Adjustable Nose Gear Bearing Block Spacer for the Lancair 320/360
by Chris Zavatson
A few years ago I had to repeatedly switch back and forth between two different nose struts. The distance between shoulders was not identical and so the steel tubing spacer that holds the bearing blocks apart was going to have to be changed each time. I don’t like to see any side to side play in this installation. It is one more factor that can contribute to shimmy in the nose gear. On the other hand, the assembly must remain free of friction in order for emergency gear extensions to work properly.
My original installation used only the kit-supplied steel tubing between the aluminum bearing blocks. This placed too much pressure on the aluminum and was leaving an impression of the tubing. I shortened the tube and placed steel washers between the tube and the bearing blocks. The washers were ground down such that when the ¼ in through bolt was torqued I had no side to side play in the nose gear pivot bearing, yet no friction. This was a tedious iterative process as the washers had to be ground precisely and installation was not pleasant. I had to make two sets of washers, one for each nose strut.
After a few cycles of strut changes, I finally designed and fabricated an alternate method of holding the bearing blocks apart that allowed for variations in the strut widths. It is much easier to install, and allows for precise control of the bearing play and friction.
The tube is replaced with a spacer that has a much larger bearing area but tapers down to clear the nose gear. One of the bearing blocks is threaded to receive an adjustment screw. It starts as a grade 8 bolt that is drilled with a through hole. The head has a recess to seat the new spacer. Since the adjustment screw can be retracted into the bearing block, fitting of all the parts to the engine mount is made much easier. The ¼” through bolt and the ½” screw are torqued against each other such that all measurable play is removed yet no friction is introduced. Fine tuning to this exact point is incredibly simple and takes less than a minute. After the final adjustment has been made, a jam nut is tightened to add an extra layer of security.