Burrengyro
John H
To my knowledge there are two different types of teeter bearings for ELA rotors. The older design had two taper roller bearings housed in the teeter block (that’s the cube that is bolted to the hub bar). Later models had two NKX 15 combined radial and thrust bearings housed in a threaded "barrel" for chordwise adjustment. These had a needle roller bearing for the teeter bolt and a ball thrust bearing.
View attachment 1153081
For me personally for 0.5 mm of axial play, I’d just tighten the teeter bolt to close the gap by deflecting the teeter towers. 0.5 mm is about 120° rotation of the nut on a 1.5 mm pitch thread (which is what the teeter bolt has from memory). If you don’t like that solution your plastic shims would be OK for me since they go between the stationary side of the thrust bearing and the stationary teeter tower so there shouldn’t be any rotation. No need for steel but there’s nothing wrong with using steel shims.
If you have the older design shims or tightening the teeter bolt should also work.
For tightening you need a little pre load on the thrust bearings and to fix your shims so I just tighten the nut by hand as hard as I can without using a spanner.
Don’t overdo it, I balanced a couple of ELAs and the local importer insisted on torqueing up the teeter bolt such that each time I found the thrust bearings damaged.
View attachment 1153082
You can check if yours are damaged by rotating them with your finger while applying an axial load, if you feel it is “lumpy” as the balls pass over the dents in the race then you need to replace them.
I replaced the damaged ones I found with a NKXZ15-2-XL with roller thrust bearings having a higher load capacity.
View attachment 1153083
As Abid said there should be no play in the ELA setup because any sliding along the teeter bolt would be done by the radial needle rollers and they aren’t designed for that it might even damage the rollers or the sleeve.
Mike G