I am planning to build a couple of English Wheels in the next few months, and one of the key elements is the adjuster. The adjusters are often made of a square rectangular tube with a solid or tubular square inside the larger tube. The inner square goes up and down. Most of the adjusters that I have seen require machine work, or are relatively complex to build. I just keep thinking that there must be a simple commercial solution, maybe using square cold roll steel for the inside, and something commercial that the square fits into.
As far as scale, the inner square bar or tube would typically be 1 to 2 inches square, and around 12 inches long.
For your convenience, there is a link below that shows a picture of what a small English wheel looks like. The adjuster moves the wheels closer together or further apart, to increase or decrease the pressure between the wheels. This article suggests using parts from a telescoping steering wheel, which I do not have in my junk box, and would not be adequate for a larger ewheel anyway. A square or rectangular inner piece keeps the upper and lower wheels in alignment, which is important. You do not want a lot of slack in the adjuster, though a few thousanth's of an inch should be acceptable.
Thanks in advance.