Here's a quick update.
I got the base layer bolted down and ran at 5 ipm. The least about of vibration I've observed. I had all sorts of small parts on the spoilboard, 6mm button head cap screws, a variety of washers, some hex wrenches and the like. Nothing moved. Nevertheless, as expected, there was still some vibration.
Marcus at Gecko asked me to remove, bench test at 5 ipm and video record so he could see/hear the stepper. An interesting exercise, but no surprises. The stepper vibrated. Standing on end (the shaft vertical) I got one level of noise. Laying on it's side, I got a higher level. Here is a link to the video: https://drive.google.com/open?id=1hA...yeruPUGu4YPBKn
I ran this latest video through Spek. Here is the result:
You will note that there are 4 distinct area. The first and third reflect the sound produced while the stepper was on end. The second and fourth are when the stepper was on its side. It looks like the lower end of the frequency range moved up quite a bit. The upper end is the same. The sound produced is probably influenced to some degree by my bench top. It's a 36" x 72" x 3" piece of phenolic. I'm thinking it is probably introducing some damping effect.
Peter, you asked about the pivot shaft. From the best I can tell without disassembling the drive, there is a generic ball bearing something like this:
.
I also removed the shaft (a shoulder bolt) from the pinion gear. It also has the same sort of ball bearing. The bearing is pressed in.
Peter, I believe you also mentioned that you doubted the folks at Gecko would be able to help. While I agree, I had already engaged with Gecko and felt I owed it to myself to see what, if anything, they might have to offer. I'm not expecting much, but who knows?
Next up: using the nylon washers I bought this morning to try to isolate some of the vibration.
Gary