that people sometimes lose when they take an engine apart. There's 2 per shaft(one on each end) & if 1's missing it causes the shaft to jump up & it makes an awful noise. Since I've been repairing my own engines, building engines & adding LED's I've found a lot of mistakes that people that owned the engine before me have left off w/out even knowing it. When I get an engine from anyone(especially from EBay) I open it up & check everything, take the trucks apart & lube, take out all the metal elect. clips & hardwire it all. Sometimes if the engine is slow I take out the brush springs & brushes & check for wear. So, there's a lot of things you can do to improve your engines & rolling stock.
I checked everything suggested and found no problems. I noticed that the noise is hardly audible with the shell off and seems to be coming from the motor itself. But only in reverse.
Many times the shell accentuates sounds you want, or don't want. I don't know how many times I've taken the shell off to do something only to put it back on and the locomotive is noiser than when I had the shell off.
Many times the shell accentuates sounds you want, or don't want. I don't know how many times I've taken the shell off to do something only to put it back on and the locomotive is noiser than when I had the shell off.
I tried caulking some polyfiber "fluff" inside a shell to absorb some sound. Didn't make a difference at all so the sound must be being conducted from the frame to the shell.
Hey Bernie. Is your locomotive one of the new Athearn RTR locos? If so,you might want to take a look at the worm gear in the truck tower. A friend of mine here in B'ham,told me about a problem he was having with one of the new RTR locos from Athearn,and he showed me one of the worm gears. It is plastic,not metal like it used to be. That might well be the source of your trouble. If it is the worm gear,you might be able to replace it,or get new ones from Athearn. Please let me know what turns up,and good luck. William.
I checked everything suggested and found no problems. I noticed that the noise is hardly audible with the shell off and seems to be coming from the motor itself. But only in reverse.
Athearn BB's are notorious for their noise. The motor is a big contributor to the noise. This is mainly due to the not so tight tolerances within the motor itself. What you need are thrust washers on one or both ends of the motor shaft. The motor shaft is too "sloppy" in the frame, (typical Athearn BB), and the change in direction and torque causes the motor shaft to move to the point where the end of the armature is rubbing against something in the motor frame causing the noise. The best thing about these BB motors are they are easy to work on and doesn't require any special tools at all. It, like the rest of the BB locos, snaps together. Just don't remove the armature from the magnets, or the motor will be damaged.
Inserting a thrush washer on to one or both ends, removes most of the sloppiness, causing the motor to run quieter. There are usually two metal washers, (one on each end of the armature), already on the shaft ends, and I just insert a gray KD washer between the washer and the armature at the rear of the motor, (the end opposite of the brushes). One washer generally works, but sometimes I have to insert another. The armature should still turn as freely as before. If the armature is tight in the frame, then I just remove the second KD washer.
I always start with the rear end but the noise can come from the brush end, so if the washer at the rear doesn't cure the noise, I just remove that washer and place it on the brush end.
