No Foolin', this is a strange problem.

Model Railroader Electronics and DCC
1

I am working on a museum display layout depicting the N&W Ry in the 1950’s. One of the locomotives we purchased (from e-bay) is a BLI Class A 2-6-6-4. On the display it is run from a MRC Tech III power pack. It was running erratically, speeding up and slowing down, so another member took it off to clean the wheels. He ran the locomotive with another Tech III attached to a small test/cleaning track, While doing this the locomotive stopped running. We felt a small vibration as the voltage went up, but there was no wheel movement.

I brought it home to try and fix it. The first thing I did was set it on my test track and bring it up on DCC (Digitrax Zephyr). The sounds and lights responded fine, so I slowly turned up the throttle. The wheels turn, but the two sets of drivers are going in opposit directions! Reversing the direction reverses both sets of drivers, with the forward set running opposit the throttle setting.

Before I take it apart, has anyone had this situation before?

John

2

Assuming that this loco has “TWO” drive motors. At some point in time one motor had the wirers reversed. I would take the shell off and hook it up on a test bench. Remove the wirering from the offending drivers and reverse them.

3

I’ve seen this before.

The problem is with the output link between the forward and aft drives. The link becomes inverted over time and will cause a similar symptom to what you encounter. It usually occures when BLI’s are run on DC then DCC. The small vibration is symtomatic with the inversion of the link.

I found a web document regarding this issue. The document covers all aspects of repairing the link in question. This problem is limited to only BLI 2-6-6-4. It has to do with the Advanced Pre-Reverse Internal Load Factor Of Output Link also know as APRILFOOL.

If you wish you can send me the loco and I will replace the output link for you. I am an in training BLI tech, self tought.