Yup, the airlock frame/shell wound up a couple about 2mm longer than intended. But it was square to the world so I figured that I could re-make the vanes and add 1mm to each end. Near as I can figure, that must have still left a path for the air to get past.
When I made the silicon rubber wipers for the vanes I cut them so I had a wiper on both ends of the vane as well as along the length of it.
This is how much sawdust that had dropped out of the airflow in the main dust collector trunk-line.
While it covers the bottom of the "bin", it's actually only about 1-1/2 to 2 cups of sawdust.
But that would have eventually built up in the duct. I may have to get out the bore-scope and look at the ducts that I can get into, now I'm curious if I still have a problem, or if I've solved it. I don't really want to, but I may have to cut an access hole into the main trunk-line so I can see if I've got dust laying in the bottom of it.
The first plant that I worked at had a poorly designed dust collection system. After the fire department had to come out and put out a smoldering fire in the duct-work another guy and I got "blessed" with the easy job of cleaning out the 24" duct where it ran across the roof, I was a few pounds lighter and a LOT more nimble then. (Confined space permit? What's that?)
Within a year, they had a repeat of this fire, only this time it blew the top off the dust collector, the top was 1/8" steel about 12' x 12' - wound up in a field about 200-300 yards away. After that the entire dust collection system was rebuilt, never had any problems after that.