I have the
pleasure frustration of owning quite a number of 1980s vintage Overland diesels. Most of them have the later dual end gear towers. Frankly, they can be miserable beasts to keep running. Some folks might say they are better off sitting in a display case... I know that folks like Jay C build top-notch drives, I don't have the $$$ for that.
Recently, while cleaning wheels for upcoming A&O O Scale convention layout tours, I found one of my GP35s that wouldn't drive the front truck. I had encountered that problem previously, on a different unit and had a strong suspicion about the cause. Some Overland diesel models used an all-Delrin universal that attaches to the gear tower input shaft by means of a 2mm set screw.
Over time, and with use, the set screw backs-out and destroys the weak Delrin threads even though there is a flat on the shaft. The existing threads are ruined. Sorry for the out-of-focus images from my iPhone. It would be great if it had macro focus, but I shot these for personal documentation to remind me what I did. Yesterday.
A somewhat
temporary fix is to drill all the way through the coupling and tap new threads on the far side. That's what I did with limited time before the convention. I say temporary because on the A&O we run our engines hard and put them back in the barn while still wet. During one op session the Dispatcher used all 44 columns on his train sheet.
Sorry, no photos about that operation since I needed both hands. A prehensile tail like Zimbu the coding monkey in Dilbert cartoons might have come in handy as well. But since the old threads were already trashed, the original hole guided my M2 tap.
Hopefully a better solution, one lasting as long as I do (none of us know the time of our demise, statistics so far suggest that 1 out of 1 will die) may be to substitute a coupler from a
different Overland model. These couplers were made of brass, which holds set screw threads quite well. The engines that used this coupler didn't have flats on the input shaft, but that's not a problem here.
The drive shaft with a brass coupler in the above photo was procured from an online vendor who purchased much of the Overland O Scale spare parts.
Wait, there's more for Overland follies!
