Thanks, Sheldon. I think the problem with mine is improper lubrication by the previous owner, not a fault with the original loco (despite the Rube Goldberg gear set-up). Since I've already resigned myself to paying for NWSL replacement gears, I may just leave it with them until new ones are available. Since I'm neither the original owner of the loco nor willing to return it to Bachmann, I'd be paying for replacement gear sets anyway.
Wayne
Thanks to your information Wayne, I popped off the top of the gear tower on both front and rear engines and dropped both engines from the boiler castings - having had to cut the wires from the front and rear driver wipers since they were soldered at both ends -wiper ends and printed circuit board at cab end, and not trusting my solder iron skills.
While removing the rear engine I found that the brass screw (and spring underneath) securing the engine to the bottom boiler casting was firmly seated, unlike the screw and spring for the front engine which had been floating and appeared to be contacting the drive shaft.
I don't understand the function of the spring under the brass screw head, since the spring is very weak and easily compressed - is it intended to be like a compressible washer? Should the brass screw be firmly seated, or some float allowed -but how to control? Firmly seating the screw and spring does not appear to effect freedom of the engines to rotate horizontaly or verticaly.
I couldn't determine how to remove the side plates on the towers to check the gears, without breaking something, but found that both engines ran freely on the track with little effort and no sounds from the gears, suggesting that nothing was broken and that I should leave well enough alone.
Assuming that the noise and rough running problem with the front engine was due to the head of the loose brass screw interfering with the driveshaft, I'm about to reassemble the engines to the boiler castings.
Any comments would be appreciated!
Isambard
Grizzly Northern history, Tales from the Grizzly and news on line at isambard5935.blogspot.com
To be perfectly honest, I don't recall how the side cover is removed. Mine was sent to NWSL in May. I'm sure that when it comes back, I'll be able to figure it out, but it's difficult to know when that will occur.
I'm almost positive that the cause of my gear problems was improper lubrication - it ran well before I purchased it and ran well when tested on the layout. Unfortunately, it sat for some time, unused, while I worked on other projects. When I finally got around to begin modifications to it, a test run revealed the trouble.
It sounds to me as if your only problem was with that screw being loose, as the engines both roll freely. My guess is that the spring may be there to help that engine's tracking ability, but it may also serve (not very well, apparently) to keep the screw from backing itself out. If you decide to replace the spring, be careful to use one that's not too much stronger, as it may inhibit the wheels from following irregularities in the track. If you stay with the current spring, you can keep the screw from backing itself out, yet still leave it easily removeable when necessary - simply de-grease the screw and apply a little contact cement to the end threads. Allow the cement to dry (10 or 15 minutes) then install it as usual. The cement will provide enough "interference" to keep the screw in place, yet still leave it removeable.