The dome which holds the filter on our PA-18 Super Cub had a wallowed hole in it. As the engine vibrates, the hole on this part becomes out of round and just continues to wear. The spinner dome is around .050" thick or so and rides on a 1/4" bolt. If we take the standard clearance of a 1/4" hole that gives a bearing area of around .022 square inches - not much. They wear quick, especially since the bolt is steel and the intake dome is 3003 aluminum.
The first "prototype" was a washer that I bolted down and carefully formed it into sort of cone/spherical shape. I ran that for a summer and it seemed to do the trick. After that I drew up the next version in Solidworks and ran it on my friends cnc lathe. The design intent of this product was to distribute the contact to a large area which will greatly reduce or eliminate wear. Another similar way to think about how this works is by picking up a basket ball by the palm of your hand.
Designed in 3D with Solidworks. Manufactured out of 6061-T6 aluminum on a high accuracy Okuma CNC lathe. Anodized type II finish in Red, Silver, or Black. Intake Dome Washer.