The rod is fully inserted into the center tube in this picture. As you can see, by leaving the lip here it acts as a stop preventing the rod from sliding out by accident. Someday I'd like to find a way to float this in the center tube without the use of those metal tabs to hold in centered in the pipe. For now I'm sticking with what others have done and leaving the experimentation for later. Note the tight clearances, here around 1/16", between the rod and ID of the pipe. If you're planning to use long chain hydrocarbons such as diesel or oil in this, you'll need more clearance here. Check the information available on the Internet for exact details. I'm planning on using mostly water with some oil, maybe 5%. This should work fine for me in this application.

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